syncular_client/

values.rs

//! Value conversions at the client's edges: driver JSON (`{"$bytes": hex}`
//! convention) ↔ the §2.4 row-codec values ↔ SQLite storage, plus the §11.2
//! canonical scope JSON (contractual across implementations).

use std::collections::HashMap;

use serde_json::{Map, Value};
use ssp2::primitives::{RawJson, Reader, Writer};
use ssp2::segment::{
    decode_row, encode_row, encode_sparse_row, Column, ColumnType, ColumnValue, Row, SparseRow,
    SparseSlot,
};

use crate::schema::TableSchema;
use crate::TransportError;

/// §5.11 client-side encryption keys (`keyId → 32-byte key`) plus optional
/// key selection. Empty ⇒ E2EE off. `key_id_for` defaults to per-table
/// (`keyId = table`). Always present on the client; the crypto is compiled
/// only under the `e2ee` feature.
#[derive(Clone, Default)]
pub struct EncryptionConfig {
    pub keys: HashMap<String, Vec<u8>>,
    /// Portable per-table selector: the named non-encrypted string column in
    /// each plaintext row contains the key id used for new envelopes.
    pub key_id_columns: HashMap<String, String>,
}

/// Manual Debug so a stray `{config:?}` log line stays free of key material:
/// key entries render as `id → <N bytes>`.
impl std::fmt::Debug for EncryptionConfig {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        struct Redacted(usize);
        impl std::fmt::Debug for Redacted {
            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                write!(f, "<{} bytes>", self.0)
            }
        }
        let keys: std::collections::BTreeMap<&String, Redacted> = self
            .keys
            .iter()
            .map(|(id, key)| (id, Redacted(key.len())))
            .collect();
        f.debug_struct("EncryptionConfig")
            .field("keys", &keys)
            .field("key_id_columns", &self.key_id_columns)
            .finish()
    }
}

impl Drop for EncryptionConfig {
    fn drop(&mut self) {
        // Best-effort native key hygiene: replacement, preflight entry, and
        // client shutdown overwrite every owned key buffer before release.
        for key in self.keys.values_mut() {
            key.fill(0);
        }
    }
}

impl EncryptionConfig {
    pub fn is_empty(&self) -> bool {
        self.keys.is_empty()
    }

    /// §5.11 portable key selection: configured row column, then table name.
    /// Encode-seam failures carry `client.encrypt_failed` (never the apply-
    /// seam `client.decrypt_failed`). The caller supplies the presence set
    /// first with the stored local row merged into an absent selector.
    pub fn key_id_for(&self, table: &TableSchema, row: &Row) -> Result<String, String> {
        let Some(column_name) = self.key_id_columns.get(&table.name) else {
            return Ok(table.name.clone());
        };
        let Some(index) = table
            .columns
            .iter()
            .position(|column| &column.name == column_name)
        else {
            return Err(format!(
                "client.encrypt_failed: encryption key-id column {column_name:?} is not present on table {:?}",
                table.name
            ));
        };
        if table
            .encrypted_columns
            .iter()
            .any(|column| column.index == index)
        {
            return Err(format!(
                "client.encrypt_failed: encryption key-id column {column_name:?} on table {:?} must not be encrypted",
                table.name
            ));
        }
        match row.get(index).and_then(|value| value.as_ref()) {
            Some(ColumnValue::String(key_id)) if !key_id.is_empty() => Ok(key_id.clone()),
            _ => Err(format!(
                "client.encrypt_failed: encryption key-id column {column_name:?} on table {:?} must contain a non-empty string",
                table.name
            )),
        }
    }
}

/// The pinned snake→camel conversion. The Rust
/// copy of the typegen/TS-client algorithm, kept in lockstep by shared test
/// vectors. Leading/trailing `_` runs are preserved; middle segments split
/// on `_` (doubled underscores drop); no acronym awareness.
pub fn snake_to_camel(name: &str) -> String {
    let is_mappable = {
        let bare = name.trim_start_matches('_');
        !bare.is_empty()
            && bare.chars().next().is_some_and(|c| c.is_ascii_alphabetic())
            && name.chars().all(|c| c.is_ascii_alphanumeric() || c == '_')
    };
    if !is_mappable {
        return name.to_owned();
    }
    let lead_len = name.len() - name.trim_start_matches('_').len();
    let (lead, bare) = name.split_at(lead_len);
    let trail_len = bare.len() - bare.trim_end_matches('_').len();
    let (middle, trail) = bare.split_at(bare.len() - trail_len);
    let mut segments = middle.split('_').filter(|s| !s.is_empty());
    let Some(first) = segments.next() else {
        return name.to_owned();
    };
    let mut out = String::with_capacity(name.len());
    out.push_str(lead);
    out.push_str(first);
    for segment in segments {
        let mut chars = segment.chars();
        if let Some(head) = chars.next() {
            out.push(head.to_ascii_uppercase());
            out.push_str(chars.as_str());
        }
    }
    out.push_str(trail);
    out
}

