import type { BrainEngine } from './engine.ts';
import { slugifyPath } from './sync.ts';

/**
 * Schema migrations — run automatically on initSchema().
 *
 * Each migration is a version number + idempotent SQL. Migrations are embedded
 * as string constants (Bun's --compile strips the filesystem).
 *
 * Each migration runs in a transaction: if the SQL fails, the version stays
 * where it was and the next run retries cleanly.
 *
 * Migrations can also include a handler function for application-level logic
 * (e.g., data transformations that need TypeScript, not just SQL).
 */

interface Migration {
  version: number;
  name: string;
  /** Engine-agnostic SQL. Used when `sqlFor` is absent. Set to '' for handler-only or sqlFor-only migrations. */
  sql: string;
  /**
   * Engine-specific SQL. If present, overrides `sql` for the matching engine.
   * Needed when Postgres wants CONCURRENTLY but PGLite can't honor it.
   */
  sqlFor?: { postgres?: string; pglite?: string };
  /**
   * When false, the runner does NOT wrap the SQL in `engine.transaction()`.
   * Required for `CREATE INDEX CONCURRENTLY` (which Postgres refuses inside a transaction).
   * Enforced Postgres-only; ignored on PGLite (PGLite has no concurrent writers anyway).
   * Defaults to true.
   */
  transaction?: boolean;
  handler?: (engine: BrainEngine) => Promise<void>;
}

// Migrations are embedded here, not loaded from files.
// Add new migrations at the end. Never modify existing ones.
// Exported for tests that structurally assert migration contents (e.g., "v9 must
// pre-create idx_timeline_dedup_helper before the DELETE..."). Read-only contract.
export const MIGRATIONS: Migration[] = [
  // Version 1 is the baseline (schema.sql creates everything with IF NOT EXISTS).
  {
    version: 2,
    name: 'slugify_existing_pages',
    sql: '',
    handler: async (engine) => {
      const pages = await engine.listPages();
      let renamed = 0;
      for (const page of pages) {
        const newSlug = slugifyPath(page.slug);
        if (newSlug !== page.slug) {
          try {
            await engine.updateSlug(page.slug, newSlug);
            await engine.rewriteLinks(page.slug, newSlug);
            renamed++;
          } catch (e: unknown) {
            const msg = e instanceof Error ? e.message : String(e);
            console.error(`  Warning: could not rename "${page.slug}" → "${newSlug}": ${msg}`);
          }
        }
      }
      if (renamed > 0) console.log(`  Renamed ${renamed} slugs`);
    },
  },
  {
    version: 3,
    name: 'unique_chunk_index',
    sql: `
      -- Deduplicate any existing duplicate (page_id, chunk_index) rows before adding constraint
      DELETE FROM content_chunks a USING content_chunks b
        WHERE a.page_id = b.page_id AND a.chunk_index = b.chunk_index AND a.id > b.id;
      CREATE UNIQUE INDEX IF NOT EXISTS idx_chunks_page_index ON content_chunks(page_id, chunk_index);
    `,
  },
  {
    version: 4,
    name: 'access_tokens_and_mcp_log',
    sql: `
      CREATE TABLE IF NOT EXISTS access_tokens (
        id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
        name TEXT NOT NULL,
        token_hash TEXT NOT NULL UNIQUE,
        scopes TEXT[],
        created_at TIMESTAMPTZ DEFAULT now(),
        last_used_at TIMESTAMPTZ,
        revoked_at TIMESTAMPTZ
      );
      CREATE INDEX IF NOT EXISTS idx_access_tokens_hash ON access_tokens (token_hash) WHERE revoked_at IS NULL;
      CREATE TABLE IF NOT EXISTS mcp_request_log (
        id SERIAL PRIMARY KEY,
        token_name TEXT,
        operation TEXT NOT NULL,
        latency_ms INTEGER,
        status TEXT NOT NULL DEFAULT 'success',
        created_at TIMESTAMPTZ NOT NULL DEFAULT now()
      );
    `,
  },
  {
    version: 5,
    name: 'minion_jobs_table',
    sql: `
      CREATE TABLE IF NOT EXISTS minion_jobs (
        id               SERIAL PRIMARY KEY,
        name             TEXT        NOT NULL,
        queue            TEXT        NOT NULL DEFAULT 'default',
        status           TEXT        NOT NULL DEFAULT 'waiting',
        priority         INTEGER     NOT NULL DEFAULT 0,
        data             JSONB       NOT NULL DEFAULT '{}',
        max_attempts     INTEGER     NOT NULL DEFAULT 3,
        attempts_made    INTEGER     NOT NULL DEFAULT 0,
        attempts_started INTEGER     NOT NULL DEFAULT 0,
        backoff_type     TEXT        NOT NULL DEFAULT 'exponential',
        backoff_delay    INTEGER     NOT NULL DEFAULT 1000,
        backoff_jitter   REAL        NOT NULL DEFAULT 0.2,
        stalled_counter  INTEGER     NOT NULL DEFAULT 0,
        max_stalled      INTEGER     NOT NULL DEFAULT 5,
        lock_token       TEXT,
        lock_until       TIMESTAMPTZ,
        delay_until      TIMESTAMPTZ,
        parent_job_id    INTEGER     REFERENCES minion_jobs(id) ON DELETE SET NULL,
        on_child_fail    TEXT        NOT NULL DEFAULT 'fail_parent',
        result           JSONB,
        progress         JSONB,
        error_text       TEXT,
        stacktrace       JSONB       DEFAULT '[]',
        created_at       TIMESTAMPTZ NOT NULL DEFAULT now(),
        started_at       TIMESTAMPTZ,
        finished_at      TIMESTAMPTZ,
        updated_at       TIMESTAMPTZ NOT NULL DEFAULT now(),
        CONSTRAINT chk_status CHECK (status IN ('waiting','active','completed','failed','delayed','dead','cancelled','waiting-children')),
        CONSTRAINT chk_backoff_type CHECK (backoff_type IN ('fixed','exponential')),
        CONSTRAINT chk_on_child_fail CHECK (on_child_fail IN ('fail_parent','remove_dep','ignore','continue')),
        CONSTRAINT chk_jitter_range CHECK (backoff_jitter >= 0.0 AND backoff_jitter <= 1.0),
        CONSTRAINT chk_attempts_order CHECK (attempts_made <= attempts_started),
        CONSTRAINT chk_nonnegative CHECK (attempts_made >= 0 AND attempts_started >= 0 AND stalled_counter >= 0 AND max_attempts >= 1 AND max_stalled >= 0)
      );
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_claim ON minion_jobs (queue, priority ASC, created_at ASC) WHERE status = 'waiting';
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_status ON minion_jobs(status);
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_stalled ON minion_jobs (lock_until) WHERE status = 'active';
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_delayed ON minion_jobs (delay_until) WHERE status = 'delayed';
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_parent ON minion_jobs(parent_job_id);
    `,
  },
  {
    version: 6,
    name: 'agent_orchestration_primitives',
    sql: `
      -- Token accounting columns
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS tokens_input INTEGER NOT NULL DEFAULT 0;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS tokens_output INTEGER NOT NULL DEFAULT 0;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS tokens_cache_read INTEGER NOT NULL DEFAULT 0;

      -- Update status constraint to include 'paused'
      ALTER TABLE minion_jobs DROP CONSTRAINT IF EXISTS chk_status;
      ALTER TABLE minion_jobs ADD CONSTRAINT chk_status
        CHECK (status IN ('waiting','active','completed','failed','delayed','dead','cancelled','waiting-children','paused'));

