migrate((app) => {
  function collectionExists(name) {
    try { app.findCollectionByNameOrId(name); return true; } catch { return false; }
  }

  // ── households ──────────────────────────────────────────────────────────────
  if (!collectionExists('households')) {
    const col = new Collection({
      name: 'households',
      type: 'base',
      listRule: '',
      viewRule: '',
      createRule: '',
      updateRule: '',
      deleteRule: '',
      fields: [
        { name: 'name',         type: 'text', required: true },
        { name: 'invite_token', type: 'text', required: true },
      ],
    });
    app.save(col);
  }

  const householdsId = app.findCollectionByNameOrId('households').id;

  // ── items ────────────────────────────────────────────────────────────────────
  if (!collectionExists('items')) {
    const col = new Collection({
      name: 'items',
      type: 'base',
      listRule: '',
      viewRule: '',
      createRule: '',
      updateRule: '',
      deleteRule: '',
      fields: [
        { name: 'household',           type: 'relation', required: true, collectionId: householdsId, cascadeDelete: true, maxSelect: 1 },
        { name: 'name',                type: 'text',    required: true },
        { name: 'description',         type: 'text' },
        { name: 'category',            type: 'text' },
        { name: 'quantity',            type: 'number' },
        { name: 'unit',                type: 'text' },
        { name: 'min_stock_threshold', type: 'number' },
        { name: 'on_shopping_list',    type: 'bool' },
        { name: 'photo',               type: 'file',    maxSelect: 1, maxSize: 5242880 },
        { name: 'storage_location',    type: 'text' },
        { name: 'shopping_location',   type: 'text' },
        { name: 'price',               type: 'number' },
        { name: 'expiry_date',         type: 'date' },
        { name: 'barcode',             type: 'text' },
        { name: 'added_by_device',     type: 'text' },
      ],
    });
    app.save(col);
  }

  // ── shopping_list ────────────────────────────────────────────────────────────
  if (!collectionExists('shopping_list')) {
    const col = new Collection({
      name: 'shopping_list',
      type: 'base',
      listRule: '',
      viewRule: '',
      createRule: '',
      updateRule: '',
      deleteRule: '',
      fields: [
        { name: 'household',          type: 'relation', required: true, collectionId: householdsId, cascadeDelete: true, maxSelect: 1 },
        { name: 'item_id',            type: 'text' },
        { name: 'name',               type: 'text',   required: true },
        { name: 'suggested_quantity', type: 'number' },
        { name: 'unit',               type: 'text' },
        { name: 'is_checked',         type: 'bool' },
        { name: 'checked_by_device',  type: 'text' },
        { name: 'auto_added',         type: 'bool' },
      ],
    });
    app.save(col);
  }

  // ── members ──────────────────────────────────────────────────────────────────
  if (!collectionExists('members')) {
    const col = new Collection({
      name: 'members',
      type: 'base',
      listRule: '',
      viewRule: '',
      createRule: '',
      updateRule: '',
      deleteRule: '',
      fields: [
        { name: 'household',             type: 'relation', required: true, collectionId: householdsId, cascadeDelete: true, maxSelect: 1 },
        { name: 'device_id',             type: 'text', required: true },
        { name: 'device_name',           type: 'text' },
        { name: 'fcm_token',             type: 'text' },
        { name: 'notifications_enabled', type: 'bool' },
      ],
    });
    app.save(col);
  }
}, (app) => {
  // rollback
  for (const name of ['members', 'shopping_list', 'items', 'households']) {
    try { app.delete(app.findCollectionByNameOrId(name)); } catch {}
  }
});