/**
 * Migration: Add ValidatedEvent weather_station_id FK
 *
 * Fixes: ValidatedEvent has station_name as varchar instead of FK to WeatherStation
 * Changes:
 * - Add weather_station_id UUID FK
 * - Migrate data by matching station_name
 * - Keep station_name for historical reference
 *
 * @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('Adding ValidatedEvent weather_station_id FK...');

  // Step 1: Add weather_station_id column
  pgm.addColumn('validated_events', {
    weather_station_id: {
      type: 'uuid',
      notNull: false,
      comment: 'Foreign key to weather_stations table',
    },
  });

  // Step 2: Migrate data by matching station_name
  pgm.sql(`
    UPDATE validated_events ve
    SET weather_station_id = ws.id
    FROM weather_stations ws
    WHERE ve.station_name IS NOT NULL
      AND ve.station_name != ''
      AND LOWER(TRIM(ve.station_name)) = LOWER(TRIM(ws.station_name));
  `);

  // Step 3: Add FK constraint
  pgm.addConstraint('validated_events', 'validated_events_weather_station_id_fkey', {
    foreignKeys: {
      columns: 'weather_station_id',
      references: 'weather_stations(id)',
      onDelete: 'SET NULL',
    },
  });

  // Step 4: Add index
  pgm.createIndex('validated_events', 'weather_station_id', {
    name: 'idx_validated_events_weather_station_id',
    where: 'weather_station_id IS NOT NULL',
  });

  // Step 5: Add comment to station_name indicating it's for historical reference
  pgm.sql(`
    COMMENT ON COLUMN validated_events.station_name IS
    'Historical station name (kept for reference). Use weather_station_id for queries.';
  `);

  console.log('ValidatedEvent weather_station_id FK added.');
  console.log('Note: station_name column preserved for historical reference.');
};

/**
 * @param pgm {import('node-pg-migrate').MigrationBuilder}
 * @param run {() => void | undefined}
 * @returns {Promise<void> | void}
 */
export const down = (pgm) => {
  console.log('Rolling back ValidatedEvent weather_station_id FK...');

  // Remove index
  pgm.dropIndex('validated_events', 'weather_station_id', {
    name: 'idx_validated_events_weather_station_id',
    ifExists: true,
  });

  // Remove FK constraint
  pgm.dropConstraint('validated_events', 'validated_events_weather_station_id_fkey', {
    ifExists: true,
  });

  // Remove column
  pgm.dropColumn('validated_events', 'weather_station_id', { ifExists: true });

  // Restore station_name comment
  pgm.sql(`
    COMMENT ON COLUMN validated_events.station_name IS
    'Name of the weather station associated with this event';
  `);

  console.log('ValidatedEvent weather_station_id FK rollback complete.');
};