solo-storage 0.11.4

// SPDX-License-Identifier: Apache-2.0

//! Daemon-side multi-tenant registry.
//!
//! Holds a `TenantsIndex` plus an in-memory map of opened
//! `Arc<TenantHandle>`. Tenants are opened **lazily**: the first request
//! for a tenant_id pays the open cost (DB connection, migration check,
//! HNSW load, writer-actor spawn, reader pool build); subsequent requests
//! are an `RwLock<HashMap>` hit.
//!
//! ## Lazy-load discipline
//!
//! `get_or_open(tenant_id)` is the hot path. Under concurrency, 100
//! simultaneous requests for the same tenant_id must:
//!   * Return the same `Arc<TenantHandle>` (no race).
//!   * Open the underlying tenant exactly once (no duplicate
//!     writer-actor / reader pool / HNSW load).
//!
//! Implementation: a `RwLock<HashMap<TenantId, Arc<TenantHandle>>>` is the
//! cached map. The slow-path (cache miss) takes the write lock, double-
//! checks the entry, and only opens the tenant if still absent. While the
//! write lock is held, every other concurrent first-access request blocks
//! on the lock and (on resumption) sees the cached entry — no duplicate
//! open. Open work happens inside `tokio::task::spawn_blocking` because
//! `TenantHandle::open` does synchronous DB + HNSW work.
//!
//! Trade-off: holding the registry write lock across the open means every
//! _other_ tenant's first-access requests also block until this one
//! finishes opening. For v0.8.0's deployment shape (≤ 10 tenants typical,
//! open is ~100-500ms), that's acceptable. A future version with hundreds
//! of tenants can move to a per-key Mutex pattern.
//!
//! ## Shutdown
//!
//! `shutdown_all()` drains every cached handle by calling
//! `TenantHandle::shutdown` on each. Designed to run once, at daemon
//! exit. Concurrent activity during shutdown is the operator's problem
//! — this is the daemon-graceful-exit path, the supervisor already
//! stopped accepting work.

use std::collections::HashMap;
use std::path::{Path, PathBuf};
use std::sync::Arc;
use tokio::runtime::Handle as TokioHandle;
use tokio::sync::{Mutex, RwLock};

use solo_core::{Embedder, Error, Result, TenantId};

use crate::key_material::KeyMaterial;
use crate::tenants::{TenantHandle, TenantOpenParams, TenantRecord, TenantsIndex};
use crate::vector_index::HnswParams;

/// Bootstrap deps shared across every tenant the registry opens. Held by
/// the registry; cloned cheaply into each `TenantOpenParams`.
struct RegistryDeps {
    data_dir: PathBuf,
    key: KeyMaterial,
    embedder: Arc<dyn Embedder>,
    hnsw_params: HnswParams,
    steward: Option<Arc<solo_steward::Steward>>,
    /// Runtime handle captured at registry-open time. Passed to each
    /// `TenantHandle::open` so writer-actors can `block_on` async
    /// embedder calls during reembed.
    runtime_handle: Option<TokioHandle>,
    /// v0.9.0 P0c: optional Steward factory threaded through to every
    /// `TenantHandle::open` so the new per-tenant `steward_slot` can be
    /// populated eagerly for static backends (Anthropic / OpenAI /
    /// Ollama / None) and stay empty for the MCP-sampling backend.
    ///
    /// When `None` (the backwards-compat path), the slot is seeded
    /// from `steward: Option<Arc<Steward>>` so the v0.8.x and v0.9.0+
    /// callers observe the same Steward identity from the slot and
    /// from the writer-actor's captured field. v0.9.0 P2 fully migrates
    /// from this dual path to the slot-only path.
    steward_factory: Option<Arc<dyn crate::steward_factory::StewardFactory>>,
    /// v0.9.0 P4-revision (P4 audit M1): optional count-based trigger
    /// signal threaded through to every tenant's writer-actor. The
    /// daemon constructs ONE `Arc<TriplesBatchSignal>` at startup and
    /// shares it with both every tenant's writer-actor (so the actor
    /// can ping after each `Remember`) AND its own
    /// `triples_batch_timer` (so the select-arm can fire on count).
    triples_batch_signal: Option<Arc<crate::triples_batch::TriplesBatchSignal>>,
}

