fakecloud-dynamodb 0.13.2

mod batch;
#[cfg(test)]
mod expression_corpus_tests;
mod global_tables;
mod items;
mod queries;
mod streams;
mod tables;

use std::collections::HashMap;
use std::sync::Arc;

use async_trait::async_trait;
use base64::Engine;
use http::StatusCode;
use serde_json::{json, Value};

use fakecloud_core::delivery::DeliveryBus;
use fakecloud_core::service::{AwsRequest, AwsResponse, AwsService, AwsServiceError};

use fakecloud_persistence::{S3Store, SnapshotStore};
use fakecloud_s3::state::SharedS3State;

use crate::state::{
    attribute_type_and_value, AttributeDefinition, AttributeValue, DynamoDbSnapshot, DynamoTable,
    GlobalSecondaryIndex, KeySchemaElement, KinesisDestination, LocalSecondaryIndex, Projection,
    ProvisionedThroughput, SharedDynamoDbState, DYNAMODB_SNAPSHOT_SCHEMA_VERSION,
};

/// Minimal subset of a ``DynamoTable`` that Kinesis streaming delivery needs.
///
/// A table can carry megabytes of items; cloning the whole table just to
/// release the write lock and deliver one change record is extremely wasteful.
/// Extracting only the fields the delivery path actually reads (destinations,
/// arn, name) keeps the clone small.
pub(super) struct KinesisDeliveryTarget {
    pub destinations: Vec<KinesisDestination>,
    pub arn: String,
    pub name: String,
}

/// Operation flavor for the per-item KMS audit-trail emitter. Reads
/// emit a paired `Decrypt` after `GenerateDataKey`; writes only emit
/// `GenerateDataKey`, mirroring AWS's audit shape.
pub(crate) enum TableKmsOp {
    Read,
    Write,
}

pub struct DynamoDbService {
    state: SharedDynamoDbState,
    pub(crate) s3_state: Option<SharedS3State>,
    pub(crate) s3_store: Option<Arc<dyn S3Store>>,
    delivery: Option<Arc<DeliveryBus>>,
    snapshot_store: Option<Arc<dyn SnapshotStore>>,
    pub(crate) kms_hook: Option<Arc<dyn fakecloud_core::delivery::KmsHook>>,
    pub(crate) region: String,
    /// Serializes concurrent snapshot writes so the newest observed
    /// state always wins on disk. Without it, two tasks could race
    /// between state.read().clone() and store.save() and leave older
    /// bytes as the final on-disk state.
    snapshot_lock: Arc<tokio::sync::Mutex<()>>,
}

impl DynamoDbService {
    pub fn new(state: SharedDynamoDbState) -> Self {
        Self {
            state,
            s3_state: None,
            s3_store: None,
            delivery: None,
            snapshot_store: None,
            kms_hook: None,
            region: "us-east-1".to_string(),
            snapshot_lock: Arc::new(tokio::sync::Mutex::new(())),
        }
    }

    pub fn with_s3(mut self, s3_state: SharedS3State) -> Self {
        self.s3_state = Some(s3_state);
        self
    }

    pub fn with_s3_store(mut self, store: Arc<dyn S3Store>) -> Self {
        self.s3_store = Some(store);
        self
    }

    pub fn with_delivery(mut self, delivery: Arc<DeliveryBus>) -> Self {
        self.delivery = Some(delivery);
        self
    }

    pub fn with_snapshot_store(mut self, store: Arc<dyn SnapshotStore>) -> Self {
        self.snapshot_store = Some(store);
        self
    }

    pub fn with_kms_hook(mut self, hook: Arc<dyn fakecloud_core::delivery::KmsHook>) -> Self {
        self.kms_hook = Some(hook);
        self
    }

    pub fn with_region(mut self, region: impl Into<String>) -> Self {
        self.region = region.into();
        self
    }

    /// Record `GenerateDataKey` + `Decrypt` for an SSE-KMS table on a
    /// PutItem/UpdateItem (write) and GetItem/Query/Scan (read). DDB
    /// item bodies are nested attribute maps — encrypting them in
    /// fakecloud would balloon scope without adding test coverage that
    /// users actually want, so we just emit the audit-trail records the
    /// AWS API produces and let callers assert KMS usage via
    /// `/_fakecloud/kms/usage`.
    pub(crate) fn record_table_kms_usage(
        &self,
        account_id: &str,
        table_arn: &str,
        kms_key_arn: Option<&str>,
        operation: TableKmsOp,
    ) {
        let Some(hook) = &self.kms_hook else { return };
        let key = kms_key_arn
            .filter(|k| !k.is_empty())
            .unwrap_or("aws/dynamodb");
        // DynamoDB SSE-KMS uses the AWS-documented encryption context:
        // {aws:dynamodb:tableName: <name>, aws:dynamodb:subscriberId: <account>}
        // — see the AWS DynamoDB encryption-at-rest docs. The table arn
        // ends with `:table/<name>`, so derive the name from it.
        let table_name = table_arn.rsplit('/').next().unwrap_or(table_arn);
        let mut ctx = std::collections::HashMap::new();
        ctx.insert("aws:dynamodb:tableName".to_string(), table_name.to_string());
        ctx.insert(
            "aws:dynamodb:subscriberId".to_string(),
            account_id.to_string(),
        );
        let envelope = match hook.encrypt(
            account_id,
            &self.region,
            key,
            b"ddb-item",
            "dynamodb.amazonaws.com",
            ctx.clone(),
        ) {
            Ok(env) => env,
            Err(_) => return,
        };
        if matches!(operation, TableKmsOp::Read) {
            let _ = hook.decrypt(account_id, &envelope, "dynamodb.amazonaws.com", ctx);
        }
    }

    /// Persist the current in-memory state as a snapshot. Called after
    /// every state-mutating action. A noop when no snapshot store is
    /// configured (i.e. `StorageMode::Memory`).
    ///
    /// The snapshot lock serializes the full clone + serialize + write
    /// so concurrent mutators cannot leave older bytes on disk, and
    /// serialization + the blocking file write are offloaded to the
    /// blocking pool to keep Tokio workers responsive.
    async fn save_snapshot(&self) {
        let Some(store) = self.snapshot_store.clone() else {
            return;
        };
        let _guard = self.snapshot_lock.lock().await;
        let snapshot = DynamoDbSnapshot {
            schema_version: DYNAMODB_SNAPSHOT_SCHEMA_VERSION,
            accounts: Some(self.state.read().clone()),
            state: None,
        };
        let join = tokio::task::spawn_blocking(move || -> std::io::Result<()> {
            let bytes = serde_json::to_vec(&snapshot)
                .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e.to_string()))?;
            store.save(&bytes)
        })
        .await;
        match join {
            Ok(Ok(())) => {}
            Ok(Err(err)) => tracing::error!(%err, "failed to write dynamodb snapshot"),
            Err(err) => tracing::error!(%err, "dynamodb snapshot task panicked"),
        }
    }

    fn kinesis_target(table: &DynamoTable) -> Option<KinesisDeliveryTarget> {
        if table
            .kinesis_destinations
            .iter()
            .any(|d| d.destination_status == "ACTIVE")
        {
            Some(KinesisDeliveryTarget {
                destinations: table.kinesis_destinations.clone(),
                arn: table.arn.clone(),
                name: table.name.clone(),
            })
        } else {
            None
        }
    }

    /// Deliver a change record to all active Kinesis streaming destinations for a table.
    pub(super) fn deliver_to_kinesis_destinations(
        &self,
        target: &KinesisDeliveryTarget,
        event_name: &str,
        keys: &HashMap<String, AttributeValue>,
        old_image: Option<&HashMap<String, AttributeValue>>,
        new_image: Option<&HashMap<String, AttributeValue>>,
    ) {
        let delivery = match &self.delivery {
            Some(d) => d,
            None => return,
        };

        let active_destinations: Vec<_> = target
            .destinations
            .iter()
            .filter(|d| d.destination_status == "ACTIVE")
            .collect();

        if active_destinations.is_empty() {
            return;
        }

        let mut record = json!({
            "eventID": uuid::Uuid::new_v4().to_string(),
            "eventName": event_name,
            "eventVersion": "1.1",
            "eventSource": "aws:dynamodb",
            "awsRegion": target.arn.split(':').nth(3).unwrap_or("us-east-1"),
            "dynamodb": {
                "Keys": keys,
                "SequenceNumber": chrono::Utc::now().timestamp_nanos_opt().unwrap_or(0).to_string(),
                "SizeBytes": serde_json::to_string(keys).map(|s| s.len()).unwrap_or(0),
                "StreamViewType": "NEW_AND_OLD_IMAGES",
            },
            "eventSourceARN": &target.arn,
            "tableName": &target.name,
        });

        if let Some(old) = old_image {
            record["dynamodb"]["OldImage"] = json!(old);
        }
        if let Some(new) = new_image {
            record["dynamodb"]["NewImage"] = json!(new);
        }

        let record_str = serde_json::to_string(&record).unwrap_or_default();
        let encoded = base64::engine::general_purpose::STANDARD.encode(&record_str);
        let partition_key = serde_json::to_string(keys).unwrap_or_default();

        for dest in active_destinations {
            delivery.send_to_kinesis(&dest.stream_arn, &encoded, &partition_key);
        }
    }

    fn parse_body(req: &AwsRequest) -> Result<Value, AwsServiceError> {
        serde_json::from_slice(&req.body).map_err(|e| {
            AwsServiceError::aws_error(
                StatusCode::BAD_REQUEST,
                "SerializationException",
                format!("Invalid JSON: {e}"),
            )
        })
    }

    fn ok_json(body: Value) -> Result<AwsResponse, AwsServiceError> {
        Ok(AwsResponse::ok_json(body))
    }
}

#[async_trait]
impl AwsService for DynamoDbService {
    fn service_name(&self) -> &str {
        "dynamodb"
    }

    async fn handle(&self, req: AwsRequest) -> Result<AwsResponse, AwsServiceError> {
        let mutates = is_mutating_action(req.action.as_str());
        let result = match req.action.as_str() {
            "CreateTable" => self.create_table(&req),
            "DeleteTable" => self.delete_table(&req),
            "DescribeTable" => self.describe_table(&req),
            "ListTables" => self.list_tables(&req),
            "UpdateTable" => self.update_table(&req),
            "PutItem" => self.put_item(&req),
            "GetItem" => self.get_item(&req),
            "DeleteItem" => self.delete_item(&req),
            "UpdateItem" => self.update_item(&req),
            "Query" => self.query(&req),
            "Scan" => self.scan(&req),
            "BatchGetItem" => self.batch_get_item(&req),
            "BatchWriteItem" => self.batch_write_item(&req),
            "TagResource" => self.tag_resource(&req),
            "UntagResource" => self.untag_resource(&req),
            "ListTagsOfResource" => self.list_tags_of_resource(&req),
            "TransactGetItems" => self.transact_get_items(&req),
            "TransactWriteItems" => self.transact_write_items(&req),
            "ExecuteStatement" => self.execute_statement(&req),
            "BatchExecuteStatement" => self.batch_execute_statement(&req),
            "ExecuteTransaction" => self.execute_transaction(&req),
            "UpdateTimeToLive" => self.update_time_to_live(&req),
            "DescribeTimeToLive" => self.describe_time_to_live(&req),
            "PutResourcePolicy" => self.put_resource_policy(&req),
            "GetResourcePolicy" => self.get_resource_policy(&req),
            "DeleteResourcePolicy" => self.delete_resource_policy(&req),
            // Synthetic defaults (no DAX endpoint discovery / no real per-account quotas tracked)
            "DescribeEndpoints" => self.describe_endpoints(&req),
            "DescribeLimits" => self.describe_limits(&req),
            // Backups
            "CreateBackup" => self.create_backup(&req),
            "DeleteBackup" => self.delete_backup(&req),
            "DescribeBackup" => self.describe_backup(&req),
            "ListBackups" => self.list_backups(&req),
            "RestoreTableFromBackup" => self.restore_table_from_backup(&req),
            "RestoreTableToPointInTime" => self.restore_table_to_point_in_time(&req),
            "UpdateContinuousBackups" => self.update_continuous_backups(&req),
            "DescribeContinuousBackups" => self.describe_continuous_backups(&req),
            // Global tables
            "CreateGlobalTable" => self.create_global_table(&req),
            "DescribeGlobalTable" => self.describe_global_table(&req),
            "DescribeGlobalTableSettings" => self.describe_global_table_settings(&req),
            "ListGlobalTables" => self.list_global_tables(&req),
            "UpdateGlobalTable" => self.update_global_table(&req),
            "UpdateGlobalTableSettings" => self.update_global_table_settings(&req),
            "DescribeTableReplicaAutoScaling" => self.describe_table_replica_auto_scaling(&req),
            "UpdateTableReplicaAutoScaling" => self.update_table_replica_auto_scaling(&req),
            // Kinesis streaming
            "EnableKinesisStreamingDestination" => self.enable_kinesis_streaming_destination(&req),
            "DisableKinesisStreamingDestination" => {
                self.disable_kinesis_streaming_destination(&req)
            }
            "DescribeKinesisStreamingDestination" => {
                self.describe_kinesis_streaming_destination(&req)
            }
            "UpdateKinesisStreamingDestination" => self.update_kinesis_streaming_destination(&req),
            // Contributor insights
            "DescribeContributorInsights" => self.describe_contributor_insights(&req),
            "UpdateContributorInsights" => self.update_contributor_insights(&req),
            "ListContributorInsights" => self.list_contributor_insights(&req),
            // Import/Export
            "ExportTableToPointInTime" => self.export_table_to_point_in_time(&req),
            "DescribeExport" => self.describe_export(&req),
            "ListExports" => self.list_exports(&req),
            "ImportTable" => self.import_table(&req),
            "DescribeImport" => self.describe_import(&req),
            "ListImports" => self.list_imports(&req),
            _ => Err(AwsServiceError::action_not_implemented(
                "dynamodb",
                &req.action,
            )),
        };
        if mutates && matches!(result.as_ref(), Ok(resp) if resp.status.is_success()) {
            self.save_snapshot().await;
        }
        result
    }

    fn supported_actions(&self) -> &[&str] {
        &[
            "CreateTable",
            "DeleteTable",
            "DescribeTable",
            "ListTables",
            "UpdateTable",
            "PutItem",
            "GetItem",
            "DeleteItem",
            "UpdateItem",
            "Query",
            "Scan",
            "BatchGetItem",
            "BatchWriteItem",
            "TagResource",
            "UntagResource",
            "ListTagsOfResource",
            "TransactGetItems",
            "TransactWriteItems",
            "ExecuteStatement",
            "BatchExecuteStatement",
            "ExecuteTransaction",
            "UpdateTimeToLive",
            "DescribeTimeToLive",
            "PutResourcePolicy",
            "GetResourcePolicy",
            "DeleteResourcePolicy",
            "DescribeEndpoints",
            "DescribeLimits",
            "CreateBackup",
            "DeleteBackup",
            "DescribeBackup",
            "ListBackups",
            "RestoreTableFromBackup",
            "RestoreTableToPointInTime",
            "UpdateContinuousBackups",
            "DescribeContinuousBackups",
            "CreateGlobalTable",
            "DescribeGlobalTable",
            "DescribeGlobalTableSettings",
            "ListGlobalTables",
            "UpdateGlobalTable",
            "UpdateGlobalTableSettings",
            "DescribeTableReplicaAutoScaling",
            "UpdateTableReplicaAutoScaling",
            "EnableKinesisStreamingDestination",
            "DisableKinesisStreamingDestination",
            "DescribeKinesisStreamingDestination",
            "UpdateKinesisStreamingDestination",
            "DescribeContributorInsights",
            "UpdateContributorInsights",
            "ListContributorInsights",
            "ExportTableToPointInTime",
            "DescribeExport",
            "ListExports",
            "ImportTable",
            "DescribeImport",
            "ListImports",
        ]
    }
}
/// Actions that mutate DynamoDB state and therefore require a snapshot
/// write after success. Kept in sync with the dispatch table above.
fn is_mutating_action(action: &str) -> bool {
    matches!(
        action,
        "CreateTable"
            | "DeleteTable"
            | "UpdateTable"
            | "PutItem"
            | "DeleteItem"
            | "UpdateItem"
            | "BatchWriteItem"
            | "TagResource"
            | "UntagResource"
            | "TransactWriteItems"
            | "ExecuteStatement"
            | "BatchExecuteStatement"
            | "ExecuteTransaction"
            | "UpdateTimeToLive"
            | "PutResourcePolicy"
            | "DeleteResourcePolicy"
            | "CreateBackup"
            | "DeleteBackup"
            | "RestoreTableFromBackup"
            | "RestoreTableToPointInTime"
            | "UpdateContinuousBackups"
            | "CreateGlobalTable"
            | "UpdateGlobalTable"
            | "UpdateGlobalTableSettings"
            | "UpdateTableReplicaAutoScaling"
            | "EnableKinesisStreamingDestination"
            | "DisableKinesisStreamingDestination"
            | "UpdateKinesisStreamingDestination"
            | "UpdateContributorInsights"
            | "ExportTableToPointInTime"
            | "ImportTable"
    )
}

// ── Helper functions ────────────────────────────────────────────────────

fn require_str<'a>(body: &'a Value, field: &str) -> Result<&'a str, AwsServiceError> {
    body[field].as_str().ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            format!("{field} is required"),
        )
    })
}

fn require_object(
    body: &Value,
    field: &str,
) -> Result<HashMap<String, AttributeValue>, AwsServiceError> {
    let obj = body[field].as_object().ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            format!("{field} is required"),
        )
    })?;
    Ok(obj.iter().map(|(k, v)| (k.clone(), v.clone())).collect())
}

fn get_table<'a>(
    tables: &'a HashMap<String, DynamoTable>,
    name: &str,
) -> Result<&'a DynamoTable, AwsServiceError> {
    tables.get(name).ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ResourceNotFoundException",
            format!("Requested resource not found: Table: {name} not found"),
        )
    })
}

fn get_table_mut<'a>(
    tables: &'a mut HashMap<String, DynamoTable>,
    name: &str,
) -> Result<&'a mut DynamoTable, AwsServiceError> {
    tables.get_mut(name).ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ResourceNotFoundException",
            format!("Requested resource not found: Table: {name} not found"),
        )
    })
}

fn find_table_by_arn<'a>(
    tables: &'a HashMap<String, DynamoTable>,
    arn: &str,
) -> Result<&'a DynamoTable, AwsServiceError> {
    tables.values().find(|t| t.arn == arn).ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ResourceNotFoundException",
            format!("Requested resource not found: {arn}"),
        )
    })
}

fn find_table_by_arn_mut<'a>(
    tables: &'a mut HashMap<String, DynamoTable>,
    arn: &str,
) -> Result<&'a mut DynamoTable, AwsServiceError> {
    tables.values_mut().find(|t| t.arn == arn).ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ResourceNotFoundException",
            format!("Requested resource not found: {arn}"),
        )
    })
}

fn parse_key_schema(val: &Value) -> Result<Vec<KeySchemaElement>, AwsServiceError> {
    let arr = val.as_array().ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "KeySchema is required",
        )
    })?;
    Ok(arr
        .iter()
        .map(|elem| KeySchemaElement {
            attribute_name: elem["AttributeName"]
                .as_str()
                .unwrap_or_default()
                .to_string(),
            key_type: elem["KeyType"].as_str().unwrap_or("HASH").to_string(),
        })
        .collect())
}

fn parse_attribute_definitions(val: &Value) -> Result<Vec<AttributeDefinition>, AwsServiceError> {
    let arr = val.as_array().ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "AttributeDefinitions is required",
        )
    })?;
    Ok(arr
        .iter()
        .map(|elem| AttributeDefinition {
            attribute_name: elem["AttributeName"]
                .as_str()
                .unwrap_or_default()
                .to_string(),
            attribute_type: elem["AttributeType"].as_str().unwrap_or("S").to_string(),
        })
        .collect())
}

fn parse_provisioned_throughput(val: &Value) -> Result<ProvisionedThroughput, AwsServiceError> {
    Ok(ProvisionedThroughput {
        read_capacity_units: val["ReadCapacityUnits"].as_i64().unwrap_or(5),
        write_capacity_units: val["WriteCapacityUnits"].as_i64().unwrap_or(5),
    })
}

fn parse_gsi(val: &Value, billing_mode: &str) -> Vec<GlobalSecondaryIndex> {
    let Some(arr) = val.as_array() else {
        return Vec::new();
    };
    arr.iter()
        .filter_map(|g| {
            Some(GlobalSecondaryIndex {
                index_name: g["IndexName"].as_str()?.to_string(),
                key_schema: parse_key_schema(&g["KeySchema"]).ok()?,
                projection: parse_projection(&g["Projection"]),
                provisioned_throughput: Some(parse_gsi_throughput(
                    &g["ProvisionedThroughput"],
                    billing_mode,
                )),
                on_demand_throughput: parse_on_demand_throughput(&g["OnDemandThroughput"]),
            })
        })
        .collect()
}

/// Parse an `OnDemandThroughput` block. Absent fields default to `-1`,
/// which is AWS's sentinel for "no cap" — and the value real AWS echoes
/// back on DescribeTable when the caller omitted either axis.
pub(super) fn parse_on_demand_throughput(val: &Value) -> Option<crate::state::OnDemandThroughput> {
    if !val.is_object() {
        return None;
    }
    Some(crate::state::OnDemandThroughput {
        max_read_request_units: val["MaxReadRequestUnits"].as_i64().unwrap_or(-1),
        max_write_request_units: val["MaxWriteRequestUnits"].as_i64().unwrap_or(-1),
    })
}

/// Resolve the provisioned-throughput slot for a GSI on a CreateTable or
/// UpdateTable Create action. Real DynamoDB returns `{0, 0}` for GSIs on
/// PAY_PER_REQUEST tables regardless of whether the caller sent a
/// `ProvisionedThroughput` block, and the Terraform provider's `flatten`
/// code keys `name`/`read_capacity`/`write_capacity` off the presence of
/// that field — returning `None` would desynchronise state.
fn parse_gsi_throughput(val: &Value, billing_mode: &str) -> ProvisionedThroughput {
    if billing_mode == "PAY_PER_REQUEST" {
        return ProvisionedThroughput {
            read_capacity_units: 0,
            write_capacity_units: 0,
        };
    }
    ProvisionedThroughput {
        read_capacity_units: val["ReadCapacityUnits"].as_i64().unwrap_or(5),
        write_capacity_units: val["WriteCapacityUnits"].as_i64().unwrap_or(5),
    }
}

fn parse_lsi(val: &Value) -> Vec<LocalSecondaryIndex> {
    let Some(arr) = val.as_array() else {
        return Vec::new();
    };
    arr.iter()
        .filter_map(|l| {
            Some(LocalSecondaryIndex {
                index_name: l["IndexName"].as_str()?.to_string(),
                key_schema: parse_key_schema(&l["KeySchema"]).ok()?,
                projection: parse_projection(&l["Projection"]),
            })
        })
        .collect()
}

pub(super) fn parse_projection(val: &Value) -> Projection {
    Projection {
        projection_type: val["ProjectionType"].as_str().unwrap_or("ALL").to_string(),
        non_key_attributes: val["NonKeyAttributes"]
            .as_array()
            .map(|arr| {
                arr.iter()
                    .filter_map(|v| v.as_str().map(|s| s.to_string()))
                    .collect()
            })
            .unwrap_or_default(),
    }
}

fn parse_tags(val: &Value) -> HashMap<String, String> {
    let mut tags = HashMap::new();
    if let Some(arr) = val.as_array() {
        for tag in arr {
            if let (Some(k), Some(v)) = (tag["Key"].as_str(), tag["Value"].as_str()) {
                tags.insert(k.to_string(), v.to_string());
            }
        }
    }
    tags
}

fn parse_expression_attribute_names(body: &Value) -> HashMap<String, String> {
    let mut names = HashMap::new();
    if let Some(obj) = body["ExpressionAttributeNames"].as_object() {
        for (k, v) in obj {
            if let Some(s) = v.as_str() {
                names.insert(k.clone(), s.to_string());
            }
        }
    }
    names
}

fn parse_expression_attribute_values(body: &Value) -> HashMap<String, Value> {
    let mut values = HashMap::new();
    if let Some(obj) = body["ExpressionAttributeValues"].as_object() {
        for (k, v) in obj {
            values.insert(k.clone(), v.clone());
        }
    }
    values
}

fn resolve_attr_name(name: &str, expr_attr_names: &HashMap<String, String>) -> String {
    if name.starts_with('#') {
        expr_attr_names
            .get(name)
            .cloned()
            .unwrap_or_else(|| name.to_string())
    } else {
        name.to_string()
    }
}

/// Resolve a (possibly dotted, possibly `#name`-containing) document path to
/// the leaf `AttributeValue` inside `item`. Single-segment paths (`foo`,
/// `#foo`) resolve to a top-level attribute. Dotted paths (`profile.email`,
/// `#p.#e`, `items[0].sku`) walk into `M`/`L` containers. Returns `None` if
/// any segment is missing or the intermediate value isn't a map/list.
fn resolve_path(
    path: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
) -> Option<Value> {
    // Fast path: a single-segment expression (no `.` and no `[` in the raw
    // input) refers to a top-level attribute by its literal name, even if the
    // resolved alias contains a `.`. Without this, `#sw` -> `Safety.Warning`
    // would be misread as the nested path `Safety` -> `Warning`.
    if !path.contains('.') && !path.contains('[') {
        return item.get(&resolve_attr_name(path, expr_attr_names)).cloned();
    }
    let resolved = resolve_projection_path(path, expr_attr_names);
    resolve_nested_path(item, &resolved)
}

fn extract_key(
    table: &DynamoTable,
    item: &HashMap<String, AttributeValue>,
) -> HashMap<String, AttributeValue> {
    let mut key = HashMap::new();
    let hash_key = table.hash_key_name();
    if let Some(v) = item.get(hash_key) {
        key.insert(hash_key.to_string(), v.clone());
    }
    if let Some(range_key) = table.range_key_name() {
        if let Some(v) = item.get(range_key) {
            key.insert(range_key.to_string(), v.clone());
        }
    }
    key
}