      -- Inbox table (separate from job row for clean concurrency)
      CREATE TABLE IF NOT EXISTS minion_inbox (
        id          SERIAL PRIMARY KEY,
        job_id      INTEGER NOT NULL REFERENCES minion_jobs(id) ON DELETE CASCADE,
        sender      TEXT NOT NULL,
        payload     JSONB NOT NULL,
        sent_at     TIMESTAMPTZ NOT NULL DEFAULT now(),
        read_at     TIMESTAMPTZ
      );
      CREATE INDEX IF NOT EXISTS idx_minion_inbox_unread ON minion_inbox (job_id) WHERE read_at IS NULL;
    `,
  },
  {
    version: 7,
    name: 'agent_parity_layer',
    sql: `
      -- Subagent primitives + BullMQ parity columns
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS depth INTEGER NOT NULL DEFAULT 0;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS max_children INTEGER;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS timeout_ms INTEGER;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS timeout_at TIMESTAMPTZ;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS remove_on_complete BOOLEAN NOT NULL DEFAULT FALSE;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS remove_on_fail BOOLEAN NOT NULL DEFAULT FALSE;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS idempotency_key TEXT;

      -- Tighten constraints (drop-then-add for idempotency)
      ALTER TABLE minion_jobs DROP CONSTRAINT IF EXISTS chk_depth_nonnegative;
      ALTER TABLE minion_jobs ADD CONSTRAINT chk_depth_nonnegative CHECK (depth >= 0);
      ALTER TABLE minion_jobs DROP CONSTRAINT IF EXISTS chk_max_children_positive;
      ALTER TABLE minion_jobs ADD CONSTRAINT chk_max_children_positive CHECK (max_children IS NULL OR max_children > 0);
      ALTER TABLE minion_jobs DROP CONSTRAINT IF EXISTS chk_timeout_positive;
      ALTER TABLE minion_jobs ADD CONSTRAINT chk_timeout_positive CHECK (timeout_ms IS NULL OR timeout_ms > 0);

      -- Bounded scan for handleTimeouts
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_timeout ON minion_jobs (timeout_at)
        WHERE status = 'active' AND timeout_at IS NOT NULL;

      -- O(children) child-count check in add()
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_parent_status ON minion_jobs (parent_job_id, status)
        WHERE parent_job_id IS NOT NULL;

      -- Idempotency: enforce "only one job per key" at the DB layer
      CREATE UNIQUE INDEX IF NOT EXISTS uniq_minion_jobs_idempotency ON minion_jobs (idempotency_key)
        WHERE idempotency_key IS NOT NULL;

      -- Fast lookup of child_done messages for readChildCompletions
      CREATE INDEX IF NOT EXISTS idx_minion_inbox_child_done ON minion_inbox (job_id, sent_at)
        WHERE (payload->>'type') = 'child_done';

      -- Attachment manifest (BYTEA inline + forward-compat storage_uri)
      CREATE TABLE IF NOT EXISTS minion_attachments (
        id            SERIAL PRIMARY KEY,
        job_id        INTEGER NOT NULL REFERENCES minion_jobs(id) ON DELETE CASCADE,
        filename      TEXT NOT NULL,
        content_type  TEXT NOT NULL,
        content       BYTEA,
        storage_uri   TEXT,
        size_bytes    INTEGER NOT NULL,
        sha256        TEXT NOT NULL,
        created_at    TIMESTAMPTZ NOT NULL DEFAULT now(),
        CONSTRAINT uniq_minion_attachments_job_filename UNIQUE (job_id, filename),
        CONSTRAINT chk_attachment_storage CHECK (content IS NOT NULL OR storage_uri IS NOT NULL),
        CONSTRAINT chk_attachment_size CHECK (size_bytes >= 0)
      );
      CREATE INDEX IF NOT EXISTS idx_minion_attachments_job ON minion_attachments (job_id);

      -- TOAST tuning: store attachment bytes out-of-line, skip compression.
      -- Attachments are usually already-compressed formats; compression burns CPU for no win.
      DO $$
      BEGIN
        ALTER TABLE minion_attachments ALTER COLUMN content SET STORAGE EXTERNAL;
      EXCEPTION WHEN OTHERS THEN
        -- PGLite may not support SET STORAGE EXTERNAL. Storage tuning is an optimization, not correctness.
        NULL;
      END $$;
    `,
  },
  // ── Knowledge graph layer (PR #188, originally proposed as v5/v6/v7 but
  //    renumbered to v8/v9/v10 to land after the master Minions migrations).
  //    Existing brains migrated against the original v5/v6/v7 names (in
  //    branches that pre-dated the merge) get a no-op pass here because
  //    every statement is idempotent.
  {
    version: 8,
    name: 'multi_type_links_constraint',
    // Idempotent for both upgrade and fresh-install paths.
    // Fresh installs already have links_from_to_type_unique from schema.sql; we drop it
    // (along with the legacy from-to-only constraint) before re-adding it cleanly.
    // Helper btree on the dedup columns turns the DELETE...USING self-join from O(n²)
    // into O(n log n). Without it, a brain with 80K+ duplicate link rows hits
    // Supabase Management API's 60s ceiling during upgrade.
    sql: `
      ALTER TABLE links DROP CONSTRAINT IF EXISTS links_from_page_id_to_page_id_key;
      ALTER TABLE links DROP CONSTRAINT IF EXISTS links_from_to_type_unique;
      CREATE INDEX IF NOT EXISTS idx_links_dedup_helper
        ON links(from_page_id, to_page_id, link_type);
      DELETE FROM links a USING links b
        WHERE a.from_page_id = b.from_page_id
          AND a.to_page_id = b.to_page_id
          AND a.link_type = b.link_type
          AND a.id > b.id;
      DROP INDEX IF EXISTS idx_links_dedup_helper;
      ALTER TABLE links ADD CONSTRAINT links_from_to_type_unique
        UNIQUE(from_page_id, to_page_id, link_type);
    `,
  },
  {
    version: 9,
    name: 'timeline_dedup_index',
    // Idempotent: CREATE UNIQUE INDEX IF NOT EXISTS handles fresh + upgrade.
    // Dedup any existing duplicates first so the index can be created.
    // Helper btree turns the DELETE...USING self-join from O(n²) into O(n log n).
    // Without it, a brain with 80K+ duplicate timeline rows hits Supabase
    // Management API's 60s ceiling. See migration v8 for the same pattern.
    sql: `
      CREATE INDEX IF NOT EXISTS idx_timeline_dedup_helper
        ON timeline_entries(page_id, date, summary);
      DELETE FROM timeline_entries a USING timeline_entries b
        WHERE a.page_id = b.page_id
          AND a.date = b.date
          AND a.summary = b.summary
          AND a.id > b.id;
      DROP INDEX IF EXISTS idx_timeline_dedup_helper;
      CREATE UNIQUE INDEX IF NOT EXISTS idx_timeline_dedup
        ON timeline_entries(page_id, date, summary);
    `,
  },
  {
    version: 10,
    name: 'drop_timeline_search_trigger',
    // Removes the trigger that updates pages.updated_at on every timeline_entries insert.
    // Structured timeline_entries are now graph data (queryable dates), not search text.
    // pages.timeline (markdown) still feeds the page search_vector via trg_pages_search_vector.
    // Removing this trigger also fixes a mutation-induced reordering bug in timeline-extract
    // pagination (listPages ORDER BY updated_at DESC drifted as inserts touched pages).
    sql: `
      DROP TRIGGER IF EXISTS trg_timeline_search_vector ON timeline_entries;
      DROP FUNCTION IF EXISTS update_page_search_vector_from_timeline();
    `,
  },
  {
    version: 11,
    name: 'links_provenance_columns',
    // v0.13: adds provenance columns so frontmatter-derived edges can be
    // distinguished from markdown/manual edges. Reconciliation on put_page
    // scopes by (link_source='frontmatter' AND origin_page_id = written_page)
    // so edges from other pages never get mis-deleted.
    //
    // Unique constraint swaps: old (from, to, type) blocks coexistence of
    // markdown + frontmatter + manual edges with the same tuple. New tuple
    // includes link_source + origin_page_id.
    //
    // Existing rows keep link_source IS NULL (legacy marker) — they are NOT
    // backfilled to 'markdown' because existing rows may be manual/imported
    // /inferred; mislabeling them as markdown would corrupt provenance.
    //
    // Idempotent via IF NOT EXISTS / DROP IF EXISTS.
    sql: `
      -- Postgres version gate: UNIQUE NULLS NOT DISTINCT requires PG15+.
      -- PGLite ships PG17.5, current Supabase is PG15+. Old Supabase projects
      -- on PG14 hit an explicit error rather than half-applying (drop old
      -- constraint but fail to add new one → brain loses uniqueness guarantee).
      DO $$ BEGIN
        IF current_setting('server_version_num')::int < 150000 THEN
          RAISE EXCEPTION
            'v0.13 migration requires Postgres 15+. Current: %. '
            'Upgrade your Postgres (Supabase: migrate project to a newer PG major). '
            'This migration intentionally stops before touching the schema to preserve data integrity.',
            current_setting('server_version');
        END IF;
      END $$;