/// Daemon-side multi-tenant registry.
pub struct TenantRegistry {
    /// Mutex around the SQLCipher connection to `tenants_index.db`. Single
    /// access at a time (the registry is the only thing that touches it).
    index: Mutex<TenantsIndex>,
    /// Opened tenant handles, keyed by tenant_id.
    handles: RwLock<HashMap<TenantId, Arc<TenantHandle>>>,
    /// Dev-log 0154 fix-up for 0152 M8: per-tenant open-coordination
    /// Mutex. The first caller for a given tenant takes its Mutex,
    /// runs `spawn_blocking(TenantHandle::open)`, inserts into
    /// `handles`, drops the Mutex. Subsequent same-tenant callers wait
    /// on the same Mutex; when they acquire, the second double-check
    /// finds the handle in `handles` and reuses it.
    ///
    /// Without this, a burst of N first-access calls for the same
    /// tenant could all pass both double-checks of `handles` before
    /// any of them completed `spawn_blocking`, paying N × 100-500 ms
    /// of open cost (correctness-safe, but a real perf regression vs.
    /// the pre-0152 single-flight behaviour).
    ///
    /// The outer Mutex is held only briefly to look up or insert the
    /// per-tenant Arc; the inner per-tenant Mutex is the one held
    /// across the `spawn_blocking` await. Both are `tokio::sync::Mutex`
    /// because the per-tenant lock crosses an await point.
    ///
    /// Map grows by one entry per tenant ever opened. Bounded by the
    /// real-world tenant count; no GC today. If tenant rotation
    /// becomes a deployment shape, prune entries with `Arc::strong_count == 1`.
    open_locks: Mutex<HashMap<TenantId, Arc<Mutex<()>>>>,
    deps: RegistryDeps,
}

/// Parameters for opening the registry.
pub struct TenantRegistryParams {
    pub data_dir: PathBuf,
    pub key: KeyMaterial,
    pub embedder: Arc<dyn Embedder>,
    pub hnsw_params: HnswParams,
    pub steward: Option<Arc<solo_steward::Steward>>,
    /// Tokio runtime handle. Required by the writer-actor spawn path for
    /// `block_on` of async embedder calls during reembed. The registry
    /// passes this through to every `TenantHandle::open`. Construct with
    /// `tokio::runtime::Handle::current()` from inside `#[tokio::main]`.
    pub runtime_handle: Option<TokioHandle>,
    /// v0.9.0 P0c: optional Steward factory. When `Some(_)`, every
    /// `TenantHandle::open` calls `factory.build()` and writes the
    /// result into the per-tenant `steward_slot`. Static-backend
    /// factories (`StaticStewardFactory` around an Anthropic / OpenAI /
    /// Ollama / Noop-backed Steward) populate the slot eagerly with
    /// zero hot-path lock-contention cost; the MCP-sampling factory
    /// returns `Ok(None)` for the eager-populate (v0.9.0 P2's
    /// `SoloMcpServer::initialize` hook bypasses the factory entirely
    /// on the sampling path and writes into the slot directly).
    ///
    /// When `None` (the backwards-compat path), the slot is seeded
    /// from `steward: Option<Arc<Steward>>` instead. Existing v0.8.x
    /// callers that pass `steward: Some(...)` without setting a
    /// factory observe consistent behavior — the slot mirrors the
    /// writer-actor's captured Steward.
    #[allow(clippy::type_complexity)]
    pub steward_factory:
        Option<Arc<dyn crate::steward_factory::StewardFactory>>,
    /// v0.9.0 P4-revision (P4 audit M1): optional count-based trigger
    /// signal. The daemon passes `Some(Arc::clone(&signal))` so its
    /// `triples_batch_timer` and every tenant's writer-actor share the
    /// same counter + notify. `None` for paths that don't drive the
    /// background batch (CLI one-shot commands, tests).
    pub triples_batch_signal:
        Option<Arc<crate::triples_batch::TriplesBatchSignal>>,
}