/// §5 mutate key normalization: accept BOTH casings for upsert value keys —
/// the SQL-truth snake_case and the generated row types' camelCase. A camel
/// key renames to its column's SQL name when that is unambiguous (the alias
/// equals no other column's exact name, and no two columns share it). A
/// column given in both casings is an error. Unknown keys fail loud, matching
/// the TypeScript core; silently dropping an app field would corrupt a
/// full-row mutation while appearing successful.
pub fn normalize_values_casing(
    table: &TableSchema,
    mut values: Map<String, Value>,
) -> Result<Map<String, Value>, String> {
    for column in &table.columns {
        let camel = snake_to_camel(&column.name);
        if camel == column.name {
            continue;
        }
        // Exact names always win; an alias colliding with another column's
        // real name (or with another column's alias) is not an alias.
        if table.columns.iter().any(|c| c.name == camel) {
            continue;
        }
        if table
            .columns
            .iter()
            .filter(|c| snake_to_camel(&c.name) == camel)
            .count()
            > 1
        {
            continue;
        }
        if let Some(value) = values.remove(&camel) {
            if values.contains_key(&column.name) {
                return Err(format!(
                    "sync.invalid_request: table {:?}: column {:?} appears twice in mutation values (as both snake_case and camelCase) — pass it once",
                    table.name, column.name
                ));
            }
            values.insert(column.name.clone(), value);
        }
    }
    for key in values.keys() {
        if !table.columns.iter().any(|column| column.name == *key) {
            if key.starts_with("_sync_") {
                return Err(format!(
                    "sync.invalid_request: table {:?}: {:?} is an internal sync column and cannot appear in mutation values",
                    table.name, key
                ));
            }
            return Err(format!(
                "sync.invalid_request: table {:?}: unknown column {:?} in mutation values (snake_case and camelCase keys are accepted)",
                table.name, key
            ));
        }
    }
    Ok(values)
}

pub fn bytes_to_hex(bytes: &[u8]) -> String {
    let mut out = String::with_capacity(bytes.len() * 2);
    for b in bytes {
        out.push(char::from(b"0123456789abcdef"[usize::from(b >> 4)]));
        out.push(char::from(b"0123456789abcdef"[usize::from(b & 15)]));
    }
    out
}

pub fn hex_to_bytes(hex: &str) -> Result<Vec<u8>, String> {
    if !hex.len().is_multiple_of(2) {
        return Err("odd-length hex string".to_owned());
    }
    let mut out = Vec::with_capacity(hex.len() / 2);
    let nibble = |byte| match byte {
        b'0'..=b'9' => byte - b'0',
        b'a'..=b'f' => byte - b'a' + 10,
        b'A'..=b'F' => byte - b'A' + 10,
        _ => u8::MAX,
    };
    for pair in hex.as_bytes().as_chunks::<2>().0 {
        // Preserve the prior radix parser's accepted +digit pair as well as
        // uppercase input. Canonical encoders continue to emit lowercase hex.
        let high = if pair[0] == b'+' { 0 } else { nibble(pair[0]) };
        let low = nibble(pair[1]);
        if high == u8::MAX || low == u8::MAX {
            return Err(if std::str::from_utf8(pair).is_err() {
                "non-ASCII hex".to_owned()
            } else {
                "bad hex: invalid digit found in string".to_owned()
            });
        }
        out.push((high << 4) | low);
    }
    Ok(out)
}

/// Driver JSON value → row-codec value for one column. `null`/absent maps to
/// NULL; bytes travel as `{"$bytes": "<hex>"}`.
pub fn json_to_column_value(
    column: &Column,
    value: Option<&Value>,
) -> Result<Option<ColumnValue>, String> {
    let value = match value {
        None | Some(Value::Null) => return Ok(None),
        Some(v) => v,
    };
    let fail = |expected: &str| {
        Err(format!(
            "column {:?}: expected {expected}, got {value}",
            column.name
        ))
    };
    match column.ty {
        ColumnType::String => match value.as_str() {
            Some(s) => Ok(Some(ColumnValue::String(s.to_owned()))),
            None => fail("a string"),
        },
        ColumnType::Integer => match value.as_i64() {
            Some(i)
                if (-ssp2::primitives::I64_SAFE_MAX..=ssp2::primitives::I64_SAFE_MAX)
                    .contains(&i) =>
            {
                Ok(Some(ColumnValue::Integer(i)))
            }
            _ => fail("an integer within the JavaScript safe-integer range"),
        },
        ColumnType::Float => match value.as_f64() {
            Some(f) => Ok(Some(ColumnValue::Float(f))),
            None => fail("a number"),
        },
        ColumnType::Boolean => match value.as_bool() {
            Some(b) => Ok(Some(ColumnValue::Boolean(b))),
            None => fail("a boolean"),
        },
        // `json` columns stay raw strings at the driver boundary (§2.4).
        ColumnType::Json => match value.as_str() {
            Some(s) => Ok(Some(ColumnValue::Json(RawJson(s.to_owned())))),
            None => fail("a raw JSON string"),
        },
        // `blob_ref` (tag 7) also stays a raw string at the boundary (§5.9.1).
        ColumnType::BlobRef => match value.as_str() {
            Some(s) => Ok(Some(ColumnValue::BlobRef(RawJson(s.to_owned())))),
            None => fail("a raw BlobRef JSON string"),
        },
        ColumnType::Bytes => match value.get("$bytes").and_then(Value::as_str) {
            Some(hex) => Ok(Some(ColumnValue::Bytes(hex_to_bytes(hex)?))),
            None => fail("a {\"$bytes\": hex} object"),
        },
        // §5.10: crdt bytes cross the boundary as {"$bytes": hex}, like bytes.
        ColumnType::Crdt => match value.get("$bytes").and_then(Value::as_str) {
            Some(hex) => Ok(Some(ColumnValue::Crdt(hex_to_bytes(hex)?))),
            None => fail("a {\"$bytes\": hex} object"),
        },
    }
}