      ALTER TABLE links ADD COLUMN IF NOT EXISTS link_source TEXT;
      DO $$ BEGIN
        IF NOT EXISTS (
          SELECT 1 FROM pg_constraint WHERE conname = 'links_link_source_check'
        ) THEN
          ALTER TABLE links ADD CONSTRAINT links_link_source_check
            CHECK (link_source IS NULL OR link_source IN ('markdown', 'frontmatter', 'manual'));
        END IF;
      END $$;
      ALTER TABLE links ADD COLUMN IF NOT EXISTS origin_page_id INTEGER
        REFERENCES pages(id) ON DELETE SET NULL;
      ALTER TABLE links ADD COLUMN IF NOT EXISTS origin_field TEXT;
      -- Backfill NULL link_source → 'markdown' for existing rows. Codex review
      -- caught that without this, pre-v0.13 legacy rows coexist with new
      -- 'markdown' writes under NULLS NOT DISTINCT (NULL ≠ 'markdown'),
      -- causing duplicate edges to accumulate. Treating legacy as markdown
      -- is the accurate best-guess: pre-v0.13 auto-link only emitted markdown
      -- edges. User-created 'manual' edges are a v0.13+ concept anyway.
      UPDATE links SET link_source = 'markdown' WHERE link_source IS NULL;
      ALTER TABLE links DROP CONSTRAINT IF EXISTS links_from_to_type_unique;
      DO $$ BEGIN
        IF NOT EXISTS (
          SELECT 1 FROM pg_constraint WHERE conname = 'links_from_to_type_source_origin_unique'
        ) THEN
          ALTER TABLE links ADD CONSTRAINT links_from_to_type_source_origin_unique
            UNIQUE NULLS NOT DISTINCT (from_page_id, to_page_id, link_type, link_source, origin_page_id);
        END IF;
      END $$;
      CREATE INDEX IF NOT EXISTS idx_links_source ON links(link_source);
      CREATE INDEX IF NOT EXISTS idx_links_origin ON links(origin_page_id);
    `,
  },
  {
    version: 12,
    name: 'budget_ledger',
    // Resolver spend tracker. Primary key {scope, resolver_id, local_date} so
    // midnight rollover in the user's TZ naturally creates a new row instead of
    // mutating yesterday's. reserved_usd and committed_usd track reservations
    // vs actuals so process death between reserve() and commit()/rollback()
    // can be cleaned up by TTL scan. Rollback: DROP TABLE (regenerable from
    // resolver call logs; no durable product data lives here).
    sql: `
      CREATE TABLE IF NOT EXISTS budget_ledger (
        scope          TEXT        NOT NULL,
        resolver_id    TEXT        NOT NULL,
        local_date     DATE        NOT NULL,
        reserved_usd   NUMERIC(12,4) NOT NULL DEFAULT 0,
        committed_usd  NUMERIC(12,4) NOT NULL DEFAULT 0,
        cap_usd        NUMERIC(12,4),
        created_at     TIMESTAMPTZ NOT NULL DEFAULT now(),
        updated_at     TIMESTAMPTZ NOT NULL DEFAULT now(),
        PRIMARY KEY (scope, resolver_id, local_date)
      );
      CREATE TABLE IF NOT EXISTS budget_reservations (
        reservation_id TEXT        PRIMARY KEY,
        scope          TEXT        NOT NULL,
        resolver_id    TEXT        NOT NULL,
        local_date     DATE        NOT NULL,
        estimate_usd   NUMERIC(12,4) NOT NULL,
        reserved_at    TIMESTAMPTZ NOT NULL DEFAULT now(),
        expires_at     TIMESTAMPTZ NOT NULL,
        status         TEXT        NOT NULL DEFAULT 'held'
      );
      CREATE INDEX IF NOT EXISTS idx_budget_reservations_expires
        ON budget_reservations(expires_at) WHERE status = 'held';
    `,
  },
  {
    version: 13,
    name: 'minion_quiet_hours_stagger',
    // Adds quiet-hours gating + deterministic stagger to Minions.
    sql: `
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS quiet_hours JSONB;
      ALTER TABLE minion_jobs ADD COLUMN IF NOT EXISTS stagger_key TEXT;
      CREATE INDEX IF NOT EXISTS idx_minion_jobs_stagger_key
        ON minion_jobs(stagger_key) WHERE stagger_key IS NOT NULL;
    `,
  },
  {
    version: 14,
    name: 'pages_updated_at_index',
    // v0.14.1 (fix wave): fixes the 14.6s "list pages newest-first" seqscan on 31k+ row brains.
    // Original report: https://github.com/garrytan/gbrain/issues/170 (PR #215).
    //
    // Engine-aware via handler (not SQL): Postgres uses CREATE INDEX CONCURRENTLY
    // to avoid the write-blocking SHARE lock on `pages`. CONCURRENTLY refuses to
    // run inside a transaction AND postgres.js's multi-statement `.unsafe()` wraps
    // in an implicit transaction, so the handler runs each statement as a separate
    // call. A failed CONCURRENTLY leaves an invalid index with the target name;
    // the handler pre-drops any invalid remnant via pg_index.indisvalid. PGLite
    // has no concurrent writers, so plain CREATE is safe.
    sql: '',
    handler: async (engine) => {
      if (engine.kind === 'postgres') {
        await engine.runMigration(
          14,
          `DO $$ BEGIN
             IF EXISTS (
               SELECT 1 FROM pg_index i
               JOIN pg_class c ON c.oid = i.indexrelid
               WHERE c.relname = 'idx_pages_updated_at_desc' AND NOT i.indisvalid
             ) THEN
               EXECUTE 'DROP INDEX CONCURRENTLY IF EXISTS idx_pages_updated_at_desc';
             END IF;
           END $$;`
        );
        await engine.runMigration(
          14,
          `CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_pages_updated_at_desc
             ON pages (updated_at DESC);`
        );
      } else {
        await engine.runMigration(
          14,
          `CREATE INDEX IF NOT EXISTS idx_pages_updated_at_desc
             ON pages (updated_at DESC);`
        );
      }
    },
  },
  {
    version: 23,
    name: 'files_source_id_page_id_ledger',
    // v0.18.0 Step 7 (Lane E) — additive only: adds files.source_id and
    // files.page_id columns + creates the file_migration_ledger that
    // drives phase-B storage object rewrites. Does NOT drop page_slug
    // yet (kept for backward compat; a later release cleans up once the
    // page_id FK is proven). PGLite has no files table, so this
    // migration is Postgres-only via a handler gate.
    //
    // Ledger PK is file_id (not storage_path_old) — two sources CAN
    // share an old path during migration, so a composite would be
    // wrong. Codex second-pass review caught this.
    //
    // State machine per row:
    //   pending → copy_done → db_updated → complete
    //   any state → failed (with error detail)
    //
    // Phase B in the v0_18_0 orchestrator processes `status != complete`
    // rows. Re-runnable: resumes from whichever state it stopped in.
    sql: '',
    handler: async (engine) => {
      if (engine.kind === 'pglite') return;

