azure_data_cosmos_driver 0.2.0

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

//! Data models for Cosmos DB management and metadata operations.
//!
//! This module contains types representing Cosmos DB resources (accounts, databases, containers)
//! and their supporting structures. These are for **metadata/management operations only**.
//!
//! **Important**: This module does NOT contain data plane item/document types.
//! The driver is schema-agnostic - data plane operations work with raw bytes (`&[u8]`).

mod account_reference;
mod activity_id;
mod connection_string;
mod consistency_level;
pub(crate) mod cosmos_headers;
mod cosmos_operation;
mod cosmos_resource_reference;
mod cosmos_response;
mod cosmos_status;
mod etag;
mod finite_f64;
pub(crate) use finite_f64::FiniteF64;
mod partition_key;
mod request_charge;
pub(crate) mod resource_id;
mod resource_reference;
mod session_token_segment;
mod user_agent;
pub(crate) mod vector_session_token;
pub(crate) use cosmos_headers::request_header_names;
#[allow(dead_code)]
pub mod effective_partition_key;
#[allow(dead_code)]
mod murmur_hash;
#[allow(dead_code)]
pub mod partition_key_range;
#[allow(dead_code)]
pub(crate) mod range;

pub use account_reference::{AccountReference, AccountReferenceBuilder, Credential};
pub use activity_id::ActivityId;
pub use connection_string::ConnectionString;
pub(crate) use consistency_level::DefaultConsistencyLevel;
pub use cosmos_headers::{
    AutoscaleAutoUpgradePolicy, AutoscaleThroughputPolicy, CosmosRequestHeaders,
    CosmosResponseHeaders, OfferAutoscaleSettings,
};
pub use cosmos_operation::CosmosOperation;
pub use cosmos_resource_reference::CosmosResourceReference;
pub(crate) use cosmos_resource_reference::ResourcePaths;
pub use cosmos_response::CosmosResponse;
pub use cosmos_status::CosmosStatus;
pub use cosmos_status::SubStatusCode;
pub use etag::{ETag, Precondition};
pub use partition_key::{PartitionKey, PartitionKeyValue};
pub use request_charge::RequestCharge;
pub use resource_reference::ContainerReference;
pub use resource_reference::{DatabaseReference, ItemReference};
pub use resource_reference::{
    PartitionKeyRangeReference, StoredProcedureReference, TriggerReference, UdfReference,
};
pub use session_token_segment::SessionTokenSegment;
pub use user_agent::UserAgent;

pub(crate) use account_reference::AccountEndpoint;

use serde::{Deserialize, Serialize};
use std::borrow::Cow;

/// Properties of a Cosmos DB database.
///
/// Returned by database read/query operations and used when creating databases.
#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq)]
#[non_exhaustive]
#[serde(rename_all = "camelCase")]
pub(crate) struct DatabaseProperties {
    /// Unique identifier for the database within the account.
    pub id: Cow<'static, str>,

    /// System-managed properties (e.g., _rid, _ts, _etag).
    #[serde(flatten)]
    pub system_properties: SystemProperties,
}

impl DatabaseProperties {}

/// Properties of a Cosmos DB container.
///
/// Returned by container read/query operations and used when creating/updating containers.
#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq)]
#[non_exhaustive]
#[serde(rename_all = "camelCase")]
pub(crate) struct ContainerProperties {
    /// Unique identifier for the container within the database.
    pub id: Cow<'static, str>,

    /// Partition key definition specifying the partition key path(s).
    pub partition_key: PartitionKeyDefinition,

    /// System-managed properties (e.g., _rid, _ts, _etag).
    #[serde(flatten)]
    pub system_properties: SystemProperties,
}

/// Partition key definition for a container.
///
/// Specifies the JSON path(s) used for partitioning data across physical partitions.
#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq)]
#[non_exhaustive]
#[serde(rename_all = "camelCase")]
pub struct PartitionKeyDefinition {
    /// List of partition key paths (e.g., `["/tenantId"]` for single partition key).
    paths: Vec<Cow<'static, str>>,

    /// Partition key kind (Hash is the standard).
    #[serde(default)]
    kind: PartitionKeyKind,