/// Parse a JSON object into a key map (used for ExclusiveStartKey).
fn parse_key_map(value: &Value) -> Option<HashMap<String, AttributeValue>> {
    let obj = value.as_object()?;
    if obj.is_empty() {
        return None;
    }
    Some(obj.iter().map(|(k, v)| (k.clone(), v.clone())).collect())
}

/// Check whether an item's key attributes match the given key map.
fn item_matches_key(
    item: &HashMap<String, AttributeValue>,
    key: &HashMap<String, AttributeValue>,
    hash_key_name: &str,
    range_key_name: Option<&str>,
) -> bool {
    let hash_match = match (item.get(hash_key_name), key.get(hash_key_name)) {
        (Some(a), Some(b)) => a == b,
        _ => false,
    };
    if !hash_match {
        return false;
    }
    match range_key_name {
        Some(rk) => match (item.get(rk), key.get(rk)) {
            (Some(a), Some(b)) => a == b,
            (None, None) => true,
            _ => false,
        },
        None => true,
    }
}

/// Extract the primary key from an item given explicit key attribute names.
fn extract_key_for_schema(
    item: &HashMap<String, AttributeValue>,
    hash_key_name: &str,
    range_key_name: Option<&str>,
) -> HashMap<String, AttributeValue> {
    let mut key = HashMap::new();
    if let Some(v) = item.get(hash_key_name) {
        key.insert(hash_key_name.to_string(), v.clone());
    }
    if let Some(rk) = range_key_name {
        if let Some(v) = item.get(rk) {
            key.insert(rk.to_string(), v.clone());
        }
    }
    key
}

fn validate_key_in_item(
    table: &DynamoTable,
    item: &HashMap<String, AttributeValue>,
) -> Result<(), AwsServiceError> {
    let hash_key = table.hash_key_name();
    if !item.contains_key(hash_key) {
        return Err(AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            format!("Missing the key {hash_key} in the item"),
        ));
    }
    if let Some(range_key) = table.range_key_name() {
        if !item.contains_key(range_key) {
            return Err(AwsServiceError::aws_error(
                StatusCode::BAD_REQUEST,
                "ValidationException",
                format!("Missing the key {range_key} in the item"),
            ));
        }
    }
    Ok(())
}

fn validate_key_attributes_in_key(
    table: &DynamoTable,
    key: &HashMap<String, AttributeValue>,
) -> Result<(), AwsServiceError> {
    let hash_key = table.hash_key_name();
    if !key.contains_key(hash_key) {
        return Err(AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            format!("Missing the key {hash_key} in the item"),
        ));
    }
    Ok(())
}

fn project_item(
    item: &HashMap<String, AttributeValue>,
    body: &Value,
) -> HashMap<String, AttributeValue> {
    let projection = body["ProjectionExpression"].as_str();
    match projection {
        Some(proj) if !proj.is_empty() => {
            let expr_attr_names = parse_expression_attribute_names(body);
            let mut result = HashMap::new();
            for raw in proj.split(',') {
                let raw = raw.trim();
                // Single-segment: treat as literal top-level attribute even if
                // the alias resolves to a name containing `.` (e.g. `#sw` ->
                // `Safety.Warning`).
                if !raw.contains('.') && !raw.contains('[') {
                    let key = resolve_attr_name(raw, &expr_attr_names);
                    if let Some(v) = item.get(&key) {
                        result.insert(key, v.clone());
                    }
                } else {
                    let resolved = resolve_projection_path(raw, &expr_attr_names);
                    if let Some(v) = resolve_nested_path(item, &resolved) {
                        insert_nested_value(&mut result, &resolved, v);
                    }
                }
            }
            result
        }
        _ => item.clone(),
    }
}

/// Resolve expression attribute names within each segment of a projection path.
/// For example, "people[0].#n" with {"#n": "name"} => "people[0].name".
fn resolve_projection_path(path: &str, expr_attr_names: &HashMap<String, String>) -> String {
    // Split on dots, resolve each part, rejoin
    let mut result = String::new();
    for (i, segment) in path.split('.').enumerate() {
        if i > 0 {
            result.push('.');
        }
        // A segment might be like "#n" or "people[0]" or "#attr[0]"
        if let Some(bracket_pos) = segment.find('[') {
            let key_part = &segment[..bracket_pos];
            let index_part = &segment[bracket_pos..];
            result.push_str(&resolve_attr_name(key_part, expr_attr_names));
            result.push_str(index_part);
        } else {
            result.push_str(&resolve_attr_name(segment, expr_attr_names));
        }
    }
    result
}

/// Resolve a potentially nested path like "a.b.c" or "a[0].b" from an item.
fn resolve_nested_path(item: &HashMap<String, AttributeValue>, path: &str) -> Option<Value> {
    let segments = parse_path_segments(path);
    if segments.is_empty() {
        return None;
    }

    let first = &segments[0];
    let top_key = match first {
        PathSegment::Key(k) => k.as_str(),
        _ => return None,
    };

    let mut current = item.get(top_key)?.clone();

    for segment in &segments[1..] {
        match segment {
            PathSegment::Key(k) => {
                // Navigate into a Map: {"M": {"key": ...}}
                current = current.get("M")?.get(k)?.clone();
            }
            PathSegment::Index(idx) => {
                // Navigate into a List: {"L": [...]}
                current = current.get("L")?.get(*idx)?.clone();
            }
        }
    }

    Some(current)
}

#[derive(Debug)]
enum PathSegment {
    Key(String),
    Index(usize),
}

/// Parse a path like "a.b[0].c" into segments: [Key("a"), Key("b"), Index(0), Key("c")]
fn parse_path_segments(path: &str) -> Vec<PathSegment> {
    let mut segments = Vec::new();
    let mut current = String::new();

    let chars: Vec<char> = path.chars().collect();
    let mut i = 0;
    while i < chars.len() {
        match chars[i] {
            '.' => {
                if !current.is_empty() {
                    segments.push(PathSegment::Key(current.clone()));
                    current.clear();
                }
            }
            '[' => {
                if !current.is_empty() {
                    segments.push(PathSegment::Key(current.clone()));
                    current.clear();
                }
                i += 1;
                let mut num = String::new();
                while i < chars.len() && chars[i] != ']' {
                    num.push(chars[i]);
                    i += 1;
                }
                if let Ok(idx) = num.parse::<usize>() {
                    segments.push(PathSegment::Index(idx));
                }
                // skip ']'
            }
            c => {
                current.push(c);
            }
        }
        i += 1;
    }
    if !current.is_empty() {
        segments.push(PathSegment::Key(current));
    }
    segments
}

/// Insert a value at a nested path in the result HashMap.
/// For a path like "a.b", we set result["a"] = {"M": {"b": value}}.
fn insert_nested_value(result: &mut HashMap<String, AttributeValue>, path: &str, value: Value) {
    // Simple case: no nesting
    if !path.contains('.') && !path.contains('[') {
        result.insert(path.to_string(), value);
        return;
    }

    let segments = parse_path_segments(path);
    if segments.is_empty() {
        return;
    }

    let top_key = match &segments[0] {
        PathSegment::Key(k) => k.clone(),
        _ => return,
    };

    if segments.len() == 1 {
        result.insert(top_key, value);
        return;
    }

    // For nested paths, wrap the value back into the nested structure
    let wrapped = wrap_value_in_path(&segments[1..], value);
    // Merge into existing value if present
    let existing = result.remove(&top_key);
    let merged = match existing {
        Some(existing) => merge_attribute_values(existing, wrapped),
        None => wrapped,
    };
    result.insert(top_key, merged);
}

/// Wrap a value in the nested path structure.
fn wrap_value_in_path(segments: &[PathSegment], value: Value) -> Value {
    if segments.is_empty() {
        return value;
    }
    let inner = wrap_value_in_path(&segments[1..], value);
    match &segments[0] {
        PathSegment::Key(k) => {
            json!({"M": {k.clone(): inner}})
        }
        PathSegment::Index(idx) => {
            let mut arr = vec![Value::Null; idx + 1];
            arr[*idx] = inner;
            json!({"L": arr})
        }
    }
}

/// Merge two attribute values (for overlapping projections).
fn merge_attribute_values(a: Value, b: Value) -> Value {
    if let (Some(a_map), Some(b_map)) = (
        a.get("M").and_then(|v| v.as_object()),
        b.get("M").and_then(|v| v.as_object()),
    ) {
        let mut merged = a_map.clone();
        for (k, v) in b_map {
            if let Some(existing) = merged.get(k) {
                merged.insert(
                    k.clone(),
                    merge_attribute_values(existing.clone(), v.clone()),
                );
            } else {
                merged.insert(k.clone(), v.clone());
            }
        }
        json!({"M": merged})
    } else {
        b
    }
}

fn evaluate_condition(
    condition: &str,
    existing: Option<&HashMap<String, AttributeValue>>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Result<(), AwsServiceError> {
    // ConditionExpression and FilterExpression share the same DynamoDB grammar,
    // so we delegate to evaluate_filter_expression. An empty map models "item
    // doesn't exist" correctly: attribute_exists → false, attribute_not_exists
    // → true, comparisons against missing attributes → None vs Some(val).
    let empty = HashMap::new();
    let item = existing.unwrap_or(&empty);
    if evaluate_filter_expression(condition, item, expr_attr_names, expr_attr_values) {
        Ok(())
    } else {
        Err(AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ConditionalCheckFailedException",
            "The conditional request failed",
        ))
    }
}

fn extract_function_arg<'a>(expr: &'a str, func_name: &str) -> Option<&'a str> {
    // aws-sdk-go v2's expression builder emits function calls with a space
    // between the name and the opening paren (`attribute_exists (#0)`),
    // while hand-written expressions usually don't — accept both.
    let with_paren = format!("{func_name}(");
    let with_space = format!("{func_name} (");
    let rest = expr
        .strip_prefix(&with_paren)
        .or_else(|| expr.strip_prefix(&with_space))?;
    let inner = rest.strip_suffix(')')?;
    Some(inner.trim())
}

fn evaluate_key_condition(
    expr: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let trimmed = expr.trim();

    let parts = split_on_and(trimmed);
    if parts.len() > 1 {
        return parts.iter().all(|part| {
            evaluate_key_condition(part.trim(), item, expr_attr_names, expr_attr_values)
        });
    }

    let stripped = strip_outer_parens(trimmed);
    if stripped != trimmed {
        return evaluate_key_condition(stripped, item, expr_attr_names, expr_attr_values);
    }

    evaluate_single_key_condition(trimmed, item, expr_attr_names, expr_attr_values)
}

/// Split a DynamoDB condition expression on a top-level keyword (``AND`` /
/// ``OR``), case-insensitive, with ASCII-whitespace word boundaries so
/// ``:s\tAND\t:o`` and ``:s\nAND\n:o`` split the same as ``:s AND :o``.
///
/// Parenthesised groups are skipped so only unparenthesised occurrences of the
/// keyword act as separators. When splitting on ``AND``, each top-level
/// ``BETWEEN`` keyword consumes the next top-level ``AND`` as its own inner
/// separator (``x BETWEEN :lo AND :hi``) rather than letting it split the
/// expression.
fn split_on_top_level_keyword<'a>(expr: &'a str, keyword: &str) -> Vec<&'a str> {
    let bytes = expr.as_bytes();
    let len = bytes.len();
    let kw = keyword.as_bytes();
    let is_and = keyword.eq_ignore_ascii_case("AND");

    let mut parts: Vec<&str> = Vec::new();
    let mut start = 0usize;
    let mut depth: i32 = 0;
    let mut between_skip: u32 = 0;
    let mut i = 0usize;

    while i < len {
        let ch = bytes[i];
        if ch == b'(' {
            depth += 1;
            i += 1;
            continue;
        }
        if ch == b')' {
            if depth > 0 {
                depth -= 1;
            }
            i += 1;
            continue;
        }
        if depth == 0 {
            if is_and {
                if let Some(end) = match_keyword(bytes, i, b"BETWEEN") {
                    between_skip = between_skip.saturating_add(1);
                    i = end;
                    continue;
                }
            }
            if let Some(end) = match_keyword(bytes, i, kw) {
                if is_and && between_skip > 0 {
                    between_skip -= 1;
                    i = end;
                    continue;
                }
                parts.push(&expr[start..i]);
                start = end;
                i = end;
                continue;
            }
        }
        i += 1;
    }
    parts.push(&expr[start..]);
    parts
}

/// Case-insensitive keyword match. For alphanumeric keywords (``AND``,
/// ``OR``, ``BETWEEN``) the match also requires ASCII-whitespace word
/// boundaries so substrings of identifiers are not mistaken for keywords.
/// Punctuation keywords (``,``) match literally.
fn match_keyword(bytes: &[u8], i: usize, keyword: &[u8]) -> Option<usize> {
    let end = i + keyword.len();
    if end > bytes.len() {
        return None;
    }
    for k in 0..keyword.len() {
        if !bytes[i + k].eq_ignore_ascii_case(&keyword[k]) {
            return None;
        }
    }
    let needs_word_boundary = keyword.iter().all(|b| b.is_ascii_alphanumeric());
    if needs_word_boundary {
        let left_ok = i == 0 || bytes[i - 1].is_ascii_whitespace();
        if !left_ok {
            return None;
        }
        let right_ok = end == bytes.len() || bytes[end].is_ascii_whitespace();
        if !right_ok {
            return None;
        }
    }
    Some(end)
}

fn split_on_and(expr: &str) -> Vec<&str> {
    split_on_top_level_keyword(expr, "AND")
}

fn split_on_or(expr: &str) -> Vec<&str> {
    split_on_top_level_keyword(expr, "OR")
}

fn evaluate_single_key_condition(
    part: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let part = part.trim();

    if let Some(rest) = part
        .strip_prefix("begins_with(")
        .or_else(|| part.strip_prefix("begins_with ("))
    {
        return key_cond_begins_with(rest, item, expr_attr_names, expr_attr_values);
    }

    if let Some(between_pos) = part.to_ascii_uppercase().find("BETWEEN") {
        return key_cond_between(part, between_pos, item, expr_attr_names, expr_attr_values);
    }

    key_cond_simple_comparison(part, item, expr_attr_names, expr_attr_values)
}

/// `begins_with(attr, :val)` — KeyCondition variant: supports only
/// S-typed attributes (mirrors AWS's behavior of returning false for
/// type mismatches). The filter-expression evaluator has its own
/// `eval_begins_with` because it operates on filter-grammar inputs.
fn key_cond_begins_with(
    rest: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let Some(inner) = rest.strip_suffix(')') else {
        return false;
    };
    let mut split = inner.splitn(2, ',');
    let (Some(attr_ref), Some(val_ref)) = (split.next(), split.next()) else {
        return false;
    };
    let attr_name = resolve_attr_name(attr_ref.trim(), expr_attr_names);
    let expected = expr_attr_values.get(val_ref.trim());
    let actual = item.get(&attr_name);
    match (actual, expected) {
        (Some(a), Some(e)) => {
            let a_str = a.get("S").and_then(|v| v.as_str());
            let e_str = e.get("S").and_then(|v| v.as_str());
            matches!((a_str, e_str), (Some(a), Some(e)) if a.starts_with(e))
        }
        _ => false,
    }
}

/// `attr BETWEEN :lo AND :hi` — inclusive range comparison via the
/// shared `compare_attribute_values` ordering.
fn key_cond_between(
    part: &str,
    between_pos: usize,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let attr_part = part[..between_pos].trim();
    let attr_name = resolve_attr_name(attr_part, expr_attr_names);
    let range_part = &part[between_pos + 7..];
    let Some(and_pos) = range_part.to_ascii_uppercase().find(" AND ") else {
        return false;
    };
    let lo_ref = range_part[..and_pos].trim();
    let hi_ref = range_part[and_pos + 5..].trim();
    let lo = expr_attr_values.get(lo_ref);
    let hi = expr_attr_values.get(hi_ref);
    let actual = item.get(&attr_name);
    match (actual, lo, hi) {
        (Some(a), Some(l), Some(h)) => {
            compare_attribute_values(Some(a), Some(l)) != std::cmp::Ordering::Less
                && compare_attribute_values(Some(a), Some(h)) != std::cmp::Ordering::Greater
        }
        _ => false,
    }
}

/// `attr <op> :val` — six operators (`=`, `<>`, `<`, `>`, `<=`, `>=`).
/// Multi-character operators come first in the search list so that `<=`
/// is not mistakenly matched as `<`.
fn key_cond_simple_comparison(
    part: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    for op in &["<=", ">=", "<>", "=", "<", ">"] {
        let Some(pos) = part.find(op) else {
            continue;
        };
        let left = part[..pos].trim();
        let right = part[pos + op.len()..].trim();
        let actual_owned = resolve_path(left, item, expr_attr_names);
        let actual = actual_owned.as_ref();
        let expected = expr_attr_values.get(right);

        return match *op {
            "=" => actual == expected,
            "<>" => actual != expected,
            "<" => compare_attribute_values(actual, expected) == std::cmp::Ordering::Less,
            ">" => compare_attribute_values(actual, expected) == std::cmp::Ordering::Greater,
            "<=" => {
                let cmp = compare_attribute_values(actual, expected);
                cmp == std::cmp::Ordering::Less || cmp == std::cmp::Ordering::Equal
            }
            ">=" => {
                let cmp = compare_attribute_values(actual, expected);
                cmp == std::cmp::Ordering::Greater || cmp == std::cmp::Ordering::Equal
            }
            _ => false,
        };
    }
    false
}

/// Returns the "size" of a DynamoDB attribute value per AWS docs:
/// - S → character count
/// - B → decoded byte count
/// - SS/NS/BS → element count
/// - L → element count
/// - M → element count
///
/// `size()` is not valid on N, BOOL, or NULL per AWS; returns None for those so
/// the enclosing comparison evaluates to false (matching AWS's behavior of
/// silently filtering type-mismatched rows in FilterExpression context).
fn attribute_size(val: &Value) -> Option<usize> {
    if let Some(s) = val.get("S").and_then(|v| v.as_str()) {
        return Some(s.len());
    }
    if let Some(b) = val.get("B").and_then(|v| v.as_str()) {
        // B is base64-encoded — return decoded byte count
        let decoded_len = base64::engine::general_purpose::STANDARD
            .decode(b)
            .map(|v| v.len())
            .unwrap_or(b.len());
        return Some(decoded_len);
    }
    if let Some(arr) = val.get("SS").and_then(|v| v.as_array()) {
        return Some(arr.len());
    }
    if let Some(arr) = val.get("NS").and_then(|v| v.as_array()) {
        return Some(arr.len());
    }
    if let Some(arr) = val.get("BS").and_then(|v| v.as_array()) {
        return Some(arr.len());
    }
    if let Some(arr) = val.get("L").and_then(|v| v.as_array()) {
        return Some(arr.len());
    }
    if let Some(obj) = val.get("M").and_then(|v| v.as_object()) {
        return Some(obj.len());
    }
    None
}

/// Evaluate a `size(path) op :val` comparison expression.
fn evaluate_size_comparison(
    part: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Option<bool> {
    // Find the closing paren of size(...)
    let open = part.find('(')?;
    let close = part[open..].find(')')? + open;
    let path = part[open + 1..close].trim();
    let remainder = part[close + 1..].trim();

    // Parse operator and value ref
    let (op, val_ref) = if let Some(rest) = remainder.strip_prefix("<=") {
        ("<=", rest.trim())
    } else if let Some(rest) = remainder.strip_prefix(">=") {
        (">=", rest.trim())
    } else if let Some(rest) = remainder.strip_prefix("<>") {
        ("<>", rest.trim())
    } else if let Some(rest) = remainder.strip_prefix('<') {
        ("<", rest.trim())
    } else if let Some(rest) = remainder.strip_prefix('>') {
        (">", rest.trim())
    } else if let Some(rest) = remainder.strip_prefix('=') {
        ("=", rest.trim())
    } else {
        return None;
    };

    let actual_owned = resolve_path(path, item, expr_attr_names)?;
    let size = attribute_size(&actual_owned)? as f64;

    let expected = extract_number(&expr_attr_values.get(val_ref).cloned())?;

    Some(match op {
        "=" => (size - expected).abs() < f64::EPSILON,
        "<>" => (size - expected).abs() >= f64::EPSILON,
        "<" => size < expected,
        ">" => size > expected,
        "<=" => size <= expected,
        ">=" => size >= expected,
        _ => false,
    })
}

fn compare_attribute_values(a: Option<&Value>, b: Option<&Value>) -> std::cmp::Ordering {
    match (a, b) {
        (None, None) => std::cmp::Ordering::Equal,
        (None, Some(_)) => std::cmp::Ordering::Less,
        (Some(_), None) => std::cmp::Ordering::Greater,
        (Some(a), Some(b)) => {
            let a_type = attribute_type_and_value(a);
            let b_type = attribute_type_and_value(b);
            match (a_type, b_type) {
                (Some(("S", a_val)), Some(("S", b_val))) => {
                    let a_str = a_val.as_str().unwrap_or("");
                    let b_str = b_val.as_str().unwrap_or("");
                    a_str.cmp(b_str)
                }
                (Some(("N", a_val)), Some(("N", b_val))) => {
                    let a_num: f64 = a_val.as_str().and_then(|s| s.parse().ok()).unwrap_or(0.0);
                    let b_num: f64 = b_val.as_str().and_then(|s| s.parse().ok()).unwrap_or(0.0);
                    a_num
                        .partial_cmp(&b_num)
                        .unwrap_or(std::cmp::Ordering::Equal)
                }
                (Some(("B", a_val)), Some(("B", b_val))) => {
                    let a_str = a_val.as_str().unwrap_or("");
                    let b_str = b_val.as_str().unwrap_or("");
                    a_str.cmp(b_str)
                }
                _ => std::cmp::Ordering::Equal,
            }
        }
    }
}

fn evaluate_filter_expression(
    expr: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let trimmed = expr.trim();

    // Split on OR first (lower precedence), respecting parentheses
    let or_parts = split_on_or(trimmed);
    if or_parts.len() > 1 {
        return or_parts.iter().any(|part| {
            evaluate_filter_expression(part.trim(), item, expr_attr_names, expr_attr_values)
        });
    }

    // Then split on AND (higher precedence), respecting parentheses
    let and_parts = split_on_and(trimmed);
    if and_parts.len() > 1 {
        return and_parts.iter().all(|part| {
            evaluate_filter_expression(part.trim(), item, expr_attr_names, expr_attr_values)
        });
    }

    // Strip outer parentheses if present
    let stripped = strip_outer_parens(trimmed);
    if stripped != trimmed {
        return evaluate_filter_expression(stripped, item, expr_attr_names, expr_attr_values);
    }

    // Handle NOT prefix (case-insensitive)
    if trimmed.len() > 4 && trimmed[..4].eq_ignore_ascii_case("NOT ") {
        return !evaluate_filter_expression(&trimmed[4..], item, expr_attr_names, expr_attr_values);
    }

    evaluate_single_filter_condition(trimmed, item, expr_attr_names, expr_attr_values)
}

/// Strip matching outer parentheses from an expression.
fn strip_outer_parens(expr: &str) -> &str {
    let trimmed = expr.trim();
    if !trimmed.starts_with('(') || !trimmed.ends_with(')') {
        return trimmed;
    }
    // Verify the outer parens actually match each other
    let inner = &trimmed[1..trimmed.len() - 1];
    let mut depth = 0;
    for ch in inner.bytes() {
        match ch {
            b'(' => depth += 1,
            b')' => {
                if depth == 0 {
                    return trimmed; // closing paren matches something inside, not the outer one
                }
                depth -= 1;
            }
            _ => {}
        }
    }
    if depth == 0 {
        inner
    } else {
        trimmed
    }
}

fn evaluate_single_filter_condition(
    part: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    if let Some(inner) = extract_function_arg(part, "attribute_exists") {
        return resolve_path(inner, item, expr_attr_names).is_some();
    }

    if let Some(inner) = extract_function_arg(part, "attribute_not_exists") {
        return resolve_path(inner, item, expr_attr_names).is_none();
    }

    if let Some(rest) = part
        .strip_prefix("begins_with(")
        .or_else(|| part.strip_prefix("begins_with ("))
    {
        return eval_begins_with(rest, item, expr_attr_names, expr_attr_values);
    }

    if let Some(rest) = part
        .strip_prefix("contains(")
        .or_else(|| part.strip_prefix("contains ("))
    {
        return eval_contains(rest, item, expr_attr_names, expr_attr_values);
    }

    if part.starts_with("size(") || part.starts_with("size (") {
        if let Some(result) =
            evaluate_size_comparison(part, item, expr_attr_names, expr_attr_values)
        {
            return result;
        }
    }

    if let Some(rest) = part
        .strip_prefix("attribute_type(")
        .or_else(|| part.strip_prefix("attribute_type ("))
    {
        return eval_attribute_type(rest, item, expr_attr_names, expr_attr_values);
    }

    if let Some((attr_ref, value_refs)) = parse_in_expression(part) {
        let attr_name = resolve_attr_name(attr_ref, expr_attr_names);
        let actual = item.get(&attr_name);
        return evaluate_in_match(actual, &value_refs, expr_attr_values);
    }

    evaluate_single_key_condition(part, item, expr_attr_names, expr_attr_values)
}

/// `begins_with(path, :val)` — only S (string) operands. Returns false on
/// any parse failure or type mismatch (this is the same shape DynamoDB
/// returns: a malformed predicate is silently false rather than an error).
fn eval_begins_with(
    rest: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let Some(inner) = rest.strip_suffix(')') else {
        return false;
    };
    let mut split = inner.splitn(2, ',');
    let (Some(attr_ref), Some(val_ref)) = (split.next(), split.next()) else {
        return false;
    };
    let actual = resolve_path(attr_ref.trim(), item, expr_attr_names);
    let expected = expr_attr_values.get(val_ref.trim());
    match (actual.as_ref(), expected) {
        (Some(a), Some(e)) => {
            let a_str = a.get("S").and_then(|v| v.as_str());
            let e_str = e.get("S").and_then(|v| v.as_str());
            matches!((a_str, e_str), (Some(a), Some(e)) if a.starts_with(e))
        }
        _ => false,
    }
}