/// Row-codec value → driver JSON value.
pub fn column_value_to_json(value: &Option<ColumnValue>) -> Value {
    match value {
        None => Value::Null,
        Some(ColumnValue::String(s)) => Value::from(s.clone()),
        Some(ColumnValue::Integer(i)) => Value::from(*i),
        Some(ColumnValue::Float(f)) => {
            serde_json::Number::from_f64(*f).map_or(Value::Null, Value::Number)
        }
        Some(ColumnValue::Boolean(b)) => Value::from(*b),
        Some(ColumnValue::Json(raw)) => Value::from(raw.0.clone()),
        Some(ColumnValue::BlobRef(raw)) => Value::from(raw.0.clone()),
        Some(ColumnValue::Bytes(bytes)) => {
            let mut map = Map::new();
            map.insert("$bytes".to_owned(), Value::from(bytes_to_hex(bytes)));
            Value::Object(map)
        }
        Some(ColumnValue::Crdt(bytes)) => {
            let mut map = Map::new();
            map.insert("$bytes".to_owned(), Value::from(bytes_to_hex(bytes)));
            Value::Object(map)
        }
    }
}

/// Turn an app-facing value map into a full-row map: every column present,
/// a missing nullable column filled with NULL, a missing non-nullable column
/// a loud error (§6.1 full-row payloads, §6.7 `mutate` marks every column).
pub fn full_row_values(
    table: &TableSchema,
    mut values: Map<String, Value>,
) -> Result<Map<String, Value>, String> {
    for column in &table.columns {
        if values.contains_key(&column.name) {
            continue;
        }
        if !column.nullable {
            return Err(format!(
                "sync.invalid_request: table {:?}: column {:?} is not nullable (§6.1 full-row payloads)",
                table.name, column.name
            ));
        }
        values.insert(column.name.clone(), Value::Null);
    }
    Ok(values)
}

/// §7.1: exactly one `$bytes` key holding an even-length hexadecimal string.
/// Uppercase digits are accepted; encoders emit lowercase.
pub(crate) fn is_canonical_bytes_envelope(value: &Value) -> bool {
    value
        .as_object()
        .filter(|map| map.len() == 1)
        .and_then(|map| map.get("$bytes"))
        .and_then(Value::as_str)
        .is_some_and(|hex| {
            hex.len().is_multiple_of(2) && hex.bytes().all(|byte| byte.is_ascii_hexdigit())
        })
}

/// §7.1: a `bytes`/`crdt` column crosses the authoring boundary only as exactly
/// one `$bytes` key holding an even-length hexadecimal string. The shared
/// decoder keeps its tolerance for persisted payloads (§7.4.4 replay), so the
/// canonical rule is enforced at the encode seams instead. `None` for every
/// other column type and for a canonical envelope.
fn author_bytes_envelope_error(column: &Column, value: &Value) -> Option<String> {
    // An explicit `null` stays with `json_to_column_value`: a nullable column
    // accepts it and a non-nullable one is classified by the required-column
    // check, not by the envelope rule.
    if value.is_null() || !matches!(column.ty, ColumnType::Bytes | ColumnType::Crdt) {
        return None;
    }
    if is_canonical_bytes_envelope(value) {
        return None;
    }
    Some(format!(
        "sync.invalid_request: column {:?}: expected exactly {{\"$bytes\": hex}} with an even number of hexadecimal digits, got {value}",
        column.name
    ))
}

/// Encode one full row (driver JSON values keyed by column name) with the
/// generated row codec (§2.4, §6.1). §5.11: encrypted columns are encrypted
/// here — the encode-at-send seam — before the codec serializes them as
/// ciphertext-envelope `bytes` using `wire_columns`.
pub fn encode_row_json(
    table: &TableSchema,
    row_id: &str,
    values: &Map<String, Value>,
    encryption: &EncryptionConfig,
) -> Result<Vec<u8>, String> {
    // Build the row from the LOCAL (declared-type) columns.
    let mut row: Row = Vec::with_capacity(table.columns.len());
    for column in &table.columns {
        if let Some(raw) = values.get(&column.name) {
            if let Some(error) = author_bytes_envelope_error(column, raw) {
                return Err(error);
            }
        }
        // §6.1/§7.1: a caller value the codec rejects is an invalid request,
        // never an internal authoring failure; the dynamic cause stays in
        // `details.legacyCause` at the `ClientError` boundary.
        let value = json_to_column_value(column, values.get(&column.name))
            .map_err(|error| format!("sync.invalid_request: {error}"))?;
        if value.is_none() && !column.nullable {
            return Err(format!(
                "sync.invalid_request: table {:?}: column {:?} is not nullable (§6.1 full-row payloads)",
                table.name, column.name
            ));
        }
        row.push(value);
    }
    if table.has_encrypted_columns() {
        encrypt_row(table, row_id, &mut row, encryption)?;
    }
    // Serialize with the WIRE columns (encrypted columns are `bytes`).
    let mut w = Writer::new();
    encode_row(&mut w, &table.wire_columns, &row);
    Ok(w.into_bytes())
}