    /// Partition key version (1 for single, 2 for hierarchical).
    #[serde(default = "default_pk_version")]
    version: PartitionKeyVersion,
}

impl PartitionKeyDefinition {
    /// Creates a new [`PartitionKeyDefinition`] from the provided partition key paths.
    ///
    /// The [`PartitionKeyKind`] is inferred automatically:
    /// - [`PartitionKeyKind::Hash`] for a single path
    /// - [`PartitionKeyKind::MultiHash`] for multiple paths (hierarchical partition keys)
    ///
    /// The version defaults to [`PartitionKeyVersion::V2`].
    pub fn new(paths: Vec<Cow<'static, str>>) -> Self {
        let kind = if paths.len() > 1 {
            PartitionKeyKind::MultiHash
        } else {
            PartitionKeyKind::Hash
        };
        Self {
            paths,
            kind,
            version: PartitionKeyVersion::V2,
        }
    }

    /// Returns the partition key paths.
    pub fn paths(&self) -> &[Cow<'static, str>] {
        &self.paths
    }

    /// Returns the partition key version.
    pub fn version(&self) -> PartitionKeyVersion {
        self.version
    }

    /// Returns the partition key kind.
    pub fn kind(&self) -> PartitionKeyKind {
        self.kind
    }
}

/// Creates a single-path [`PartitionKeyDefinition`] from a string slice.
///
/// # Examples
///
/// ```
/// use azure_data_cosmos_driver::models::PartitionKeyDefinition;
///
/// let pk_def: PartitionKeyDefinition = "/tenantId".into();
/// assert_eq!(pk_def.paths()[0].as_ref(), "/tenantId");
/// ```
impl From<&str> for PartitionKeyDefinition {
    fn from(value: &str) -> Self {
        Self::new(vec![Cow::from(value.to_string())])
    }
}

/// Creates a single-path [`PartitionKeyDefinition`] from a [`String`].
impl From<String> for PartitionKeyDefinition {
    fn from(value: String) -> Self {
        Self::new(vec![Cow::from(value)])
    }
}

/// Creates a two-path (hierarchical) [`PartitionKeyDefinition`] from a tuple.
///
/// # Examples
///
/// ```
/// use azure_data_cosmos_driver::models::{PartitionKeyDefinition, PartitionKeyKind};
///
/// let pk_def: PartitionKeyDefinition = ("/tenantId", "/userId").into();
/// assert_eq!(pk_def.paths().len(), 2);
/// assert_eq!(pk_def.kind(), PartitionKeyKind::MultiHash);
/// ```
impl<S1: Into<String>, S2: Into<String>> From<(S1, S2)> for PartitionKeyDefinition {
    fn from(value: (S1, S2)) -> Self {
        Self::new(vec![Cow::from(value.0.into()), Cow::from(value.1.into())])
    }
}

/// Creates a three-path (hierarchical) [`PartitionKeyDefinition`] from a tuple.
impl<S1: Into<String>, S2: Into<String>, S3: Into<String>> From<(S1, S2, S3)>
    for PartitionKeyDefinition
{
    fn from(value: (S1, S2, S3)) -> Self {
        Self::new(vec![
            Cow::from(value.0.into()),
            Cow::from(value.1.into()),
            Cow::from(value.2.into()),
        ])
    }
}

fn default_pk_version() -> PartitionKeyVersion {
    PartitionKeyVersion::V2
}

/// Partition key version.
///
/// Cosmos DB uses numeric wire values for partition key version:
/// - `1` -> `V1`
/// - `2` -> `V2`
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(try_from = "u32", into = "u32")]
pub enum PartitionKeyVersion {
    /// Partition key version 1.
    V1,
    /// Partition key version 2.
    V2,
}

impl PartitionKeyVersion {
    /// Returns the wire value used by Cosmos DB.
    pub const fn value(self) -> u32 {
        match self {
            PartitionKeyVersion::V1 => 1,
            PartitionKeyVersion::V2 => 2,
        }
    }
}

impl TryFrom<u32> for PartitionKeyVersion {
    type Error = &'static str;

    fn try_from(value: u32) -> Result<Self, Self::Error> {
        match value {
            1 => Ok(Self::V1),
            2 => Ok(Self::V2),
            _ => Err("invalid partition key version; expected 1 or 2"),
        }
    }
}

impl From<PartitionKeyVersion> for u32 {
    fn from(version: PartitionKeyVersion) -> Self {
        version.value()
    }
}

/// Partition key kind.
#[derive(Clone, Copy, Debug, Default, Deserialize, Serialize, PartialEq, Eq)]
#[non_exhaustive]
pub enum PartitionKeyKind {
    /// Hash partitioning (standard, single partition key path).
    #[default]
    Hash,
    /// Multi-path (hierarchical) partition keys.
    MultiHash,
    /// Range partitioning (legacy).
    Range,
}