impl TenantRegistry {
    /// Open the registry. Opens `tenants_index.db`, applies its
    /// migrations, and (if the v0.7.1 layout is detected) runs the
    /// mass-data-move helper before returning. Does NOT auto-open any
    /// tenant handle; that happens lazily on first `get_or_open`.
    pub fn open(params: TenantRegistryParams) -> Result<Self> {
        let TenantRegistryParams {
            data_dir,
            key,
            embedder,
            hnsw_params,
            steward,
            runtime_handle,
            steward_factory,
            triples_batch_signal,
        } = params;

        // Auto-detect v0.7.1 layout → run mass-data-move BEFORE opening
        // the registry. Idempotent if the helper already ran. We replicate
        // the detection logic from `startup::run` so the registry-open
        // path works whether called from daemon or one-shot.
        let tenants_index_path = data_dir.join(crate::tenants::TENANTS_INDEX_FILENAME);
        let legacy_db_path = data_dir.join("solo.db");
        if !tenants_index_path.is_file() && legacy_db_path.is_file() {
            tracing::info!(
                data_dir = %data_dir.display(),
                "v0.7.1 single-DB layout detected; running v0.7.1 → v0.8.0 mass-data-move"
            );
            crate::tenants::migrate_v071_to_v080(&data_dir, &key)?;
        }

        let index = TenantsIndex::open(&data_dir, &key)?;

        Ok(Self {
            index: Mutex::new(index),
            handles: RwLock::new(HashMap::new()),
            open_locks: Mutex::new(HashMap::new()),
            deps: RegistryDeps {
                data_dir,
                key,
                embedder,
                hnsw_params,
                steward,
                runtime_handle,
                steward_factory,
                triples_batch_signal,
            },
        })
    }

    /// Data dir this registry serves.
    pub fn data_dir(&self) -> &Path {
        &self.deps.data_dir
    }

    /// Get (or lazily open) the handle for `tenant_id`.
    ///
    /// Concurrent first-access for the same tenant: see module docs. All
    /// callers see the same `Arc<TenantHandle>`; no duplicate handle is
    /// opened.
    ///
    /// v0.9.0 P1: every call (cache miss OR cache hit) stamps
    /// `tenants.last_accessed = now_ms` in the registry before returning
    /// the handle. This closes the v0.8.0 doc-vs-code gap (lesson #39
    /// second incident — the column was documented but never written).
    /// Failures of the stamp are non-fatal: they emit a single
    /// `tracing::warn!` but do not block the open, because the
    /// last_accessed value is observational, not load-bearing for any
    /// invariant.
    pub async fn get_or_open(
        &self,
        tenant_id: &TenantId,
    ) -> Result<Arc<TenantHandle>> {
        // Fast path: read lock + HashMap::get.
        {
            let map = self.handles.read().await;
            if let Some(h) = map.get(tenant_id) {
                let handle = h.clone();
                // Release the read lock BEFORE acquiring the index
                // mutex so concurrent slow-path opens aren't blocked by
                // our stamp write.
                drop(map);
                self.touch_last_accessed_best_effort(tenant_id).await;
                return Ok(handle);
            }
        }

        // Dev-log 0152 M8 + 0154 fix-up: open serialised through a
        // per-tenant Mutex so a burst of N same-tenant callers pays
        // ONE open cost, not N. The map-level `handles` write lock is
        // never held across `spawn_blocking` so other tenants and
        // `forget_handle` can still make progress concurrently.
        //
        // Sequence:
        //   1. Look up (or insert) the per-tenant Mutex Arc under a
        //      brief `open_locks` lock; release `open_locks`.
        //   2. Await the per-tenant Mutex. Same-tenant callers serialise
        //      here; different-tenant callers do not block each other.
        //   3. Inside the per-tenant lock, double-check `handles` —
        //      if a prior caller already inserted, return their handle.
        //   4. Otherwise: lookup index, `spawn_blocking(TenantHandle::open)`,
        //      insert into `handles`. Drop per-tenant lock.
        //   5. Touch last-accessed, return.

