meerkat-store 0.8.4

//! Storage errors

use meerkat_core::{SessionId, SessionStoreError};

/// Backend-specific error type used internally by meerkat-store implementations.
///
/// External consumers should use [`SessionStoreError`] (from `meerkat-core`) for
/// the `SessionStore` trait boundary. This type carries backend-specific variants
/// (for example rusqlite) that the trait contract intentionally erases.
#[derive(Debug, thiserror::Error)]
pub enum StoreError {
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),

    #[error("Serialization error: {0}")]
    Serialization(#[from] serde_json::Error),

    #[cfg(not(target_arch = "wasm32"))]
    #[error("SQLite error: {0}")]
    Sqlite(#[source] rusqlite::Error),

    /// Transient SQLite contention (SQLITE_BUSY / SQLITE_LOCKED /
    /// interrupt) that escaped the bounded busy handler. Retry is sound
    /// only for idempotent or CAS-keyed operations (see the meerkat-sqlite
    /// crate-level retryability note).
    #[cfg(not(target_arch = "wasm32"))]
    #[error("SQLite busy: {0}")]
    Busy(#[source] rusqlite::Error),

    /// The database file is not (or no longer) a usable SQLite database.
    /// File-level corruption, distinct from the row-level
    /// [`StoreError::Corrupted`].
    #[cfg(not(target_arch = "wasm32"))]
    #[error("SQLite database corrupt: {0}")]
    CorruptDatabase(#[source] rusqlite::Error),

    /// The file's `meerkat_schema` migration ledger is malformed (wrong
    /// pinned shape, duplicate domain rows, non-positive version). On-disk
    /// corruption of the ledger itself — refused, never healed by re-running
    /// migrations over it. Corruption-shaped sibling of
    /// [`StoreError::CorruptDatabase`] (which carries the SQLite-level
    /// source; the ledger check is shape-level and carries only its detail).
    #[cfg(not(target_arch = "wasm32"))]
    #[error("SQLite schema ledger malformed: {detail}")]
    CorruptLedger { detail: String },

    #[error("Session not found: {0}")]
    NotFound(SessionId),

    #[error("Session corrupted: {0}")]
    Corrupted(SessionId),

    #[cfg(not(target_arch = "wasm32"))]
    #[error("Task join error: {0}")]
    Join(#[from] tokio::task::JoinError),

    #[error("Internal error: {0}")]
    Internal(String),

    #[cfg(not(target_arch = "wasm32"))]
    #[error("timed out acquiring realm manifest lock for '{realm_id}'")]
    RealmManifestLockTimeout { realm_id: String },

    #[cfg(not(target_arch = "wasm32"))]
    #[error(
        "realm backend mismatch for '{realm_id}': requested '{requested}', existing '{existing}'"
    )]
    RealmBackendMismatch {
        realm_id: String,
        requested: String,
        existing: String,
    },

    #[cfg(not(target_arch = "wasm32"))]
    #[error("unsupported realm backend for '{realm_id}': '{backend}'")]
    UnsupportedRealmBackend { realm_id: String, backend: String },

    /// The requested realm id sanitizes to the same on-disk path as an
    /// existing manifest that pins a *different* realm identity (e.g. the
    /// raw slugs `a.b` and `a_b` both sanitize to the `a_b` directory).
    /// Two distinct realm identities must never silently share one
    /// manifest, so the path-aliased open is rejected fail-closed rather
    /// than handing back the wrong realm's manifest.
    #[cfg(not(target_arch = "wasm32"))]
    #[error(
        "realm identity mismatch: requested '{requested}' aliases existing manifest '{existing}'"
    )]
    RealmIdentityMismatch { requested: String, existing: String },

    /// Persisted manifest carried a realm id that fails the typed
    /// slug validator (wave-c C-12 sibling retype — the on-disk form
    /// is free-string but the domain type is `RealmId` which enforces
    /// the slug grammar). Reported when an on-disk manifest was
    /// hand-edited to an unparseable realm slug.
    #[cfg(not(target_arch = "wasm32"))]
    #[error("invalid realm id slug in persisted manifest: '{0}'")]
    InvalidRealmSlug(String),

