/**
 * Reconcile-historical-add-scripts convoy — Brief 2.
 *
 * Backfills the `collections`-table columns that historical scripts added to
 * prod but which `migrations/1779853647564_initial-schema.js` never captured:
 *
 *   - `visibility VARCHAR(20) DEFAULT 'private'`  (from `scripts/add-collaboration-features.js`, lines 15-21 — collections half only)
 *   - `tcg VARCHAR(50) DEFAULT 'MTG'`             (from `scripts/add-collaboration-features.js`, lines 15-21 — collections half only)
 *   - `tags TEXT`                                 (from `scripts/add-collaboration-features.js`, lines 15-21 — collections half only)
 *   - `slug VARCHAR(100) UNIQUE`                  (from `scripts/add-collection-slugs.js`, lines 17-20)
 *   - `idx_collections_slug` UNIQUE INDEX         (from `scripts/add-collection-slugs.js`, line 79)
 *   - `check_slug_format` CHECK constraint        (from `scripts/add-collection-slugs.js`, line 91)
 *   - `image TEXT`                                (from `scripts/add-image-column.js`, lines 14-17)
 *
 * Excluded from B2 (out of scope per architect inventory):
 *   - `collection_permissions`, `collection_activity`, `users.is_pending`,
 *     `idx_collection_permissions_*`, `idx_collection_activity_collection_id`
 *     — B3 (`reconcile-collaboration-tables`).
 *     `idx_collections_visibility` — ships in
 *     `1786757312884_add-collections-visibility-index` (B3's timestamp
 *     precedes this file's `visibility` column add).
 *   - `is_system_collection` — already captured by
 *     `migrations/1780378340194_system-collection-description.js`.
 *
 * Excluded DML: per-row UPDATE that backfills slugs from `name` via
 * `lib/slug-utils.js::generateUniqueSlug` (script lines 41-74). Generating
 * slugs on a fresh env is moot — there are no pre-existing collections to
 * backfill — and replicating the runtime helper inside a migration would
 * couple the schema timeline to application code. Operators of long-lived
 * envs already ran the backfill historically; this migration does NOT
 * re-run it.
 *
 * Idempotency strategy (D2): every statement is `IF NOT EXISTS`-guarded.
 *
 *   - `ADD COLUMN IF NOT EXISTS` — Postgres native; the `UNIQUE` inline
 *     clause on `slug` is ignored when the column already exists, so prod
 *     (which already has the autogen `collections_slug_key` constraint)
 *     and fresh envs (where the autogen constraint will be added) both
 *     converge correctly.
 *   - `CREATE UNIQUE INDEX IF NOT EXISTS` — Postgres native.
 *   - `ALTER TABLE ... ADD CONSTRAINT` for CHECK — Postgres has no
 *     `IF NOT EXISTS` clause for named constraints, so we wrap in a
 *     `DO $$ BEGIN ... END $$` block that checks `pg_constraint` first.
 *
 * Down-migration is a hard stub. See `down()` below — matches
 * `1779853647564_initial-schema.js` style.
 *
 * @type {import('node-pg-migrate').ColumnDefinitions | undefined}
 */
export const shorthands = undefined;

/**
 * @param {import('node-pg-migrate').MigrationBuilder} pgm
 * @returns {void}
 */
export const up = (pgm) => {
  pgm.sql(`
    ALTER TABLE collections
      ADD COLUMN IF NOT EXISTS visibility VARCHAR(20) DEFAULT 'private',
      ADD COLUMN IF NOT EXISTS tcg VARCHAR(50) DEFAULT 'MTG',
      ADD COLUMN IF NOT EXISTS tags TEXT
  `);

  pgm.sql(`
    ALTER TABLE collections
      ADD COLUMN IF NOT EXISTS image TEXT
  `);

  pgm.sql(`
    ALTER TABLE collections
      ADD COLUMN IF NOT EXISTS slug VARCHAR(100) UNIQUE
  `);

  pgm.sql(`
    CREATE UNIQUE INDEX IF NOT EXISTS idx_collections_slug
      ON collections(slug)
  `);

  pgm.sql(`
    DO $$
    BEGIN
      IF NOT EXISTS (
        SELECT 1
        FROM pg_constraint
        WHERE conname = 'check_slug_format'
          AND conrelid = 'collections'::regclass
      ) THEN
        ALTER TABLE collections
          ADD CONSTRAINT check_slug_format
          CHECK (slug ~ '^[a-z0-9]([a-z0-9-]*[a-z0-9])?$' AND length(slug) <= 50);
      END IF;
    END
    $$;
  `);
};

/**
 * Down-migration is a hard stub. This is a reconciliation migration: the
 * prod schema state is the source of truth, and dropping these columns
 * would discard slugs / visibility flags / tcg labels / tags / images that
 * application code reads on every collection page render. If you need a
 * clean schema for testing, branch the Neon database and run
 * `npm run migrate up` against the branch instead of rolling this back.
 *
 * @returns {void}
 */
export const down = () => {
  throw new Error(
    '[migration:1781000000002_reconcile-collections-columns] Refusing to drop reconciled columns. ' +
      'Rolling back this migration would erase visibility/tcg/tags/slug/image data on every ' +
      'collections row in the database. If you need a clean schema for testing, branch the ' +
      'Neon database and run `npm run migrate up` against the branch instead. See ' +
      'migrations/1781000000002_reconcile-collections-columns.js up() docstring for the ' +
      'reconciliation rationale.'
  );
};