/// `contains(path, :val)` — substring check on S, set membership on
/// SS/NS/BS, and element membership on L. Other type pairings return
/// false.
fn eval_contains(
    rest: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let Some(inner) = rest.strip_suffix(')') else {
        return false;
    };
    let mut split = inner.splitn(2, ',');
    let (Some(attr_ref), Some(val_ref)) = (split.next(), split.next()) else {
        return false;
    };
    let actual = resolve_path(attr_ref.trim(), item, expr_attr_names);
    let expected = expr_attr_values.get(val_ref.trim());
    let (Some(a), Some(e)) = (actual.as_ref(), expected) else {
        return false;
    };

    if let (Some(a_s), Some(e_s)) = (
        a.get("S").and_then(|v| v.as_str()),
        e.get("S").and_then(|v| v.as_str()),
    ) {
        return a_s.contains(e_s);
    }
    if let Some(set) = a.get("SS").and_then(|v| v.as_array()) {
        if let Some(val) = e.get("S") {
            return set.contains(val);
        }
    }
    if let Some(set) = a.get("NS").and_then(|v| v.as_array()) {
        if let Some(val) = e.get("N") {
            return set.contains(val);
        }
    }
    if let Some(set) = a.get("BS").and_then(|v| v.as_array()) {
        if let Some(val) = e.get("B") {
            return set.contains(val);
        }
    }
    if let Some(list) = a.get("L").and_then(|v| v.as_array()) {
        return list.contains(e);
    }
    false
}

/// `attribute_type(path, :type)` — checks whether the attribute at `path`
/// is stored under the wire type identified by `:type` (one of the
/// DynamoDB type letters S/N/B/BOOL/NULL/SS/NS/BS/L/M).
fn eval_attribute_type(
    rest: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    let Some(inner) = rest.strip_suffix(')') else {
        return false;
    };
    let mut split = inner.splitn(2, ',');
    let (Some(attr_ref), Some(val_ref)) = (split.next(), split.next()) else {
        return false;
    };
    let actual = resolve_path(attr_ref.trim(), item, expr_attr_names);
    let expected_type = expr_attr_values
        .get(val_ref.trim())
        .and_then(|v| v.get("S"))
        .and_then(|v| v.as_str());
    let (Some(val), Some(t)) = (actual.as_ref(), expected_type) else {
        return false;
    };
    match t {
        "S" => val.get("S").is_some(),
        "N" => val.get("N").is_some(),
        "B" => val.get("B").is_some(),
        "BOOL" => val.get("BOOL").is_some(),
        "NULL" => val.get("NULL").is_some(),
        "SS" => val.get("SS").is_some(),
        "NS" => val.get("NS").is_some(),
        "BS" => val.get("BS").is_some(),
        "L" => val.get("L").is_some(),
        "M" => val.get("M").is_some(),
        _ => false,
    }
}

/// Parse an `attr IN (:v1, :v2, ...)` expression. Mirrors the DynamoDB
/// ConditionExpression / FilterExpression grammar where IN takes a single
/// operand on the left and 1–100 comma-separated value refs inside parens
/// on the right. Case-insensitive; tolerates missing spaces after commas
/// (aws-sdk-go's `expression` builder emits ", " but hand-built expressions
/// often use `strings.Join(..., ",")`). Returns None for non-IN inputs so
/// callers can fall through to their other grammar branches.
fn parse_in_expression(expr: &str) -> Option<(&str, Vec<&str>)> {
    let upper = expr.to_ascii_uppercase();
    let in_pos = upper.find(" IN ")?;
    let attr_ref = expr[..in_pos].trim();
    if attr_ref.is_empty() {
        return None;
    }
    let rest = expr[in_pos + 4..].trim_start();
    let inner = rest.strip_prefix('(')?.strip_suffix(')')?;
    let values: Vec<&str> = inner
        .split(',')
        .map(|s| s.trim())
        .filter(|s| !s.is_empty())
        .collect();
    if values.is_empty() {
        return None;
    }
    Some((attr_ref, values))
}

/// Return true iff `actual` equals any of the `value_refs` resolved through
/// `expr_attr_values`. A missing attribute never matches (mirrors AWS, which
/// evaluates `IN` against undefined attributes as false).
fn evaluate_in_match(
    actual: Option<&AttributeValue>,
    value_refs: &[&str],
    expr_attr_values: &HashMap<String, Value>,
) -> bool {
    value_refs.iter().any(|v_ref| {
        let expected = expr_attr_values.get(*v_ref);
        matches!((actual, expected), (Some(a), Some(e)) if a == e)
    })
}

/// One of the four DynamoDB ``UpdateExpression`` action keywords.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum UpdateAction {
    Set,
    Remove,
    Add,
    Delete,
}

impl UpdateAction {
    /// All four keywords as written on the wire — these double as the search
    /// terms for ``parse_update_clauses``.
    const KEYWORDS: &'static [(&'static str, UpdateAction)] = &[
        ("SET", UpdateAction::Set),
        ("REMOVE", UpdateAction::Remove),
        ("ADD", UpdateAction::Add),
        ("DELETE", UpdateAction::Delete),
    ];

    fn keyword(self) -> &'static str {
        match self {
            UpdateAction::Set => "SET",
            UpdateAction::Remove => "REMOVE",
            UpdateAction::Add => "ADD",
            UpdateAction::Delete => "DELETE",
        }
    }
}

fn apply_update_expression(
    item: &mut HashMap<String, AttributeValue>,
    expr: &str,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Result<(), AwsServiceError> {
    let clauses = parse_update_clauses(expr);
    if clauses.is_empty() && !expr.trim().is_empty() {
        return Err(AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "Invalid UpdateExpression: Syntax error; token: \"<expression>\"",
        ));
    }
    for (action, assignments) in &clauses {
        match action {
            UpdateAction::Set => {
                for assignment in assignments {
                    apply_set_assignment(item, assignment, expr_attr_names, expr_attr_values)?;
                }
            }
            UpdateAction::Remove => {
                for attr_ref in assignments {
                    let attr = resolve_attr_name(attr_ref.trim(), expr_attr_names);
                    item.remove(&attr);
                }
            }
            UpdateAction::Add => {
                for assignment in assignments {
                    apply_add_assignment(item, assignment, expr_attr_names, expr_attr_values)?;
                }
            }
            UpdateAction::Delete => {
                for assignment in assignments {
                    apply_delete_assignment(item, assignment, expr_attr_names, expr_attr_values)?;
                }
            }
        }
    }
    Ok(())
}

fn parse_update_clauses(expr: &str) -> Vec<(UpdateAction, Vec<String>)> {
    let mut clauses: Vec<(UpdateAction, Vec<String>)> = Vec::new();
    let upper = expr.to_ascii_uppercase();
    let mut positions: Vec<(usize, UpdateAction)> = Vec::new();

    for &(kw, action) in UpdateAction::KEYWORDS {
        let mut search_from = 0;
        while let Some(pos) = upper[search_from..].find(kw) {
            let abs_pos = search_from + pos;
            let before_ok = abs_pos == 0 || !expr.as_bytes()[abs_pos - 1].is_ascii_alphanumeric();
            let after_pos = abs_pos + kw.len();
            let after_ok =
                after_pos >= expr.len() || !expr.as_bytes()[after_pos].is_ascii_alphanumeric();
            if before_ok && after_ok {
                positions.push((abs_pos, action));
            }
            search_from = abs_pos + kw.len();
        }
    }

    positions.sort_by_key(|(pos, _)| *pos);

    for (i, &(pos, action)) in positions.iter().enumerate() {
        let start = pos + action.keyword().len();
        let end = if i + 1 < positions.len() {
            positions[i + 1].0
        } else {
            expr.len()
        };
        let content = expr[start..end].trim();
        // Use a paren-aware split so that function-call arguments such as
        // `list_append(#a, :b)` are kept as a single assignment rather than
        // being torn apart at the inner comma.
        let assignments: Vec<String> = split_on_top_level_keyword(content, ",")
            .into_iter()
            .map(|s| s.trim().to_string())
            .collect();
        clauses.push((action, assignments));
    }

    clauses
}

fn apply_set_assignment(
    item: &mut HashMap<String, AttributeValue>,
    assignment: &str,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Result<(), AwsServiceError> {
    let Some((left, right)) = assignment.split_once('=') else {
        return Ok(());
    };

    let left_trimmed = left.trim();
    let right = right.trim();

    // One RHS evaluator used for every LHS shape so `SET a.b = a.b + :d`,
    // `SET a.b = list_append(a.b, :list)`, and `SET a.b = if_not_exists(a.b, :v)`
    // all work against nested paths, not just top-level attributes. The evaluator
    // returns Ok(None) when the RHS is a no-op (if_not_exists where the target
    // already has a value, or an unresolvable plain reference).
    let new_value = evaluate_set_rhs(right, item, expr_attr_names, expr_attr_values)?;

    if is_dotted_path(left_trimmed) {
        // A None value is a no-op (if_not_exists skip, or unresolvable plain
        // ref) — matches top-level SET's silent-skip behavior for the same
        // shapes. Structural errors (missing parent map, non-map intermediate)
        // surface from assign_nested_path itself.
        let Some(v) = new_value else {
            return Ok(());
        };
        return assign_nested_path(item, left_trimmed, expr_attr_names, v);
    }

    // Split off a trailing `[N]` list-index suffix so we can resolve the
    // attribute name ref on its own. Without this, `resolve_attr_name` sees
    // "#items[0]" as a whole and misses the `#items` → `items` mapping.
    let (attr_ref, list_index) = match parse_list_index_suffix(left_trimmed) {
        Some((name, idx)) => (name, Some(idx)),
        None => (left_trimmed, None),
    };
    let attr = resolve_attr_name(attr_ref, expr_attr_names);

    let Some(v) = new_value else {
        return Ok(());
    };
    match list_index {
        Some(idx) => assign_list_index(item, &attr, idx, v),
        None => {
            item.insert(attr, v);
            Ok(())
        }
    }
}

/// Evaluate the RHS of a `SET` assignment without writing it anywhere.
/// Returns `Ok(Some(value))` with the computed value, `Ok(None)` for
/// no-op cases (if_not_exists where the target already has a value, or
/// an unresolvable plain reference in dotted-path context), or
/// `Err(ValidationException)` for type-mismatched arithmetic.
fn evaluate_set_rhs(
    right: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Result<Option<Value>, AwsServiceError> {
    if let Some(rest) = right
        .strip_prefix("if_not_exists(")
        .or_else(|| right.strip_prefix("if_not_exists ("))
    {
        return Ok(evaluate_if_not_exists_rhs(
            rest,
            item,
            expr_attr_names,
            expr_attr_values,
        ));
    }

    if let Some(rest) = right
        .strip_prefix("list_append(")
        .or_else(|| right.strip_prefix("list_append ("))
    {
        return Ok(evaluate_list_append_rhs(
            rest,
            item,
            expr_attr_names,
            expr_attr_values,
        ));
    }

    if let Some((arith_left, arith_right, is_add)) = parse_arithmetic(right) {
        return evaluate_arithmetic_rhs(
            arith_left,
            arith_right,
            is_add,
            item,
            expr_attr_names,
            expr_attr_values,
        );
    }

    Ok(resolve_ref_or_path(
        right,
        item,
        expr_attr_names,
        expr_attr_values,
    ))
}

/// `if_not_exists(path, :val)` — evaluates to nothing when `path` already
/// resolves to a value, and to the default ref otherwise. `path` may be a
/// top-level attribute, a placeholder, or a dotted path inside an M-typed
/// attribute.
fn evaluate_if_not_exists_rhs(
    rest: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Option<Value> {
    let inner = rest.strip_suffix(')')?;
    let mut split = inner.splitn(2, ',');
    let (check, default) = (split.next()?, split.next()?);
    if resolve_ref_or_path(check.trim(), item, expr_attr_names, expr_attr_values).is_some() {
        return None;
    }
    resolve_ref_or_path(default.trim(), item, expr_attr_names, expr_attr_values)
}

/// `list_append(a, b)` — concatenate the L arrays of two list operands.
/// Either operand may be missing or non-list, in which case it contributes
/// nothing. Both operands may be value refs (`:list`) or document paths
/// (top-level or dotted).
fn evaluate_list_append_rhs(
    rest: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Option<Value> {
    let inner = rest.strip_suffix(')')?;
    let mut split = inner.splitn(2, ',');
    let (a_ref, b_ref) = (split.next()?, split.next()?);
    let a_val = resolve_ref_or_path(a_ref.trim(), item, expr_attr_names, expr_attr_values);
    let b_val = resolve_ref_or_path(b_ref.trim(), item, expr_attr_names, expr_attr_values);

    let mut merged = Vec::new();
    for v in [&a_val, &b_val].iter().copied().flatten() {
        if let Value::Object(obj) = v {
            if let Some(Value::Array(arr)) = obj.get("L") {
                merged.extend(arr.clone());
            }
        }
    }
    Some(json!({ "L": merged }))
}

/// `<arith_left> +/- <arith_right>` — both operands must resolve to N values
/// (or the LHS may be missing, in which case it's treated as 0). Anything
/// else is rejected with the same `ValidationException` AWS returns.
fn evaluate_arithmetic_rhs(
    arith_left: &str,
    arith_right: &str,
    is_add: bool,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Result<Option<Value>, AwsServiceError> {
    let left_val = resolve_ref_or_path(arith_left.trim(), item, expr_attr_names, expr_attr_values);
    let right_val =
        resolve_ref_or_path(arith_right.trim(), item, expr_attr_names, expr_attr_values);

    let left_num = match extract_number(&left_val) {
        Some(n) => n,
        None if left_val.is_some() => {
            return Err(AwsServiceError::aws_error(
                StatusCode::BAD_REQUEST,
                "ValidationException",
                "An operand in the update expression has an incorrect data type",
            ));
        }
        None => 0.0,
    };
    let right_num = extract_number(&right_val).ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "An operand in the update expression has an incorrect data type",
        )
    })?;

    let result = if is_add {
        left_num + right_num
    } else {
        left_num - right_num
    };

    let num_str = if result == result.trunc() {
        format!("{}", result as i64)
    } else {
        format!("{result}")
    };

    Ok(Some(json!({ "N": num_str })))
}

/// Parse a trailing `[N]` list-index suffix off the LHS of a SET assignment.
/// Returns the bare attribute reference and the index, or None when the LHS
/// is a plain attribute (or a path shape we don't yet support).
fn parse_list_index_suffix(path: &str) -> Option<(&str, usize)> {
    let path = path.trim();
    if !path.ends_with(']') {
        return None;
    }
    let open = path.rfind('[')?;
    // Require no further `.` / `[` / `]` inside the bracketed portion and no
    // further path segments after — we only handle the single-index case
    // `name[N]`, not nested shapes like `a.b[0].c`.
    let idx_str = &path[open + 1..path.len() - 1];
    let idx: usize = idx_str.parse().ok()?;
    let name = &path[..open];
    if name.is_empty() || name.contains('[') || name.contains(']') || name.contains('.') {
        return None;
    }
    Some((name, idx))
}

/// Assign a value to a specific index of a `L`-typed attribute. If `idx` is
/// within the current list, replaces that slot; if it's at the end, appends.
/// AWS rejects writes beyond `len`, so we return a `ValidationException` for
/// out-of-range indices and non-list attributes.
fn assign_list_index(
    item: &mut HashMap<String, AttributeValue>,
    attr: &str,
    idx: usize,
    value: Value,
) -> Result<(), AwsServiceError> {
    let Some(existing) = item.get_mut(attr) else {
        return Err(invalid_document_path());
    };
    let Some(list) = existing.get_mut("L").and_then(|l| l.as_array_mut()) else {
        return Err(invalid_document_path());
    };
    if idx < list.len() {
        list[idx] = value;
    } else if idx == list.len() {
        list.push(value);
    } else {
        return Err(invalid_document_path());
    }
    Ok(())
}

fn invalid_document_path() -> AwsServiceError {
    AwsServiceError::aws_error(
        StatusCode::BAD_REQUEST,
        "ValidationException",
        "The document path provided in the update expression is invalid for update",
    )
}

/// Resolve a SET-RHS operand that may be either a value placeholder
/// (``:foo``) or a document path (top-level attribute, ``#name``, or a
/// dotted path like ``profile.email`` / ``#web.#count``).
fn resolve_ref_or_path(
    reference: &str,
    item: &HashMap<String, AttributeValue>,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Option<Value> {
    let reference = reference.trim();
    if reference.starts_with(':') {
        return expr_attr_values.get(reference).cloned();
    }
    resolve_path(reference, item, expr_attr_names)
}

/// True if `path` targets a nested key inside an M-typed attribute. Bracketed
/// list indices (`a[0]`, `a.b[0]`) are not supported by the nested-SET writer.
fn is_dotted_path(path: &str) -> bool {
    path.contains('.') && !path.contains('[')
}

/// Write `value` at a dotted path inside an M-typed attribute.
///
/// Resolves each `#name` segment through `expr_attr_names`. The top-level
/// attribute and every intermediate segment must already exist as a Map —
/// DynamoDB rejects writes through missing parents with ValidationException.
fn assign_nested_path(
    item: &mut HashMap<String, AttributeValue>,
    path: &str,
    expr_attr_names: &HashMap<String, String>,
    value: Value,
) -> Result<(), AwsServiceError> {
    let mut segments: Vec<String> = path
        .split('.')
        .map(|seg| resolve_attr_name(seg.trim(), expr_attr_names))
        .collect();
    if segments.len() < 2 {
        return Err(invalid_document_path());
    }

    let leaf = segments.pop().expect("len >= 2");
    let top = segments.remove(0);

    let top_attr = item.get_mut(&top).ok_or_else(invalid_document_path)?;
    let mut current = top_attr
        .get_mut("M")
        .and_then(|m| m.as_object_mut())
        .ok_or_else(invalid_document_path)?;

    for seg in &segments {
        current = current
            .get_mut(seg)
            .and_then(|v| v.get_mut("M"))
            .and_then(|m| m.as_object_mut())
            .ok_or_else(invalid_document_path)?;
    }

    current.insert(leaf, value);
    Ok(())
}

fn extract_number(val: &Option<Value>) -> Option<f64> {
    val.as_ref()
        .and_then(|v| v.get("N"))
        .and_then(|n| n.as_str())
        .and_then(|s| s.parse().ok())
}

fn parse_arithmetic(expr: &str) -> Option<(&str, &str, bool)> {
    let mut depth = 0;
    for (i, c) in expr.char_indices() {
        match c {
            '(' => depth += 1,
            ')' => depth -= 1,
            '+' if depth == 0 && i > 0 => {
                return Some((&expr[..i], &expr[i + 1..], true));
            }
            '-' if depth == 0 && i > 0 => {
                return Some((&expr[..i], &expr[i + 1..], false));
            }
            _ => {}
        }
    }
    None
}

fn apply_add_assignment(
    item: &mut HashMap<String, AttributeValue>,
    assignment: &str,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Result<(), AwsServiceError> {
    let parts: Vec<&str> = assignment.splitn(2, ' ').collect();
    if parts.len() != 2 {
        return Ok(());
    }

    let attr = resolve_attr_name(parts[0].trim(), expr_attr_names);
    let val_ref = parts[1].trim();
    let add_val = expr_attr_values.get(val_ref);

    if let Some(add_val) = add_val {
        if let Some(existing) = item.get(&attr) {
            if let (Some(existing_num), Some(add_num)) = (
                extract_number(&Some(existing.clone())),
                extract_number(&Some(add_val.clone())),
            ) {
                let result = existing_num + add_num;
                let num_str = if result == result.trunc() {
                    format!("{}", result as i64)
                } else {
                    format!("{result}")
                };
                item.insert(attr, json!({"N": num_str}));
            } else if let Some(existing_set) = existing.get("SS").and_then(|v| v.as_array()) {
                if let Some(add_set) = add_val.get("SS").and_then(|v| v.as_array()) {
                    let mut merged: Vec<Value> = existing_set.clone();
                    for v in add_set {
                        if !merged.contains(v) {
                            merged.push(v.clone());
                        }
                    }
                    item.insert(attr, json!({"SS": merged}));
                }
            } else if let Some(existing_set) = existing.get("NS").and_then(|v| v.as_array()) {
                if let Some(add_set) = add_val.get("NS").and_then(|v| v.as_array()) {
                    let mut merged: Vec<Value> = existing_set.clone();
                    for v in add_set {
                        if !merged.contains(v) {
                            merged.push(v.clone());
                        }
                    }
                    item.insert(attr, json!({"NS": merged}));
                }
            } else if let Some(existing_set) = existing.get("BS").and_then(|v| v.as_array()) {
                if let Some(add_set) = add_val.get("BS").and_then(|v| v.as_array()) {
                    let mut merged: Vec<Value> = existing_set.clone();
                    for v in add_set {
                        if !merged.contains(v) {
                            merged.push(v.clone());
                        }
                    }
                    item.insert(attr, json!({"BS": merged}));
                }
            }
        } else {
            item.insert(attr, add_val.clone());
        }
    }

    Ok(())
}

fn apply_delete_assignment(
    item: &mut HashMap<String, AttributeValue>,
    assignment: &str,
    expr_attr_names: &HashMap<String, String>,
    expr_attr_values: &HashMap<String, Value>,
) -> Result<(), AwsServiceError> {
    let parts: Vec<&str> = assignment.splitn(2, ' ').collect();
    if parts.len() != 2 {
        return Ok(());
    }

    let attr = resolve_attr_name(parts[0].trim(), expr_attr_names);
    let val_ref = parts[1].trim();
    let del_val = expr_attr_values.get(val_ref);

    if let (Some(existing), Some(del_val)) = (item.get(&attr).cloned(), del_val) {
        if let (Some(existing_set), Some(del_set)) = (
            existing.get("SS").and_then(|v| v.as_array()),
            del_val.get("SS").and_then(|v| v.as_array()),
        ) {
            let filtered: Vec<Value> = existing_set
                .iter()
                .filter(|v| !del_set.contains(v))
                .cloned()
                .collect();
            if filtered.is_empty() {
                item.remove(&attr);
            } else {
                item.insert(attr, json!({"SS": filtered}));
            }
        } else if let (Some(existing_set), Some(del_set)) = (
            existing.get("NS").and_then(|v| v.as_array()),
            del_val.get("NS").and_then(|v| v.as_array()),
        ) {
            let filtered: Vec<Value> = existing_set
                .iter()
                .filter(|v| !del_set.contains(v))
                .cloned()
                .collect();
            if filtered.is_empty() {
                item.remove(&attr);
            } else {
                item.insert(attr, json!({"NS": filtered}));
            }
        } else if let (Some(existing_set), Some(del_set)) = (
            existing.get("BS").and_then(|v| v.as_array()),
            del_val.get("BS").and_then(|v| v.as_array()),
        ) {
            let filtered: Vec<Value> = existing_set
                .iter()
                .filter(|v| !del_set.contains(v))
                .cloned()
                .collect();
            if filtered.is_empty() {
                item.remove(&attr);
            } else {
                item.insert(attr, json!({"BS": filtered}));
            }
        }
    }

