/**
 * Migration: Switch from Serial to UUID primary keys
 *
 * Phase 3 of 3 for migrating Serial primary keys to UUID
 * This migration performs the actual switch:
 * 1. Drop old foreign key constraints
 * 2. Drop old primary keys
 * 3. Drop old columns
 * 4. Rename new columns
 * 5. Add new primary keys and foreign keys
 *
 * WARNING: This is a destructive migration. Ensure you have backups!
 *
 * @type {import('node-pg-migrate').ColumnDefinitions | undefined}
 */
export const shorthands = undefined;

/**
 * @param pgm {import('node-pg-migrate').MigrationBuilder}
 * @param run {() => void | undefined}
 * @returns {Promise<void> | void}
 */
export const up = (pgm) => {
  console.log('Phase 3: Switching to UUID primary keys...');
  console.log('WARNING: This is a destructive migration. Ensure backups exist!');

  // =====================================================
  // Step 1: Drop existing foreign key constraints
  // =====================================================
  console.log('  Step 1: Dropping existing foreign key constraints...');

  // Drop FK constraints (dependent tables first)
  pgm.dropConstraint('payment_records', 'payment_records_user_subscription_id_fkey', {
    ifExists: true,
  });
  pgm.dropConstraint('subscription_history', 'subscription_history_user_subscription_id_fkey', {
    ifExists: true,
  });
  pgm.dropConstraint('user_subscriptions', 'user_subscriptions_subscription_plan_id_fkey', {
    ifExists: true,
  });
  pgm.dropConstraint('weather_forecasts', 'weather_forecasts_station_id_fkey', {
    ifExists: true,
  });
  pgm.dropConstraint('weather_observations', 'weather_observations_weather_station_id_fkey', {
    ifExists: true,
  });

  // =====================================================
  // Step 2: Drop old indexes on FK columns
  // =====================================================
  console.log('  Step 2: Dropping old indexes...');

  // Drop indexes that reference old columns
  pgm.dropIndex('weather_forecasts', 'station_id', { ifExists: true });
  pgm.dropIndex('weather_observations', 'weather_station_id', { ifExists: true });
  pgm.dropIndex('user_subscriptions', 'subscription_plan_id', { ifExists: true });
  pgm.dropIndex('subscription_history', 'user_subscription_id', { ifExists: true });
  pgm.dropIndex('payment_records', 'user_subscription_id', { ifExists: true });

  // =====================================================
  // Step 3: Drop old primary keys
  // =====================================================
  console.log('  Step 3: Dropping old primary keys...');

  const tablesToMigrate = [
    'analysis_results',
    'weather_stations',
    'weather_forecasts',
    'weather_observations',
    'subscription_plans',
    'user_subscriptions',
    'subscription_history',
    'payment_records',
    'camera_devices',
  ];

  tablesToMigrate.forEach((table) => {
    pgm.dropConstraint(table, `${table}_pkey`, { ifExists: true });
  });

  // =====================================================
  // Step 4: Drop old columns and rename new columns
  // =====================================================
  console.log('  Step 4: Dropping old columns and renaming new columns...');

  // For each table, drop old id and rename new_id to id
  tablesToMigrate.forEach((table) => {
    // Drop old id column
    pgm.dropColumn(table, 'id', { ifExists: true });

    // Rename new_id to id
    pgm.renameColumn(table, 'new_id', 'id');

    // Make id NOT NULL
    pgm.alterColumn(table, 'id', { notNull: true });
  });

  // Rename FK columns
  pgm.dropColumn('weather_forecasts', 'station_id', { ifExists: true });
  pgm.renameColumn('weather_forecasts', 'new_station_id', 'station_id');

  pgm.dropColumn('weather_observations', 'weather_station_id', { ifExists: true });
  pgm.renameColumn('weather_observations', 'new_weather_station_id', 'weather_station_id');

  pgm.dropColumn('user_subscriptions', 'subscription_plan_id', { ifExists: true });
  pgm.renameColumn('user_subscriptions', 'new_subscription_plan_id', 'subscription_plan_id');

  pgm.dropColumn('subscription_history', 'user_subscription_id', { ifExists: true });
  pgm.renameColumn('subscription_history', 'new_user_subscription_id', 'user_subscription_id');

  pgm.dropColumn('payment_records', 'user_subscription_id', { ifExists: true });
  pgm.renameColumn('payment_records', 'new_user_subscription_id', 'user_subscription_id');

  // =====================================================
  // Step 5: Add new primary key constraints
  // =====================================================
  console.log('  Step 5: Adding new primary key constraints...');

  tablesToMigrate.forEach((table) => {
    pgm.addConstraint(table, `${table}_pkey`, { primaryKey: 'id' });
  });