      // Atomic: FK drop + UNIQUE swap + files.page_id addition +
      // backfill + ledger, all in one transaction. Closes the
      // pre-v23 integrity window where files_page_slug_fkey was
      // dropped in v21 but the replacement files.page_id didn't
      // exist until v23 ran — process death in between left files
      // unconstrained while file_upload kept writing (codex finding).
      //
      // Rollback scenarios:
      //   - Die mid-transaction → Postgres rolls back, files_page_slug_fkey
      //     still exists, config.version stays at 22. Retry restarts cleanly.
      //   - Die after commit but before setConfig(version=23) → all DDL
      //     committed, config.version still 22, retry re-runs everything
      //     with IF NOT EXISTS / NOT EXISTS guards idempotently.
      await engine.transaction(async (tx) => {
        // 0a. Drop files_page_slug_fkey (deferred from v21 to keep
        //     the FK intact across v21/v22 and remove it inside the
        //     same txn that adds the replacement page_id path).
        //     Guard against PGLite just in case (already returned above).
        await tx.runMigration(23, `
          DO $$ BEGIN
            IF EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'files') THEN
              ALTER TABLE files DROP CONSTRAINT IF EXISTS files_page_slug_fkey;
            END IF;
          END $$;
        `);

        // 0b. Swap pages.UNIQUE(slug) → UNIQUE(source_id, slug).
        //     Deferred from v21 so PR #356 closes the integrity
        //     window. PGLite already did this swap in its v21 path.
        await tx.runMigration(23, `
          ALTER TABLE pages DROP CONSTRAINT IF EXISTS pages_slug_key;
          DO $$ BEGIN
            IF NOT EXISTS (
              SELECT 1 FROM pg_constraint WHERE conname = 'pages_source_slug_key'
            ) THEN
              ALTER TABLE pages ADD CONSTRAINT pages_source_slug_key
                UNIQUE (source_id, slug);
            END IF;
          END $$;
        `);

        // 1a. source_id with DEFAULT 'default' (idempotent)
        await tx.runMigration(23, `
          ALTER TABLE files ADD COLUMN IF NOT EXISTS source_id TEXT
            NOT NULL DEFAULT 'default' REFERENCES sources(id) ON DELETE CASCADE;
          CREATE INDEX IF NOT EXISTS idx_files_source_id ON files(source_id);

          -- 1b. page_id (nullable; pre-v0.17 files pointed at page_slug
          --     which was ON DELETE SET NULL, so we keep the same nullable
          --     semantic — orphaned files are legal).
          ALTER TABLE files ADD COLUMN IF NOT EXISTS page_id INTEGER
            REFERENCES pages(id) ON DELETE SET NULL;
          CREATE INDEX IF NOT EXISTS idx_files_page_id ON files(page_id);
        `);

        // 1c. Backfill page_id from existing page_slug. Scoped to
        //     source_id='default' because pre-v0.17 pages ALL lived in
        //     the default source. Without this scope, after new sources
        //     get added mid-migration, the JOIN could hit the wrong
        //     page (different source, same slug).
        await tx.runMigration(23, `
          UPDATE files f
             SET page_id = p.id
            FROM pages p
           WHERE f.page_slug = p.slug
             AND p.source_id = 'default'
             AND f.page_id IS NULL;
        `);

        // 2. file_migration_ledger — drives the storage object rewrite
        //    in the v0_18_0 orchestrator's phase B. Seeded from current
        //    files rows; re-seed is idempotent via NOT EXISTS guard.
        await tx.runMigration(23, `
          CREATE TABLE IF NOT EXISTS file_migration_ledger (
            file_id           INTEGER PRIMARY KEY REFERENCES files(id) ON DELETE CASCADE,
            storage_path_old  TEXT   NOT NULL,
            storage_path_new  TEXT   NOT NULL,
            status            TEXT   NOT NULL DEFAULT 'pending',
            error             TEXT,
            updated_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
            CONSTRAINT chk_ledger_status CHECK (status IN ('pending','copy_done','db_updated','complete','failed'))
          );
          CREATE INDEX IF NOT EXISTS idx_file_migration_ledger_status
            ON file_migration_ledger(status) WHERE status != 'complete';

          -- Seed the ledger with every existing file. New path prefixes
          -- source_id so multi-source can land assets under their own
          -- bucket path without collision.
          INSERT INTO file_migration_ledger (file_id, storage_path_old, storage_path_new, status)
          SELECT
            f.id,
            f.storage_path,
            COALESCE(f.source_id, 'default') || '/' || f.storage_path,
            'pending'
          FROM files f
          WHERE NOT EXISTS (
            SELECT 1 FROM file_migration_ledger l WHERE l.file_id = f.id
          );
        `);
      });
    },
  },
  {
    version: 22,
    name: 'links_resolution_type',
    // v0.18.0 Step 4 (Lane B) — adds links.resolution_type column so
    // each edge records whether its target source was pinned at
    // extraction time via `[[source:slug]]` (qualified) or resolved
    // via local-first fallback (unqualified). Unqualified edges are
    // candidates for re-resolution via `gbrain extract
    // --refresh-unqualified` when the source topology changes.
    //
    // Nullable because legacy edges (pre-v0.17) have no resolution
    // concept. `frontmatter` and `manual` edges remain NULL — they're
    // not subject to staleness under source churn.
    sql: `
      ALTER TABLE links ADD COLUMN IF NOT EXISTS resolution_type TEXT;
      DO $$ BEGIN
        IF NOT EXISTS (
          SELECT 1 FROM pg_constraint WHERE conname = 'links_resolution_type_check'
        ) THEN
          ALTER TABLE links ADD CONSTRAINT links_resolution_type_check
            CHECK (resolution_type IS NULL OR resolution_type IN ('qualified', 'unqualified'));
        END IF;
      END $$;
    `,
  },
  {
    version: 21,
    name: 'pages_source_id_composite_unique',
    // v0.18.0 Step 2 (Lane B) — adds pages.source_id. Engine-split after
    // codex caught the pre-v23 integrity window:
    //
    //   Original v21 dropped files_page_slug_fkey and swapped
    //   UNIQUE(slug) → UNIQUE(source_id, slug) in one go. Between v21
    //   committing and v23 (which adds the replacement files.page_id
    //   path), a process-death left files WITHOUT any FK to pages
    //   while file_upload / `gbrain files` kept accepting writes.
    //
    // On Postgres: additive-only here. The FK drop + UNIQUE swap move
    // into v23's handler (wrapped in engine.transaction) so they commit
    // atomically with the files.page_id addition + backfill. See v23.
    //
    // On PGLite: no concurrent writers, no pool, no partial-state risk.
    // Do the full add + swap here so PGLite brains reach the composite
    // unique immediately (PGLite has no files table, so no FK drop
    // needed).
    //
    // DEFAULT 'default' on source_id is load-bearing: closes the race
    // where an INSERT between ADD COLUMN and SET NOT NULL could leave
    // source_id NULL. The default already references a valid sources
    // row (seeded in v16), so new INSERTs immediately get a valid FK.
    sql: '',
    sqlFor: {
      postgres: `
        ALTER TABLE pages ADD COLUMN IF NOT EXISTS source_id TEXT
          NOT NULL DEFAULT 'default' REFERENCES sources(id) ON DELETE CASCADE;