    Ok(())
}

pub(super) struct TableDescriptionInput<'a> {
    pub arn: &'a str,
    pub table_id: &'a str,
    pub key_schema: &'a [KeySchemaElement],
    pub attribute_definitions: &'a [AttributeDefinition],
    pub provisioned_throughput: &'a ProvisionedThroughput,
    pub gsi: &'a [GlobalSecondaryIndex],
    pub lsi: &'a [LocalSecondaryIndex],
    pub billing_mode: &'a str,
    pub created_at: chrono::DateTime<chrono::Utc>,
    pub item_count: i64,
    pub size_bytes: i64,
    pub status: &'a str,
    pub deletion_protection_enabled: bool,
    pub on_demand_throughput: Option<&'a crate::state::OnDemandThroughput>,
}

fn build_table_description_json(input: &TableDescriptionInput<'_>) -> Value {
    let TableDescriptionInput {
        arn,
        table_id,
        key_schema,
        attribute_definitions,
        provisioned_throughput,
        gsi,
        lsi,
        billing_mode,
        created_at,
        item_count,
        size_bytes,
        status,
        deletion_protection_enabled,
        on_demand_throughput,
    } = *input;
    let table_name = arn.rsplit('/').next().unwrap_or("");
    let creation_timestamp =
        created_at.timestamp() as f64 + created_at.timestamp_subsec_millis() as f64 / 1000.0;

    let ks: Vec<Value> = key_schema
        .iter()
        .map(|k| json!({"AttributeName": k.attribute_name, "KeyType": k.key_type}))
        .collect();

    let ad: Vec<Value> = attribute_definitions
        .iter()
        .map(|a| json!({"AttributeName": a.attribute_name, "AttributeType": a.attribute_type}))
        .collect();

    let mut desc = json!({
        "TableName": table_name,
        "TableArn": arn,
        "TableId": table_id,
        "TableStatus": status,
        "KeySchema": ks,
        "AttributeDefinitions": ad,
        "CreationDateTime": creation_timestamp,
        "ItemCount": item_count,
        "TableSizeBytes": size_bytes,
        "BillingModeSummary": { "BillingMode": billing_mode },
        "DeletionProtectionEnabled": deletion_protection_enabled,
    });

    if billing_mode != "PAY_PER_REQUEST" {
        desc["ProvisionedThroughput"] = json!({
            "ReadCapacityUnits": provisioned_throughput.read_capacity_units,
            "WriteCapacityUnits": provisioned_throughput.write_capacity_units,
            "NumberOfDecreasesToday": 0,
        });
    } else {
        desc["ProvisionedThroughput"] = json!({
            "ReadCapacityUnits": 0,
            "WriteCapacityUnits": 0,
            "NumberOfDecreasesToday": 0,
        });
    }

    if let Some(odt) = on_demand_throughput {
        desc["OnDemandThroughput"] = json!({
            "MaxReadRequestUnits": odt.max_read_request_units,
            "MaxWriteRequestUnits": odt.max_write_request_units,
        });
    }

    // Terraform's AWS provider now waits on WarmThroughput after CreateTable.
    // Real AWS returns an ACTIVE warm throughput object for active tables,
    // including PAY_PER_REQUEST tables. Returning null keeps the provider in a
    // perpetual "still creating" loop.
    if status == "ACTIVE" {
        desc["WarmThroughput"] = json!({
            "ReadUnitsPerSecond": 0,
            "WriteUnitsPerSecond": 0,
            "Status": "ACTIVE",
        });
    }

    if !gsi.is_empty() {
        let gsi_json: Vec<Value> = gsi
            .iter()
            .map(|g| {
                let gks: Vec<Value> = g
                    .key_schema
                    .iter()
                    .map(|k| json!({"AttributeName": k.attribute_name, "KeyType": k.key_type}))
                    .collect();
                let mut idx = json!({
                    "IndexName": g.index_name,
                    "KeySchema": gks,
                    "Projection": { "ProjectionType": g.projection.projection_type },
                    "IndexStatus": "ACTIVE",
                    "IndexArn": format!("{arn}/index/{}", g.index_name),
                    "ItemCount": 0,
                    "IndexSizeBytes": 0,
                });
                if !g.projection.non_key_attributes.is_empty() {
                    idx["Projection"]["NonKeyAttributes"] = json!(g.projection.non_key_attributes);
                }
                if let Some(ref pt) = g.provisioned_throughput {
                    idx["ProvisionedThroughput"] = json!({
                        "ReadCapacityUnits": pt.read_capacity_units,
                        "WriteCapacityUnits": pt.write_capacity_units,
                        "NumberOfDecreasesToday": 0,
                    });
                }
                if let Some(ref odt) = g.on_demand_throughput {
                    idx["OnDemandThroughput"] = json!({
                        "MaxReadRequestUnits": odt.max_read_request_units,
                        "MaxWriteRequestUnits": odt.max_write_request_units,
                    });
                }
                idx
            })
            .collect();
        desc["GlobalSecondaryIndexes"] = json!(gsi_json);
    }

    if !lsi.is_empty() {
        let lsi_json: Vec<Value> = lsi
            .iter()
            .map(|l| {
                let lks: Vec<Value> = l
                    .key_schema
                    .iter()
                    .map(|k| json!({"AttributeName": k.attribute_name, "KeyType": k.key_type}))
                    .collect();
                let mut idx = json!({
                    "IndexName": l.index_name,
                    "KeySchema": lks,
                    "Projection": { "ProjectionType": l.projection.projection_type },
                    "IndexArn": format!("{arn}/index/{}", l.index_name),
                    "ItemCount": 0,
                    "IndexSizeBytes": 0,
                });
                if !l.projection.non_key_attributes.is_empty() {
                    idx["Projection"]["NonKeyAttributes"] = json!(l.projection.non_key_attributes);
                }
                idx
            })
            .collect();
        desc["LocalSecondaryIndexes"] = json!(lsi_json);
    }

    desc
}

fn build_table_description(table: &DynamoTable) -> Value {
    let mut desc = build_table_description_json(&TableDescriptionInput {
        arn: &table.arn,
        table_id: &table.table_id,
        key_schema: &table.key_schema,
        attribute_definitions: &table.attribute_definitions,
        provisioned_throughput: &table.provisioned_throughput,
        gsi: &table.gsi,
        lsi: &table.lsi,
        billing_mode: &table.billing_mode,
        created_at: table.created_at,
        item_count: table.item_count,
        size_bytes: table.size_bytes,
        status: &table.status,
        deletion_protection_enabled: table.deletion_protection_enabled,
        on_demand_throughput: table.on_demand_throughput.as_ref(),
    });

    // `LatestStreamArn` / `LatestStreamLabel` persist after a stream has
    // been created, even if streams are currently disabled — real AWS
    // keeps them for ~24h post-disable so DescribeTable callers can still
    // observe the last active stream. fakecloud keeps them for the
    // table's lifetime, which is sufficient for any single test run.
    if let Some(ref stream_arn) = table.stream_arn {
        desc["LatestStreamArn"] = json!(stream_arn);
        desc["LatestStreamLabel"] = json!(stream_arn.rsplit('/').next().unwrap_or(""));
    }
    // The `StreamSpecification` block is only present while streams are
    // actively enabled. When absent, the Terraform provider Read falls
    // through to the prior `stream_view_type` from its own state rather
    // than clearing it, which matches the diff behaviour the upstream
    // acceptance tests assert on.
    if table.stream_enabled {
        if let Some(ref view_type) = table.stream_view_type {
            desc["StreamSpecification"] = json!({
                "StreamEnabled": true,
                "StreamViewType": view_type,
            });
        }
    }

    // SSEDescription is only returned when the customer explicitly enabled
    // a KMS-backed SSE. Real AWS tables using the default AWS-owned key omit
    // this field entirely, and the Terraform provider's Read asserts
    // `server_side_encryption.#` == 0 in that case.
    if let Some(ref sse_type) = table.sse_type {
        let mut sse_desc = json!({
            "Status": "ENABLED",
            "SSEType": sse_type,
        });
        if let Some(ref key_arn) = table.sse_kms_key_arn {
            sse_desc["KMSMasterKeyArn"] = json!(key_arn);
        }
        desc["SSEDescription"] = sse_desc;
    }

    desc
}

fn execute_partiql_statement(
    state: &SharedDynamoDbState,
    statement: &str,
    parameters: &[Value],
) -> Result<AwsResponse, AwsServiceError> {
    let trimmed = statement.trim();
    let upper = trimmed.to_ascii_uppercase();

    if upper.starts_with("SELECT") {
        execute_partiql_select(state, trimmed, parameters)
    } else if upper.starts_with("INSERT") {
        execute_partiql_insert(state, trimmed, parameters)
    } else if upper.starts_with("UPDATE") {
        execute_partiql_update(state, trimmed, parameters)
    } else if upper.starts_with("DELETE") {
        execute_partiql_delete(state, trimmed, parameters)
    } else {
        Err(AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            format!("Unsupported PartiQL statement: {trimmed}"),
        ))
    }
}

/// Parse a simple `SELECT * FROM tablename WHERE pk = 'value'` or with parameters.
fn execute_partiql_select(
    state: &SharedDynamoDbState,
    statement: &str,
    parameters: &[Value],
) -> Result<AwsResponse, AwsServiceError> {
    // Pattern: SELECT * FROM "tablename" [WHERE col = 'val' | WHERE col = ?]
    let upper = statement.to_ascii_uppercase();
    let from_pos = upper.find("FROM").ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "Invalid SELECT statement: missing FROM",
        )
    })?;

    let after_from = statement[from_pos + 4..].trim();
    let (table_name, rest) = parse_partiql_table_name(after_from);

    let __mas = state.read();
    let state = __mas.default_ref();
    let table = get_table(&state.tables, &table_name)?;

    let rest_upper = rest.trim().to_ascii_uppercase();
    if rest_upper.starts_with("WHERE") {
        let where_clause = rest.trim()[5..].trim();
        let matched = evaluate_partiql_where(table, where_clause, parameters)?;
        let items: Vec<Value> = matched.iter().map(|item| json!(item)).collect();
        DynamoDbService::ok_json(json!({ "Items": items }))
    } else {
        // No WHERE, return all items
        let items: Vec<Value> = table.items.iter().map(|item| json!(item)).collect();
        DynamoDbService::ok_json(json!({ "Items": items }))
    }
}

fn execute_partiql_insert(
    state: &SharedDynamoDbState,
    statement: &str,
    parameters: &[Value],
) -> Result<AwsResponse, AwsServiceError> {
    // Pattern: INSERT INTO "tablename" VALUE {'pk': 'val', 'attr': 'val'}
    // or with parameters: INSERT INTO "tablename" VALUE {'pk': ?, 'attr': ?}
    let upper = statement.to_ascii_uppercase();
    let into_pos = upper.find("INTO").ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "Invalid INSERT statement: missing INTO",
        )
    })?;

    let after_into = statement[into_pos + 4..].trim();
    let (table_name, rest) = parse_partiql_table_name(after_into);

    let rest_upper = rest.trim().to_ascii_uppercase();
    let value_pos = rest_upper.find("VALUE").ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "Invalid INSERT statement: missing VALUE",
        )
    })?;

    let value_str = rest.trim()[value_pos + 5..].trim();
    let item = parse_partiql_value_object(value_str, parameters)?;

    let mut __mas = state.write();
    let state = __mas.default_mut();
    let table = get_table_mut(&mut state.tables, &table_name)?;
    let key = extract_key(table, &item);
    if table.find_item_index(&key).is_some() {
        // DynamoDB PartiQL INSERT fails if item exists
        return Err(AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "DuplicateItemException",
            "Duplicate primary key exists in table",
        ));
    } else {
        table.items.push(item);
    }
    table.recalculate_stats();

    DynamoDbService::ok_json(json!({}))
}

fn execute_partiql_update(
    state: &SharedDynamoDbState,
    statement: &str,
    parameters: &[Value],
) -> Result<AwsResponse, AwsServiceError> {
    // Pattern: UPDATE "tablename" SET attr='val' WHERE pk='val'
    // or: UPDATE "tablename" SET attr=? WHERE pk=?
    let after_update = statement[6..].trim(); // skip "UPDATE"
    let (table_name, rest) = parse_partiql_table_name(after_update);

    let rest_upper = rest.trim().to_ascii_uppercase();
    let set_pos = rest_upper.find("SET").ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "Invalid UPDATE statement: missing SET",
        )
    })?;

    let after_set = rest.trim()[set_pos + 3..].trim();

    // Split on WHERE
    let where_pos = after_set.to_ascii_uppercase().find("WHERE");
    let (set_clause, where_clause) = if let Some(wp) = where_pos {
        (&after_set[..wp], after_set[wp + 5..].trim())
    } else {
        (after_set, "")
    };

    let mut __mas = state.write();
    let state = __mas.default_mut();
    let table = get_table_mut(&mut state.tables, &table_name)?;

    let matched_indices = if !where_clause.is_empty() {
        find_partiql_where_indices(table, where_clause, parameters)?
    } else {
        (0..table.items.len()).collect()
    };

    // Parse SET assignments: attr=value, attr2=value2
    let param_offset = count_params_in_str(where_clause);
    let assignments: Vec<&str> = set_clause.split(',').collect();
    for idx in &matched_indices {
        let mut local_offset = param_offset;
        for assignment in &assignments {
            let assignment = assignment.trim();
            if let Some((attr, val_str)) = assignment.split_once('=') {
                let attr = attr.trim().trim_matches('"');
                let val_str = val_str.trim();
                let value = parse_partiql_literal(val_str, parameters, &mut local_offset);
                if let Some(v) = value {
                    table.items[*idx].insert(attr.to_string(), v);
                }
            }
        }
    }
    table.recalculate_stats();

    DynamoDbService::ok_json(json!({}))
}

fn execute_partiql_delete(
    state: &SharedDynamoDbState,
    statement: &str,
    parameters: &[Value],
) -> Result<AwsResponse, AwsServiceError> {
    // Pattern: DELETE FROM "tablename" WHERE pk='val'
    let upper = statement.to_ascii_uppercase();
    let from_pos = upper.find("FROM").ok_or_else(|| {
        AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "Invalid DELETE statement: missing FROM",
        )
    })?;

    let after_from = statement[from_pos + 4..].trim();
    let (table_name, rest) = parse_partiql_table_name(after_from);

    let rest_upper = rest.trim().to_ascii_uppercase();
    if !rest_upper.starts_with("WHERE") {
        return Err(AwsServiceError::aws_error(
            StatusCode::BAD_REQUEST,
            "ValidationException",
            "DELETE requires a WHERE clause",
        ));
    }
    let where_clause = rest.trim()[5..].trim();

    let mut __mas = state.write();
    let state = __mas.default_mut();
    let table = get_table_mut(&mut state.tables, &table_name)?;

    let mut indices = find_partiql_where_indices(table, where_clause, parameters)?;
    // Remove from highest index first to avoid invalidating lower indices
    indices.sort_unstable();
    indices.reverse();
    for idx in indices {
        table.items.remove(idx);
    }
    table.recalculate_stats();

    DynamoDbService::ok_json(json!({}))
}

/// Parse a table name that may be quoted with double quotes.
/// Returns (table_name, rest_of_string).
fn parse_partiql_table_name(s: &str) -> (String, &str) {
    let s = s.trim();
    if let Some(stripped) = s.strip_prefix('"') {
        // Quoted name
        if let Some(end) = stripped.find('"') {
            let name = &stripped[..end];
            let rest = &stripped[end + 1..];
            (name.to_string(), rest)
        } else {
            let end = s.find(' ').unwrap_or(s.len());
            (s[..end].trim_matches('"').to_string(), &s[end..])
        }
    } else {
        let end = s.find(|c: char| c.is_whitespace()).unwrap_or(s.len());
        (s[..end].to_string(), &s[end..])
    }
}

/// Evaluate a simple WHERE clause: `col = 'value'` or `col = ?`
/// Returns matching items.
fn evaluate_partiql_where<'a>(
    table: &'a DynamoTable,
    where_clause: &str,
    parameters: &[Value],
) -> Result<Vec<&'a HashMap<String, AttributeValue>>, AwsServiceError> {
    let indices = find_partiql_where_indices(table, where_clause, parameters)?;
    Ok(indices.iter().map(|i| &table.items[*i]).collect())
}

fn find_partiql_where_indices(
    table: &DynamoTable,
    where_clause: &str,
    parameters: &[Value],
) -> Result<Vec<usize>, AwsServiceError> {
    let conditions = split_partiql_and_clauses(where_clause);
    let parsed_conditions = parse_partiql_equality_conditions(&conditions, parameters);

    let mut indices = Vec::new();
    for (i, item) in table.items.iter().enumerate() {
        let all_match = parsed_conditions
            .iter()
            .all(|(attr, expected)| item.get(attr) == Some(expected));
        if all_match {
            indices.push(i);
        }
    }

    Ok(indices)
}

/// Split a PartiQL WHERE clause on case-insensitive ` AND ` boundaries.
fn split_partiql_and_clauses(where_clause: &str) -> Vec<&str> {
    let upper = where_clause.to_uppercase();
    if !upper.contains(" AND ") {
        return vec![where_clause.trim()];
    }
    let mut parts = Vec::new();
    let mut last = 0;
    for (i, _) in upper.match_indices(" AND ") {
        parts.push(where_clause[last..i].trim());
        last = i + 5;
    }
    parts.push(where_clause[last..].trim());
    parts
}

/// Parse each `col = literal` (or `col = ?`) condition into an
/// `(attribute_name, expected_AttributeValue)` pair. Conditions that
/// don't parse as equality, or whose RHS literal can't be resolved, are
/// silently dropped — that mirrors the prior inline behavior.
fn parse_partiql_equality_conditions(
    conditions: &[&str],
    parameters: &[Value],
) -> Vec<(String, Value)> {
    let mut param_idx = 0usize;
    let mut parsed = Vec::new();
    for cond in conditions {
        let cond = cond.trim();
        if let Some((left, right)) = cond.split_once('=') {
            let attr = left.trim().trim_matches('"').to_string();
            let val_str = right.trim();
            if let Some(value) = parse_partiql_literal(val_str, parameters, &mut param_idx) {
                parsed.push((attr, value));
            }
        }
    }
    parsed
}

/// Parse a PartiQL literal value. Supports:
/// - 'string' -> {"S": "string"}
/// - 123 -> {"N": "123"}
/// - ? -> parameter from list
fn parse_partiql_literal(s: &str, parameters: &[Value], param_idx: &mut usize) -> Option<Value> {
    let s = s.trim();
    if s == "?" {
        let idx = *param_idx;
        *param_idx += 1;
        parameters.get(idx).cloned()
    } else if s.starts_with('\'') && s.ends_with('\'') && s.len() >= 2 {
        let inner = &s[1..s.len() - 1];
        Some(json!({"S": inner}))
    } else if let Ok(n) = s.parse::<f64>() {
        let num_str = if n == n.trunc() {
            format!("{}", n as i64)
        } else {
            format!("{n}")
        };
        Some(json!({"N": num_str}))
    } else {
        None
    }
}

/// Parse a PartiQL VALUE object like `{'pk': 'val1', 'attr': 'val2'}` or with ? params.
fn parse_partiql_value_object(
    s: &str,
    parameters: &[Value],
) -> Result<HashMap<String, AttributeValue>, AwsServiceError> {
    let s = s.trim();
    let inner = s
        .strip_prefix('{')
        .and_then(|s| s.strip_suffix('}'))
        .ok_or_else(|| {
            AwsServiceError::aws_error(
                StatusCode::BAD_REQUEST,
                "ValidationException",
                "Invalid VALUE: expected object literal",
            )
        })?;

    let mut item = HashMap::new();
    let mut param_idx = 0usize;

    // Simple comma-separated key:value parsing
    for pair in split_partiql_pairs(inner) {
        let pair = pair.trim();
        if pair.is_empty() {
            continue;
        }
        if let Some((key_part, val_part)) = pair.split_once(':') {
            let key = key_part
                .trim()
                .trim_matches('\'')
                .trim_matches('"')
                .to_string();
            if let Some(val) = parse_partiql_literal(val_part.trim(), parameters, &mut param_idx) {
                item.insert(key, val);
            }
        }
    }

    Ok(item)
}

/// Split PartiQL object pairs on commas, respecting nested braces and quotes.
fn split_partiql_pairs(s: &str) -> Vec<&str> {
    let mut parts = Vec::new();
    let mut start = 0;
    let mut depth = 0;
    let mut in_quote = false;

    for (i, c) in s.char_indices() {
        match c {
            '\'' if !in_quote => in_quote = true,
            '\'' if in_quote => in_quote = false,
            '{' if !in_quote => depth += 1,
            '}' if !in_quote => depth -= 1,
            ',' if !in_quote && depth == 0 => {
                parts.push(&s[start..i]);
                start = i + 1;
            }
            _ => {}
        }
    }
    parts.push(&s[start..]);
    parts
}

/// Count ? parameters in a string.
fn count_params_in_str(s: &str) -> usize {
    s.chars().filter(|c| *c == '?').count()
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;

    #[test]
    fn test_parse_update_clauses_set() {
        let clauses = parse_update_clauses("SET #a = :val1, #b = :val2");
        assert_eq!(clauses.len(), 1);
        assert_eq!(clauses[0].0, UpdateAction::Set);
        assert_eq!(clauses[0].1.len(), 2);
    }

    #[test]
    fn test_parse_update_clauses_set_and_remove() {
        let clauses = parse_update_clauses("SET #a = :val1 REMOVE #b");
        assert_eq!(clauses.len(), 2);
        assert_eq!(clauses[0].0, UpdateAction::Set);
        assert_eq!(clauses[1].0, UpdateAction::Remove);
    }

    #[test]
    fn test_parse_update_clauses_list_append_single_assignment() {
        // Before fix: naive comma split tore list_append(#0, :0) at the
        // inner comma, producing two bogus assignments instead of one.
        let clauses = parse_update_clauses("SET #0 = list_append(#0, :0)");
        assert_eq!(clauses.len(), 1);
        assert_eq!(clauses[0].0, UpdateAction::Set);
        assert_eq!(
            clauses[0].1.len(),
            1,
            "list_append(a, b) must be kept as a single assignment, not split at the inner comma"
        );
    }

    #[test]
    fn test_parse_update_clauses_list_append_mixed_with_plain_set() {
        // list_append assignment followed by a plain SET — the comma between
        // the two assignments must still split them, while the comma inside
        // the list_append call must not.
        let clauses = parse_update_clauses("SET #0 = list_append(#0, :new), #1 = :other");
        assert_eq!(clauses.len(), 1);
        assert_eq!(clauses[0].0, UpdateAction::Set);
        assert_eq!(
            clauses[0].1.len(),
            2,
            "two SET assignments: one list_append and one plain"
        );
    }

    #[test]
    fn test_evaluate_key_condition_simple() {
        let mut item = HashMap::new();
        item.insert("pk".to_string(), json!({"S": "user1"}));
        item.insert("sk".to_string(), json!({"S": "order1"}));

        let mut expr_values = HashMap::new();
        expr_values.insert(":pk".to_string(), json!({"S": "user1"}));

        assert!(evaluate_key_condition(
            "pk = :pk",
            &item,
            &HashMap::new(),
            &expr_values,
        ));
    }

    #[test]
    fn test_compare_attribute_values_numbers() {
        let a = json!({"N": "10"});
        let b = json!({"N": "20"});
        assert_eq!(
            compare_attribute_values(Some(&a), Some(&b)),
            std::cmp::Ordering::Less
        );
    }

    #[test]
    fn test_compare_attribute_values_strings() {
        let a = json!({"S": "apple"});
        let b = json!({"S": "banana"});
        assert_eq!(
            compare_attribute_values(Some(&a), Some(&b)),
            std::cmp::Ordering::Less
        );
    }

    #[test]
    fn test_split_on_and() {
        let parts = split_on_and("pk = :pk AND sk > :sk");
        assert_eq!(parts.len(), 2);
        assert_eq!(parts[0].trim(), "pk = :pk");
        assert_eq!(parts[1].trim(), "sk > :sk");
    }

    #[test]
    fn test_split_on_and_respects_parentheses() {
        // Before fix: split_on_and would split inside the parens
        let parts = split_on_and("(a = :a AND b = :b) OR c = :c");
        // Should NOT split on the AND inside parentheses
        assert_eq!(parts.len(), 1);
        assert_eq!(parts[0].trim(), "(a = :a AND b = :b) OR c = :c");
    }

    #[test]
    fn test_evaluate_filter_expression_parenthesized_and_with_or() {
        // (a AND b) OR c — should match when c is true but a is false
        let mut item = HashMap::new();
        item.insert("x".to_string(), json!({"S": "no"}));
        item.insert("y".to_string(), json!({"S": "no"}));
        item.insert("z".to_string(), json!({"S": "yes"}));

        let mut expr_values = HashMap::new();
        expr_values.insert(":yes".to_string(), json!({"S": "yes"}));

        // x=yes AND y=yes => false, but z=yes => true => overall true
        let result = evaluate_filter_expression(
            "(x = :yes AND y = :yes) OR z = :yes",
            &item,
            &HashMap::new(),
            &expr_values,
        );
        assert!(result, "should match because z = :yes is true");

        // x=yes AND y=yes => false, z=yes => false => overall false
        let mut item2 = HashMap::new();
        item2.insert("x".to_string(), json!({"S": "no"}));
        item2.insert("y".to_string(), json!({"S": "no"}));
        item2.insert("z".to_string(), json!({"S": "no"}));

        let result2 = evaluate_filter_expression(
            "(x = :yes AND y = :yes) OR z = :yes",
            &item2,
            &HashMap::new(),
            &expr_values,
        );
        assert!(!result2, "should not match because nothing is true");
    }

    #[test]
    fn test_project_item_nested_path() {
        // Item with a list attribute containing maps
        let mut item = HashMap::new();
        item.insert("pk".to_string(), json!({"S": "key1"}));
        item.insert(
            "data".to_string(),
            json!({"L": [{"M": {"name": {"S": "Alice"}, "age": {"N": "30"}}}, {"M": {"name": {"S": "Bob"}}}]}),
        );

        let body = json!({
            "ProjectionExpression": "data[0].name"
        });

        let projected = project_item(&item, &body);
        // Should contain data[0].name = "Alice", not the entire data[0] element
        let name = projected
            .get("data")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.get(0))
            .and_then(|v| v.get("M"))
            .and_then(|v| v.get("name"))
            .and_then(|v| v.get("S"))
            .and_then(|v| v.as_str());
        assert_eq!(name, Some("Alice"));

        // Should NOT contain the "age" field
        let age = projected
            .get("data")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.get(0))
            .and_then(|v| v.get("M"))
            .and_then(|v| v.get("age"));
        assert!(age.is_none(), "age should not be present in projection");
    }

    #[test]
    fn test_resolve_nested_path_map() {
        let mut item = HashMap::new();
        item.insert(
            "info".to_string(),
            json!({"M": {"address": {"M": {"city": {"S": "NYC"}}}}}),
        );

        let result = resolve_nested_path(&item, "info.address.city");
        assert_eq!(result, Some(json!({"S": "NYC"})));
    }