        // 1. Get-or-insert per-tenant open lock.
        let open_lock: Arc<Mutex<()>> = {
            let mut locks = self.open_locks.lock().await;
            locks
                .entry(tenant_id.clone())
                .or_insert_with(|| Arc::new(Mutex::new(())))
                .clone()
        };

        // 2. Serialise same-tenant opens here.
        let _open_guard = open_lock.lock().await;

        // 3. Second double-check after acquiring the per-tenant lock.
        //    If a prior same-tenant caller already opened, reuse.
        {
            let map = self.handles.read().await;
            if let Some(h) = map.get(tenant_id) {
                let handle = h.clone();
                drop(map);
                drop(_open_guard);
                self.touch_last_accessed_best_effort(tenant_id).await;
                return Ok(handle);
            }
        }

        // 4. Lookup the tenant's row in the index. Drop the index
        //    mutex BEFORE the open work so a concurrent `forget_handle`
        //    can make progress. v0.8.1 P3: also capture quota_bytes so
        //    the writer-actor can enforce it.
        let (db_filename, quota_bytes) = {
            let index = self.index.lock().await;
            let rec = index.lookup(tenant_id)?.ok_or_else(|| {
                Error::not_found(format!(
                    "tenant `{tenant_id}` not found in tenants_index"
                ))
            })?;
            if rec.status != crate::tenants::TenantStatus::Active {
                return Err(Error::conflict(format!(
                    "tenant `{tenant_id}` has status `{}`; refusing to open",
                    rec.status.as_sql_str()
                )));
            }
            (rec.db_filename, rec.quota_bytes)
        };

        // Build params + open the tenant. This is sync + blocking, so run
        // it on a blocking thread to avoid stalling the tokio runtime.
        // The per-tenant `_open_guard` is held across the await — but
        // only blocks OTHER same-tenant callers, not the world.
        let tenant_id_clone = tenant_id.clone();
        let open_params = TenantOpenParams {
            data_dir: self.deps.data_dir.clone(),
            key: self.deps.key.clone(),
            db_filename,
            embedder: self.deps.embedder.clone(),
            hnsw_params: self.deps.hnsw_params.clone(),
            steward: self.deps.steward.clone(),
            runtime_handle: self.deps.runtime_handle.clone(),
            quota_bytes,
            steward_factory: self.deps.steward_factory.clone(),
            triples_batch_signal: self.deps.triples_batch_signal.clone(),
        };
        let handle = tokio::task::spawn_blocking(move || {
            TenantHandle::open(tenant_id_clone, open_params)
        })
        .await
        .map_err(|e| Error::storage(format!("join spawn_blocking for TenantHandle::open: {e}")))??;

        let arc = Arc::new(handle);
        {
            let mut map = self.handles.write().await;
            map.insert(tenant_id.clone(), arc.clone());
        }
        drop(_open_guard);

        self.touch_last_accessed_best_effort(tenant_id).await;
        Ok(arc)
    }

    /// v0.9.0 P1: helper for `get_or_open` — writes
    /// `tenants.last_accessed = now_ms` on the registry row.
    ///
    /// Best-effort: failures (registry write contention, transient
    /// SQLite error) log `tracing::warn!` but never bubble to the
    /// caller. The `last_accessed` column is observational — it powers
    /// the `solo tenants list` "last_accessed" column and informs
    /// future tenant-eviction heuristics. A missed stamp doesn't
    /// compromise any invariant.
    ///
    /// Failure path also covers the "tenant was concurrently deleted
    /// between cache hit and stamp" case: `touch_last_accessed` returns
    /// `Ok(0)` in that case, which we silently ignore — the caller has
    /// already received the cached handle.
    async fn touch_last_accessed_best_effort(&self, tenant_id: &TenantId) {
        let now_ms: i64 = chrono::Utc::now().timestamp_millis();
        let mut index = self.index.lock().await;
        if let Err(e) = index.touch_last_accessed(tenant_id, now_ms) {
            tracing::warn!(
                tenant = %tenant_id,
                error = %e,
                "touch_last_accessed: registry stamp failed; tenant open \
                 succeeded but the last_accessed column will not reflect \
                 this open until the next successful call"
            );
        }
    }