/// Encode one SPARSE push payload (§2.4, §6.1): the keys of `values` ARE the
/// presence set — a column with no key stays absent. §5.11: only present
/// encrypted columns are encrypted, and key resolution runs only then;
/// absent selector slots fall back to `fallback` (the stored local row).
/// Serialized with the `wire_columns` table.
pub fn encode_sparse_row_json(
    table: &TableSchema,
    row_id: &str,
    values: &Map<String, Value>,
    encryption: &EncryptionConfig,
    fallback: Option<&Row>,
) -> Result<Vec<u8>, String> {
    let mut row: SparseRow = Vec::with_capacity(table.columns.len());
    for column in &table.columns {
        let Some(raw) = values.get(&column.name) else {
            row.push(SparseSlot::Absent);
            continue;
        };
        if let Some(error) = author_bytes_envelope_error(column, raw) {
            return Err(error);
        }
        // §2.4/§7.1: the push admission values the server rejects. A float
        // read from JSON is always finite.
        let refused = match (column.ty, raw) {
            (ColumnType::String, Value::String(text)) => text.contains('\0'),
            (ColumnType::Json, Value::String(text)) => {
                ssp2::primitives::parse_json_document(text, "json value").is_err()
            }
            (ColumnType::BlobRef, Value::String(text)) => {
                ssp2::blob_ref::validate_blob_ref(text).is_err()
            }
            _ => false,
        };
        if refused {
            return Err(format!(
                "sync.invalid_request: column {:?}: the value is not a push admission value (§2.4)",
                column.name
            ));
        }
        let value = json_to_column_value(column, Some(raw))
            .map_err(|error| format!("sync.invalid_request: {error}"))?;
        if value.is_none() && !column.nullable {
            return Err(format!(
                "sync.invalid_request: table {:?}: column {:?} is not nullable (§6.1)",
                table.name, column.name
            ));
        }
        row.push(value.map_or(SparseSlot::Null, SparseSlot::Value));
    }
    if table.has_encrypted_columns() {
        encrypt_sparse_row(table, row_id, &mut row, encryption, fallback)?;
    }
    Ok(encode_sparse_row(&table.wire_columns, table.pk_index, &row))
}

/// Decode one row-codec payload; trailing bytes are a decode error. §5.11:
/// encrypted columns are decrypted here — the apply seam — back to their
/// declared-type plaintext value for the local mirror.
pub fn decode_row_bytes(
    table: &TableSchema,
    payload: &[u8],
    encryption: &EncryptionConfig,
) -> Result<Row, TransportError> {
    let mut r = Reader::new(payload);
    // Decode with the WIRE columns (encrypted columns arrive as `bytes`).
    let mut row = decode_row(&mut r, &table.wire_columns)
        .map_err(|e| TransportError::new("sync.invalid_request", e.to_string()))?;
    if !r.is_empty() {
        return Err(TransportError::new(
            "sync.invalid_request",
            "row payload has trailing bytes",
        ));
    }
    if table.has_encrypted_columns() {
        decrypt_row(table, &mut row, encryption)?;
    }
    Ok(row)
}

/// §5.11: decrypt the encrypted columns of an already-decoded segment row
/// (rows segments decode via their own column table, so decryption is a
/// post-decode pass over the positional values).
pub fn decrypt_segment_row(
    table: &TableSchema,
    row: &mut Row,
    encryption: &EncryptionConfig,
) -> Result<(), TransportError> {
    decrypt_row(table, row, encryption)
}

// -- §5.11 encrypt/decrypt seam (feature-gated) ------------------------------

#[cfg(feature = "e2ee")]
fn encrypt_row(
    table: &TableSchema,
    _row_id: &str,
    row: &mut Row,
    encryption: &EncryptionConfig,
) -> Result<(), String> {
    use rand_core::RngCore;
    use ssp2::crypto::{encrypt_value, NONCE_LENGTH};
    for enc in &table.encrypted_columns {
        let Some(value) = row.get(enc.index).and_then(|v| v.as_ref()) else {
            continue; // NULL stays NULL (§5.11)
        };
        let plain = column_value_to_plain(value)?;
        let key_id = encryption.key_id_for(table, row)?;
        let key = encryption
            .keys
            .get(&key_id)
            .ok_or_else(|| format!("client.encrypt_failed: no key for keyId {key_id:?}"))?;
        let mut nonce = [0u8; NONCE_LENGTH];
        rand_core::OsRng.fill_bytes(&mut nonce);
        let envelope = encrypt_value(&plain, &key_id, key, nonce)?;
        row[enc.index] = Some(ColumnValue::Bytes(envelope));
    }
    Ok(())
}

#[cfg(feature = "e2ee")]
fn encrypt_sparse_row(
    table: &TableSchema,
    _row_id: &str,
    row: &mut SparseRow,
    encryption: &EncryptionConfig,
    fallback: Option<&Row>,
) -> Result<(), String> {
    use rand_core::RngCore;
    use ssp2::crypto::{encrypt_value, NONCE_LENGTH};
    // Sparse semantics: absent and NULL columns are never re-encrypted, so
    // a patch presenting no encrypted value needs no key (§5.11).
    let has_present_encrypted = table
        .encrypted_columns
        .iter()
        .any(|enc| matches!(row.get(enc.index), Some(SparseSlot::Value(_))));
    if !has_present_encrypted {
        return Ok(());
    }
    // Densify absent columns to NULL for key-id selection only; an absent
    // selector falls back to the stored local row. Absent ≠ NULL (§6.1):
    // only an ABSENT slot reads the fallback, a present NULL never does.
    let mut dense: Row = row
        .iter()
        .map(|slot| match slot {
            SparseSlot::Value(value) => Some(value.clone()),
            _ => None,
        })
        .collect();
    if let Some(selector) = encryption.key_id_columns.get(&table.name) {
        if let Some(index) = table
            .columns
            .iter()
            .position(|column| &column.name == selector)
        {
            if matches!(row.get(index), None | Some(SparseSlot::Absent)) {
                let stored: Option<&str> = match fallback
                    .and_then(|row| row.get(index))
                    .and_then(|value| value.as_ref())
                {
                    Some(ColumnValue::String(key_id)) => Some(key_id),
                    _ => None,
                };
                if let Some(key_id) = stored.filter(|key_id| !key_id.is_empty()) {
                    dense[index] = Some(ColumnValue::String(key_id.to_owned()));
                }
            }
        }
    }
    let key_id = encryption.key_id_for(table, &dense)?;
    for enc in &table.encrypted_columns {
        let Some(SparseSlot::Value(value)) = row.get(enc.index) else {
            continue; // absent or NULL stays untouched (§5.11)
        };
        let plain = column_value_to_plain(value)?;
        let key = encryption
            .keys
            .get(&key_id)
            .ok_or_else(|| format!("client.encrypt_failed: no key for keyId {key_id:?}"))?;
        let mut nonce = [0u8; NONCE_LENGTH];
        rand_core::OsRng.fill_bytes(&mut nonce);
        let envelope = encrypt_value(&plain, &key_id, key, nonce)?;
        row[enc.index] = SparseSlot::Value(ColumnValue::Bytes(envelope));
    }
    Ok(())
}