/// System-managed properties present on all Cosmos DB resources.
#[derive(Clone, Default, Debug, Deserialize, Serialize, PartialEq, Eq)]
#[non_exhaustive]
pub(crate) struct SystemProperties {
    /// Resource ID (internal identifier).
    #[serde(rename = "_rid", skip_serializing_if = "Option::is_none")]
    pub rid: Option<String>,

    /// Resource timestamp (last modified time in Unix epoch seconds).
    #[serde(rename = "_ts", skip_serializing_if = "Option::is_none")]
    pub ts: Option<u64>,

    /// ETag for optimistic concurrency control.
    #[serde(rename = "_etag", skip_serializing_if = "Option::is_none")]
    pub etag: Option<String>,
}

/// The type of resource being operated on.
///
/// Used to identify the Cosmos DB resource category for routing and authorization.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum ResourceType {
    /// Database account (root level).
    DatabaseAccount,
    /// A database within an account.
    Database,
    /// A container (collection) within a database.
    DocumentCollection,
    /// A document (item) within a container.
    Document,
    /// A stored procedure within a container.
    StoredProcedure,
    /// A trigger within a container.
    Trigger,
    /// A user-defined function within a container.
    UserDefinedFunction,
    /// A partition key range within a container.
    PartitionKeyRange,
    /// An offer (throughput configuration).
    Offer,
}

impl ResourceType {
    /// Returns the string representation of this resource type.
    pub fn as_str(self) -> &'static str {
        match self {
            ResourceType::DatabaseAccount => "database_account",
            ResourceType::Database => "database",
            ResourceType::DocumentCollection => "document_collection",
            ResourceType::Document => "document",
            ResourceType::StoredProcedure => "stored_procedure",
            ResourceType::Trigger => "trigger",
            ResourceType::UserDefinedFunction => "user_defined_function",
            ResourceType::PartitionKeyRange => "partition_key_range",
            ResourceType::Offer => "offer",
        }
    }

    /// Returns the URL path segment for this resource type.
    pub fn path_segment(self) -> &'static str {
        match self {
            ResourceType::DatabaseAccount => "",
            ResourceType::Database => "dbs",
            ResourceType::DocumentCollection => "colls",
            ResourceType::Document => "docs",
            ResourceType::StoredProcedure => "sprocs",
            ResourceType::Trigger => "triggers",
            ResourceType::UserDefinedFunction => "udfs",
            ResourceType::PartitionKeyRange => "pkranges",
            ResourceType::Offer => "offers",
        }
    }

    /// Returns true if this resource type is metadata (not data plane items).
    pub fn is_metadata(self) -> bool {
        matches!(
            self,
            ResourceType::DatabaseAccount
                | ResourceType::Database
                | ResourceType::DocumentCollection
                | ResourceType::PartitionKeyRange
                | ResourceType::Offer
        )
    }

    /// Returns true if this resource type requires a container reference.
    pub fn requires_container(self) -> bool {
        matches!(
            self,
            ResourceType::Document
                | ResourceType::DocumentCollection
                | ResourceType::StoredProcedure
                | ResourceType::Trigger
                | ResourceType::UserDefinedFunction
                | ResourceType::PartitionKeyRange
        )
    }

    /// Returns true if this resource type requires a database reference.
    pub fn requires_database(self) -> bool {
        matches!(
            self,
            ResourceType::Database
                | ResourceType::DocumentCollection
                | ResourceType::Document
                | ResourceType::StoredProcedure
                | ResourceType::Trigger
                | ResourceType::UserDefinedFunction
                | ResourceType::PartitionKeyRange
        )
    }
}

impl std::fmt::Display for ResourceType {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl AsRef<str> for ResourceType {
    fn as_ref(&self) -> &str {
        self.as_str()
    }
}

impl std::str::FromStr for ResourceType {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s.to_lowercase().replace(' ', "_").as_str() {
            "database_account" | "account" => Ok(ResourceType::DatabaseAccount),
            "database" | "db" => Ok(ResourceType::Database),
            "document_collection" | "collection" | "container" => {
                Ok(ResourceType::DocumentCollection)
            }
            "document" | "item" => Ok(ResourceType::Document),
            "stored_procedure" | "sproc" => Ok(ResourceType::StoredProcedure),
            "trigger" => Ok(ResourceType::Trigger),
            "user_defined_function" | "udf" => Ok(ResourceType::UserDefinedFunction),
            "partition_key_range" | "pkrange" => Ok(ResourceType::PartitionKeyRange),
            "offer" => Ok(ResourceType::Offer),
            _ => Err(format!(
                "Unknown resource type: '{}'. Expected one of: database_account, database, \
                 document_collection, document, stored_procedure, trigger, \
                 user_defined_function, partition_key_range, offer",
                s
            )),
        }
    }
}