        CREATE INDEX IF NOT EXISTS idx_pages_source_id ON pages(source_id);
      `,
      pglite: `
        ALTER TABLE pages ADD COLUMN IF NOT EXISTS source_id TEXT
          NOT NULL DEFAULT 'default' REFERENCES sources(id) ON DELETE CASCADE;

        CREATE INDEX IF NOT EXISTS idx_pages_source_id ON pages(source_id);

        ALTER TABLE pages DROP CONSTRAINT IF EXISTS pages_slug_key;
        DO $$ BEGIN
          IF NOT EXISTS (
            SELECT 1 FROM pg_constraint WHERE conname = 'pages_source_slug_key'
          ) THEN
            ALTER TABLE pages ADD CONSTRAINT pages_source_slug_key
              UNIQUE (source_id, slug);
          END IF;
        END $$;
      `,
    },
  },
  {
    version: 20,
    name: 'sources_table_additive',
    // v0.18.0 Step 1 (Lane A) — **additive only** so Step 1 is a safe
    // standalone commit. This migration installs the sources primitive
    // WITHOUT breaking the engine's existing ON CONFLICT (slug) upserts.
    //
    // What this migration does now:
    //   - CREATE sources table
    //   - INSERT default source (federated=true, inherits sync.repo_path
    //     and sync.last_commit from config so post-upgrade identity is
    //     preserved)
    //
    // What this migration does NOT do yet (deferred to v17 which ships
    // with Step 2 engine rewrite, so they land atomically):
    //   - ALTER pages ADD source_id
    //   - DROP UNIQUE(slug) + ADD UNIQUE(source_id, slug)
    //   - files.page_slug → page_id rewrite
    //   - file_migration_ledger
    //   - links.resolution_type
    //
    // The v0.18.0 orchestrator's phaseCVerify allows this split: it
    // checks for sources('default'), but the "composite UNIQUE" +
    // "pages.source_id NOT NULL" assertions only run after v17 lands.
    //
    // Idempotent via IF NOT EXISTS. Safe to re-run.
    sql: `
      CREATE TABLE IF NOT EXISTS sources (
        id            TEXT PRIMARY KEY,
        name          TEXT NOT NULL UNIQUE,
        local_path    TEXT,
        last_commit   TEXT,
        last_sync_at  TIMESTAMPTZ,
        config        JSONB NOT NULL DEFAULT '{}'::jsonb,
        created_at    TIMESTAMPTZ NOT NULL DEFAULT now()
      );

      -- Seed 'default' source, inheriting the existing sync.repo_path /
      -- sync.last_commit config values. federated=true for backward compat.
      -- Pre-v0.17 brains behave exactly as before.
      INSERT INTO sources (id, name, local_path, last_commit, config)
      SELECT
        'default',
        'default',
        (SELECT value FROM config WHERE key = 'sync.repo_path'),
        (SELECT value FROM config WHERE key = 'sync.last_commit'),
        '{"federated": true}'::jsonb
      WHERE NOT EXISTS (SELECT 1 FROM sources WHERE id = 'default');
    `,
  },
  {
    version: 15,
    name: 'minion_jobs_max_stalled_default_5',
    // v0.14.1 (fix wave): fixes https://github.com/garrytan/gbrain/issues/219
    // Shipped default was 1 — first stall = dead-letter, contradicting the
    // "SIGKILL rescued" claim. New default 5. UPDATE backfills existing non-
    // terminal rows so upgrading brains don't keep dead-lettering queued work.
    // Statuses come from MinionJobStatus in types.ts. Row locks serialize
    // against claim()'s FOR UPDATE SKIP LOCKED — race-safe. Idempotent.
    sql: `
      ALTER TABLE minion_jobs ALTER COLUMN max_stalled SET DEFAULT 5;
      UPDATE minion_jobs
         SET max_stalled = 5
       WHERE status IN ('waiting','active','delayed','waiting-children','paused')
         AND max_stalled < 5;
    `,
  },
  {
    version: 16,
    name: 'cycle_locks_table',
    // v0.17 brain maintenance cycle (runCycle primitive).
    // PgBouncer transaction pooling strips session-scoped advisory locks
    // (pg_try_advisory_lock) across connection checkouts, so we can't use
    // them as the cycle-coordination primitive. A row with a TTL works
    // through every pooler: any backend can SELECT/UPDATE/DELETE it, no
    // session state required.
    //
    // Acquire: INSERT ... ON CONFLICT (id) DO UPDATE ... WHERE ttl_expires_at < NOW()
    //          returning ... — empty RETURNING = lock held by live holder.
    // Refresh: UPDATE ... SET ttl_expires_at = NOW() + interval '30 min'
    //          WHERE id = 'gbrain-cycle' AND holder_pid = <my pid> — between phases.
    // Release: DELETE WHERE id = 'gbrain-cycle' AND holder_pid = <my pid>.
    sql: `
      CREATE TABLE IF NOT EXISTS gbrain_cycle_locks (
        id TEXT PRIMARY KEY,
        holder_pid INT NOT NULL,
        holder_host TEXT,
        acquired_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
        ttl_expires_at TIMESTAMPTZ NOT NULL
      );
      CREATE INDEX IF NOT EXISTS idx_cycle_locks_ttl ON gbrain_cycle_locks(ttl_expires_at);
    `,
  },
  {
    version: 24,
    name: 'rls_backfill_missing_tables',
    // v0.18.1 RLS hardening: 10 gbrain-managed public tables shipped
    // without RLS enabled (access_tokens, mcp_request_log, minion_inbox,
    // minion_attachments, subagent_messages, subagent_tool_executions,
    // subagent_rate_leases, gbrain_cycle_locks, budget_ledger,
    // budget_reservations). Supabase exposes the public schema via
    // PostgREST, so tables without RLS are readable by anyone with the
    // anon key.
    //
    // Numbered v24 to slot after v0.18.0's v20-v23 sources-migration
    // wave. The 'sources' and 'file_migration_ledger' tables added in
    // v0.18.0 already get RLS from schema.sql's base DO block; v24
    // backfills the 10 older tables that never had it.
    //
    // Gated on BYPASSRLS matching the pattern in schema.sql: enabling RLS
    // on a table in a session that does NOT hold BYPASSRLS would lock
    // the session out of its own data. RAISE WARNING is visible to the
    // migration runner's log stream.
    sql: `
      DO $$
      DECLARE
        has_bypass BOOLEAN;
      BEGIN
        SELECT rolbypassrls INTO has_bypass FROM pg_roles WHERE rolname = current_user;
        IF NOT has_bypass THEN
          -- Fail the migration loudly instead of WARNING + version-bump.
          -- The runner unconditionally records schema_version on success,
          -- so a silent WARNING here would permanently lock the backfill out
          -- on future runs even after switching to a bypass role. Raising
          -- aborts the transaction, leaves schema_version at the prior value,
          -- and lets the next invocation retry after the role is fixed.
          RAISE EXCEPTION 'v24 rls_backfill_missing_tables: role % does not have BYPASSRLS privilege — cannot enable RLS safely. Re-run as postgres (or another BYPASSRLS role). The migration will retry automatically on the next initSchema call.', current_user;
        END IF;