    #[test]
    fn test_resolve_nested_path_list_then_map() {
        let mut item = HashMap::new();
        item.insert(
            "items".to_string(),
            json!({"L": [{"M": {"sku": {"S": "ABC"}}}]}),
        );

        let result = resolve_nested_path(&item, "items[0].sku");
        assert_eq!(result, Some(json!({"S": "ABC"})));
    }

    #[test]
    fn test_resolve_path_alias_with_dot_is_top_level_attr() {
        // Top-level attribute name literally contains a dot; user aliases it
        // via ExpressionAttributeNames and references the alias. Must resolve
        // to the top-level attribute, NOT be walked as a nested path.
        let mut item = HashMap::new();
        item.insert("Safety.Warning".to_string(), json!({"S": "high"}));
        let mut names = HashMap::new();
        names.insert("#sw".to_string(), "Safety.Warning".to_string());

        let result = resolve_path("#sw", &item, &names);
        assert_eq!(result, Some(json!({"S": "high"})));
    }

    #[test]
    fn test_resolve_path_dotted_expression_still_walks_nested() {
        // When the expression itself contains `.`, we still walk the nested
        // path (the dot is a path separator, not part of an attribute name).
        let mut item = HashMap::new();
        item.insert("profile".to_string(), json!({"M": {"email": {"S": "x@y"}}}));
        let names = HashMap::new();

        let result = resolve_path("profile.email", &item, &names);
        assert_eq!(result, Some(json!({"S": "x@y"})));
    }

    #[test]
    fn test_project_item_alias_with_dot_is_top_level_attr() {
        // Same invariant must hold for ProjectionExpression.
        let mut item = HashMap::new();
        item.insert("Safety.Warning".to_string(), json!({"S": "high"}));
        item.insert("other".to_string(), json!({"S": "ignored"}));
        let body = json!({
            "ProjectionExpression": "#sw",
            "ExpressionAttributeNames": {"#sw": "Safety.Warning"},
        });

        let projected = project_item(&item, &body);
        assert_eq!(projected.get("Safety.Warning"), Some(&json!({"S": "high"})));
        assert!(!projected.contains_key("other"));
    }

    // -- Integration-style tests using DynamoDbService --

    use crate::state::SharedDynamoDbState;
    use parking_lot::RwLock;
    use std::sync::Arc;

    fn make_service() -> DynamoDbService {
        let state: SharedDynamoDbState = Arc::new(RwLock::new(
            fakecloud_core::multi_account::MultiAccountState::new("123456789012", "us-east-1", ""),
        ));
        DynamoDbService::new(state)
    }

    fn make_request(action: &str, body: Value) -> AwsRequest {
        AwsRequest {
            service: "dynamodb".to_string(),
            action: action.to_string(),
            region: "us-east-1".to_string(),
            account_id: "123456789012".to_string(),
            request_id: "test-id".to_string(),
            headers: http::HeaderMap::new(),
            query_params: HashMap::new(),
            body: serde_json::to_vec(&body).unwrap().into(),
            body_stream: parking_lot::Mutex::new(None),
            path_segments: vec![],
            raw_path: "/".to_string(),
            raw_query: String::new(),
            method: http::Method::POST,
            is_query_protocol: false,
            access_key_id: None,
            principal: None,
        }
    }

    fn create_test_table(svc: &DynamoDbService) {
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "test-table",
                "KeySchema": [
                    { "AttributeName": "pk", "KeyType": "HASH" }
                ],
                "AttributeDefinitions": [
                    { "AttributeName": "pk", "AttributeType": "S" }
                ],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        );
        svc.create_table(&req).unwrap();
    }

    #[test]
    fn describe_table_returns_stable_table_id_and_active_warm_throughput() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "warm-throughput-table",
                "KeySchema": [
                    { "AttributeName": "pk", "KeyType": "HASH" }
                ],
                "AttributeDefinitions": [
                    { "AttributeName": "pk", "AttributeType": "S" }
                ],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        );
        let create_resp = svc.create_table(&req).unwrap();
        let create_body: Value = serde_json::from_slice(create_resp.body.expect_bytes()).unwrap();
        let create_table = &create_body["TableDescription"];

        assert_eq!(create_table["TableStatus"], "ACTIVE");
        assert_eq!(create_table["WarmThroughput"]["Status"], "ACTIVE");
        let table_id = create_table["TableId"].as_str().unwrap().to_string();
        assert!(!table_id.is_empty());

        let describe_req = make_request(
            "DescribeTable",
            json!({ "TableName": "warm-throughput-table" }),
        );
        let describe_resp = svc.describe_table(&describe_req).unwrap();
        let describe_body: Value =
            serde_json::from_slice(describe_resp.body.expect_bytes()).unwrap();
        let described_table = &describe_body["Table"];

        assert_eq!(described_table["TableStatus"], "ACTIVE");
        assert_eq!(described_table["WarmThroughput"]["Status"], "ACTIVE");
        assert_eq!(described_table["TableId"], table_id);

        let describe_resp_again = svc.describe_table(&describe_req).unwrap();
        let describe_body_again: Value =
            serde_json::from_slice(describe_resp_again.body.expect_bytes()).unwrap();
        assert_eq!(describe_body_again["Table"]["TableId"], table_id);
    }

    #[test]
    fn delete_item_return_values_all_old() {
        let svc = make_service();
        create_test_table(&svc);

        // Put an item
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {
                    "pk": { "S": "key1" },
                    "name": { "S": "Alice" },
                    "age": { "N": "30" }
                }
            }),
        );
        svc.put_item(&req).unwrap();

        // Delete with ReturnValues=ALL_OLD
        let req = make_request(
            "DeleteItem",
            json!({
                "TableName": "test-table",
                "Key": { "pk": { "S": "key1" } },
                "ReturnValues": "ALL_OLD"
            }),
        );
        let resp = svc.delete_item(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();

        // Verify the old item is returned
        let attrs = &body["Attributes"];
        assert_eq!(attrs["pk"]["S"].as_str().unwrap(), "key1");
        assert_eq!(attrs["name"]["S"].as_str().unwrap(), "Alice");
        assert_eq!(attrs["age"]["N"].as_str().unwrap(), "30");

        // Verify the item is actually deleted
        let req = make_request(
            "GetItem",
            json!({
                "TableName": "test-table",
                "Key": { "pk": { "S": "key1" } }
            }),
        );
        let resp = svc.get_item(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert!(body.get("Item").is_none(), "item should be deleted");
    }

    #[test]
    fn transact_get_items_returns_existing_and_missing() {
        let svc = make_service();
        create_test_table(&svc);

        // Put one item
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {
                    "pk": { "S": "exists" },
                    "val": { "S": "hello" }
                }
            }),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "TransactGetItems",
            json!({
                "TransactItems": [
                    { "Get": { "TableName": "test-table", "Key": { "pk": { "S": "exists" } } } },
                    { "Get": { "TableName": "test-table", "Key": { "pk": { "S": "missing" } } } }
                ]
            }),
        );
        let resp = svc.transact_get_items(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let responses = body["Responses"].as_array().unwrap();
        assert_eq!(responses.len(), 2);
        assert_eq!(responses[0]["Item"]["pk"]["S"].as_str().unwrap(), "exists");
        assert!(responses[1].get("Item").is_none());
    }

    #[test]
    fn transact_write_items_put_and_delete() {
        let svc = make_service();
        create_test_table(&svc);

        // Put initial item
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {
                    "pk": { "S": "to-delete" },
                    "val": { "S": "bye" }
                }
            }),
        );
        svc.put_item(&req).unwrap();

        // TransactWrite: put new + delete existing
        let req = make_request(
            "TransactWriteItems",
            json!({
                "TransactItems": [
                    {
                        "Put": {
                            "TableName": "test-table",
                            "Item": {
                                "pk": { "S": "new-item" },
                                "val": { "S": "hi" }
                            }
                        }
                    },
                    {
                        "Delete": {
                            "TableName": "test-table",
                            "Key": { "pk": { "S": "to-delete" } }
                        }
                    }
                ]
            }),
        );
        let resp = svc.transact_write_items(&req).unwrap();
        assert_eq!(resp.status, StatusCode::OK);

        // Verify new item exists
        let req = make_request(
            "GetItem",
            json!({
                "TableName": "test-table",
                "Key": { "pk": { "S": "new-item" } }
            }),
        );
        let resp = svc.get_item(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Item"]["val"]["S"].as_str().unwrap(), "hi");

        // Verify deleted item is gone
        let req = make_request(
            "GetItem",
            json!({
                "TableName": "test-table",
                "Key": { "pk": { "S": "to-delete" } }
            }),
        );
        let resp = svc.get_item(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert!(body.get("Item").is_none());
    }

    #[test]
    fn transact_write_items_condition_check_failure() {
        let svc = make_service();
        create_test_table(&svc);

        // TransactWrite with a ConditionCheck that fails (item doesn't exist)
        let req = make_request(
            "TransactWriteItems",
            json!({
                "TransactItems": [
                    {
                        "ConditionCheck": {
                            "TableName": "test-table",
                            "Key": { "pk": { "S": "nonexistent" } },
                            "ConditionExpression": "attribute_exists(pk)"
                        }
                    }
                ]
            }),
        );
        let resp = svc.transact_write_items(&req).unwrap();
        // Should be a 400 error response
        assert_eq!(resp.status, StatusCode::BAD_REQUEST);
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["__type"].as_str().unwrap(),
            "TransactionCanceledException"
        );
        assert!(body["CancellationReasons"].as_array().is_some());
    }

    #[test]
    fn update_and_describe_time_to_live() {
        let svc = make_service();
        create_test_table(&svc);

        // Enable TTL
        let req = make_request(
            "UpdateTimeToLive",
            json!({
                "TableName": "test-table",
                "TimeToLiveSpecification": {
                    "AttributeName": "ttl",
                    "Enabled": true
                }
            }),
        );
        let resp = svc.update_time_to_live(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["TimeToLiveSpecification"]["AttributeName"]
                .as_str()
                .unwrap(),
            "ttl"
        );
        assert!(body["TimeToLiveSpecification"]["Enabled"]
            .as_bool()
            .unwrap());

        // Describe TTL
        let req = make_request("DescribeTimeToLive", json!({ "TableName": "test-table" }));
        let resp = svc.describe_time_to_live(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["TimeToLiveDescription"]["TimeToLiveStatus"]
                .as_str()
                .unwrap(),
            "ENABLED"
        );
        assert_eq!(
            body["TimeToLiveDescription"]["AttributeName"]
                .as_str()
                .unwrap(),
            "ttl"
        );

        // Disable TTL
        let req = make_request(
            "UpdateTimeToLive",
            json!({
                "TableName": "test-table",
                "TimeToLiveSpecification": {
                    "AttributeName": "ttl",
                    "Enabled": false
                }
            }),
        );
        svc.update_time_to_live(&req).unwrap();

        let req = make_request("DescribeTimeToLive", json!({ "TableName": "test-table" }));
        let resp = svc.describe_time_to_live(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["TimeToLiveDescription"]["TimeToLiveStatus"]
                .as_str()
                .unwrap(),
            "DISABLED"
        );
    }

    #[test]
    fn resource_policy_lifecycle() {
        let svc = make_service();
        create_test_table(&svc);

        let table_arn = {
            let __mas = svc.state.read();
            let state = __mas.default_ref();
            state.tables.get("test-table").unwrap().arn.clone()
        };

        // Put policy
        let policy_doc = r#"{"Version":"2012-10-17","Statement":[]}"#;
        let req = make_request(
            "PutResourcePolicy",
            json!({
                "ResourceArn": table_arn,
                "Policy": policy_doc
            }),
        );
        let resp = svc.put_resource_policy(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert!(body["RevisionId"].as_str().is_some());

        // Get policy
        let req = make_request("GetResourcePolicy", json!({ "ResourceArn": table_arn }));
        let resp = svc.get_resource_policy(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Policy"].as_str().unwrap(), policy_doc);

        // Delete policy
        let req = make_request("DeleteResourcePolicy", json!({ "ResourceArn": table_arn }));
        svc.delete_resource_policy(&req).unwrap();

        // Get should return null now
        let req = make_request("GetResourcePolicy", json!({ "ResourceArn": table_arn }));
        let resp = svc.get_resource_policy(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert!(body["Policy"].is_null());
    }

    #[test]
    fn describe_endpoints() {
        let svc = make_service();
        let req = make_request("DescribeEndpoints", json!({}));
        let resp = svc.describe_endpoints(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Endpoints"][0]["CachePeriodInMinutes"], 1440);
    }

    #[test]
    fn describe_limits() {
        let svc = make_service();
        let req = make_request("DescribeLimits", json!({}));
        let resp = svc.describe_limits(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["TableMaxReadCapacityUnits"], 40000);
    }

    #[test]
    fn backup_lifecycle() {
        let svc = make_service();
        create_test_table(&svc);

        // Create backup
        let req = make_request(
            "CreateBackup",
            json!({ "TableName": "test-table", "BackupName": "my-backup" }),
        );
        let resp = svc.create_backup(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let backup_arn = body["BackupDetails"]["BackupArn"]
            .as_str()
            .unwrap()
            .to_string();
        assert_eq!(body["BackupDetails"]["BackupStatus"], "AVAILABLE");

        // Describe backup
        let req = make_request("DescribeBackup", json!({ "BackupArn": backup_arn }));
        let resp = svc.describe_backup(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["BackupDescription"]["BackupDetails"]["BackupName"],
            "my-backup"
        );

        // List backups
        let req = make_request("ListBackups", json!({}));
        let resp = svc.list_backups(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["BackupSummaries"].as_array().unwrap().len(), 1);

        // Restore from backup
        let req = make_request(
            "RestoreTableFromBackup",
            json!({ "BackupArn": backup_arn, "TargetTableName": "restored-table" }),
        );
        svc.restore_table_from_backup(&req).unwrap();

        // Verify restored table exists
        let req = make_request("DescribeTable", json!({ "TableName": "restored-table" }));
        let resp = svc.describe_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Table"]["TableStatus"], "ACTIVE");

        // Delete backup
        let req = make_request("DeleteBackup", json!({ "BackupArn": backup_arn }));
        svc.delete_backup(&req).unwrap();

        // List should be empty
        let req = make_request("ListBackups", json!({}));
        let resp = svc.list_backups(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["BackupSummaries"].as_array().unwrap().len(), 0);
    }

    #[test]
    fn continuous_backups() {
        let svc = make_service();
        create_test_table(&svc);

        // Initially disabled
        let req = make_request(
            "DescribeContinuousBackups",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_continuous_backups(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["ContinuousBackupsDescription"]["PointInTimeRecoveryDescription"]
                ["PointInTimeRecoveryStatus"],
            "DISABLED"
        );

        // Enable
        let req = make_request(
            "UpdateContinuousBackups",
            json!({
                "TableName": "test-table",
                "PointInTimeRecoverySpecification": {
                    "PointInTimeRecoveryEnabled": true
                }
            }),
        );
        svc.update_continuous_backups(&req).unwrap();

        // Verify
        let req = make_request(
            "DescribeContinuousBackups",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_continuous_backups(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["ContinuousBackupsDescription"]["PointInTimeRecoveryDescription"]
                ["PointInTimeRecoveryStatus"],
            "ENABLED"
        );
    }

    #[test]
    fn restore_table_to_point_in_time() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "RestoreTableToPointInTime",
            json!({
                "SourceTableName": "test-table",
                "TargetTableName": "pitr-restored"
            }),
        );
        svc.restore_table_to_point_in_time(&req).unwrap();

        let req = make_request("DescribeTable", json!({ "TableName": "pitr-restored" }));
        let resp = svc.describe_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Table"]["TableStatus"], "ACTIVE");
    }

    #[test]
    fn global_table_lifecycle() {
        let svc = make_service();

        // Create global table
        let req = make_request(
            "CreateGlobalTable",
            json!({
                "GlobalTableName": "my-global",
                "ReplicationGroup": [
                    { "RegionName": "us-east-1" },
                    { "RegionName": "eu-west-1" }
                ]
            }),
        );
        let resp = svc.create_global_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["GlobalTableDescription"]["GlobalTableStatus"],
            "ACTIVE"
        );

        // Describe
        let req = make_request(
            "DescribeGlobalTable",
            json!({ "GlobalTableName": "my-global" }),
        );
        let resp = svc.describe_global_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["GlobalTableDescription"]["ReplicationGroup"]
                .as_array()
                .unwrap()
                .len(),
            2
        );

        // List
        let req = make_request("ListGlobalTables", json!({}));
        let resp = svc.list_global_tables(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["GlobalTables"].as_array().unwrap().len(), 1);

        // Update - add a region
        let req = make_request(
            "UpdateGlobalTable",
            json!({
                "GlobalTableName": "my-global",
                "ReplicaUpdates": [
                    { "Create": { "RegionName": "ap-southeast-1" } }
                ]
            }),
        );
        let resp = svc.update_global_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["GlobalTableDescription"]["ReplicationGroup"]
                .as_array()
                .unwrap()
                .len(),
            3
        );

        // Describe settings
        let req = make_request(
            "DescribeGlobalTableSettings",
            json!({ "GlobalTableName": "my-global" }),
        );
        let resp = svc.describe_global_table_settings(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ReplicaSettings"].as_array().unwrap().len(), 3);

        // Update settings (no-op, just verify no error)
        let req = make_request(
            "UpdateGlobalTableSettings",
            json!({ "GlobalTableName": "my-global" }),
        );
        svc.update_global_table_settings(&req).unwrap();
    }

    #[test]
    fn table_replica_auto_scaling() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "DescribeTableReplicaAutoScaling",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_table_replica_auto_scaling(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["TableAutoScalingDescription"]["TableName"],
            "test-table"
        );

        let req = make_request(
            "UpdateTableReplicaAutoScaling",
            json!({ "TableName": "test-table" }),
        );
        svc.update_table_replica_auto_scaling(&req).unwrap();
    }

    #[test]
    fn kinesis_streaming_lifecycle() {
        let svc = make_service();
        create_test_table(&svc);

        // Enable
        let req = make_request(
            "EnableKinesisStreamingDestination",
            json!({
                "TableName": "test-table",
                "StreamArn": "arn:aws:kinesis:us-east-1:123456789012:stream/my-stream"
            }),
        );
        let resp = svc.enable_kinesis_streaming_destination(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["DestinationStatus"], "ACTIVE");

        // Describe
        let req = make_request(
            "DescribeKinesisStreamingDestination",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_kinesis_streaming_destination(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["KinesisDataStreamDestinations"]
                .as_array()
                .unwrap()
                .len(),
            1
        );

        // Update
        let req = make_request(
            "UpdateKinesisStreamingDestination",
            json!({
                "TableName": "test-table",
                "StreamArn": "arn:aws:kinesis:us-east-1:123456789012:stream/my-stream",
                "UpdateKinesisStreamingConfiguration": {
                    "ApproximateCreationDateTimePrecision": "MICROSECOND"
                }
            }),
        );
        svc.update_kinesis_streaming_destination(&req).unwrap();

        // Disable
        let req = make_request(
            "DisableKinesisStreamingDestination",
            json!({
                "TableName": "test-table",
                "StreamArn": "arn:aws:kinesis:us-east-1:123456789012:stream/my-stream"
            }),
        );
        let resp = svc.disable_kinesis_streaming_destination(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["DestinationStatus"], "DISABLED");
    }

    #[test]
    fn contributor_insights_lifecycle() {
        let svc = make_service();
        create_test_table(&svc);

        // Initially disabled
        let req = make_request(
            "DescribeContributorInsights",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_contributor_insights(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ContributorInsightsStatus"], "DISABLED");

        // Enable
        let req = make_request(
            "UpdateContributorInsights",
            json!({
                "TableName": "test-table",
                "ContributorInsightsAction": "ENABLE"
            }),
        );
        let resp = svc.update_contributor_insights(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ContributorInsightsStatus"], "ENABLED");

        // List
        let req = make_request("ListContributorInsights", json!({}));
        let resp = svc.list_contributor_insights(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["ContributorInsightsSummaries"]
                .as_array()
                .unwrap()
                .len(),
            1
        );
    }

    #[test]
    fn export_lifecycle() {
        let svc = make_service();
        create_test_table(&svc);

        let table_arn = "arn:aws:dynamodb:us-east-1:123456789012:table/test-table".to_string();

        // Export
        let req = make_request(
            "ExportTableToPointInTime",
            json!({
                "TableArn": table_arn,
                "S3Bucket": "my-bucket"
            }),
        );
        let resp = svc.export_table_to_point_in_time(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let export_arn = body["ExportDescription"]["ExportArn"]
            .as_str()
            .unwrap()
            .to_string();
        assert_eq!(body["ExportDescription"]["ExportStatus"], "COMPLETED");

        // Describe
        let req = make_request("DescribeExport", json!({ "ExportArn": export_arn }));
        let resp = svc.describe_export(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ExportDescription"]["S3Bucket"], "my-bucket");

        // List
        let req = make_request("ListExports", json!({}));
        let resp = svc.list_exports(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ExportSummaries"].as_array().unwrap().len(), 1);
    }

    #[test]
    fn import_lifecycle() {
        let svc = make_service();

        let req = make_request(
            "ImportTable",
            json!({
                "InputFormat": "DYNAMODB_JSON",
                "S3BucketSource": { "S3Bucket": "import-bucket" },
                "TableCreationParameters": {
                    "TableName": "imported-table",
                    "KeySchema": [{ "AttributeName": "pk", "KeyType": "HASH" }],
                    "AttributeDefinitions": [{ "AttributeName": "pk", "AttributeType": "S" }]
                }
            }),
        );
        let resp = svc.import_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let import_arn = body["ImportTableDescription"]["ImportArn"]
            .as_str()
            .unwrap()
            .to_string();
        assert_eq!(body["ImportTableDescription"]["ImportStatus"], "COMPLETED");

        // Describe import
        let req = make_request("DescribeImport", json!({ "ImportArn": import_arn }));
        let resp = svc.describe_import(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ImportTableDescription"]["ImportStatus"], "COMPLETED");

        // List imports
        let req = make_request("ListImports", json!({}));
        let resp = svc.list_imports(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ImportSummaryList"].as_array().unwrap().len(), 1);

        // Verify the table was created
        let req = make_request("DescribeTable", json!({ "TableName": "imported-table" }));
        let resp = svc.describe_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Table"]["TableStatus"], "ACTIVE");
    }

    #[test]
    fn backup_restore_preserves_items() {
        let svc = make_service();
        create_test_table(&svc);

        // Put 3 items
        for i in 1..=3 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "test-table",
                    "Item": {
                        "pk": { "S": format!("key{i}") },
                        "data": { "S": format!("value{i}") }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Create backup
        let req = make_request(
            "CreateBackup",
            json!({
                "TableName": "test-table",
                "BackupName": "my-backup"
            }),
        );
        let resp = svc.create_backup(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let backup_arn = body["BackupDetails"]["BackupArn"]
            .as_str()
            .unwrap()
            .to_string();

        // Delete all items from the original table
        for i in 1..=3 {
            let req = make_request(
                "DeleteItem",
                json!({
                    "TableName": "test-table",
                    "Key": { "pk": { "S": format!("key{i}") } }
                }),
            );
            svc.delete_item(&req).unwrap();
        }

        // Verify original table is empty
        let req = make_request("Scan", json!({ "TableName": "test-table" }));
        let resp = svc.scan(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 0);

        // Restore from backup
        let req = make_request(
            "RestoreTableFromBackup",
            json!({
                "BackupArn": backup_arn,
                "TargetTableName": "restored-table"
            }),
        );
        svc.restore_table_from_backup(&req).unwrap();

        // Scan restored table — should have 3 items
        let req = make_request("Scan", json!({ "TableName": "restored-table" }));
        let resp = svc.scan(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 3);
        assert_eq!(body["Items"].as_array().unwrap().len(), 3);
    }

    #[test]
    fn global_table_replicates_writes() {
        let svc = make_service();
        create_test_table(&svc);

        // Create global table with replicas
        let req = make_request(
            "CreateGlobalTable",
            json!({
                "GlobalTableName": "test-table",
                "ReplicationGroup": [
                    { "RegionName": "us-east-1" },
                    { "RegionName": "eu-west-1" }
                ]
            }),
        );
        let resp = svc.create_global_table(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(
            body["GlobalTableDescription"]["GlobalTableStatus"],
            "ACTIVE"
        );

        // Put an item
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {
                    "pk": { "S": "replicated-key" },
                    "data": { "S": "replicated-value" }
                }
            }),
        );
        svc.put_item(&req).unwrap();

        // Verify the item is readable (since all replicas share the same table)
        let req = make_request(
            "GetItem",
            json!({
                "TableName": "test-table",
                "Key": { "pk": { "S": "replicated-key" } }
            }),
        );
        let resp = svc.get_item(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Item"]["pk"]["S"], "replicated-key");
        assert_eq!(body["Item"]["data"]["S"], "replicated-value");
    }

    #[test]
    fn contributor_insights_tracks_access() {
        let svc = make_service();
        create_test_table(&svc);

        // Enable contributor insights
        let req = make_request(
            "UpdateContributorInsights",
            json!({
                "TableName": "test-table",
                "ContributorInsightsAction": "ENABLE"
            }),
        );
        svc.update_contributor_insights(&req).unwrap();