    /// Evict a tenant from the in-memory cache (used by the P6
    /// hard-delete sequence). The caller is responsible for calling
    /// `TenantHandle::shutdown` on the returned handle.
    ///
    /// Returns the evicted handle if it was in the cache, or `None` if
    /// it wasn't open.
    pub async fn forget_handle(
        &self,
        tenant_id: &TenantId,
    ) -> Option<Arc<TenantHandle>> {
        let mut map = self.handles.write().await;
        map.remove(tenant_id)
    }

    /// List every tenant in the registry index (regardless of open state).
    pub async fn list_active(&self) -> Result<Vec<TenantRecord>> {
        let index = self.index.lock().await;
        index.list()
    }

    /// v0.10.1: hydrate per-tenant cost numbers for the `/v1/tenants`
    /// wire-shape fields that v0.10.0 always reported as `null`. Returns
    /// one [`TenantCostNumbers`] per input record, in the same order.
    ///
    /// For each tenant:
    ///   * `size_bytes` — `std::fs::metadata(<data_dir>/tenants/<db_filename>).len()`,
    ///     or `None` if the file is missing / unreadable. Cheap (no DB
    ///     open).
    ///   * `episode_count` — `SELECT COUNT(*) FROM episodes WHERE
    ///     status='active'` against the per-tenant SQLCipher DB. Opens a
    ///     short-lived connection per tenant; the connection is closed
    ///     before the next tenant is touched. `None` if the DB file is
    ///     missing OR the open / count failed (caller logs).
    ///
    /// **Cap**: only the first `cap` records have `episode_count`
    /// hydrated (the expensive DB-open path). Records beyond the cap
    /// return `None` for `episode_count`. `size_bytes` is computed for
    /// every record regardless of the cap — `std::fs::metadata` is
    /// cheap (no DB open). Callers (e.g. the HTTP handler) surface the
    /// cap-reached condition via a response header so clients can
    /// fetch counts for the tail tenants out-of-band if needed. The
    /// cap is load-bearing for performance: N×10ms tenant-open is
    /// unbounded otherwise, and the `/v1/tenants` first-paint budget
    /// is tight.
    ///
    /// **Error semantics**: a single tenant's count failure is logged
    /// at WARN and surfaced as `None` for that tenant's counts. The
    /// other tenants' counts are unaffected. The method never returns
    /// `Err` — caller cannot distinguish "missing DB" from "count SQL
    /// failed" and shouldn't have to.
    ///
    /// Test-only note: if the registry was constructed via
    /// `for_tests_with_single_tenant`, the tenant DB on disk is a plain
    /// SQLite file (no SQLCipher encryption), and our SQLCipher-keyed
    /// open will fail with a header mismatch. The method falls back to
    /// a plain `Connection::open` for that case — which works on real
    /// SQLCipher files too, because PRAGMA key without a key just
    /// produces an error and `Connection::open` succeeds at the file
    /// layer. To be safe, the fallback only runs when SQLCipher open
    /// errors out, and the fallback's COUNT query itself fails on a
    /// real encrypted DB (decrypt error on schema read) — preserving
    /// production semantics.
    pub async fn hydrate_tenant_cost_numbers(
        &self,
        records: &[TenantRecord],
        cap: usize,
    ) -> Vec<TenantCostNumbers> {
        // Dev-log 0152 M7: the inner work is synchronous filesystem
        // metadata + (cap-limited) SQLCipher COUNT(*) queries. Moved
        // into `spawn_blocking` so the tokio worker doesn't stall
        // proportionally to tenant count.
        let data_dir = self.deps.data_dir.clone();
        let key = self.deps.key.clone();
        // Take a snapshot of the records the closure needs. Cloning the
        // db_filename per record is cheap relative to the metadata +
        // SQLCipher open work the closure will then do.
        let snapshot: Vec<(usize, String)> = records
            .iter()
            .enumerate()
            .map(|(i, r)| (i, r.db_filename.clone()))
            .collect();
        let total = snapshot.len();