    /// The file's schema ledger records a version newer than this binary
    /// supports: a newer binary migrated the file and this one must refuse
    /// it (typed, health-visible refusal — never a crash loop).
    #[cfg(not(target_arch = "wasm32"))]
    #[error(
        "schema for domain '{domain}' is from the future: file has version {found}, \
         this binary supports up to {supported}"
    )]
    SchemaFromTheFuture {
        domain: String,
        found: i64,
        supported: i64,
    },

    /// The exclusive maintenance fence is held for this database; storage is
    /// under offline maintenance.
    #[cfg(not(target_arch = "wasm32"))]
    #[error("maintenance fence is held for '{path}'; storage is under offline maintenance")]
    MaintenanceFenceHeld { path: std::path::PathBuf },

    /// The realm manifest's format version is newer than this binary
    /// supports (typed refusal: an unknown format may have relocated
    /// storage this binary would otherwise recreate empty).
    #[cfg(not(target_arch = "wasm32"))]
    #[error(
        "realm manifest for '{realm_id}' has format {found}, this binary supports up to \
         {supported}; refusing to open"
    )]
    ManifestFromTheFuture {
        realm_id: String,
        found: u32,
        supported: u32,
    },

    /// The realm is pinned to an external storage provider that this
    /// composition does not supply.
    #[cfg(not(target_arch = "wasm32"))]
    #[error("realm '{realm_id}' is pinned to external storage provider '{provider}'")]
    ExternalProviderRealm { realm_id: String, provider: String },

    /// A provider-aware open found the realm pinned to a different storage
    /// provider (or to a built-in disk backend).
    #[cfg(not(target_arch = "wasm32"))]
    #[error(
        "realm '{realm_id}' is pinned to '{found}', not to storage provider '{expected}'; \
         refusing to open"
    )]
    RealmProviderMismatch {
        realm_id: String,
        expected: String,
        found: String,
    },
}

/// Classify raw SQLite failures at the boundary where they enter the store
/// error taxonomy: bounded-wait contention and file corruption get their
/// typed variants, everything else stays the generic `Sqlite` backend error.
#[cfg(not(target_arch = "wasm32"))]
impl From<rusqlite::Error> for StoreError {
    fn from(err: rusqlite::Error) -> Self {
        use meerkat_sqlite::SqliteErrorClass;
        match meerkat_sqlite::classify_sqlite_error(&err) {
            SqliteErrorClass::Transient => StoreError::Busy(err),
            SqliteErrorClass::Corrupt => StoreError::CorruptDatabase(err),
            SqliteErrorClass::Other => StoreError::Sqlite(err),
        }
    }
}

#[cfg(not(target_arch = "wasm32"))]
impl From<meerkat_sqlite::SqliteStoreError> for StoreError {
    fn from(err: meerkat_sqlite::SqliteStoreError) -> Self {
        use meerkat_sqlite::SqliteStoreError as E;
        match err {
            E::Io(io) => StoreError::Io(io),
            // Route through the rusqlite classifier so shared-mechanics
            // failures carry the same transient/corrupt typing as direct
            // store statements.
            E::Sqlite(sql) => StoreError::from(sql),
            E::SchemaFromTheFuture {
                domain,
                found,
                supported,
            } => StoreError::SchemaFromTheFuture {
                domain,
                found,
                supported,
            },
            E::MaintenanceFenceHeld { path } => StoreError::MaintenanceFenceHeld { path },
            // A malformed ledger IS on-disk corruption of the file's
            // migration bookkeeping.
            E::LedgerMalformed { detail } => StoreError::CorruptLedger { detail },
            other @ (E::MigrationFailed { .. }
            | E::MigrationBrokeTransaction { .. }
            | E::WalNotEstablished { .. }
            | E::InvalidMigrationList { .. }
            | E::OpenRefused { .. }) => StoreError::Internal(other.to_string()),
        }
    }
}

