/**
 * Migration: Add audit fields for tracking who made changes
 *
 * Fixes: No created_by/updated_by tracking on important tables
 * Changes:
 * - Add created_by and updated_by to key tables
 * - These are nullable to support system-generated records
 *
 * @type {import('node-pg-migrate').ColumnDefinitions | undefined}
 */
export const shorthands = undefined;

/**
 * Tables that should have audit fields
 */
const TABLES_WITH_AUDIT_FIELDS = [
  'devices',
  'device_configurations',
  'device_certificates',
  'subscription_plans',
  'validated_events',
  'analysis_results',
  'weather_stations',
];

/**
 * @param pgm {import('node-pg-migrate').MigrationBuilder}
 * @param run {() => void | undefined}
 * @returns {Promise<void> | void}
 */
export const up = (pgm) => {
  console.log('Adding audit fields to key tables...');

  TABLES_WITH_AUDIT_FIELDS.forEach((table) => {
    console.log(`  Adding audit fields to ${table}...`);

    pgm.addColumns(table, {
      created_by: {
        type: 'uuid',
        notNull: false,
        comment: 'User who created this record (null for system-generated)',
      },
      updated_by: {
        type: 'uuid',
        notNull: false,
        comment: 'User who last updated this record (null for system updates)',
      },
    });

    // Add FK constraints to user_profiles
    pgm.addConstraint(table, `${table}_created_by_fkey`, {
      foreignKeys: {
        columns: 'created_by',
        references: 'user_profiles(id)',
        onDelete: 'SET NULL',
      },
    });

    pgm.addConstraint(table, `${table}_updated_by_fkey`, {
      foreignKeys: {
        columns: 'updated_by',
        references: 'user_profiles(id)',
        onDelete: 'SET NULL',
      },
    });
  });

  // Create a function to automatically set updated_by from context
  // This works with the application setting a session variable
  pgm.sql(`
    -- Function to get current user from session context
    CREATE OR REPLACE FUNCTION get_current_user_id()
    RETURNS UUID AS $$
    BEGIN
      -- Try to get user_id from session context (set by application)
      RETURN NULLIF(current_setting('app.current_user_id', true), '')::UUID;
    EXCEPTION
      WHEN OTHERS THEN
        RETURN NULL;
    END;
    $$ LANGUAGE plpgsql STABLE;

    COMMENT ON FUNCTION get_current_user_id() IS
    'Get current user ID from session context. Returns NULL if not set.
     Application should call: SET LOCAL app.current_user_id = ''<uuid>''; before operations.';
  `);

  // Create triggers to automatically set audit fields
  TABLES_WITH_AUDIT_FIELDS.forEach((table) => {
    pgm.sql(`
      CREATE OR REPLACE FUNCTION ${table}_audit_trigger()
      RETURNS TRIGGER AS $$
      BEGIN
        IF TG_OP = 'INSERT' THEN
          NEW.created_by = COALESCE(NEW.created_by, get_current_user_id());
          NEW.updated_by = NEW.created_by;
        ELSIF TG_OP = 'UPDATE' THEN
          NEW.updated_by = COALESCE(get_current_user_id(), NEW.updated_by);
        END IF;
        RETURN NEW;
      END;
      $$ LANGUAGE plpgsql;

      DROP TRIGGER IF EXISTS ${table}_audit ON ${table};
      CREATE TRIGGER ${table}_audit
        BEFORE INSERT OR UPDATE ON ${table}
        FOR EACH ROW
        EXECUTE FUNCTION ${table}_audit_trigger();
    `);
  });

  console.log('Audit fields added to key tables.');
  console.log('');
  console.log('Usage: Set session context before operations:');
  console.log("  SET LOCAL app.current_user_id = '<user-uuid>';");
};

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

  // Drop triggers and functions
  TABLES_WITH_AUDIT_FIELDS.forEach((table) => {
    pgm.sql(`
      DROP TRIGGER IF EXISTS ${table}_audit ON ${table};
      DROP FUNCTION IF EXISTS ${table}_audit_trigger();
    `);
  });

  // Drop the helper function
  pgm.sql('DROP FUNCTION IF EXISTS get_current_user_id();');

  // Drop FK constraints and columns
  TABLES_WITH_AUDIT_FIELDS.forEach((table) => {
    console.log(`  Removing audit fields from ${table}...`);

    pgm.dropConstraint(table, `${table}_created_by_fkey`, { ifExists: true });
    pgm.dropConstraint(table, `${table}_updated_by_fkey`, { ifExists: true });

    pgm.dropColumns(table, ['created_by', 'updated_by']);
  });

  console.log('Audit fields rollback complete.');
};