        tokio::task::spawn_blocking(move || {
            let mut out = Vec::with_capacity(total);
            for (i, db_filename) in snapshot {
                let db_path = data_dir
                    .join(crate::tenants::TENANTS_SUBDIR)
                    .join(&db_filename);
                let size_bytes = match std::fs::metadata(&db_path) {
                    Ok(meta) => Some(meta.len()),
                    Err(_) => None,
                };
                let episode_count = if i < cap && db_path.is_file() {
                    hydrate_episode_count(&db_path, &key)
                } else {
                    None
                };
                out.push(TenantCostNumbers {
                    size_bytes,
                    episode_count,
                });
            }
            out
        })
        .await
        .unwrap_or_else(|join_err| {
            tracing::warn!(
                error = %join_err,
                "hydrate_tenant_cost_numbers: spawn_blocking join failed; returning empty"
            );
            Vec::new()
        })
    }

    /// Borrow the underlying TenantsIndex for admin operations (P6/P7
    /// create/delete/backup/restore). Avoids re-opening the SQLCipher
    /// connection for every admin call.
    pub async fn with_index<F, R>(&self, f: F) -> R
    where
        F: FnOnce(&mut TenantsIndex) -> R,
    {
        let mut index = self.index.lock().await;
        f(&mut *index)
    }

    /// Graceful shutdown of every cached handle. Saves snapshots, drains
    /// writers, drops pools. Designed for daemon exit.
    pub async fn shutdown_all(&self) {
        // Drain the map into an owned Vec so we can run shutdowns
        // sequentially without holding the write lock for the whole run.
        let handles: Vec<(TenantId, Arc<TenantHandle>)> = {
            let mut map = self.handles.write().await;
            map.drain().collect()
        };
        for (tenant_id, handle) in handles {
            // We only have an Arc<TenantHandle> in the map; shutdown
            // consumes a `TenantHandle` (not Arc). If we hold the only
            // remaining Arc, unwrap is fine; if not (e.g., a handler
            // still holds one), we fall back to logging a warning and
            // moving on — the next process restart will reopen + flush.
            match Arc::try_unwrap(handle) {
                Ok(owned) => {
                    if let Err(e) = owned.shutdown(true).await {
                        tracing::warn!(
                            tenant = %tenant_id,
                            error = %e,
                            "tenant shutdown returned error"
                        );
                    }
                }
                Err(_still_shared) => {
                    tracing::warn!(
                        tenant = %tenant_id,
                        "tenant handle still has outstanding Arc clones at \
                         shutdown_all; skipping. The next process restart \
                         will reload from snapshot + replay pending_index."
                    );
                }
            }
        }
    }

    /// True iff this tenant is currently in the in-memory cache. Test
    /// helper / metric surface.
    pub async fn is_open(&self, tenant_id: &TenantId) -> bool {
        let map = self.handles.read().await;
        map.contains_key(tenant_id)
    }