#[cfg(not(feature = "e2ee"))]
fn encrypt_sparse_row(
    table: &TableSchema,
    _row_id: &str,
    row: &mut SparseRow,
    _encryption: &EncryptionConfig,
    _fallback: Option<&Row>,
) -> Result<(), String> {
    if !table
        .encrypted_columns
        .iter()
        .any(|enc| matches!(row.get(enc.index), Some(SparseSlot::Value(_))))
    {
        return Ok(());
    }
    Err(format!(
        "table {:?} has encrypted columns but this build lacks the e2ee feature (§5.11)",
        table.name
    ))
}

/// §5.11 apply seam: an unknown `keyId` is `client.encryption_key_missing`
/// with `{ table, keyId }` details; every other failure is
/// `client.decrypt_failed`.
#[cfg(feature = "e2ee")]
fn decrypt_row(
    table: &TableSchema,
    row: &mut Row,
    encryption: &EncryptionConfig,
) -> Result<(), TransportError> {
    use ssp2::crypto::{decrypt_value, DeclaredType, DecryptValueError};
    let failed = |message: String| TransportError::new("client.decrypt_failed", message);
    for enc in &table.encrypted_columns {
        let Some(value) = row.get(enc.index).and_then(|v| v.as_ref()) else {
            continue;
        };
        let ColumnValue::Bytes(envelope) = value else {
            return Err(failed(format!(
                "encrypted column at index {} is not bytes",
                enc.index
            )));
        };
        let declared = DeclaredType::from_name(&enc.declared_type)
            .ok_or_else(|| failed(format!("unknown declaredType {:?}", enc.declared_type)))?;
        let keys = &encryption.keys;
        let plain =
            decrypt_value(declared, envelope, |id| keys.get(id).cloned()).map_err(|error| {
                match error {
                    DecryptValueError::KeyMissing { key_id } => TransportError {
                        code: "client.encryption_key_missing".to_owned(),
                        message: "no key for the envelope keyId".to_owned(),
                        details: Some(serde_json::json!({ "table": table.name, "keyId": key_id })),
                    },
                    DecryptValueError::Failed(error) => failed(error.0),
                }
            })?;
        row[enc.index] = Some(plain_to_column_value(plain));
    }
    Ok(())
}

/// Without the `e2ee` feature, a schema with encrypted columns is a
/// misconfiguration — fail loud rather than ship plaintext.
#[cfg(not(feature = "e2ee"))]
fn encrypt_row(
    table: &TableSchema,
    _row_id: &str,
    _row: &mut Row,
    _encryption: &EncryptionConfig,
) -> Result<(), String> {
    Err(format!(
        "table {:?} has encrypted columns but this build lacks the e2ee feature (§5.11)",
        table.name
    ))
}

#[cfg(not(feature = "e2ee"))]
fn decrypt_row(
    table: &TableSchema,
    _row: &mut Row,
    _encryption: &EncryptionConfig,
) -> Result<(), TransportError> {
    Err(TransportError::new(
        "client.decrypt_failed",
        format!(
            "table {:?} has encrypted columns but this build lacks the e2ee feature (§5.11)",
            table.name
        ),
    ))
}

#[cfg(feature = "e2ee")]
fn column_value_to_plain(value: &ColumnValue) -> Result<ssp2::crypto::PlainValue, String> {
    use ssp2::crypto::PlainValue;
    Ok(match value {
        ColumnValue::String(s) => PlainValue::String(s.clone()),
        ColumnValue::Integer(i) => PlainValue::Integer(*i),
        ColumnValue::Float(f) => PlainValue::Float(*f),
        ColumnValue::Boolean(b) => PlainValue::Boolean(*b),
        ColumnValue::Json(j) => PlainValue::Json(j.0.clone()),
        ColumnValue::BlobRef(j) => PlainValue::BlobRef(j.0.clone()),
        ColumnValue::Bytes(b) => PlainValue::Bytes(b.clone()),
        ColumnValue::Crdt(_) => return Err("crdt columns cannot be encrypted (§5.11)".to_owned()),
    })
}

#[cfg(feature = "e2ee")]
fn plain_to_column_value(value: ssp2::crypto::PlainValue) -> ColumnValue {
    use ssp2::crypto::PlainValue;
    match value {
        PlainValue::String(s) => ColumnValue::String(s),
        PlainValue::Integer(i) => ColumnValue::Integer(i),
        PlainValue::Float(f) => ColumnValue::Float(f),
        PlainValue::Boolean(b) => ColumnValue::Boolean(b),
        PlainValue::Json(s) => ColumnValue::Json(RawJson(s)),
        PlainValue::BlobRef(s) => ColumnValue::BlobRef(RawJson(s)),
        PlainValue::Bytes(b) => ColumnValue::Bytes(b),
    }
}