        // Put items with different partition keys
        for key in &["alpha", "beta", "alpha", "alpha", "beta"] {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "test-table",
                    "Item": {
                        "pk": { "S": key },
                        "data": { "S": "value" }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Get items (to also track read access)
        for _ in 0..3 {
            let req = make_request(
                "GetItem",
                json!({
                    "TableName": "test-table",
                    "Key": { "pk": { "S": "alpha" } }
                }),
            );
            svc.get_item(&req).unwrap();
        }

        // Describe contributor insights — should show top contributors
        let req = make_request(
            "DescribeContributorInsights",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_contributor_insights(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ContributorInsightsStatus"], "ENABLED");

        let contributors = body["TopContributors"].as_array().unwrap();
        assert!(
            !contributors.is_empty(),
            "TopContributors should not be empty"
        );

        // alpha was accessed 3 (put) + 3 (get) = 6 times, beta 2 times
        // alpha should be the top contributor
        let top = &contributors[0];
        assert!(top["Count"].as_u64().unwrap() > 0);

        // Verify the rule list is populated
        let rules = body["ContributorInsightsRuleList"].as_array().unwrap();
        assert!(!rules.is_empty());
    }

    #[test]
    fn contributor_insights_not_tracked_when_disabled() {
        let svc = make_service();
        create_test_table(&svc);

        // Put items without enabling insights
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {
                    "pk": { "S": "key1" },
                    "data": { "S": "value" }
                }
            }),
        );
        svc.put_item(&req).unwrap();

        // Describe — should show empty contributors
        let req = make_request(
            "DescribeContributorInsights",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_contributor_insights(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["ContributorInsightsStatus"], "DISABLED");

        let contributors = body["TopContributors"].as_array().unwrap();
        assert!(contributors.is_empty());
    }

    #[test]
    fn contributor_insights_disabled_table_no_counters_after_scan() {
        let svc = make_service();
        create_test_table(&svc);

        // Put items
        for key in &["alpha", "beta"] {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "test-table",
                    "Item": { "pk": { "S": key } }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Enable insights, then scan, then disable, then check counters are cleared
        let req = make_request(
            "UpdateContributorInsights",
            json!({
                "TableName": "test-table",
                "ContributorInsightsAction": "ENABLE"
            }),
        );
        svc.update_contributor_insights(&req).unwrap();

        // Scan to trigger counter collection
        let req = make_request("Scan", json!({ "TableName": "test-table" }));
        svc.scan(&req).unwrap();

        // Verify counters were collected
        let req = make_request(
            "DescribeContributorInsights",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_contributor_insights(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let contributors = body["TopContributors"].as_array().unwrap();
        assert!(
            !contributors.is_empty(),
            "counters should be non-empty while enabled"
        );

        // Disable insights (this clears counters)
        let req = make_request(
            "UpdateContributorInsights",
            json!({
                "TableName": "test-table",
                "ContributorInsightsAction": "DISABLE"
            }),
        );
        svc.update_contributor_insights(&req).unwrap();

        // Scan again -- should NOT accumulate counters since insights is disabled
        let req = make_request("Scan", json!({ "TableName": "test-table" }));
        svc.scan(&req).unwrap();

        // Verify counters are still empty
        let req = make_request(
            "DescribeContributorInsights",
            json!({ "TableName": "test-table" }),
        );
        let resp = svc.describe_contributor_insights(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let contributors = body["TopContributors"].as_array().unwrap();
        assert!(
            contributors.is_empty(),
            "counters should be empty after disabling insights"
        );
    }

    #[test]
    fn scan_pagination_with_limit() {
        let svc = make_service();
        create_test_table(&svc);

        // Insert 5 items
        for i in 0..5 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "test-table",
                    "Item": {
                        "pk": { "S": format!("item{i}") },
                        "data": { "S": format!("value{i}") }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Scan with limit=2
        let req = make_request("Scan", json!({ "TableName": "test-table", "Limit": 2 }));
        let resp = svc.scan(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 2);
        assert!(
            body["LastEvaluatedKey"].is_object(),
            "should have LastEvaluatedKey when limit < total items"
        );
        assert!(body["LastEvaluatedKey"]["pk"].is_object());

        // Page through all items
        let mut all_items: Vec<Value> = body["Items"].as_array().unwrap().clone();
        let mut lek = body["LastEvaluatedKey"].clone();

        while lek.is_object() {
            let req = make_request(
                "Scan",
                json!({
                    "TableName": "test-table",
                    "Limit": 2,
                    "ExclusiveStartKey": lek
                }),
            );
            let resp = svc.scan(&req).unwrap();
            let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
            all_items.extend(body["Items"].as_array().unwrap().iter().cloned());
            lek = body["LastEvaluatedKey"].clone();
        }

        assert_eq!(
            all_items.len(),
            5,
            "should retrieve all 5 items via pagination"
        );
    }

    #[test]
    fn scan_no_pagination_when_all_fit() {
        let svc = make_service();
        create_test_table(&svc);

        for i in 0..3 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "test-table",
                    "Item": {
                        "pk": { "S": format!("item{i}") }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Scan with limit > item count
        let req = make_request("Scan", json!({ "TableName": "test-table", "Limit": 10 }));
        let resp = svc.scan(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 3);
        assert!(
            body["LastEvaluatedKey"].is_null(),
            "should not have LastEvaluatedKey when all items fit"
        );

        // Scan without limit
        let req = make_request("Scan", json!({ "TableName": "test-table" }));
        let resp = svc.scan(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 3);
        assert!(body["LastEvaluatedKey"].is_null());
    }

    fn create_composite_table(svc: &DynamoDbService) {
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "composite-table",
                "KeySchema": [
                    { "AttributeName": "pk", "KeyType": "HASH" },
                    { "AttributeName": "sk", "KeyType": "RANGE" }
                ],
                "AttributeDefinitions": [
                    { "AttributeName": "pk", "AttributeType": "S" },
                    { "AttributeName": "sk", "AttributeType": "S" }
                ],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        );
        svc.create_table(&req).unwrap();
    }

    #[test]
    fn query_pagination_with_composite_key() {
        let svc = make_service();
        create_composite_table(&svc);

        // Insert 5 items under the same partition key
        for i in 0..5 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "composite-table",
                    "Item": {
                        "pk": { "S": "user1" },
                        "sk": { "S": format!("item{i:03}") },
                        "data": { "S": format!("value{i}") }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Query with limit=2
        let req = make_request(
            "Query",
            json!({
                "TableName": "composite-table",
                "KeyConditionExpression": "pk = :pk",
                "ExpressionAttributeValues": { ":pk": { "S": "user1" } },
                "Limit": 2
            }),
        );
        let resp = svc.query(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 2);
        assert!(body["LastEvaluatedKey"].is_object());
        assert!(body["LastEvaluatedKey"]["pk"].is_object());
        assert!(body["LastEvaluatedKey"]["sk"].is_object());

        // Page through all items
        let mut all_items: Vec<Value> = body["Items"].as_array().unwrap().clone();
        let mut lek = body["LastEvaluatedKey"].clone();

        while lek.is_object() {
            let req = make_request(
                "Query",
                json!({
                    "TableName": "composite-table",
                    "KeyConditionExpression": "pk = :pk",
                    "ExpressionAttributeValues": { ":pk": { "S": "user1" } },
                    "Limit": 2,
                    "ExclusiveStartKey": lek
                }),
            );
            let resp = svc.query(&req).unwrap();
            let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
            all_items.extend(body["Items"].as_array().unwrap().iter().cloned());
            lek = body["LastEvaluatedKey"].clone();
        }

        assert_eq!(
            all_items.len(),
            5,
            "should retrieve all 5 items via pagination"
        );

        // Verify items came back sorted by sort key
        let sks: Vec<String> = all_items
            .iter()
            .map(|item| item["sk"]["S"].as_str().unwrap().to_string())
            .collect();
        let mut sorted = sks.clone();
        sorted.sort();
        assert_eq!(sks, sorted, "items should be sorted by sort key");
    }

    #[test]
    fn query_no_pagination_when_all_fit() {
        let svc = make_service();
        create_composite_table(&svc);

        for i in 0..2 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "composite-table",
                    "Item": {
                        "pk": { "S": "user1" },
                        "sk": { "S": format!("item{i}") }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        let req = make_request(
            "Query",
            json!({
                "TableName": "composite-table",
                "KeyConditionExpression": "pk = :pk",
                "ExpressionAttributeValues": { ":pk": { "S": "user1" } },
                "Limit": 10
            }),
        );
        let resp = svc.query(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 2);
        assert!(
            body["LastEvaluatedKey"].is_null(),
            "should not have LastEvaluatedKey when all items fit"
        );
    }

    fn create_gsi_table(svc: &DynamoDbService) {
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "gsi-table",
                "KeySchema": [
                    { "AttributeName": "pk", "KeyType": "HASH" }
                ],
                "AttributeDefinitions": [
                    { "AttributeName": "pk", "AttributeType": "S" },
                    { "AttributeName": "gsi_pk", "AttributeType": "S" },
                    { "AttributeName": "gsi_sk", "AttributeType": "S" }
                ],
                "BillingMode": "PAY_PER_REQUEST",
                "GlobalSecondaryIndexes": [
                    {
                        "IndexName": "gsi-index",
                        "KeySchema": [
                            { "AttributeName": "gsi_pk", "KeyType": "HASH" },
                            { "AttributeName": "gsi_sk", "KeyType": "RANGE" }
                        ],
                        "Projection": { "ProjectionType": "ALL" }
                    }
                ]
            }),
        );
        svc.create_table(&req).unwrap();
    }

    #[test]
    fn gsi_query_last_evaluated_key_includes_table_pk() {
        let svc = make_service();
        create_gsi_table(&svc);

        // Insert 3 items with the SAME GSI key but different table PKs
        for i in 0..3 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "gsi-table",
                    "Item": {
                        "pk": { "S": format!("item{i}") },
                        "gsi_pk": { "S": "shared" },
                        "gsi_sk": { "S": "sort" }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Query GSI with Limit=1 to trigger pagination
        let req = make_request(
            "Query",
            json!({
                "TableName": "gsi-table",
                "IndexName": "gsi-index",
                "KeyConditionExpression": "gsi_pk = :v",
                "ExpressionAttributeValues": { ":v": { "S": "shared" } },
                "Limit": 1
            }),
        );
        let resp = svc.query(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 1);
        let lek = &body["LastEvaluatedKey"];
        assert!(lek.is_object(), "should have LastEvaluatedKey");
        // Must contain the index keys
        assert!(lek["gsi_pk"].is_object(), "LEK must contain gsi_pk");
        assert!(lek["gsi_sk"].is_object(), "LEK must contain gsi_sk");
        // Must also contain the table PK
        assert!(
            lek["pk"].is_object(),
            "LEK must contain table PK for GSI queries"
        );
    }

    #[test]
    fn gsi_query_pagination_returns_all_items() {
        let svc = make_service();
        create_gsi_table(&svc);

        // Insert 4 items with the SAME GSI key but different table PKs
        for i in 0..4 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "gsi-table",
                    "Item": {
                        "pk": { "S": format!("item{i:03}") },
                        "gsi_pk": { "S": "shared" },
                        "gsi_sk": { "S": "sort" }
                    }
                }),
            );
            svc.put_item(&req).unwrap();
        }

        // Paginate through all items with Limit=2
        let mut all_pks = Vec::new();
        let mut lek: Option<Value> = None;

        loop {
            let mut query = json!({
                "TableName": "gsi-table",
                "IndexName": "gsi-index",
                "KeyConditionExpression": "gsi_pk = :v",
                "ExpressionAttributeValues": { ":v": { "S": "shared" } },
                "Limit": 2
            });
            if let Some(ref start_key) = lek {
                query["ExclusiveStartKey"] = start_key.clone();
            }

            let req = make_request("Query", query);
            let resp = svc.query(&req).unwrap();
            let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();

            for item in body["Items"].as_array().unwrap() {
                let pk = item["pk"]["S"].as_str().unwrap().to_string();
                all_pks.push(pk);
            }

            if body["LastEvaluatedKey"].is_object() {
                lek = Some(body["LastEvaluatedKey"].clone());
            } else {
                break;
            }
        }

        all_pks.sort();
        assert_eq!(
            all_pks,
            vec!["item000", "item001", "item002", "item003"],
            "pagination should return all items without duplicates"
        );
    }

    fn cond_item(pairs: &[(&str, &str)]) -> HashMap<String, AttributeValue> {
        pairs
            .iter()
            .map(|(k, v)| (k.to_string(), json!({"S": v})))
            .collect()
    }

    fn cond_names(pairs: &[(&str, &str)]) -> HashMap<String, String> {
        pairs
            .iter()
            .map(|(k, v)| (k.to_string(), v.to_string()))
            .collect()
    }

    fn cond_values(pairs: &[(&str, &str)]) -> HashMap<String, Value> {
        pairs
            .iter()
            .map(|(k, v)| (k.to_string(), json!({"S": v})))
            .collect()
    }

    #[test]
    fn test_evaluate_condition_bare_not_equal() {
        let item = cond_item(&[("state", "active")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":c", "complete")]);

        assert!(evaluate_condition("#s <> :c", Some(&item), &names, &values).is_ok());

        let item2 = cond_item(&[("state", "complete")]);
        assert!(evaluate_condition("#s <> :c", Some(&item2), &names, &values).is_err());
    }

    #[test]
    fn test_evaluate_condition_parenthesized_not_equal() {
        let item = cond_item(&[("state", "active")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":c", "complete")]);

        assert!(evaluate_condition("(#s <> :c)", Some(&item), &names, &values).is_ok());
    }

    #[test]
    fn test_evaluate_condition_parenthesized_equal_mismatch() {
        let item = cond_item(&[("state", "active")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":c", "complete")]);

        assert!(evaluate_condition("(#s = :c)", Some(&item), &names, &values).is_err());
    }

    #[test]
    fn test_evaluate_condition_compound_and() {
        let item = cond_item(&[("state", "active")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":c", "complete"), (":f", "failed")]);

        // active <> complete AND active <> failed => true
        assert!(
            evaluate_condition("(#s <> :c) AND (#s <> :f)", Some(&item), &names, &values).is_ok()
        );
    }

    #[test]
    fn test_evaluate_condition_compound_and_mismatch() {
        let item = cond_item(&[("state", "inactive")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":a", "active"), (":b", "active")]);

        // inactive = active AND inactive = active => false
        assert!(
            evaluate_condition("(#s = :a) AND (#s = :b)", Some(&item), &names, &values).is_err()
        );
    }

    #[test]
    fn test_evaluate_condition_compound_or() {
        let item = cond_item(&[("state", "running")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":a", "active"), (":b", "idle")]);

        // running = active OR running = idle => false
        assert!(
            evaluate_condition("(#s = :a) OR (#s = :b)", Some(&item), &names, &values).is_err()
        );

        // running = active OR running = running => true
        let values2 = cond_values(&[(":a", "active"), (":b", "running")]);
        assert!(
            evaluate_condition("(#s = :a) OR (#s = :b)", Some(&item), &names, &values2).is_ok()
        );
    }

    #[test]
    fn test_evaluate_condition_not_operator() {
        let item = cond_item(&[("state", "active")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":c", "complete")]);

        // NOT (active = complete) => NOT false => true
        assert!(evaluate_condition("NOT (#s = :c)", Some(&item), &names, &values).is_ok());

        // NOT (active <> complete) => NOT true => false
        assert!(evaluate_condition("NOT (#s <> :c)", Some(&item), &names, &values).is_err());

        // NOT attribute_exists(#s) on existing item => NOT true => false
        assert!(
            evaluate_condition("NOT attribute_exists(#s)", Some(&item), &names, &values).is_err()
        );

        // NOT attribute_exists(#s) on missing item => NOT false => true
        assert!(evaluate_condition("NOT attribute_exists(#s)", None, &names, &values).is_ok());
    }

    #[test]
    fn test_evaluate_condition_begins_with() {
        // After unification, conditions support begins_with via
        // evaluate_single_filter_condition (previously only filters had it).
        let item = cond_item(&[("name", "fakecloud-dynamodb")]);
        let names = cond_names(&[("#n", "name")]);
        let values = cond_values(&[(":p", "fakecloud")]);

        assert!(evaluate_condition("begins_with(#n, :p)", Some(&item), &names, &values).is_ok());

        let values2 = cond_values(&[(":p", "realcloud")]);
        assert!(evaluate_condition("begins_with(#n, :p)", Some(&item), &names, &values2).is_err());
    }

    #[test]
    fn test_evaluate_condition_contains() {
        let item = cond_item(&[("tags", "alpha,beta,gamma")]);
        let names = cond_names(&[("#t", "tags")]);
        let values = cond_values(&[(":v", "beta")]);

        assert!(evaluate_condition("contains(#t, :v)", Some(&item), &names, &values).is_ok());

        let values2 = cond_values(&[(":v", "delta")]);
        assert!(evaluate_condition("contains(#t, :v)", Some(&item), &names, &values2).is_err());
    }

    #[test]
    fn test_evaluate_condition_no_existing_item() {
        // When no item exists (PutItem with condition), attribute_not_exists
        // should succeed and attribute_exists should fail.
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":v", "active")]);

        assert!(evaluate_condition("attribute_not_exists(#s)", None, &names, &values).is_ok());
        assert!(evaluate_condition("attribute_exists(#s)", None, &names, &values).is_err());
        // Comparison against missing item: None != Some(val) => true for <>
        assert!(evaluate_condition("#s <> :v", None, &names, &values).is_ok());
        // None == Some(val) => false for =
        assert!(evaluate_condition("#s = :v", None, &names, &values).is_err());
    }

    #[test]
    fn test_evaluate_filter_not_operator() {
        let item = cond_item(&[("status", "pending")]);
        let names = cond_names(&[("#s", "status")]);
        let values = cond_values(&[(":v", "pending")]);

        assert!(!evaluate_filter_expression(
            "NOT (#s = :v)",
            &item,
            &names,
            &values
        ));
        assert!(evaluate_filter_expression(
            "NOT (#s <> :v)",
            &item,
            &names,
            &values
        ));
    }

    #[test]
    fn test_evaluate_filter_expression_in_match() {
        // aws-sdk-go v2's expression.Name("state").In(Value("active"), Value("pending"))
        // emits "#0 IN (:0, :1)". Before fix: neither evaluate_single_filter_condition
        // nor evaluate_single_key_condition handled IN, so the filter leaf fell through
        // to the simple-comparison loop, hit no operators, and returned `true` — meaning
        // every item matched every IN filter regardless of value.
        let item = cond_item(&[("state", "active")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":a", "active"), (":p", "pending")]);

        assert!(
            evaluate_filter_expression("#s IN (:a, :p)", &item, &names, &values),
            "state=active should match IN (active, pending)"
        );
    }

    #[test]
    fn test_evaluate_filter_expression_in_no_match() {
        let item = cond_item(&[("state", "complete")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":a", "active"), (":p", "pending")]);

        assert!(
            !evaluate_filter_expression("#s IN (:a, :p)", &item, &names, &values),
            "state=complete should not match IN (active, pending)"
        );
    }

    #[test]
    fn test_evaluate_filter_expression_in_no_spaces() {
        // orderbot emits the raw form
        //     "#status IN (" + strings.Join(keys, ",") + ")"
        // which produces "IN (:v0,:v1,:v2)" — no spaces after commas. Must parse.
        let item = cond_item(&[("status", "shipped")]);
        let names = cond_names(&[("#s", "status")]);
        let values = cond_values(&[(":a", "pending"), (":b", "shipped"), (":c", "delivered")]);

        assert!(
            evaluate_filter_expression("#s IN (:a,:b,:c)", &item, &names, &values),
            "no-space IN list should still parse"
        );
    }

    #[test]
    fn test_evaluate_filter_expression_in_missing_attribute() {
        // A missing attribute must not match any IN list — the silent-true
        // fallthrough would wrongly accept these items.
        let item: HashMap<String, AttributeValue> = HashMap::new();
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":a", "active")]);

        assert!(
            !evaluate_filter_expression("#s IN (:a)", &item, &names, &values),
            "missing attribute should not match any IN list"
        );
    }

    #[test]
    fn test_evaluate_filter_expression_compound_in_and_eq() {
        // Shape emitted by `Name("state").In(...).And(Name("priority").Equal(...))`:
        //     "(#0 IN (:0, :1)) AND (#1 = :2)"
        // split_on_and handles the outer parens, but the IN leaf had the
        // silent-true fallthrough, so any item with priority=high would match
        // regardless of state.
        let item = cond_item(&[("state", "active"), ("priority", "high")]);
        let names = cond_names(&[("#s", "state"), ("#p", "priority")]);
        let values = cond_values(&[(":a", "active"), (":pe", "pending"), (":h", "high")]);

        assert!(
            evaluate_filter_expression("(#s IN (:a, :pe)) AND (#p = :h)", &item, &names, &values,),
            "(active IN (active, pending)) AND (high = high) should match"
        );

        let item2 = cond_item(&[("state", "complete"), ("priority", "high")]);
        assert!(
            !evaluate_filter_expression("(#s IN (:a, :pe)) AND (#p = :h)", &item2, &names, &values,),
            "(complete IN (active, pending)) AND (high = high) should not match"
        );
    }

    #[test]
    fn test_evaluate_condition_attribute_exists_with_space() {
        // aws-sdk-go v2's expression.NewBuilder emits function calls with a
        // space between the name and the opening paren:
        //     "(attribute_exists (#0)) AND ((attribute_not_exists (#1)) OR (#1 = :0))"
        // Before fix: extract_function_arg used strip_prefix("attribute_exists(")
        // with no space, so these fell through the filter leaf entirely and
        // hit evaluate_single_key_condition's silent-true fallthrough —
        // every conditional write was silently accepted.
        let item = cond_item(&[("store_id", "s-1")]);
        let names = cond_names(&[("#0", "store_id"), ("#1", "active_viewer_tab_id")]);
        let values = cond_values(&[(":0", "tab-A")]);

        // On an existing item without active_viewer_tab_id: exists(store_id)
        // is true, not_exists(active_viewer_tab_id) is true → OK.
        assert!(
            evaluate_condition(
                "(attribute_exists (#0)) AND ((attribute_not_exists (#1)) OR (#1 = :0))",
                Some(&item),
                &names,
                &values,
            )
            .is_ok(),
            "claim-lease compound on free item should succeed"
        );

        // On a missing item: exists(store_id) is false → whole AND false → Err.
        assert!(
            evaluate_condition(
                "(attribute_exists (#0)) AND ((attribute_not_exists (#1)) OR (#1 = :0))",
                None,
                &names,
                &values,
            )
            .is_err(),
            "claim-lease compound on missing item must fail attribute_exists branch"
        );

        // On an item already held by tab-B: exists ✓, not_exists ✗, #1 = :0 ✗
        // → (✓) AND ((✗) OR (✗)) → false → Err.
        let held = cond_item(&[("store_id", "s-1"), ("active_viewer_tab_id", "tab-B")]);
        assert!(
            evaluate_condition(
                "(attribute_exists (#0)) AND ((attribute_not_exists (#1)) OR (#1 = :0))",
                Some(&held),
                &names,
                &values,
            )
            .is_err(),
            "claim-lease compound on item held by another tab must fail"
        );

        // Same tab re-claiming: exists ✓, not_exists ✗, #1 = :0 ✓
        // → (✓) AND ((✗) OR (✓)) → true → Ok.
        let self_held = cond_item(&[("store_id", "s-1"), ("active_viewer_tab_id", "tab-A")]);
        assert!(
            evaluate_condition(
                "(attribute_exists (#0)) AND ((attribute_not_exists (#1)) OR (#1 = :0))",
                Some(&self_held),
                &names,
                &values,
            )
            .is_ok(),
            "same-tab re-claim must succeed"
        );
    }

    #[test]
    fn test_evaluate_condition_in_match() {
        // evaluate_condition delegates to evaluate_filter_expression, so this
        // also proves the ConditionExpression path. Before fix: silently Ok.
        let item = cond_item(&[("state", "active")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":a", "active"), (":p", "pending")]);

        assert!(
            evaluate_condition("#s IN (:a, :p)", Some(&item), &names, &values).is_ok(),
            "IN should succeed when actual value is in the list"
        );
    }

    #[test]
    fn test_evaluate_condition_in_no_match() {
        // Before fix: evaluate_condition silently returned Ok(()) for IN — any
        // conditional write was accepted regardless of actual state, the
        // opposite of what the caller asked for.
        let item = cond_item(&[("state", "complete")]);
        let names = cond_names(&[("#s", "state")]);
        let values = cond_values(&[(":a", "active"), (":p", "pending")]);

        assert!(
            evaluate_condition("#s IN (:a, :p)", Some(&item), &names, &values).is_err(),
            "IN should fail when actual value is not in the list"
        );
    }

    #[test]
    fn test_apply_update_set_list_index_replaces_existing() {
        // Shape emitted by orderbot's order-item update retry loop:
        //     UpdateExpression: fmt.Sprintf("SET #items[%d] = :item", index)
        // Before fix: apply_set_assignment called resolve_attr_name on the
        // whole "#items[0]" token, which misses the name map, and then
        // item.insert("#items[0]", :item), producing a top-level key
        // literally named "#items[0]" rather than mutating the list.
        let mut item = HashMap::new();
        item.insert(
            "items".to_string(),
            json!({"L": [
                {"M": {"sku": {"S": "OLD-A"}}},
                {"M": {"sku": {"S": "OLD-B"}}},
            ]}),
        );

        let names = cond_names(&[("#items", "items")]);
        let mut values = HashMap::new();
        values.insert(":item".to_string(), json!({"M": {"sku": {"S": "NEW-A"}}}));

        apply_update_expression(&mut item, "SET #items[0] = :item", &names, &values).unwrap();

        let items_list = item
            .get("items")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.as_array())
            .expect("items should still be a list");
        assert_eq!(items_list.len(), 2, "list length should be unchanged");
        let sku0 = items_list[0]
            .get("M")
            .and_then(|m| m.get("sku"))
            .and_then(|s| s.get("S"))
            .and_then(|s| s.as_str());
        assert_eq!(sku0, Some("NEW-A"), "index 0 should be replaced");
        let sku1 = items_list[1]
            .get("M")
            .and_then(|m| m.get("sku"))
            .and_then(|s| s.get("S"))
            .and_then(|s| s.as_str());
        assert_eq!(sku1, Some("OLD-B"), "index 1 should be untouched");

        assert!(!item.contains_key("items[0]"));
        assert!(!item.contains_key("#items[0]"));
    }