/// The type of operation being performed.
///
/// Used to determine HTTP method, retry behavior, and authorization requirements.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum OperationType {
    /// Create a new resource.
    Create,
    /// Read an existing resource.
    Read,
    /// Read a feed (list) of resources.
    ReadFeed,
    /// Replace an existing resource.
    Replace,
    /// Delete a resource.
    Delete,
    /// Create or replace a resource.
    Upsert,
    /// Execute a query.
    Query,
    /// Execute a SQL query.
    SqlQuery,
    /// Get a query plan.
    QueryPlan,
    /// Execute a batch operation.
    Batch,
    /// Check resource existence (HEAD).
    Head,
    /// Check feed existence (HEAD).
    HeadFeed,
    /// Execute a stored procedure.
    Execute,
}

impl OperationType {
    /// Returns the HTTP method for this operation type.
    pub fn http_method(self) -> azure_core::http::Method {
        use azure_core::http::Method;
        match self {
            OperationType::Create
            | OperationType::Upsert
            | OperationType::Query
            | OperationType::SqlQuery
            | OperationType::Batch
            | OperationType::QueryPlan
            | OperationType::Execute => Method::Post,
            OperationType::Delete => Method::Delete,
            OperationType::Read => Method::Get,
            OperationType::ReadFeed => Method::Get,
            OperationType::Replace => Method::Put,
            OperationType::Head | OperationType::HeadFeed => Method::Head,
        }
    }

    /// Returns true if the operation does not modify server state.
    pub fn is_read_only(self) -> bool {
        matches!(
            self,
            OperationType::Read
                | OperationType::ReadFeed
                | OperationType::Query
                | OperationType::SqlQuery
                | OperationType::QueryPlan
                | OperationType::Head
                | OperationType::HeadFeed
        )
    }

    /// Returns true if the operation is idempotent (safe to retry).
    pub fn is_idempotent(self) -> bool {
        matches!(
            self,
            OperationType::Read
                | OperationType::ReadFeed
                | OperationType::Query
                | OperationType::SqlQuery
                | OperationType::QueryPlan
                | OperationType::Head
                | OperationType::HeadFeed
                | OperationType::Replace
                | OperationType::Delete
        )
    }

    /// Returns the string representation of this operation type.
    pub fn as_str(self) -> &'static str {
        match self {
            OperationType::Create => "create",
            OperationType::Read => "read",
            OperationType::ReadFeed => "read_feed",
            OperationType::Replace => "replace",
            OperationType::Delete => "delete",
            OperationType::Upsert => "upsert",
            OperationType::Query => "query",
            OperationType::SqlQuery => "sql_query",
            OperationType::QueryPlan => "query_plan",
            OperationType::Batch => "batch",
            OperationType::Head => "head",
            OperationType::HeadFeed => "head_feed",
            OperationType::Execute => "execute",
        }
    }
}

impl std::fmt::Display for OperationType {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl AsRef<str> for OperationType {
    fn as_ref(&self) -> &str {
        self.as_str()
    }
}

/// A session token for maintaining session consistency.
///
/// Session tokens track the logical sequence number of operations, enabling
/// read-your-writes consistency within a session.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct SessionToken(pub Cow<'static, str>);

impl SessionToken {
    /// Creates a new session token with the given value.
    pub fn new(value: impl Into<Cow<'static, str>>) -> Self {
        Self(value.into())
    }

    /// Returns the session token value as a string slice.
    pub fn as_str(&self) -> &str {
        &self.0
    }