/// Render a primary-key value as the wire `rowId` string.
pub fn render_row_id(value: &Option<ColumnValue>) -> Result<String, String> {
    match value {
        Some(ColumnValue::String(s)) => Ok(s.clone()),
        Some(ColumnValue::Integer(i)) => Ok(i.to_string()),
        Some(ColumnValue::Float(f)) => Ok(f.to_string()),
        Some(ColumnValue::Boolean(b)) => Ok(b.to_string()),
        Some(ColumnValue::Json(raw)) => Ok(raw.0.clone()),
        Some(ColumnValue::BlobRef(_)) => Err("blob_ref column cannot be a rowId".to_owned()),
        Some(ColumnValue::Bytes(_)) => Err("bytes column cannot be a rowId".to_owned()),
        Some(ColumnValue::Crdt(_)) => Err("crdt column cannot be a rowId".to_owned()),
        None => Err("primary key value is missing".to_owned()),
    }
}

/// Driver JSON value → wire `rowId` string (for optimistic upserts).
pub fn render_row_id_json(value: Option<&Value>) -> Result<String, String> {
    match value {
        Some(Value::String(s)) => Ok(s.clone()),
        Some(Value::Number(n)) => Ok(n.to_string()),
        Some(Value::Bool(b)) => Ok(b.to_string()),
        _ => Err("sync.invalid_request: primary key value is missing or not renderable".to_owned()),
    }
}

/// Scope map as a driver JSON object (`variable → list of values`, §3.2).
pub fn scope_map_to_json(scopes: &[(String, Vec<String>)]) -> Value {
    let mut map = Map::new();
    for (key, values) in scopes {
        map.insert(
            key.clone(),
            Value::Array(values.iter().map(|v| Value::from(v.clone())).collect()),
        );
    }
    Value::Object(map)
}

/// Driver JSON object → scope map, preserving key order.
pub fn json_to_scope_map(value: &Value) -> Result<Vec<(String, Vec<String>)>, String> {
    let object = value
        .as_object()
        .ok_or_else(|| "scope map must be an object".to_owned())?;
    let mut out = Vec::with_capacity(object.len());
    for (key, values) in object {
        let list = values
            .as_array()
            .ok_or_else(|| format!("scope values for {key:?} must be a list (§0)"))?;
        let mut strings = Vec::with_capacity(list.len());
        for v in list {
            strings.push(
                v.as_str()
                    .ok_or_else(|| format!("scope value for {key:?} is not a string"))?
                    .to_owned(),
            );
        }
        out.push((key.clone(), strings));
    }
    Ok(out)
}

#[cfg(test)]
mod naming_tests {
    use serde_json::{json, Map, Value};
    use ssp2::segment::{Column, ColumnType, ColumnValue, Row};

    use super::{
        bytes_to_hex, hex_to_bytes, normalize_values_casing, snake_to_camel, EncryptionConfig,
    };
    use crate::schema::{EncryptedColumn, TableSchema};

    #[test]
    fn authored_integer_cells_respect_the_wire_safe_range() {
        let column = Column {
            name: "n".into(),
            ty: ColumnType::Integer,
            nullable: false,
        };
        for value in [
            9007199254740992_i64,
            9007199254740993,
            i64::MAX,
            -9007199254740992,
            i64::MIN,
        ] {
            assert!(super::json_to_column_value(&column, Some(&json!(value))).is_err());
        }
        for value in [-9007199254740991_i64, 0, 9007199254740991] {
            assert!(super::json_to_column_value(&column, Some(&json!(value))).is_ok());
        }
    }

    #[test]
    fn byte_envelopes_preserve_canonical_hex_for_every_byte() {
        let bytes: Vec<u8> = (0..=255).collect();
        let expected: String = bytes.iter().map(|byte| format!("{byte:02x}")).collect();
        assert_eq!(bytes_to_hex(&bytes), expected);
        assert_eq!(hex_to_bytes(&expected).expect("decode"), bytes);
        assert_eq!(bytes_to_hex(&[]), "");
        assert_eq!(bytes_to_hex(&[0, 15, 16, 255]), "000f10ff");
        let large = bytes.repeat(8192);
        assert_eq!(bytes_to_hex(&large), expected.repeat(8192));
        assert_eq!(
            hex_to_bytes(&bytes_to_hex(&large)).expect("large decode"),
            large
        );
    }

    #[test]
    fn byte_decoder_preserves_radix_parser_inputs_and_errors() {
        for first in 0_u8..=127 {
            for second in 0_u8..=127 {
                let pair = [first, second];
                let input = std::str::from_utf8(&pair).unwrap();
                let expected = u8::from_str_radix(input, 16)
                    .map(|byte| vec![byte])
                    .map_err(|error| format!("bad hex: {error}"));
                assert_eq!(hex_to_bytes(input), expected, "ASCII pair {pair:?}");
            }
        }
        assert_eq!(hex_to_bytes("+fA0+100"), Ok(vec![15, 160, 1, 0]));
        for input in [
            "", "0", "abc", "é", "雪", "😀", "0é0", "é00", "00é", "00😀", "😀00", "\0\0",
        ] {
            let expected = if !input.len().is_multiple_of(2) {
                Err("odd-length hex string".to_owned())
            } else {
                input
                    .as_bytes()
                    .chunks(2)
                    .map(|pair| {
                        let text =
                            std::str::from_utf8(pair).map_err(|_| "non-ASCII hex".to_owned())?;
                        u8::from_str_radix(text, 16).map_err(|error| format!("bad hex: {error}"))
                    })
                    .collect::<Result<Vec<_>, _>>()
            };
            assert_eq!(hex_to_bytes(input), expected, "input {input:?}");
        }
    }