        -- These 8 are guaranteed to exist: schema.sql creates them (idempotent
        -- via IF NOT EXISTS) on every initSchema call, and initSchema runs
        -- before this migration. Bare ALTER TABLE is safe.
        ALTER TABLE access_tokens ENABLE ROW LEVEL SECURITY;
        ALTER TABLE mcp_request_log ENABLE ROW LEVEL SECURITY;
        ALTER TABLE minion_inbox ENABLE ROW LEVEL SECURITY;
        ALTER TABLE minion_attachments ENABLE ROW LEVEL SECURITY;
        ALTER TABLE subagent_messages ENABLE ROW LEVEL SECURITY;
        ALTER TABLE subagent_tool_executions ENABLE ROW LEVEL SECURITY;
        ALTER TABLE subagent_rate_leases ENABLE ROW LEVEL SECURITY;
        ALTER TABLE gbrain_cycle_locks ENABLE ROW LEVEL SECURITY;

        -- budget_ledger + budget_reservations are migration-only (v12). Not
        -- in schema.sql, not re-created on every initSchema. In normal flow
        -- v12 runs before v24 so they exist, but if an operator manually
        -- dropped them (unusual — budget data is regenerable from resolver
        -- logs) or was pinned to a pre-v12 gbrain version when the table
        -- went away, the bare ALTER would fail with 42P01 and abort v24.
        -- information_schema.tables lookup makes the statement self-healing.
        IF EXISTS (SELECT 1 FROM information_schema.tables
                    WHERE table_schema = 'public' AND table_name = 'budget_ledger') THEN
          ALTER TABLE budget_ledger ENABLE ROW LEVEL SECURITY;
        END IF;
        IF EXISTS (SELECT 1 FROM information_schema.tables
                    WHERE table_schema = 'public' AND table_name = 'budget_reservations') THEN
          ALTER TABLE budget_reservations ENABLE ROW LEVEL SECURITY;
        END IF;

        RAISE NOTICE 'v24: RLS backfill complete (role % has BYPASSRLS)', current_user;
      END $$;
    `,
  },
  {
    version: 25,
    name: 'pages_page_kind',
    // v0.19.0 Layer 3 — pages.page_kind distinguishes markdown vs code pages
    // at the DB level. Needed so orphans filter, link-extraction auto-link,
    // and query --lang can branch on kind without sniffing `type` or chunk
    // metadata. Existing rows backfill to 'markdown' (pre-v0.19.0 all pages
    // were markdown).
    //
    // Postgres: ADD COLUMN with DEFAULT is O(1) for nullable columns (no
    // rewrite). The CHECK constraint is added NOT VALID so the initial
    // statement does not scan the table, then VALIDATE CONSTRAINT runs
    // separately. Tables with millions of pages would otherwise hold a
    // write lock during the full scan.
    sqlFor: {
      postgres: `
        ALTER TABLE pages
          ADD COLUMN IF NOT EXISTS page_kind TEXT NOT NULL DEFAULT 'markdown';

        ALTER TABLE pages
          DROP CONSTRAINT IF EXISTS pages_page_kind_check;
        ALTER TABLE pages
          ADD CONSTRAINT pages_page_kind_check
          CHECK (page_kind IN ('markdown','code')) NOT VALID;
        ALTER TABLE pages VALIDATE CONSTRAINT pages_page_kind_check;
      `,
      pglite: `
        ALTER TABLE pages
          ADD COLUMN IF NOT EXISTS page_kind TEXT NOT NULL DEFAULT 'markdown'
          CHECK (page_kind IN ('markdown','code'));
      `,
    },
    sql: `
      ALTER TABLE pages
        ADD COLUMN IF NOT EXISTS page_kind TEXT NOT NULL DEFAULT 'markdown'
        CHECK (page_kind IN ('markdown','code'));
    `,
  },
  {
    version: 26,
    name: 'content_chunks_code_metadata',
    // v0.19.0 Layer 3 — content_chunks gains code-specific metadata columns
    // so C6 (query --lang), C7 (code-def / code-refs), and the new
    // searchCodeChunks engine method can filter + surface symbol context
    // without parsing chunk_text.
    //
    // All new columns are nullable — existing markdown chunks carry NULL.
    // importCodeFile populates them from the tree-sitter AST.
    //
    // Partial indexes (WHERE <col> IS NOT NULL) keep the index small: a
    // brain with 20K markdown chunks + 20K code chunks indexes only the
    // code chunks for symbol lookups. Measured ~200ms → ~15ms on code-refs.
    sql: `
      ALTER TABLE content_chunks
        ADD COLUMN IF NOT EXISTS language TEXT,
        ADD COLUMN IF NOT EXISTS symbol_name TEXT,
        ADD COLUMN IF NOT EXISTS symbol_type TEXT,
        ADD COLUMN IF NOT EXISTS start_line INTEGER,
        ADD COLUMN IF NOT EXISTS end_line INTEGER;

      CREATE INDEX IF NOT EXISTS idx_chunks_symbol_name
        ON content_chunks(symbol_name) WHERE symbol_name IS NOT NULL;
      CREATE INDEX IF NOT EXISTS idx_chunks_language
        ON content_chunks(language) WHERE language IS NOT NULL;
    `,
  },
  {
    version: 27,
    name: 'cathedral_ii_foundation',
    // v0.20.0 Cathedral II Layer 1 — schema-only foundation.
    //
    // Lands BEFORE any consumer layer to eliminate forward references
    // (codex SP-4). All Cathedral II DDL arrives here as one atomic
    // transaction:
    //
    //   1. content_chunks gains 4 columns:
    //      - parent_symbol_path TEXT[]   — scope chain for nested symbols (A3)
    //      - doc_comment TEXT            — extracted JSDoc/docstring (A4)
    //      - symbol_name_qualified TEXT  — 'Admin::UsersController#render' (A1)
    //      - search_vector TSVECTOR      — chunk-grain FTS (Layer 1b)
    //
    //   2. sources.chunker_version TEXT — SP-1 gate. performSync forces
    //      full walk on mismatch with CURRENT_CHUNKER_VERSION, bypassing
    //      the up_to_date git-HEAD early-return that made the bare
    //      CHUNKER_VERSION bump a silent no-op.
    //
    //   3. code_edges_chunk — resolved call-graph / type-ref edges.
    //      FK CASCADE from content_chunks on both endpoints; deleting a
    //      chunk wipes its edges. UNIQUE (from, to, edge_type) holds
    //      idempotency. source_id TEXT matches sources.id actual type
    //      (codex F4). Source scoping is enforced in resolution logic,
    //      not in the key, because from_chunk_id → pages.source_id
    //      already determines it.
    //
    //   4. code_edges_symbol — unresolved refs. Target symbol is known
    //      by qualified name but the defining chunk hasn't been imported
    //      yet. Rows UNION with code_edges_chunk on read (codex 1.3b);
    //      no promotion step.
    //
    //   5. update_chunk_search_vector trigger — BEFORE INSERT/UPDATE
    //      OF (chunk_text, doc_comment, symbol_name_qualified). Builds
    //      search_vector with weight A on doc_comment + symbol_name_qualified,
    //      B on chunk_text. Natural-language queries rank doc-comment hits
    //      above body-text hits (A4 intent).
    //
    // Consumer layers (Layer 5 A1, Layer 6 A3, Layer 10 C CLI, Layer 12
    // CHUNKER_VERSION bump, Layer 13 E2 reindex-code) all depend on this
    // foundation. Absent it, every downstream layer would have forward
    // refs.
    sql: `
      -- content_chunks: new Cathedral II columns
      ALTER TABLE content_chunks
        ADD COLUMN IF NOT EXISTS parent_symbol_path TEXT[],
        ADD COLUMN IF NOT EXISTS doc_comment TEXT,
        ADD COLUMN IF NOT EXISTS symbol_name_qualified TEXT,
        ADD COLUMN IF NOT EXISTS search_vector TSVECTOR;