    /// Merges this session token with another, returning the combined result.
    ///
    /// Both tokens may be compound (comma-separated segments). Segments with
    /// the same partition key range ID are merged using version-aware logic
    /// (higher version wins, then per-region LSN max). Segments with distinct
    /// IDs are kept as separate entries in the resulting compound token.
    ///
    /// This is the primary API for combining session tokens without exposing
    /// internal token format details.
    pub fn merge(&self, other: &Self) -> azure_core::Result<Self> {
        use std::collections::HashMap;

        let mut pk_order: Vec<String> = Vec::new();
        let mut pk_map: HashMap<String, SessionTokenSegment> = HashMap::new();

        for raw in self.as_str().split(',').chain(other.as_str().split(',')) {
            let trimmed = raw.trim();
            if trimmed.is_empty() {
                continue;
            }
            let seg: SessionTokenSegment = trimmed.parse()?;
            let pk_id = seg.pk_range_id().to_owned();
            match pk_map.get_mut(&pk_id) {
                Some(existing) => {
                    existing.merge_value(&seg);
                }
                None => {
                    pk_order.push(pk_id.clone());
                    pk_map.insert(pk_id, seg);
                }
            }
        }

        let merged: Vec<String> = pk_order
            .iter()
            .filter_map(|id| pk_map.get(id).map(|seg| seg.to_string()))
            .collect();

        Ok(Self::new(merged.join(",")))
    }
}

impl<T: Into<Cow<'static, str>>> From<T> for SessionToken {
    fn from(value: T) -> Self {
        Self::new(value)
    }
}

impl AsRef<str> for SessionToken {
    fn as_ref(&self) -> &str {
        self.as_str()
    }
}

impl std::fmt::Display for SessionToken {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

/// Unique name identifying a throughput control group.
///
/// This name is serialized into request headers when referencing a control group.
/// The group configuration is defined separately via [`ThroughputControlGroupOptions`](crate::options::ThroughputControlGroupOptions).
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct ThroughputControlGroupName(pub Cow<'static, str>);

impl ThroughputControlGroupName {
    /// Creates a new throughput control group name.
    pub fn new(name: impl Into<Cow<'static, str>>) -> Self {
        Self(name.into())
    }

    /// Returns the name as a string slice.
    pub fn as_str(&self) -> &str {
        &self.0
    }
}

impl From<&'static str> for ThroughputControlGroupName {
    fn from(name: &'static str) -> Self {
        Self::new(name)
    }
}

impl From<String> for ThroughputControlGroupName {
    fn from(name: String) -> Self {
        Self::new(name)
    }
}

impl From<Cow<'static, str>> for ThroughputControlGroupName {
    fn from(name: Cow<'static, str>) -> Self {
        Self::new(name)
    }
}

impl AsRef<str> for ThroughputControlGroupName {
    fn as_ref(&self) -> &str {
        self.as_str()
    }
}

impl std::fmt::Display for ThroughputControlGroupName {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde::{Deserialize, Serialize};

    #[test]
    fn partition_key_version_numeric_mapping() {
        assert_eq!(
            PartitionKeyVersion::try_from(1),
            Ok(PartitionKeyVersion::V1)
        );
        assert_eq!(
            PartitionKeyVersion::try_from(2),
            Ok(PartitionKeyVersion::V2)
        );
        assert!(PartitionKeyVersion::try_from(3).is_err());
        assert_eq!(u32::from(PartitionKeyVersion::V1), 1);
        assert_eq!(u32::from(PartitionKeyVersion::V2), 2);
    }

    #[derive(Debug, Deserialize, Serialize, PartialEq, Eq)]
    struct VersionEnvelope {
        version: PartitionKeyVersion,
    }

    #[test]
    fn partition_key_version_serde_uses_wire_values() {
        let parsed_v1: VersionEnvelope = serde_json::from_str(r#"{"version":1}"#).unwrap();
        let parsed_v2: VersionEnvelope = serde_json::from_str(r#"{"version":2}"#).unwrap();

        assert_eq!(parsed_v1.version, PartitionKeyVersion::V1);
        assert_eq!(parsed_v2.version, PartitionKeyVersion::V2);

        let serialized = serde_json::to_string(&VersionEnvelope {
            version: PartitionKeyVersion::V2,
        })
        .unwrap();
        assert_eq!(serialized, r#"{"version":2}"#);
    }

    #[test]
    fn partition_key_definition_defaults_and_getters() {
        let parsed: PartitionKeyDefinition = serde_json::from_str(r#"{"paths":["/pk"]}"#).unwrap();

        assert_eq!(parsed.paths().len(), 1);
        assert_eq!(parsed.paths()[0].as_ref(), "/pk");
        assert_eq!(parsed.version(), PartitionKeyVersion::V2);
        assert_eq!(parsed.kind(), PartitionKeyKind::Hash);
    }