    #[test]
    fn snake_to_camel_pinned_vectors() {
        for (input, expected) in [
            ("created_at", "createdAt"),
            ("col_2", "col2"),
            ("user_id", "userId"),
            ("_internal", "_internal"),
            ("__foo_bar", "__fooBar"),
            ("row_", "row_"),
            ("id_url", "idUrl"),
            ("api_key", "apiKey"),
            ("title", "title"),
            ("alreadyCamel", "alreadyCamel"),
            ("a__b", "aB"),
            ("_lead_and_trail_", "_leadAndTrail_"),
            ("count(*)", "count(*)"),
        ] {
            assert_eq!(snake_to_camel(input), expected, "input {input:?}");
        }
    }

    #[test]
    fn portable_key_selector_reads_a_non_encrypted_string_column() {
        let columns = vec![
            Column {
                name: "id".to_owned(),
                ty: ColumnType::String,
                nullable: false,
            },
            Column {
                name: "encryption_key_id".to_owned(),
                ty: ColumnType::String,
                nullable: false,
            },
            Column {
                name: "note".to_owned(),
                ty: ColumnType::String,
                nullable: false,
            },
        ];
        let table = TableSchema {
            name: "patients".to_owned(),
            columns: columns.clone(),
            wire_columns: columns,
            primary_key: "id".to_owned(),
            pk_index: 0,
            scope_variables: Vec::new(),
            indexes: Vec::new(),
            fts_indexes: Vec::new(),
            encrypted_columns: vec![EncryptedColumn {
                index: 2,
                declared_type: "string".to_owned(),
            }],
        };
        let mut config = EncryptionConfig::default();
        config
            .key_id_columns
            .insert("patients".to_owned(), "encryption_key_id".to_owned());
        let row: Row = vec![
            Some(ColumnValue::String("patient-1".to_owned())),
            Some(ColumnValue::String("practice-key-v1".to_owned())),
            Some(ColumnValue::String("Identity".to_owned())),
        ];
        assert_eq!(
            config.key_id_for(&table, &row).expect("selects key"),
            "practice-key-v1"
        );
    }

    #[test]
    fn debug_render_redacts_key_material() {
        let mut config = EncryptionConfig::default();
        config
            .keys
            .insert("practice-key-v1".to_owned(), vec![0xAB; 32]);
        config
            .key_id_columns
            .insert("patients".to_owned(), "encryption_key_id".to_owned());
        let rendered = format!("{config:?}");
        assert!(rendered.contains("practice-key-v1"), "{rendered}");
        assert!(rendered.contains("<32 bytes>"), "{rendered}");
        assert!(rendered.contains("encryption_key_id"), "{rendered}");
        // Raw byte values never appear (0xAB renders as 171 under derive).
        assert!(!rendered.contains("171"), "{rendered}");
        assert!(!rendered.contains("0xAB"), "{rendered}");
    }

    fn table(names: &[&str]) -> TableSchema {
        let columns: Vec<Column> = names
            .iter()
            .map(|n| Column {
                name: (*n).to_owned(),
                ty: ColumnType::String,
                nullable: true,
            })
            .collect();
        TableSchema {
            name: "t".to_owned(),
            columns: columns.clone(),
            wire_columns: columns,
            primary_key: "id".to_owned(),
            pk_index: 0,
            scope_variables: Vec::new(),
            indexes: Vec::new(),
            fts_indexes: Vec::new(),
            encrypted_columns: Vec::new(),
        }
    }

    fn map(entries: &[(&str, &str)]) -> Map<String, Value> {
        entries
            .iter()
            .map(|(k, v)| ((*k).to_owned(), json!(v)))
            .collect()
    }

    #[test]
    fn camel_keys_normalize_to_sql_names() {
        let t = table(&["id", "list_id", "updated_at_ms"]);
        let out = normalize_values_casing(
            &t,
            map(&[("id", "x"), ("listId", "l"), ("updatedAtMs", "9")]),
        )
        .expect("normalizes");
        assert_eq!(out.get("list_id"), Some(&json!("l")));
        assert_eq!(out.get("updated_at_ms"), Some(&json!("9")));
        assert!(!out.contains_key("listId"));
    }

    #[test]
    fn snake_keys_pass_through() {
        let t = table(&["id", "list_id"]);
        let out = normalize_values_casing(&t, map(&[("id", "x"), ("list_id", "l")])).expect("ok");
        assert_eq!(out.get("list_id"), Some(&json!("l")));
    }

    #[test]
    fn both_casings_for_one_column_is_an_error() {
        let t = table(&["id", "list_id"]);
        let err = normalize_values_casing(&t, map(&[("list_id", "a"), ("listId", "b")]))
            .expect_err("rejects");
        assert!(err.contains("both snake_case and camelCase"), "{err}");
    }

    #[test]
    fn an_alias_colliding_with_a_real_column_never_steals_it() {
        // `col_2` camel-maps to `col2`, which IS a column: exact wins, no rename.
        let t = table(&["id", "col_2", "col2"]);
        let out = normalize_values_casing(&t, map(&[("id", "x"), ("col2", "v")])).expect("ok");
        assert_eq!(out.get("col2"), Some(&json!("v")));
        assert!(!out.contains_key("col_2"));
    }