    #[test]
    fn test_apply_update_set_list_index_second_slot() {
        let mut item = HashMap::new();
        item.insert(
            "items".to_string(),
            json!({"L": [
                {"M": {"sku": {"S": "A"}}},
                {"M": {"sku": {"S": "B"}}},
                {"M": {"sku": {"S": "C"}}},
            ]}),
        );

        let names = cond_names(&[("#items", "items")]);
        let mut values = HashMap::new();
        values.insert(":item".to_string(), json!({"M": {"sku": {"S": "B-PRIME"}}}));

        apply_update_expression(&mut item, "SET #items[1] = :item", &names, &values).unwrap();

        let items_list = item
            .get("items")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.as_array())
            .unwrap();
        let skus: Vec<&str> = items_list
            .iter()
            .map(|v| {
                v.get("M")
                    .and_then(|m| m.get("sku"))
                    .and_then(|s| s.get("S"))
                    .and_then(|s| s.as_str())
                    .unwrap()
            })
            .collect();
        assert_eq!(skus, vec!["A", "B-PRIME", "C"]);
    }

    #[test]
    fn test_apply_update_set_list_index_without_name_ref() {
        // Same fix must also work when the LHS is a literal attribute name,
        // not an expression attribute name ref.
        let mut item = HashMap::new();
        item.insert(
            "tags".to_string(),
            json!({"L": [{"S": "red"}, {"S": "blue"}]}),
        );

        let names: HashMap<String, String> = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":t".to_string(), json!({"S": "green"}));

        apply_update_expression(&mut item, "SET tags[1] = :t", &names, &values).unwrap();

        let tags = item
            .get("tags")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.as_array())
            .unwrap();
        assert_eq!(tags[0].get("S").and_then(|s| s.as_str()), Some("red"));
        assert_eq!(tags[1].get("S").and_then(|s| s.as_str()), Some("green"));
    }

    #[test]
    fn test_list_append_into_empty_list() {
        // Regression: UpdateItem with `SET #0 = list_append(#0, :0)` where
        // the attribute already exists as an empty list silently no-oped.
        // Root cause: parse_update_clauses split `list_append(#0, :0)` at
        // the inner comma, so apply_set_list_append received a truncated
        // `rest` with no closing ')' and returned early without writing.
        let mut item = HashMap::new();
        item.insert("files".to_string(), json!({"L": []}));

        let names = cond_names(&[("#0", "files")]);
        let mut values = HashMap::new();
        values.insert(
            ":0".to_string(),
            json!({"L": [{"M": {"field": {"S": "value"}}}]}),
        );

        apply_update_expression(&mut item, "SET #0 = list_append(#0, :0)", &names, &values)
            .unwrap();

        let list = item
            .get("files")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.as_array())
            .expect("files should be an L-typed attribute");
        assert_eq!(list.len(), 1, "one element should have been appended");
    }

    #[test]
    fn test_list_append_into_nonempty_list() {
        // Verifies the same fix works when the existing list already has elements.
        let mut item = HashMap::new();
        item.insert(
            "files".to_string(),
            json!({"L": [{"M": {"field": {"S": "existing"}}}]}),
        );

        let names = cond_names(&[("#0", "files")]);
        let mut values = HashMap::new();
        values.insert(
            ":0".to_string(),
            json!({"L": [{"M": {"field": {"S": "new"}}}]}),
        );

        apply_update_expression(&mut item, "SET #0 = list_append(#0, :0)", &names, &values)
            .unwrap();

        let list = item
            .get("files")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.as_array())
            .expect("files should be an L-typed attribute");
        assert_eq!(list.len(), 2, "existing element plus one new element");
    }

    #[test]
    fn test_list_append_combined_with_plain_set() {
        // Verifies that a mixed expression like
        // `SET #a = list_append(#a, :v), #b = :other` correctly applies
        // both assignments after the paren-aware comma split fix.
        let mut item = HashMap::new();
        item.insert("logs".to_string(), json!({"L": []}));
        item.insert("count".to_string(), json!({"N": "0"}));

        let names = cond_names(&[("#a", "logs"), ("#b", "count")]);
        let mut values = HashMap::new();
        values.insert(":v".to_string(), json!({"L": [{"S": "entry"}]}));
        values.insert(":other".to_string(), json!({"N": "1"}));

        apply_update_expression(
            &mut item,
            "SET #a = list_append(#a, :v), #b = :other",
            &names,
            &values,
        )
        .unwrap();

        let list = item
            .get("logs")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.as_array())
            .expect("logs should be an L-typed attribute");
        assert_eq!(list.len(), 1, "one log entry appended");

        let count = item
            .get("count")
            .and_then(|v| v.get("N"))
            .and_then(|v| v.as_str())
            .expect("count should be an N-typed attribute");
        assert_eq!(count, "1", "count updated to 1");
    }

    #[test]
    fn test_unrecognized_expression_returns_false() {
        // evaluate_single_key_condition must fail-closed: an expression shape
        // it doesn't recognize should return false (reject), not true (accept).
        let item = cond_item(&[("x", "1")]);
        let names: HashMap<String, String> = HashMap::new();
        let values: HashMap<String, Value> = HashMap::new();

        assert!(
            !evaluate_single_key_condition("GARBAGE NONSENSE", &item, &names, &values),
            "unrecognized expression must return false"
        );
    }

    #[test]
    fn test_set_list_index_out_of_range_returns_error() {
        // SET list[N] where N > len must return a ValidationException,
        // not silently no-op.
        let mut item = HashMap::new();
        item.insert("items".to_string(), json!({"L": [{"S": "a"}, {"S": "b"}]}));

        let names: HashMap<String, String> = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":v".to_string(), json!({"S": "z"}));

        let result = apply_update_expression(&mut item, "SET items[5] = :v", &names, &values);
        assert!(
            result.is_err(),
            "out-of-range list index must return an error"
        );

        // List should be unchanged
        let list = item
            .get("items")
            .and_then(|v| v.get("L"))
            .and_then(|v| v.as_array())
            .unwrap();
        assert_eq!(list.len(), 2);
    }

    #[test]
    fn test_set_list_index_on_non_list_returns_error() {
        // SET attr[0] = :v where attr is a string (not a list) must return
        // a ValidationException.
        let mut item = HashMap::new();
        item.insert("name".to_string(), json!({"S": "hello"}));

        let names: HashMap<String, String> = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":v".to_string(), json!({"S": "z"}));

        let result = apply_update_expression(&mut item, "SET name[0] = :v", &names, &values);
        assert!(
            result.is_err(),
            "list index on non-list attribute must return an error"
        );
    }

    #[test]
    fn test_unrecognized_update_action_returns_error() {
        let mut item = HashMap::new();
        item.insert("name".to_string(), json!({"S": "hello"}));

        let names: HashMap<String, String> = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":bar".to_string(), json!({"S": "baz"}));

        let result = apply_update_expression(&mut item, "INVALID foo = :bar", &names, &values);
        assert!(
            result.is_err(),
            "unrecognized UpdateExpression action must return an error"
        );
        let err_msg = format!("{}", result.unwrap_err());
        assert!(
            err_msg.contains("Invalid UpdateExpression") || err_msg.contains("Syntax error"),
            "error should mention Invalid UpdateExpression, got: {err_msg}"
        );
    }

    // ── size() function tests ──────────────────────────────────────────

    #[test]
    fn test_size_string() {
        let mut item = HashMap::new();
        item.insert("name".to_string(), json!({"S": "hello"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":limit".to_string(), json!({"N": "5"}));

        assert!(evaluate_single_filter_condition(
            "size(name) = :limit",
            &item,
            &names,
            &values,
        ));
        values.insert(":limit".to_string(), json!({"N": "4"}));
        assert!(evaluate_single_filter_condition(
            "size(name) > :limit",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_size_list() {
        let mut item = HashMap::new();
        item.insert(
            "items".to_string(),
            json!({"L": [{"S": "a"}, {"S": "b"}, {"S": "c"}]}),
        );
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":limit".to_string(), json!({"N": "3"}));

        assert!(evaluate_single_filter_condition(
            "size(items) = :limit",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_size_map() {
        let mut item = HashMap::new();
        item.insert(
            "data".to_string(),
            json!({"M": {"a": {"S": "1"}, "b": {"S": "2"}}}),
        );
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":limit".to_string(), json!({"N": "2"}));

        assert!(evaluate_single_filter_condition(
            "size(data) = :limit",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_size_set() {
        let mut item = HashMap::new();
        item.insert("tags".to_string(), json!({"SS": ["a", "b", "c", "d"]}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":limit".to_string(), json!({"N": "3"}));

        assert!(evaluate_single_filter_condition(
            "size(tags) > :limit",
            &item,
            &names,
            &values,
        ));
    }

    // ── attribute_type() function tests ────────────────────────────────

    #[test]
    fn test_attribute_type_string() {
        let mut item = HashMap::new();
        item.insert("name".to_string(), json!({"S": "hello"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":t".to_string(), json!({"S": "S"}));

        assert!(evaluate_single_filter_condition(
            "attribute_type(name, :t)",
            &item,
            &names,
            &values,
        ));

        values.insert(":t".to_string(), json!({"S": "N"}));
        assert!(!evaluate_single_filter_condition(
            "attribute_type(name, :t)",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_attribute_type_number() {
        let mut item = HashMap::new();
        item.insert("age".to_string(), json!({"N": "42"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":t".to_string(), json!({"S": "N"}));

        assert!(evaluate_single_filter_condition(
            "attribute_type(age, :t)",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_attribute_type_list() {
        let mut item = HashMap::new();
        item.insert("items".to_string(), json!({"L": [{"S": "a"}]}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":t".to_string(), json!({"S": "L"}));

        assert!(evaluate_single_filter_condition(
            "attribute_type(items, :t)",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_attribute_type_map() {
        let mut item = HashMap::new();
        item.insert("data".to_string(), json!({"M": {"key": {"S": "val"}}}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":t".to_string(), json!({"S": "M"}));

        assert!(evaluate_single_filter_condition(
            "attribute_type(data, :t)",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_attribute_type_bool() {
        let mut item = HashMap::new();
        item.insert("active".to_string(), json!({"BOOL": true}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":t".to_string(), json!({"S": "BOOL"}));

        assert!(evaluate_single_filter_condition(
            "attribute_type(active, :t)",
            &item,
            &names,
            &values,
        ));
    }

    // ── begins_with rejects non-string types ───────────────────────────

    #[test]
    fn test_begins_with_rejects_number_type() {
        let mut item = HashMap::new();
        item.insert("code".to_string(), json!({"N": "12345"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":prefix".to_string(), json!({"S": "123"}));

        assert!(
            !evaluate_single_filter_condition("begins_with(code, :prefix)", &item, &names, &values,),
            "begins_with must return false for N-type attributes"
        );
    }

    #[test]
    fn test_begins_with_works_on_string_type() {
        let mut item = HashMap::new();
        item.insert("code".to_string(), json!({"S": "abc123"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":prefix".to_string(), json!({"S": "abc"}));

        assert!(evaluate_single_filter_condition(
            "begins_with(code, :prefix)",
            &item,
            &names,
            &values,
        ));
    }

    // ── contains on sets ───────────────────────────────────────────────

    #[test]
    fn test_contains_string_set() {
        let mut item = HashMap::new();
        item.insert("tags".to_string(), json!({"SS": ["red", "blue", "green"]}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"S": "blue"}));

        assert!(evaluate_single_filter_condition(
            "contains(tags, :val)",
            &item,
            &names,
            &values,
        ));

        values.insert(":val".to_string(), json!({"S": "yellow"}));
        assert!(!evaluate_single_filter_condition(
            "contains(tags, :val)",
            &item,
            &names,
            &values,
        ));
    }

    #[test]
    fn test_contains_number_set() {
        let mut item = HashMap::new();
        item.insert("scores".to_string(), json!({"NS": ["1", "2", "3"]}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"N": "2"}));

        assert!(evaluate_single_filter_condition(
            "contains(scores, :val)",
            &item,
            &names,
            &values,
        ));
    }

    // ── SET arithmetic type validation ─────────────────────────────────

    #[test]
    fn test_set_arithmetic_rejects_string_operand() {
        let mut item = HashMap::new();
        item.insert("name".to_string(), json!({"S": "hello"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"N": "1"}));

        let result = apply_update_expression(&mut item, "SET name = name + :val", &names, &values);
        assert!(
            result.is_err(),
            "arithmetic on S-type attribute must return a ValidationException"
        );
    }

    #[test]
    fn test_set_arithmetic_rejects_string_value() {
        let mut item = HashMap::new();
        item.insert("count".to_string(), json!({"N": "5"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"S": "notanumber"}));

        let result =
            apply_update_expression(&mut item, "SET count = count + :val", &names, &values);
        assert!(
            result.is_err(),
            "arithmetic with S-type value must return a ValidationException"
        );
    }

    #[test]
    fn test_set_arithmetic_valid_numbers() {
        let mut item = HashMap::new();
        item.insert("count".to_string(), json!({"N": "10"}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"N": "3"}));

        let result =
            apply_update_expression(&mut item, "SET count = count + :val", &names, &values);
        assert!(result.is_ok());
        assert_eq!(item["count"], json!({"N": "13"}));
    }

    // ── Binary Set (BS) support in ADD/DELETE ──────────────────────────

    #[test]
    fn test_add_binary_set() {
        let mut item = HashMap::new();
        item.insert("data".to_string(), json!({"BS": ["YQ==", "Yg=="]}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"BS": ["Yw==", "YQ=="]}));

        let result = apply_update_expression(&mut item, "ADD data :val", &names, &values);
        assert!(result.is_ok());
        let bs = item["data"]["BS"].as_array().unwrap();
        assert_eq!(bs.len(), 3, "should merge sets without duplicates");
        assert!(bs.contains(&json!("YQ==")));
        assert!(bs.contains(&json!("Yg==")));
        assert!(bs.contains(&json!("Yw==")));
    }

    #[test]
    fn test_delete_binary_set() {
        let mut item = HashMap::new();
        item.insert("data".to_string(), json!({"BS": ["YQ==", "Yg==", "Yw=="]}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"BS": ["Yg=="]}));

        let result = apply_update_expression(&mut item, "DELETE data :val", &names, &values);
        assert!(result.is_ok());
        let bs = item["data"]["BS"].as_array().unwrap();
        assert_eq!(bs.len(), 2);
        assert!(!bs.contains(&json!("Yg==")));
    }

    #[test]
    fn test_delete_binary_set_removes_attr_when_empty() {
        let mut item = HashMap::new();
        item.insert("data".to_string(), json!({"BS": ["YQ=="]}));
        let names = HashMap::new();
        let mut values = HashMap::new();
        values.insert(":val".to_string(), json!({"BS": ["YQ=="]}));

        let result = apply_update_expression(&mut item, "DELETE data :val", &names, &values);
        assert!(result.is_ok());
        assert!(
            !item.contains_key("data"),
            "attribute should be removed when set becomes empty"
        );
    }

    fn body_json(resp: &AwsResponse) -> Value {
        serde_json::from_slice(resp.body.expect_bytes()).unwrap()
    }

    fn expect_err(result: Result<AwsResponse, AwsServiceError>) -> AwsServiceError {
        match result {
            Err(e) => e,
            Ok(_) => panic!("expected error, got Ok"),
        }
    }

    // ── CreateTable ──

    #[test]
    fn create_table_basic() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "my-table",
                "KeySchema": [{"AttributeName": "id", "KeyType": "HASH"}],
                "AttributeDefinitions": [{"AttributeName": "id", "AttributeType": "S"}],
                "BillingMode": "PAY_PER_REQUEST",
            }),
        );
        let resp = svc.create_table(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["TableDescription"]["TableName"], "my-table");
        assert_eq!(b["TableDescription"]["TableStatus"], "ACTIVE");
        assert!(b["TableDescription"]["TableArn"].as_str().is_some());
    }

    #[test]
    fn create_table_with_sort_key_and_gsi() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "gsi-table",
                "KeySchema": [
                    {"AttributeName": "pk", "KeyType": "HASH"},
                    {"AttributeName": "sk", "KeyType": "RANGE"},
                ],
                "AttributeDefinitions": [
                    {"AttributeName": "pk", "AttributeType": "S"},
                    {"AttributeName": "sk", "AttributeType": "S"},
                    {"AttributeName": "gsi_key", "AttributeType": "N"},
                ],
                "GlobalSecondaryIndexes": [{
                    "IndexName": "gsi1",
                    "KeySchema": [{"AttributeName": "gsi_key", "KeyType": "HASH"}],
                    "Projection": {"ProjectionType": "ALL"},
                }],
                "BillingMode": "PAY_PER_REQUEST",
            }),
        );
        let resp = svc.create_table(&req).unwrap();
        let b = body_json(&resp);
        let gsi = b["TableDescription"]["GlobalSecondaryIndexes"]
            .as_array()
            .unwrap();
        assert_eq!(gsi.len(), 1);
        assert_eq!(gsi[0]["IndexName"], "gsi1");
    }

    #[test]
    fn create_table_duplicate_fails() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "test-table",
                "KeySchema": [{"AttributeName": "pk", "KeyType": "HASH"}],
                "AttributeDefinitions": [{"AttributeName": "pk", "AttributeType": "S"}],
                "BillingMode": "PAY_PER_REQUEST",
            }),
        );
        let err = expect_err(svc.create_table(&req));
        assert!(err.to_string().contains("ResourceInUseException"));
    }

    #[test]
    fn create_table_missing_key_attr_in_definitions() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "bad",
                "KeySchema": [{"AttributeName": "pk", "KeyType": "HASH"}],
                "AttributeDefinitions": [{"AttributeName": "other", "AttributeType": "S"}],
                "BillingMode": "PAY_PER_REQUEST",
            }),
        );
        let err = expect_err(svc.create_table(&req));
        assert!(err.to_string().contains("ValidationException"));
    }

    // ── DescribeTable ──

    #[test]
    fn describe_table_found() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request("DescribeTable", json!({"TableName": "test-table"}));
        let resp = svc.describe_table(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Table"]["TableName"], "test-table");
        assert_eq!(b["Table"]["TableStatus"], "ACTIVE");
    }

    #[test]
    fn describe_table_not_found() {
        let svc = make_service();
        let req = make_request("DescribeTable", json!({"TableName": "nope"}));
        let err = expect_err(svc.describe_table(&req));
        assert!(err.to_string().contains("ResourceNotFoundException"));
    }

    // ── DeleteTable ──

    #[test]
    fn delete_table_removes_table() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request("DeleteTable", json!({"TableName": "test-table"}));
        let resp = svc.delete_table(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["TableDescription"]["TableName"], "test-table");

        // Should be gone
        let req = make_request("DescribeTable", json!({"TableName": "test-table"}));
        assert!(svc.describe_table(&req).is_err());
    }

    // ── ListTables ──

    #[test]
    fn list_tables_returns_names() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request("ListTables", json!({}));
        let resp = svc.list_tables(&req).unwrap();
        let b = body_json(&resp);
        let names = b["TableNames"].as_array().unwrap();
        assert!(names.iter().any(|n| n == "test-table"));
    }

    // ── PutItem / GetItem / DeleteItem ──

    #[test]
    fn put_and_get_item() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {
                    "pk": {"S": "key1"},
                    "name": {"S": "Alice"},
                    "age": {"N": "30"},
                },
            }),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "GetItem",
            json!({
                "TableName": "test-table",
                "Key": {"pk": {"S": "key1"}},
            }),
        );
        let resp = svc.get_item(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Item"]["name"]["S"], "Alice");
        assert_eq!(b["Item"]["age"]["N"], "30");
    }

    #[test]
    fn get_item_not_found() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "GetItem",
            json!({
                "TableName": "test-table",
                "Key": {"pk": {"S": "nonexistent"}},
            }),
        );
        let resp = svc.get_item(&req).unwrap();
        let b = body_json(&resp);
        assert!(b.get("Item").is_none() || b["Item"].is_null());
    }

    #[test]
    fn delete_item_removes_item() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {"pk": {"S": "del-me"}},
            }),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "DeleteItem",
            json!({
                "TableName": "test-table",
                "Key": {"pk": {"S": "del-me"}},
            }),
        );
        svc.delete_item(&req).unwrap();

        let req = make_request(
            "GetItem",
            json!({
                "TableName": "test-table",
                "Key": {"pk": {"S": "del-me"}},
            }),
        );
        let resp = svc.get_item(&req).unwrap();
        let b = body_json(&resp);
        assert!(b.get("Item").is_none() || b["Item"].is_null());
    }

    #[test]
    fn put_item_returns_old_item() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {"pk": {"S": "overwrite"}, "v": {"N": "1"}},
            }),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {"pk": {"S": "overwrite"}, "v": {"N": "2"}},
                "ReturnValues": "ALL_OLD",
            }),
        );
        let resp = svc.put_item(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Attributes"]["v"]["N"], "1");
    }

    // ── UpdateItem ──

    #[test]
    fn update_item_set_attribute() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "PutItem",
            json!({
                "TableName": "test-table",
                "Item": {"pk": {"S": "upd"}, "count": {"N": "0"}},
            }),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "UpdateItem",
            json!({
                "TableName": "test-table",
                "Key": {"pk": {"S": "upd"}},
                "UpdateExpression": "SET #c = :val",
                "ExpressionAttributeNames": {"#c": "count"},
                "ExpressionAttributeValues": {":val": {"N": "42"}},
                "ReturnValues": "ALL_NEW",
            }),
        );
        let resp = svc.update_item(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Attributes"]["count"]["N"], "42");
    }

    // ── Query ──

    #[test]
    fn query_returns_matching_items() {
        let svc = make_service();
        // Table with hash+range
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "query-table",
                "KeySchema": [
                    {"AttributeName": "pk", "KeyType": "HASH"},
                    {"AttributeName": "sk", "KeyType": "RANGE"},
                ],
                "AttributeDefinitions": [
                    {"AttributeName": "pk", "AttributeType": "S"},
                    {"AttributeName": "sk", "AttributeType": "S"},
                ],
                "BillingMode": "PAY_PER_REQUEST",
            }),
        );
        svc.create_table(&req).unwrap();

        for i in 0..3 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "query-table",
                    "Item": {
                        "pk": {"S": "user1"},
                        "sk": {"S": format!("item-{i}")},
                    },
                }),
            );
            svc.put_item(&req).unwrap();
        }
        // Different partition
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "query-table",
                "Item": {"pk": {"S": "user2"}, "sk": {"S": "item-0"}},
            }),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "Query",
            json!({
                "TableName": "query-table",
                "KeyConditionExpression": "pk = :pk",
                "ExpressionAttributeValues": {":pk": {"S": "user1"}},
            }),
        );
        let resp = svc.query(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Count"], 3);
        assert_eq!(b["Items"].as_array().unwrap().len(), 3);
    }

    // ── Scan ──

    #[test]
    fn scan_returns_all_items() {
        let svc = make_service();
        create_test_table(&svc);

        for i in 0..5 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "test-table",
                    "Item": {"pk": {"S": format!("scan-{i}")}},
                }),
            );
            svc.put_item(&req).unwrap();
        }

        let req = make_request("Scan", json!({"TableName": "test-table"}));
        let resp = svc.scan(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Count"], 5);
    }

    // ── BatchWriteItem / BatchGetItem ──

    #[test]
    fn batch_write_and_get_items() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "BatchWriteItem",
            json!({
                "RequestItems": {
                    "test-table": [
                        {"PutRequest": {"Item": {"pk": {"S": "b1"}, "val": {"S": "v1"}}}},
                        {"PutRequest": {"Item": {"pk": {"S": "b2"}, "val": {"S": "v2"}}}},
                        {"PutRequest": {"Item": {"pk": {"S": "b3"}, "val": {"S": "v3"}}}},
                    ]
                }
            }),
        );
        let resp = svc.batch_write_item(&req).unwrap();
        let b = body_json(&resp);
        // Unprocessed should be empty
        assert!(
            b["UnprocessedItems"].as_object().unwrap().is_empty()
                || b["UnprocessedItems"]["test-table"]
                    .as_array()
                    .is_none_or(|a| a.is_empty())
        );

        // BatchGetItem
        let req = make_request(
            "BatchGetItem",
            json!({
                "RequestItems": {
                    "test-table": {
                        "Keys": [
                            {"pk": {"S": "b1"}},
                            {"pk": {"S": "b2"}},
                            {"pk": {"S": "b3"}},
                        ]
                    }
                }
            }),
        );
        let resp = svc.batch_get_item(&req).unwrap();
        let b = body_json(&resp);
        let items = b["Responses"]["test-table"].as_array().unwrap();
        assert_eq!(items.len(), 3);
    }