impl StoreError {
    /// Convert to the backend-agnostic [`SessionStoreError`] at the trait boundary.
    pub fn into_session_store_error(self) -> SessionStoreError {
        match self {
            StoreError::Io(e) => SessionStoreError::Io(e),
            StoreError::Serialization(e) => SessionStoreError::Serialization(e.to_string()),
            StoreError::NotFound(id) => SessionStoreError::NotFound(id),
            StoreError::Corrupted(id) => SessionStoreError::Corrupted(id),
            other => SessionStoreError::Internal(other.to_string()),
        }
    }
}

/// Convert [`StoreError`] to [`SessionStoreError`] at the trait boundary.
///
/// Used as `.map_err(into_session_store_error)` in `SessionStore` trait impls.
/// Only needed on native targets where the persistent store backends exist.
#[cfg(not(target_arch = "wasm32"))]
#[cfg(any(feature = "jsonl", feature = "sqlite"))]
pub(crate) fn into_session_store_error(e: StoreError) -> SessionStoreError {
    e.into_session_store_error()
}

#[cfg(all(test, not(target_arch = "wasm32")))]
#[allow(clippy::expect_used, clippy::unwrap_used)]
mod tests {
    use super::*;

    fn sqlite_failure(code: rusqlite::ErrorCode) -> rusqlite::Error {
        rusqlite::Error::SqliteFailure(
            rusqlite::ffi::Error {
                code,
                extended_code: 0,
            },
            None,
        )
    }

    #[test]
    fn busy_and_locked_classify_to_the_transient_variant() {
        for code in [
            rusqlite::ErrorCode::DatabaseBusy,
            rusqlite::ErrorCode::DatabaseLocked,
        ] {
            assert!(matches!(
                StoreError::from(sqlite_failure(code)),
                StoreError::Busy(_)
            ));
        }
    }

    #[test]
    fn corruption_classifies_to_the_corrupt_database_variant() {
        for code in [
            rusqlite::ErrorCode::DatabaseCorrupt,
            rusqlite::ErrorCode::NotADatabase,
        ] {
            assert!(matches!(
                StoreError::from(sqlite_failure(code)),
                StoreError::CorruptDatabase(_)
            ));
        }
    }

    #[test]
    fn other_sqlite_failures_stay_the_generic_backend_variant() {
        assert!(matches!(
            StoreError::from(sqlite_failure(rusqlite::ErrorCode::ConstraintViolation)),
            StoreError::Sqlite(_)
        ));
    }

    #[test]
    fn shared_mechanics_sqlite_errors_are_classified_too() {
        let err = meerkat_sqlite::SqliteStoreError::Sqlite(sqlite_failure(
            rusqlite::ErrorCode::DatabaseBusy,
        ));
        assert!(matches!(StoreError::from(err), StoreError::Busy(_)));
    }

    #[test]
    fn malformed_ledger_maps_to_the_corruption_shaped_variant() {
        let err = meerkat_sqlite::SqliteStoreError::LedgerMalformed {
            detail: "domain row count".to_string(),
        };
        assert!(matches!(
            StoreError::from(err),
            StoreError::CorruptLedger { detail } if detail == "domain row count"
        ));
    }

    #[test]
    fn broken_transaction_and_wal_failures_preserve_display_as_internal() {
        for err in [
            meerkat_sqlite::SqliteStoreError::MigrationBrokeTransaction {
                domain: "session-store".to_string(),
                version: 1,
                name: "base-schema".to_string(),
            },
            meerkat_sqlite::SqliteStoreError::WalNotEstablished {
                path: std::path::PathBuf::from("/tmp/db.sqlite3"),
                actual: "delete".to_string(),
            },
        ] {
            let display = err.to_string();
            assert!(matches!(
                StoreError::from(err),
                StoreError::Internal(detail) if detail == display
            ));
        }
    }
}