      CREATE INDEX IF NOT EXISTS idx_chunks_search_vector
        ON content_chunks USING GIN(search_vector);
      CREATE INDEX IF NOT EXISTS idx_chunks_symbol_qualified
        ON content_chunks(symbol_name_qualified) WHERE symbol_name_qualified IS NOT NULL;

      -- sources: SP-1 chunker_version gate
      ALTER TABLE sources
        ADD COLUMN IF NOT EXISTS chunker_version TEXT;

      -- code_edges_chunk: resolved edges
      CREATE TABLE IF NOT EXISTS code_edges_chunk (
        id                    SERIAL PRIMARY KEY,
        from_chunk_id         INTEGER NOT NULL REFERENCES content_chunks(id) ON DELETE CASCADE,
        to_chunk_id           INTEGER NOT NULL REFERENCES content_chunks(id) ON DELETE CASCADE,
        from_symbol_qualified TEXT NOT NULL,
        to_symbol_qualified   TEXT NOT NULL,
        edge_type             TEXT NOT NULL,
        edge_metadata         JSONB NOT NULL DEFAULT '{}',
        source_id             TEXT REFERENCES sources(id) ON DELETE CASCADE,
        created_at            TIMESTAMPTZ NOT NULL DEFAULT now(),
        CONSTRAINT code_edges_chunk_unique UNIQUE (from_chunk_id, to_chunk_id, edge_type)
      );

      CREATE INDEX IF NOT EXISTS idx_code_edges_chunk_from
        ON code_edges_chunk(from_chunk_id, edge_type);
      CREATE INDEX IF NOT EXISTS idx_code_edges_chunk_to
        ON code_edges_chunk(to_chunk_id, edge_type);
      CREATE INDEX IF NOT EXISTS idx_code_edges_chunk_to_symbol
        ON code_edges_chunk(to_symbol_qualified, edge_type);

      -- code_edges_symbol: unresolved refs
      CREATE TABLE IF NOT EXISTS code_edges_symbol (
        id                    SERIAL PRIMARY KEY,
        from_chunk_id         INTEGER NOT NULL REFERENCES content_chunks(id) ON DELETE CASCADE,
        from_symbol_qualified TEXT NOT NULL,
        to_symbol_qualified   TEXT NOT NULL,
        edge_type             TEXT NOT NULL,
        edge_metadata         JSONB NOT NULL DEFAULT '{}',
        source_id             TEXT REFERENCES sources(id) ON DELETE CASCADE,
        created_at            TIMESTAMPTZ NOT NULL DEFAULT now(),
        CONSTRAINT code_edges_symbol_unique UNIQUE (from_chunk_id, to_symbol_qualified, edge_type)
      );

      CREATE INDEX IF NOT EXISTS idx_code_edges_symbol_from
        ON code_edges_symbol(from_chunk_id, edge_type);
      CREATE INDEX IF NOT EXISTS idx_code_edges_symbol_to
        ON code_edges_symbol(to_symbol_qualified, edge_type);

      -- Chunk-grain FTS trigger (Layer 1b consumer — column exists from this
      -- migration, trigger installed now so newly-written chunks get vectors
      -- from day one). NULL-safe: markdown chunks leave doc_comment and
      -- symbol_name_qualified NULL; COALESCE('') keeps the vector build
      -- from failing on missing weights.
      CREATE OR REPLACE FUNCTION update_chunk_search_vector() RETURNS TRIGGER AS $fn$
      BEGIN
        NEW.search_vector :=
          setweight(to_tsvector('english', COALESCE(NEW.doc_comment, '')), 'A') ||
          setweight(to_tsvector('english', COALESCE(NEW.symbol_name_qualified, '')), 'A') ||
          setweight(to_tsvector('english', COALESCE(NEW.chunk_text, '')), 'B');
        RETURN NEW;
      END;
      $fn$ LANGUAGE plpgsql;

      DROP TRIGGER IF EXISTS chunk_search_vector_trigger ON content_chunks;
      CREATE TRIGGER chunk_search_vector_trigger
        BEFORE INSERT OR UPDATE OF chunk_text, doc_comment, symbol_name_qualified
        ON content_chunks
        FOR EACH ROW EXECUTE FUNCTION update_chunk_search_vector();
    `,
  },
  {
    version: 28,
    name: 'cathedral_ii_chunk_fts_backfill',
    // v0.20.0 Cathedral II Layer 3 (1b) — backfill content_chunks.search_vector
    // for rows inserted before v27 ran. The v27 trigger only fires on
    // INSERT/UPDATE, so every chunk that existed before upgrade has a NULL
    // search_vector and would match zero rows in the new chunk-grain
    // searchKeyword. Compute the vector in-place here so upgraded brains
    // have full keyword coverage the moment v28 commits — no need to wait
    // for every page to get touched by sync.
    //
    // Direct vector compute (not UPDATE chunk_text = chunk_text to trigger):
    //   - UPDATE-to-same-value fires the trigger unconditionally on Postgres
    //     even if no column value changes, so trigger-based backfill DOES
    //     work, but writing the vector directly is cheaper (single pass
    //     instead of trigger overhead per row).
    //   - Idempotent via `WHERE search_vector IS NULL` — re-running v28
    //     after a partial run picks up only the remaining NULL rows.
    //
    // On a 20K-chunk brain: ~2-3s total. No blocking concerns: chunks are
    // append-only in steady state; the UPDATE takes a row lock per chunk
    // briefly while computing the tsvector.
    sql: `
      UPDATE content_chunks
      SET search_vector =
        setweight(to_tsvector('english', COALESCE(doc_comment, '')), 'A') ||
        setweight(to_tsvector('english', COALESCE(symbol_name_qualified, '')), 'A') ||
        setweight(to_tsvector('english', COALESCE(chunk_text, '')), 'B')
      WHERE search_vector IS NULL;
    `,
  },
  {
    version: 29,
    name: 'cathedral_ii_code_edges_rls',
    // v0.21.0 Cathedral II — RLS hardening for the two new tables added by
    // v27 (code_edges_chunk, code_edges_symbol). The v24 RLS-backfill
    // pattern: gated on BYPASSRLS (so we don't lock the migrating session
    // out of its own data on a non-bypass role) + bare ALTER TABLE since
    // both tables are guaranteed to exist after v27.
    //
    // Postgres-only via sqlFor: PGLite doesn't enforce RLS the same way
    // and v24 already runs only against Postgres in practice. The E2E
    // test "RLS is enabled on every public table" runs against Docker
    // postgres exclusively and was failing because v27 created the new
    // tables without RLS enabled.
    sqlFor: {
      postgres: `
        DO $$
        DECLARE
          has_bypass BOOLEAN;
        BEGIN
          SELECT rolbypassrls INTO has_bypass FROM pg_roles WHERE rolname = current_user;
          IF NOT has_bypass THEN
            RAISE EXCEPTION 'v29 cathedral_ii_code_edges_rls: role % does not have BYPASSRLS privilege — cannot enable RLS safely. Re-run as postgres (or another BYPASSRLS role). The migration will retry automatically on the next initSchema call.', current_user;
          END IF;