    // ── TransactWriteItems / TransactGetItems ──

    #[test]
    fn transact_write_and_get() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "TransactWriteItems",
            json!({
                "TransactItems": [
                    {"Put": {"TableName": "test-table", "Item": {"pk": {"S": "tx1"}}}},
                    {"Put": {"TableName": "test-table", "Item": {"pk": {"S": "tx2"}}}},
                ]
            }),
        );
        svc.transact_write_items(&req).unwrap();

        let req = make_request(
            "TransactGetItems",
            json!({
                "TransactItems": [
                    {"Get": {"TableName": "test-table", "Key": {"pk": {"S": "tx1"}}}},
                    {"Get": {"TableName": "test-table", "Key": {"pk": {"S": "tx2"}}}},
                ]
            }),
        );
        let resp = svc.transact_get_items(&req).unwrap();
        let b = body_json(&resp);
        let responses = b["Responses"].as_array().unwrap();
        assert_eq!(responses.len(), 2);
    }

    // ── TagResource / UntagResource / ListTagsOfResource ──

    #[test]
    fn tag_operations() {
        let svc = make_service();
        create_test_table(&svc);
        let arn = {
            let s = svc.state.read();
            s.default_ref()
                .tables
                .get("test-table")
                .unwrap()
                .arn
                .clone()
        };

        let req = make_request(
            "TagResource",
            json!({
                "ResourceArn": arn,
                "Tags": [{"Key": "env", "Value": "test"}],
            }),
        );
        svc.tag_resource(&req).unwrap();

        let req = make_request("ListTagsOfResource", json!({"ResourceArn": arn}));
        let resp = svc.list_tags_of_resource(&req).unwrap();
        let b = body_json(&resp);
        let tags = b["Tags"].as_array().unwrap();
        assert_eq!(tags.len(), 1);
        assert_eq!(tags[0]["Key"], "env");

        let req = make_request(
            "UntagResource",
            json!({
                "ResourceArn": arn,
                "TagKeys": ["env"],
            }),
        );
        svc.untag_resource(&req).unwrap();

        let req = make_request("ListTagsOfResource", json!({"ResourceArn": arn}));
        let resp = svc.list_tags_of_resource(&req).unwrap();
        let b = body_json(&resp);
        assert!(b["Tags"].as_array().unwrap().is_empty());
    }

    // ── UpdateTable ──

    #[test]
    fn update_table_add_gsi() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "upd-table",
                "KeySchema": [{"AttributeName": "pk", "KeyType": "HASH"}],
                "AttributeDefinitions": [
                    {"AttributeName": "pk", "AttributeType": "S"},
                    {"AttributeName": "gk", "AttributeType": "S"},
                ],
                "BillingMode": "PAY_PER_REQUEST",
            }),
        );
        svc.create_table(&req).unwrap();

        let req = make_request(
            "UpdateTable",
            json!({
                "TableName": "upd-table",
                "GlobalSecondaryIndexUpdates": [{
                    "Create": {
                        "IndexName": "new-gsi",
                        "KeySchema": [{"AttributeName": "gk", "KeyType": "HASH"}],
                        "Projection": {"ProjectionType": "ALL"},
                    }
                }],
            }),
        );
        let resp = svc.update_table(&req).unwrap();
        let b = body_json(&resp);
        let gsi = b["TableDescription"]["GlobalSecondaryIndexes"]
            .as_array()
            .unwrap();
        assert_eq!(gsi.len(), 1);
        assert_eq!(gsi[0]["IndexName"], "new-gsi");
    }

    // ── Scan with FilterExpression ──

    #[test]
    fn scan_with_filter_expression() {
        let svc = make_service();
        create_test_table(&svc);

        for i in 0..5 {
            let req = make_request(
                "PutItem",
                json!({
                    "TableName": "test-table",
                    "Item": {
                        "pk": {"S": format!("f-{i}")},
                        "status": {"S": if i % 2 == 0 { "active" } else { "inactive" }},
                    },
                }),
            );
            svc.put_item(&req).unwrap();
        }

        let req = make_request(
            "Scan",
            json!({
                "TableName": "test-table",
                "FilterExpression": "#s = :val",
                "ExpressionAttributeNames": {"#s": "status"},
                "ExpressionAttributeValues": {":val": {"S": "active"}},
            }),
        );
        let resp = svc.scan(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Count"], 3);
    }

    // ── PartiQL operations (batch.rs coverage) ──

    #[test]
    fn execute_statement_select() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "PutItem",
            json!({"TableName": "test-table", "Item": {"pk": {"S": "qs1"}, "val": {"S": "hello"}}}),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "ExecuteStatement",
            json!({"Statement": "SELECT * FROM \"test-table\" WHERE pk='qs1'"}),
        );
        let resp = svc.execute_statement(&req).unwrap();
        let b = body_json(&resp);
        assert!(!b["Items"].as_array().unwrap().is_empty());
    }

    #[test]
    fn execute_statement_insert() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "ExecuteStatement",
            json!({"Statement": "INSERT INTO \"test-table\" VALUE {'pk': 'ins1', 'data': 'val'}"}),
        );
        svc.execute_statement(&req).unwrap();

        let req = make_request(
            "GetItem",
            json!({"TableName": "test-table", "Key": {"pk": {"S": "ins1"}}}),
        );
        let resp = svc.get_item(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Item"]["data"]["S"], "val");
    }

    #[test]
    fn batch_execute_statement() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "PutItem",
            json!({"TableName": "test-table", "Item": {"pk": {"S": "be1"}}}),
        );
        svc.put_item(&req).unwrap();

        let req = make_request(
            "BatchExecuteStatement",
            json!({
                "Statements": [
                    {"Statement": "SELECT * FROM \"test-table\" WHERE pk='be1'"},
                ]
            }),
        );
        let resp = svc.batch_execute_statement(&req).unwrap();
        let b = body_json(&resp);
        assert!(b["Responses"].as_array().is_some());
    }

    #[test]
    fn execute_transaction() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "ExecuteTransaction",
            json!({
                "TransactStatements": [
                    {"Statement": "INSERT INTO \"test-table\" VALUE {'pk': 'tx1'}"},
                    {"Statement": "INSERT INTO \"test-table\" VALUE {'pk': 'tx2'}"},
                ]
            }),
        );
        svc.execute_transaction(&req).unwrap();

        let req = make_request(
            "GetItem",
            json!({"TableName": "test-table", "Key": {"pk": {"S": "tx1"}}}),
        );
        let resp = svc.get_item(&req).unwrap();
        let b = body_json(&resp);
        assert!(b["Item"].is_object());
    }

    // ── Batch write with delete ──

    #[test]
    fn batch_write_with_delete_requests() {
        let svc = make_service();
        create_test_table(&svc);

        // Put items first
        for key in &["bwd1", "bwd2", "bwd3"] {
            let req = make_request(
                "PutItem",
                json!({"TableName": "test-table", "Item": {"pk": {"S": key}}}),
            );
            svc.put_item(&req).unwrap();
        }

        // Batch delete two
        let req = make_request(
            "BatchWriteItem",
            json!({
                "RequestItems": {
                    "test-table": [
                        {"DeleteRequest": {"Key": {"pk": {"S": "bwd1"}}}},
                        {"DeleteRequest": {"Key": {"pk": {"S": "bwd2"}}}},
                    ]
                }
            }),
        );
        svc.batch_write_item(&req).unwrap();

        // bwd3 should still exist
        let req = make_request(
            "GetItem",
            json!({"TableName": "test-table", "Key": {"pk": {"S": "bwd3"}}}),
        );
        let resp = svc.get_item(&req).unwrap();
        let b = body_json(&resp);
        assert!(b["Item"].is_object());

        // bwd1 should be gone
        let req = make_request(
            "GetItem",
            json!({"TableName": "test-table", "Key": {"pk": {"S": "bwd1"}}}),
        );
        let resp = svc.get_item(&req).unwrap();
        let b = body_json(&resp);
        assert!(b.get("Item").is_none() || b["Item"].is_null());
    }

    // ── Query with sort key condition ──

    #[test]
    fn query_with_sort_key_begins_with() {
        let svc = make_service();
        // Table with hash+range
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "sk-table",
                "KeySchema": [
                    {"AttributeName": "pk", "KeyType": "HASH"},
                    {"AttributeName": "sk", "KeyType": "RANGE"},
                ],
                "AttributeDefinitions": [
                    {"AttributeName": "pk", "AttributeType": "S"},
                    {"AttributeName": "sk", "AttributeType": "S"},
                ],
                "BillingMode": "PAY_PER_REQUEST",
            }),
        );
        svc.create_table(&req).unwrap();

        for sk in &["order#001", "order#002", "profile#main"] {
            let req = make_request(
                "PutItem",
                json!({"TableName": "sk-table", "Item": {"pk": {"S": "u1"}, "sk": {"S": sk}}}),
            );
            svc.put_item(&req).unwrap();
        }

        let req = make_request(
            "Query",
            json!({
                "TableName": "sk-table",
                "KeyConditionExpression": "pk = :pk AND begins_with(sk, :prefix)",
                "ExpressionAttributeValues": {":pk": {"S": "u1"}, ":prefix": {"S": "order#"}},
            }),
        );
        let resp = svc.query(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Count"], 2);
    }

    // ── Scan with limit ──

    #[test]
    fn scan_with_limit() {
        let svc = make_service();
        create_test_table(&svc);

        for i in 0..10 {
            let req = make_request(
                "PutItem",
                json!({"TableName": "test-table", "Item": {"pk": {"S": format!("lim{i}")}}}),
            );
            svc.put_item(&req).unwrap();
        }

        let req = make_request("Scan", json!({"TableName": "test-table", "Limit": 3}));
        let resp = svc.scan(&req).unwrap();
        let b = body_json(&resp);
        assert_eq!(b["Count"], 3);
        assert!(b["LastEvaluatedKey"].is_object());
    }

    // ── Error branches ──

    #[test]
    fn batch_get_item_table_not_found() {
        let svc = make_service();
        let req = make_request(
            "BatchGetItem",
            json!({"RequestItems": {"ghost": {"Keys": [{"pk": {"S": "k"}}]}}}),
        );
        assert!(svc.batch_get_item(&req).is_err());
    }

    #[test]
    fn batch_write_item_table_not_found() {
        let svc = make_service();
        let req = make_request(
            "BatchWriteItem",
            json!({"RequestItems": {"ghost": [{"PutRequest": {"Item": {"pk": {"S": "k"}}}}]}}),
        );
        assert!(svc.batch_write_item(&req).is_err());
    }

    // ── Global tables ──

    #[test]
    fn create_and_describe_global_table() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "CreateGlobalTable",
            json!({
                "GlobalTableName": "test-table",
                "ReplicationGroup": [{"RegionName": "us-east-1"}, {"RegionName": "eu-west-1"}],
            }),
        );
        svc.create_global_table(&req).unwrap();

        let req = make_request(
            "DescribeGlobalTable",
            json!({"GlobalTableName": "test-table"}),
        );
        let resp = svc.describe_global_table(&req).unwrap();
        let b = body_json(&resp);
        assert!(b["GlobalTableDescription"].is_object());
    }

    #[test]
    fn list_global_tables() {
        let svc = make_service();
        let req = make_request("ListGlobalTables", json!({}));
        let resp = svc.list_global_tables(&req).unwrap();
        let b = body_json(&resp);
        assert!(b["GlobalTables"].as_array().is_some());
    }

    // ── Backup operations ──

    #[test]
    fn create_and_list_backups() {
        let svc = make_service();
        create_test_table(&svc);

        let req = make_request(
            "CreateBackup",
            json!({"TableName": "test-table", "BackupName": "bak1"}),
        );
        let resp = svc.create_backup(&req).unwrap();
        let b = body_json(&resp);
        assert!(b["BackupDetails"]["BackupArn"].as_str().is_some());

        let req = make_request("ListBackups", json!({}));
        let resp = svc.list_backups(&req).unwrap();
        let b = body_json(&resp);
        assert!(!b["BackupSummaries"].as_array().unwrap().is_empty());
    }

    // ── Import/Export ──

    #[test]
    fn describe_import_not_found() {
        let svc = make_service();
        let req = make_request(
            "DescribeImport",
            json!({"ImportArn": "arn:aws:dynamodb:us-east-1:123:table/t/import/ghost"}),
        );
        assert!(svc.describe_import(&req).is_err());
    }

    #[test]
    fn describe_export_not_found() {
        let svc = make_service();
        let req = make_request(
            "DescribeExport",
            json!({"ExportArn": "arn:aws:dynamodb:us-east-1:123:table/t/export/ghost"}),
        );
        assert!(svc.describe_export(&req).is_err());
    }

    // ── tables.rs error branches ──

    #[test]
    fn create_table_missing_name_errors() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "AttributeDefinitions": [{"AttributeName": "k", "AttributeType": "S"}],
                "KeySchema": [{"AttributeName": "k", "KeyType": "HASH"}],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        );
        assert!(svc.create_table(&req).is_err());
    }

    #[test]
    fn create_table_duplicate_errors() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "dup",
                "AttributeDefinitions": [{"AttributeName": "k", "AttributeType": "S"}],
                "KeySchema": [{"AttributeName": "k", "KeyType": "HASH"}],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        );
        svc.create_table(&req).unwrap();
        assert!(svc.create_table(&req).is_err());
    }

    #[test]
    fn delete_table_missing_name_errors() {
        let svc = make_service();
        let req = make_request("DeleteTable", json!({}));
        assert!(svc.delete_table(&req).is_err());
    }

    #[test]
    fn delete_table_not_found_errors() {
        let svc = make_service();
        let req = make_request("DeleteTable", json!({"TableName": "ghost"}));
        assert!(svc.delete_table(&req).is_err());
    }

    #[test]
    fn describe_table_missing_name_errors() {
        let svc = make_service();
        let req = make_request("DescribeTable", json!({}));
        assert!(svc.describe_table(&req).is_err());
    }

    #[test]
    fn describe_table_not_found_errors() {
        let svc = make_service();
        let req = make_request("DescribeTable", json!({"TableName": "ghost"}));
        assert!(svc.describe_table(&req).is_err());
    }

    #[test]
    fn update_table_missing_name_errors() {
        let svc = make_service();
        let req = make_request("UpdateTable", json!({}));
        assert!(svc.update_table(&req).is_err());
    }

    #[test]
    fn update_table_not_found_errors() {
        let svc = make_service();
        let req = make_request("UpdateTable", json!({"TableName": "ghost"}));
        assert!(svc.update_table(&req).is_err());
    }

    #[test]
    fn list_tables_pagination() {
        let svc = make_service();
        for i in 0..5 {
            let req = make_request(
                "CreateTable",
                json!({
                    "TableName": format!("pt{i}"),
                    "AttributeDefinitions": [{"AttributeName": "k", "AttributeType": "S"}],
                    "KeySchema": [{"AttributeName": "k", "KeyType": "HASH"}],
                    "BillingMode": "PAY_PER_REQUEST"
                }),
            );
            svc.create_table(&req).unwrap();
        }
        let req = make_request("ListTables", json!({"Limit": 2}));
        let resp = svc.list_tables(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["TableNames"].as_array().unwrap().len(), 2);
        assert!(body["LastEvaluatedTableName"].is_string());
    }

    #[test]
    fn list_tables_start_exclusive() {
        let svc = make_service();
        for i in 0..3 {
            let req = make_request(
                "CreateTable",
                json!({
                    "TableName": format!("pt{i}"),
                    "AttributeDefinitions": [{"AttributeName": "k", "AttributeType": "S"}],
                    "KeySchema": [{"AttributeName": "k", "KeyType": "HASH"}],
                    "BillingMode": "PAY_PER_REQUEST"
                }),
            );
            svc.create_table(&req).unwrap();
        }
        let req = make_request("ListTables", json!({"ExclusiveStartTableName": "pt0"}));
        let resp = svc.list_tables(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        let names = body["TableNames"].as_array().unwrap();
        assert!(!names.iter().any(|n| n == "pt0"));
    }

    #[test]
    fn update_time_to_live_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "UpdateTimeToLive",
            json!({
                "TableName": "ghost",
                "TimeToLiveSpecification": {"Enabled": true, "AttributeName": "ttl"}
            }),
        );
        assert!(svc.update_time_to_live(&req).is_err());
    }

    #[test]
    fn describe_time_to_live_unknown_table_errors() {
        let svc = make_service();
        let req = make_request("DescribeTimeToLive", json!({"TableName": "ghost"}));
        assert!(svc.describe_time_to_live(&req).is_err());
    }

    // ── resource policy ──

    #[test]
    fn put_resource_policy_missing_policy_errors() {
        let svc = make_service();
        let req = make_request(
            "CreateTable",
            json!({
                "TableName": "rp",
                "AttributeDefinitions": [{"AttributeName": "k", "AttributeType": "S"}],
                "KeySchema": [{"AttributeName": "k", "KeyType": "HASH"}],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        );
        svc.create_table(&req).unwrap();
        let req = make_request(
            "PutResourcePolicy",
            json!({"ResourceArn": "arn:aws:dynamodb:us-east-1:123456789012:table/rp"}),
        );
        assert!(svc.put_resource_policy(&req).is_err());
    }

    #[test]
    fn get_resource_policy_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "GetResourcePolicy",
            json!({"ResourceArn": "arn:aws:dynamodb:us-east-1:123456789012:table/ghost"}),
        );
        assert!(svc.get_resource_policy(&req).is_err());
    }

    // ── tags ──

    #[test]
    fn tag_resource_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "TagResource",
            json!({
                "ResourceArn": "arn:aws:dynamodb:us-east-1:123456789012:table/ghost",
                "Tags": [{"Key": "k", "Value": "v"}]
            }),
        );
        assert!(svc.tag_resource(&req).is_err());
    }

    #[test]
    fn list_tags_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "ListTagsOfResource",
            json!({"ResourceArn": "arn:aws:dynamodb:us-east-1:123456789012:table/ghost"}),
        );
        assert!(svc.list_tags_of_resource(&req).is_err());
    }

    // ── backups ──

    #[test]
    fn create_backup_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "CreateBackup",
            json!({"TableName": "ghost", "BackupName": "b1"}),
        );
        assert!(svc.create_backup(&req).is_err());
    }

    #[test]
    fn delete_backup_not_found_errors() {
        let svc = make_service();
        let req = make_request(
            "DeleteBackup",
            json!({"BackupArn": "arn:aws:dynamodb:us-east-1:123:table/t/backup/ghost"}),
        );
        assert!(svc.delete_backup(&req).is_err());
    }

    #[test]
    fn describe_backup_not_found_errors() {
        let svc = make_service();
        let req = make_request(
            "DescribeBackup",
            json!({"BackupArn": "arn:aws:dynamodb:us-east-1:123:table/t/backup/ghost"}),
        );
        assert!(svc.describe_backup(&req).is_err());
    }

    #[test]
    fn restore_table_from_backup_not_found_errors() {
        let svc = make_service();
        let req = make_request(
            "RestoreTableFromBackup",
            json!({
                "TargetTableName": "restored",
                "BackupArn": "arn:aws:dynamodb:us-east-1:123:table/t/backup/ghost"
            }),
        );
        assert!(svc.restore_table_from_backup(&req).is_err());
    }

    #[test]
    fn update_continuous_backups_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "UpdateContinuousBackups",
            json!({
                "TableName": "ghost",
                "PointInTimeRecoverySpecification": {"PointInTimeRecoveryEnabled": true}
            }),
        );
        assert!(svc.update_continuous_backups(&req).is_err());
    }

    // ── items.rs: put_item error branches ──

    #[test]
    fn put_item_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "ghost",
                "Item": {"k": {"S": "v"}}
            }),
        );
        assert!(svc.put_item(&req).is_err());
    }

    #[test]
    fn put_item_missing_key_attribute_errors() {
        let svc = make_service();
        svc.create_table(&make_request(
            "CreateTable",
            json!({
                "TableName": "pmk",
                "AttributeDefinitions": [{"AttributeName": "k", "AttributeType": "S"}],
                "KeySchema": [{"AttributeName": "k", "KeyType": "HASH"}],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        ))
        .unwrap();
        let req = make_request(
            "PutItem",
            json!({
                "TableName": "pmk",
                "Item": {"other": {"S": "v"}}
            }),
        );
        assert!(svc.put_item(&req).is_err());
    }

    #[test]
    fn get_item_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "GetItem",
            json!({"TableName": "ghost", "Key": {"k": {"S": "1"}}}),
        );
        assert!(svc.get_item(&req).is_err());
    }

    #[test]
    fn delete_item_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "DeleteItem",
            json!({"TableName": "ghost", "Key": {"k": {"S": "1"}}}),
        );
        assert!(svc.delete_item(&req).is_err());
    }

    #[test]
    fn update_item_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "UpdateItem",
            json!({
                "TableName": "ghost",
                "Key": {"k": {"S": "1"}},
                "UpdateExpression": "SET x = :v",
                "ExpressionAttributeValues": {":v": {"S": "val"}}
            }),
        );
        assert!(svc.update_item(&req).is_err());
    }

    #[test]
    fn query_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "Query",
            json!({
                "TableName": "ghost",
                "KeyConditionExpression": "k = :v",
                "ExpressionAttributeValues": {":v": {"S": "x"}}
            }),
        );
        assert!(svc.query(&req).is_err());
    }

    #[test]
    fn scan_unknown_table_errors() {
        let svc = make_service();
        let req = make_request("Scan", json!({"TableName": "ghost"}));
        assert!(svc.scan(&req).is_err());
    }

    #[test]
    fn scan_with_limit_returns_ok() {
        let svc = make_service();
        svc.create_table(&make_request(
            "CreateTable",
            json!({
                "TableName": "slt",
                "AttributeDefinitions": [{"AttributeName": "k", "AttributeType": "S"}],
                "KeySchema": [{"AttributeName": "k", "KeyType": "HASH"}],
                "BillingMode": "PAY_PER_REQUEST"
            }),
        ))
        .unwrap();
        for i in 0..5 {
            svc.put_item(&make_request(
                "PutItem",
                json!({
                    "TableName": "slt",
                    "Item": {"k": {"S": format!("key-{i}")}}
                }),
            ))
            .unwrap();
        }
        let req = make_request("Scan", json!({"TableName": "slt", "Limit": 2}));
        let resp = svc.scan(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert_eq!(body["Count"], 2);
    }

    #[test]
    fn batch_get_item_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "BatchGetItem",
            json!({
                "RequestItems": {
                    "ghost": {"Keys": [{"k": {"S": "1"}}]}
                }
            }),
        );
        assert!(svc.batch_get_item(&req).is_err());
    }

    #[test]
    fn batch_write_item_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "BatchWriteItem",
            json!({
                "RequestItems": {
                    "ghost": [{"PutRequest": {"Item": {"k": {"S": "1"}}}}]
                }
            }),
        );
        assert!(svc.batch_write_item(&req).is_err());
    }

    #[test]
    fn transact_write_items_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "TransactWriteItems",
            json!({
                "TransactItems": [{
                    "Put": {"TableName": "ghost", "Item": {"k": {"S": "1"}}}
                }]
            }),
        );
        assert!(svc.transact_write_items(&req).is_err());
    }

    #[test]
    fn transact_get_items_unknown_table_errors() {
        let svc = make_service();
        let req = make_request(
            "TransactGetItems",
            json!({
                "TransactItems": [{
                    "Get": {"TableName": "ghost", "Key": {"k": {"S": "1"}}}
                }]
            }),
        );
        assert!(svc.transact_get_items(&req).is_err());
    }

    #[test]
    fn describe_global_table_not_found_b() {
        let svc = make_service();
        let req = make_request("DescribeGlobalTable", json!({"GlobalTableName": "ghost"}));
        assert!(svc.describe_global_table(&req).is_err());
    }

    #[test]
    fn list_global_tables_empty_ok() {
        let svc = make_service();
        let req = make_request("ListGlobalTables", json!({}));
        let resp = svc.list_global_tables(&req).unwrap();
        let body: Value = serde_json::from_slice(resp.body.expect_bytes()).unwrap();
        assert!(body["GlobalTables"].is_array());
    }

    #[test]
    fn split_on_top_level_keyword_between_swallows_inner_and() {
        let parts = split_on_top_level_keyword("x = :a AND y BETWEEN :lo AND :hi", "AND");
        assert_eq!(
            parts.len(),
            2,
            "BETWEEN's inner AND must not split; got parts = {parts:?}"
        );
    }

    #[test]
    fn split_on_top_level_keyword_between_nested_parens() {
        let parts = split_on_top_level_keyword("(x = :a) AND (y BETWEEN :lo AND :hi)", "AND");
        assert_eq!(parts.len(), 2);
    }

    #[test]
    fn split_on_top_level_keyword_whitespace_variants() {
        for expr in [
            "x = :a AND y = :b",
            "x=:a AND y=:b",
            "  x = :a   AND   y = :b  ",
            "x\t=\t:a\tAND\ty\t=\t:b",
            "x = :a\nAND\ny = :b",
        ] {
            let parts = split_on_top_level_keyword(expr, "AND");
            assert_eq!(parts.len(), 2, "whitespace variant failed: {expr:?}");
        }
    }

    #[test]
    fn split_on_top_level_keyword_case_insensitive() {
        let parts = split_on_top_level_keyword("x = :a and y = :b", "AND");
        assert_eq!(parts.len(), 2);
        let parts = split_on_top_level_keyword("x = :a OR y = :b", "OR");
        assert_eq!(parts.len(), 2);
    }

    #[test]
    fn split_on_top_level_keyword_does_not_match_inside_identifiers() {
        // `land` contains "AND" but isn't word-bounded — must not split.
        let parts = split_on_top_level_keyword("land = :a", "AND");
        assert_eq!(parts.len(), 1);
    }
}