    #[test]
    fn partition_key_definition_new_single_path() {
        let pk_def = PartitionKeyDefinition::new(vec![Cow::from("/tenantId")]);
        assert_eq!(pk_def.paths().len(), 1);
        assert_eq!(pk_def.paths()[0].as_ref(), "/tenantId");
        assert_eq!(pk_def.kind(), PartitionKeyKind::Hash);
        assert_eq!(pk_def.version(), PartitionKeyVersion::V2);
    }

    #[test]
    fn partition_key_definition_new_multi_path() {
        let pk_def =
            PartitionKeyDefinition::new(vec![Cow::from("/tenantId"), Cow::from("/userId")]);
        assert_eq!(pk_def.paths().len(), 2);
        assert_eq!(pk_def.kind(), PartitionKeyKind::MultiHash);
    }

    #[test]
    fn partition_key_definition_from_str() {
        let pk_def: PartitionKeyDefinition = "/pk".into();
        assert_eq!(pk_def.paths().len(), 1);
        assert_eq!(pk_def.paths()[0].as_ref(), "/pk");
        assert_eq!(pk_def.kind(), PartitionKeyKind::Hash);
    }

    #[test]
    fn partition_key_definition_from_string() {
        let pk_def: PartitionKeyDefinition = String::from("/pk").into();
        assert_eq!(pk_def.paths().len(), 1);
        assert_eq!(pk_def.kind(), PartitionKeyKind::Hash);
    }

    #[test]
    fn partition_key_definition_from_pair() {
        let pk_def: PartitionKeyDefinition = ("/a", "/b").into();
        assert_eq!(pk_def.paths().len(), 2);
        assert_eq!(pk_def.kind(), PartitionKeyKind::MultiHash);
    }

    #[test]
    fn partition_key_definition_from_triple() {
        let pk_def: PartitionKeyDefinition = ("/a", "/b", "/c").into();
        assert_eq!(pk_def.paths().len(), 3);
        assert_eq!(pk_def.kind(), PartitionKeyKind::MultiHash);
    }

    #[test]
    fn partition_key_kind_multihash_serde() {
        let json = r#"{"paths":["/a","/b"],"kind":"MultiHash","version":2}"#;
        let parsed: PartitionKeyDefinition = serde_json::from_str(json).unwrap();
        assert_eq!(parsed.kind(), PartitionKeyKind::MultiHash);
        assert_eq!(parsed.paths().len(), 2);

        let serialized = serde_json::to_string(&parsed).unwrap();
        assert_eq!(serialized, json);
    }

    #[test]
    fn partition_key_definition_round_trip_serde() {
        let pk_def: PartitionKeyDefinition = "/partitionKey".into();
        let json = serde_json::to_string(&pk_def).unwrap();
        assert_eq!(
            json,
            r#"{"paths":["/partitionKey"],"kind":"Hash","version":2}"#
        );
        let parsed: PartitionKeyDefinition = serde_json::from_str(&json).unwrap();
        assert_eq!(parsed, pk_def);
    }

    #[test]
    fn session_token_merge_same_pk_range() {
        let a = SessionToken::new("0:1#100#3=50");
        let b = SessionToken::new("0:1#200#3=60");
        let merged = a.merge(&b).unwrap();
        assert_eq!(merged.as_str(), "0:1#200#3=60");
    }

    #[test]
    fn session_token_merge_different_pk_ranges() {
        let a = SessionToken::new("0:1#100#3=50");
        let b = SessionToken::new("1:1#200#3=60");
        let merged = a.merge(&b).unwrap();
        assert_eq!(merged.as_str(), "0:1#100#3=50,1:1#200#3=60");
    }

    #[test]
    fn session_token_merge_compound() {
        let a = SessionToken::new("0:1#100#3=50,1:1#200#3=60");
        let b = SessionToken::new("0:1#150#3=55,2:1#300#3=70");
        let merged = a.merge(&b).unwrap();
        // pk 0: merged (max), pk 1: kept, pk 2: kept
        assert_eq!(merged.as_str(), "0:1#150#3=55,1:1#200#3=60,2:1#300#3=70");
    }

    #[test]
    fn session_token_merge_cross_version() {
        let a = SessionToken::new("0:1#500#1=100");
        let b = SessionToken::new("0:2#200#1=50");
        let merged = a.merge(&b).unwrap();
        // Higher version (2) wins for globalLSN; region 1: max(100, 50) = 100
        assert_eq!(merged.as_str(), "0:2#200#1=100");
    }
}