    /// Test-only constructor that builds a registry around a single
    /// pre-built `TenantHandle`. Skips opening `tenants_index.db` (which
    /// requires SQLCipher) so test harnesses can drive transport-layer
    /// flows without paying the full bootstrap cost.
    ///
    /// The supplied handle becomes the registry's only cached tenant.
    /// `get_or_open(tenant_id)` returns it for the handle's own
    /// tenant_id; any other tenant_id errors with NotFound (no index to
    /// lazy-open from).
    #[cfg(any(test, feature = "test-support"))]
    pub fn for_tests_with_single_tenant(
        data_dir: std::path::PathBuf,
        key: KeyMaterial,
        embedder: Arc<dyn solo_core::Embedder>,
        handle: Arc<TenantHandle>,
    ) -> Self {
        let tenant_id = handle.tenant_id().clone();
        let mut handles_map = HashMap::new();
        handles_map.insert(tenant_id, handle);
        // Open an in-memory TenantsIndex stub. We won't really persist
        // through it; the harness's get_or_open() lookups hit the
        // cached HashMap and never reach the index.
        // For simplicity, use an in-memory SQLite connection bypassing
        // SQLCipher entirely.
        let conn = rusqlite::Connection::open_in_memory()
            .expect("open in-memory tenants_index stub for tests");
        // Apply the registry's schema so any code that does happen to
        // touch the index (e.g. list_active) doesn't blow up.
        let mut conn = conn;
        crate::migration::run_tenants_index_migrations(&mut conn)
            .expect("apply tenants_index migrations to in-memory test stub");
        let index = TenantsIndex::from_connection_for_tests(conn);
        Self {
            index: Mutex::new(index),
            handles: RwLock::new(handles_map),
            open_locks: Mutex::new(HashMap::new()),
            deps: RegistryDeps {
                data_dir,
                key,
                embedder,
                hnsw_params: crate::vector_index::HnswParams::default(),
                steward: None,
                runtime_handle: None,
                steward_factory: None,
                triples_batch_signal: None,
            },
        }
    }
}

/// v0.10.1: per-tenant cost numbers returned by
/// [`TenantRegistry::hydrate_tenant_cost_numbers`]. One per input
/// tenant, in the same order. `None` for any field whose source could
/// not be read (missing DB file, opaque SQLite error, capped-out of
/// the per-request budget).
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct TenantCostNumbers {
    /// File size of the per-tenant SQLCipher DB on disk. `None` if the
    /// file is missing or unreadable.
    pub size_bytes: Option<u64>,
    /// Count of `episodes WHERE status='active'`. `None` if the DB
    /// could not be opened or queried, or if the per-request cap was
    /// reached before this tenant.
    pub episode_count: Option<i64>,
}

/// Open the per-tenant SQLCipher DB at `db_path`, count active
/// episodes, and return the result. Returns `None` on any open / count
/// failure (logged at WARN). Sync — caller may run from blocking
/// context (the `/v1/tenants` hydration loop does so).
///
/// Performance: one SQLCipher open + one indexed COUNT per call.
/// Typical wall is ~5-10ms per tenant on a warm filesystem. The cap on
/// the calling side bounds the total per-request cost.
///
/// Test-only fallback: if the SQLCipher open fails (e.g. the test
/// harness's plain-SQLite tenant DB), retry with a plain
/// `rusqlite::Connection::open`. On a real encrypted DB the fallback's
/// COUNT will itself fail because the schema page can't be decoded
/// without the key — so production semantics are preserved.
fn hydrate_episode_count(
    db_path: &std::path::Path,
    key: &KeyMaterial,
) -> Option<i64> {
    let count = match crate::init::open_sqlcipher(db_path, key) {
        Ok(conn) => count_active_episodes(&conn),
        Err(_) => {
            // Test-mode fallback: harness DBs are plain SQLite, not
            // SQLCipher. Try a plain open.
            match rusqlite::Connection::open(db_path) {
                Ok(conn) => count_active_episodes(&conn),
                Err(e) => {
                    tracing::warn!(
                        db = %db_path.display(),
                        error = %e,
                        "hydrate_episode_count: open failed (both SQLCipher and plain)"
                    );
                    return None;
                }
            }
        }
    };
    match count {
        Ok(n) => Some(n),
        Err(e) => {
            tracing::warn!(
                db = %db_path.display(),
                error = %e,
                "hydrate_episode_count: COUNT(*) failed"
            );
            None
        }
    }
}

fn count_active_episodes(conn: &rusqlite::Connection) -> Result<i64> {
    conn.query_row(
        "SELECT COUNT(*) FROM episodes WHERE status = 'active'",
        [],
        |r| r.get::<_, i64>(0),
    )
    .map_err(|e| Error::storage(format!("COUNT(*) FROM episodes: {e}")))
}