    #[test]
    fn unknown_and_internal_columns_fail_loud() {
        let t = table(&["id", "title"]);
        let unknown = normalize_values_casing(&t, map(&[("id", "x"), ("typo", "v")]))
            .expect_err("unknown field");
        assert!(unknown.contains("unknown column"), "{unknown}");
        let internal = normalize_values_casing(&t, map(&[("id", "x"), ("_sync_version", "1")]))
            .expect_err("internal field");
        assert!(internal.contains("internal sync column"), "{internal}");
    }
}

#[cfg(test)]
mod sparse_key_tests {
    use ssp2::segment::{Column, ColumnType, ColumnValue, Row};

    use super::EncryptionConfig;
    use crate::schema::{EncryptedColumn, TableSchema};

    #[cfg(feature = "e2ee")]
    use super::encode_sparse_row_json;
    #[cfg(feature = "e2ee")]
    use serde_json::{json, Map, Value};

    fn keyed_table() -> TableSchema {
        let columns = vec![
            Column {
                name: "id".to_owned(),
                ty: ColumnType::String,
                nullable: false,
            },
            Column {
                name: "encryption_key_id".to_owned(),
                ty: ColumnType::String,
                nullable: true,
            },
            Column {
                name: "note".to_owned(),
                ty: ColumnType::String,
                nullable: true,
            },
        ];
        let wire_columns = vec![
            Column {
                name: "id".to_owned(),
                ty: ColumnType::String,
                nullable: false,
            },
            Column {
                name: "encryption_key_id".to_owned(),
                ty: ColumnType::String,
                nullable: true,
            },
            Column {
                name: "note".to_owned(),
                ty: ColumnType::Bytes,
                nullable: true,
            },
        ];
        TableSchema {
            name: "t".to_owned(),
            columns,
            wire_columns,
            primary_key: "id".to_owned(),
            pk_index: 0,
            scope_variables: Vec::new(),
            indexes: Vec::new(),
            fts_indexes: Vec::new(),
            encrypted_columns: vec![EncryptedColumn {
                index: 2,
                declared_type: "string".to_owned(),
            }],
        }
    }

    fn keyed_config() -> EncryptionConfig {
        let mut config = EncryptionConfig::default();
        config.keys.insert("k1".to_owned(), vec![0x2A; 32]);
        config
            .key_id_columns
            .insert("t".to_owned(), "encryption_key_id".to_owned());
        config
    }

    #[cfg(feature = "e2ee")]
    fn values(entries: &[(&str, Value)]) -> Map<String, Value> {
        entries
            .iter()
            .map(|(key, value)| ((*key).to_owned(), value.clone()))
            .collect()
    }

    #[test]
    fn key_selection_failures_carry_the_encode_seam_code() {
        let table = keyed_table();
        let config = keyed_config();
        // Absent selector: absent is not NULL and never densifies into one.
        let row: Row = vec![
            Some(ColumnValue::String("r1".to_owned())),
            None,
            Some(ColumnValue::String("hi".to_owned())),
        ];
        let error = config.key_id_for(&table, &row).expect_err("rejects");
        assert!(error.starts_with("client.encrypt_failed"), "{error}");
        assert!(!error.starts_with("client.decrypt_failed"), "{error}");
    }

    #[cfg(feature = "e2ee")]
    #[test]
    fn sparse_patch_without_an_encrypted_slot_needs_no_key() {
        let table = keyed_table();
        // No keys at all: resolution must be skipped, not failed.
        let config = EncryptionConfig::default();
        let payload =
            encode_sparse_row_json(&table, "r1", &values(&[("id", json!("r1"))]), &config, None)
                .expect("encodes without key resolution");
        assert!(!payload.is_empty());
    }

    #[cfg(feature = "e2ee")]
    #[test]
    fn sparse_patch_falls_back_to_the_stored_key_id() {
        let table = keyed_table();
        let config = keyed_config();
        // The patch presents an encrypted column but not the selector.
        let sparse = values(&[("id", json!("r1")), ("note", json!("hi"))]);
        let error = encode_sparse_row_json(&table, "r1", &sparse, &config, None)
            .expect_err("absent selector with no fallback fails");
        assert!(error.contains("client.encrypt_failed"), "{error}");
        let fallback: Row = vec![
            Some(ColumnValue::String("r1".to_owned())),
            Some(ColumnValue::String("k1".to_owned())),
            None,
        ];
        encode_sparse_row_json(&table, "r1", &sparse, &config, Some(&fallback))
            .expect("stored key id encrypts the patch");
    }

    #[cfg(feature = "e2ee")]
    #[test]
    fn sparse_patch_keeps_a_present_null_selector() {
        let table = keyed_table();
        let config = keyed_config();
        // The patch presents the selector explicitly as NULL alongside an
        // encrypted column. Absent is not NULL: the stored row must not
        // rescue a present NULL, and a NULL key id is unusable.
        let sparse = values(&[
            ("id", json!("r1")),
            ("encryption_key_id", json!(null)),
            ("note", json!("hi")),
        ]);
        let fallback: Row = vec![
            Some(ColumnValue::String("r1".to_owned())),
            Some(ColumnValue::String("k1".to_owned())),
            None,
        ];
        let error = encode_sparse_row_json(&table, "r1", &sparse, &config, Some(&fallback))
            .expect_err("a present NULL selector must not read the stored fallback");
        assert!(error.contains("client.encrypt_failed"), "{error}");
    }
}