          ALTER TABLE code_edges_chunk ENABLE ROW LEVEL SECURITY;
          ALTER TABLE code_edges_symbol ENABLE ROW LEVEL SECURITY;

          RAISE NOTICE 'v29: code_edges RLS enabled (role % has BYPASSRLS)', current_user;
        END $$;
      `,
      pglite: `-- PGLite: no-op. RLS check runs only against Postgres E2E.`,
    },
    sql: '',
  },
];

export const LATEST_VERSION = MIGRATIONS.length > 0
  ? Math.max(...MIGRATIONS.map(m => m.version))
  : 1;

/**
 * Row returned by `getIdleBlockers`. The shape is the public contract
 * for both `gbrain doctor --locks` output and the internal DDL pre-flight.
 */
export interface IdleBlocker {
  pid: number;
  state: string;
  query_start: string;
  query: string;
}

/**
 * Find idle-in-transaction connections older than 5 minutes that might
 * block DDL. Postgres-only. Returns `[]` on PGLite, query failure, or
 * no blockers. The query-failure path is intentionally silent because
 * some managed Postgres configs restrict `pg_stat_activity` — a partial
 * view of the server is still useful for doctor/pre-flight.
 *
 * Single source of truth shared by:
 *   - `checkForBlockingConnections` (DDL pre-flight warning)
 *   - `gbrain doctor --locks` (CLI diagnostic)
 *   - any future `--exclusive` drain-wait logic
 */
export async function getIdleBlockers(engine: BrainEngine): Promise<IdleBlocker[]> {
  if (engine.kind !== 'postgres') return [];
  try {
    return await engine.executeRaw<IdleBlocker>(
      `SELECT pid, state, query_start::text, substring(query, 1, 120) as query
       FROM pg_stat_activity
       WHERE state = 'idle in transaction'
         AND query_start < NOW() - INTERVAL '5 minutes'
         AND pid != pg_backend_pid()`
    );
  } catch {
    return [];
  }
}

/**
 * Check for idle-in-transaction connections that might block DDL.
 * Returns true if blockers were found (logged as warnings).
 */
async function checkForBlockingConnections(engine: BrainEngine): Promise<boolean> {
  const rows = await getIdleBlockers(engine);
  if (rows.length > 0) {
    console.warn(`\n⚠️  Found ${rows.length} idle-in-transaction connection(s) older than 5 minutes:`);
    for (const r of rows) {
      console.warn(`  PID ${r.pid} — idle since ${r.query_start}`);
      console.warn(`    Query: ${r.query}`);
    }
    console.warn(`  These may block ALTER TABLE DDL. To kill: SELECT pg_terminate_backend(<pid>);\n`);
    return true;
  }
  return false;
}

/**
 * Wrap migration SQL execution with Supabase-compatible timeout.
 * Uses SET LOCAL statement_timeout inside a transaction to override
 * server-enforced timeouts (required for Supabase Postgres).
 */
async function runMigrationSQL(
  engine: BrainEngine,
  m: Migration,
  sql: string,
): Promise<void> {
  const useTransaction = m.transaction !== false;

  if (useTransaction || engine.kind === 'pglite') {
    // Wrap in transaction with extended timeout for Supabase compatibility.
    // SET LOCAL scopes the timeout to this transaction only.
    await engine.transaction(async (tx) => {
      if (engine.kind === 'postgres') {
        try {
          await tx.runMigration(m.version, "SET LOCAL statement_timeout = '600000'");
        } catch {
          // Non-fatal: PGLite or older Postgres versions may not support this
        }
      }
      await tx.runMigration(m.version, sql);
    });
  } else {
    // Postgres + transaction:false → can't use SET LOCAL (needs a txn),
    // can't use plain SET on the pooled connection (leaks to other
    // queries). Instead: reserve a dedicated backend, set session-level
    // statement_timeout on just that connection, run the DDL there.
    //
    // On Supabase (both PgBouncer 6543 and direct 5432) a server-level
    // statement_timeout of ~2 min is enforced. Without this override a
    // CREATE INDEX CONCURRENTLY on a large table (e.g. 500K pages) hits
    // the timeout and aborts. SET on the reserved connection cleanly
    // overrides because the GUC scope is connection-local (session-scope
    // is fine when nobody else uses the connection).
    //
    // The reserved-connection primitive is new in PR #356. See
    // BrainEngine.withReservedConnection.
    await engine.withReservedConnection(async (conn) => {
      try {
        await conn.executeRaw("SET statement_timeout = '600000'");
      } catch {
        // Non-fatal: some managed Postgres may restrict this GUC.
        // Falling through means the DDL runs with the server default.
      }
      await conn.executeRaw(sql);
    });
  }
}

export async function runMigrations(engine: BrainEngine): Promise<{ applied: number; current: number }> {
  const currentStr = await engine.getConfig('version');
  const current = parseInt(currentStr || '1', 10);

  // Sort by version ascending so array insertion order doesn't affect
  // correctness. Migrations MUST run in version order; if v16 accidentally
  // precedes v15 in MIGRATIONS, setConfig(version, 16) would cause v15 to
  // be skipped on the next iteration.
  const sorted = [...MIGRATIONS].sort((a, b) => a.version - b.version);

  const pending = sorted.filter(m => m.version > current);
  if (pending.length === 0) {
    return { applied: 0, current };
  }

  console.log(`  Schema version ${current} → ${LATEST_VERSION} (${pending.length} migration(s) pending)`);

  // Pre-flight: warn about connections that might block DDL
  await checkForBlockingConnections(engine);

  let applied = 0;
  for (const m of pending) {
    console.log(`  [${m.version}] ${m.name}...`);

    // Pick SQL: engine-specific `sqlFor` wins over engine-agnostic `sql`.
    const sql = m.sqlFor?.[engine.kind] ?? m.sql;

    if (sql) {
      try {
        await runMigrationSQL(engine, m, sql);
      } catch (err: unknown) {
        // Actionable diagnostics for statement timeout (Postgres error 57014).
        // Shape matches the 4-part error standard (what / why / fix / verify).
        const code = (err as { code?: string })?.code;
        if (code === '57014') {
          console.error(`\n❌ Migration ${m.version} (${m.name}) hit statement_timeout (SQLSTATE 57014).`);
          console.error('');
          console.error('   Cause: another connection holds a lock on the target table, or the');
          console.error('   server statement_timeout (~2 min on Supabase) is too short for this DDL.');
          console.error('');
          console.error('   Fix:');
          console.error('     1. gbrain doctor --locks    # find idle-in-transaction blockers');
          console.error('     2. Terminate blocker(s) shown by step 1 via pg_terminate_backend(<pid>)');
          console.error('     3. gbrain apply-migrations --yes  # re-run from the version that failed');
          console.error('');
          console.error('   Verify:');
          console.error('     gbrain doctor              # schema_version should match latest');
          console.error('');
        }
        throw err;
      }
    }

    // Application-level handler (runs outside transaction for flexibility)
    if (m.handler) {
      await m.handler(engine);
    }

    // Update version after both SQL and handler succeed
    await engine.setConfig('version', String(m.version));
    console.log(`  [${m.version}] ✓ ${m.name}`);
    applied++;
  }

  return { applied, current: LATEST_VERSION };
}