  // =====================================================
  // Step 6: Add new foreign key constraints
  // =====================================================
  console.log('  Step 6: Adding new foreign key constraints...');

  pgm.addConstraint('weather_forecasts', 'weather_forecasts_station_id_fkey', {
    foreignKeys: {
      columns: 'station_id',
      references: 'weather_stations(id)',
      onDelete: 'CASCADE',
    },
  });

  pgm.addConstraint('weather_observations', 'weather_observations_weather_station_id_fkey', {
    foreignKeys: {
      columns: 'weather_station_id',
      references: 'weather_stations(id)',
      onDelete: 'CASCADE',
    },
  });

  pgm.addConstraint('user_subscriptions', 'user_subscriptions_subscription_plan_id_fkey', {
    foreignKeys: {
      columns: 'subscription_plan_id',
      references: 'subscription_plans(id)',
      onDelete: 'CASCADE',
    },
  });

  pgm.addConstraint('subscription_history', 'subscription_history_user_subscription_id_fkey', {
    foreignKeys: {
      columns: 'user_subscription_id',
      references: 'user_subscriptions(id)',
      onDelete: 'CASCADE',
    },
  });

  pgm.addConstraint('payment_records', 'payment_records_user_subscription_id_fkey', {
    foreignKeys: {
      columns: 'user_subscription_id',
      references: 'user_subscriptions(id)',
      onDelete: 'CASCADE',
    },
  });

  // =====================================================
  // Step 7: Recreate indexes on FK columns
  // =====================================================
  console.log('  Step 7: Recreating indexes on FK columns...');

  pgm.createIndex('weather_forecasts', 'station_id', {
    name: 'idx_weather_forecasts_station_id',
  });

  pgm.createIndex('weather_observations', 'weather_station_id', {
    name: 'idx_weather_observations_station_id',
  });

  pgm.createIndex('user_subscriptions', 'subscription_plan_id', {
    name: 'idx_user_subscriptions_plan_id',
  });

  pgm.createIndex('subscription_history', 'user_subscription_id', {
    name: 'idx_subscription_history_sub_id',
  });

  pgm.createIndex('payment_records', 'user_subscription_id', {
    name: 'idx_payment_records_sub_id',
  });

  // =====================================================
  // Step 8: Clean up temporary indexes
  // =====================================================
  console.log('  Step 8: Cleaning up temporary indexes...');

  tablesToMigrate.forEach((table) => {
    pgm.dropIndex(table, [], { name: `idx_${table}_new_id`, ifExists: true });
  });

  // Drop temporary indexes from Phase 2
  pgm.dropIndex('weather_forecasts', [], {
    name: 'idx_weather_forecasts_new_station_id',
    ifExists: true,
  });
  pgm.dropIndex('weather_observations', [], {
    name: 'idx_weather_observations_new_station_id',
    ifExists: true,
  });
  pgm.dropIndex('user_subscriptions', [], {
    name: 'idx_user_subscriptions_new_plan_id',
    ifExists: true,
  });
  pgm.dropIndex('subscription_history', [], {
    name: 'idx_subscription_history_new_sub_id',
    ifExists: true,
  });
  pgm.dropIndex('payment_records', [], {
    name: 'idx_payment_records_new_sub_id',
    ifExists: true,
  });

  console.log('Phase 3 complete: All tables now use UUID primary keys.');
  console.log('');
  console.log('IMPORTANT: The _migration_id_mapping table has been preserved for reference.');
  console.log('You may drop it manually after verifying the migration: DROP TABLE _migration_id_mapping;');
};

/**
 * @param pgm {import('node-pg-migrate').MigrationBuilder}
 * @param run {() => void | undefined}
 * @returns {Promise<void> | void}
 */
export const down = (pgm) => {
  console.log('Rolling back Phase 3...');
  console.log('WARNING: This rollback requires the _migration_id_mapping table to exist!');

  // This rollback is complex and requires the mapping table
  // In production, consider using a backup restore instead

  pgm.sql(`
    -- Check if mapping table exists
    DO $$
    BEGIN
      IF NOT EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = '_migration_id_mapping') THEN
        RAISE EXCEPTION 'Cannot rollback: _migration_id_mapping table does not exist. Restore from backup.';
      END IF;
    END $$;
  `);

  // The full rollback would be very complex.
  // In practice, recommend restoring from backup before Phase 3.
  console.log('');
  console.log('ROLLBACK NOTE: For Phase 3, it is recommended to restore from a backup');
  console.log('taken before the migration rather than attempting to reverse the changes.');
  console.log('');
  console.log('If you must rollback, the _migration_id_mapping table contains the');
  console.log('old_id -> new_id mappings needed to reconstruct the serial IDs.');

  throw new Error(
    'Phase 3 rollback requires manual intervention or backup restore. ' +
      'See migration comments for details.',
  );
};