import { QueryInterface } from 'sequelize';

/**
 * Migration: Convert tat_days to GENERATED STORED column
 * 
 * This ensures tat_days is auto-calculated from tat_hours across all environments.
 * Production already has this as a generated column, this migration makes other environments consistent.
 */
export async function up(queryInterface: QueryInterface): Promise<void> {
  // Check if tat_days is already a generated column
  const result = await queryInterface.sequelize.query(`
    SELECT 
      a.attname as column_name,
      a.attgenerated as is_generated
    FROM pg_attribute a
    JOIN pg_class c ON a.attrelid = c.oid
    WHERE c.relname = 'approval_levels' 
      AND a.attname = 'tat_days'
      AND NOT a.attisdropped;
  `, { type: 'SELECT' });

  const column = result[0] as any;
  
  if (column && column.is_generated === 's') {
    // Already a GENERATED column, skipping
    return;
  }

  // Converting tat_days to GENERATED column

  // Step 1: Drop the existing regular column
  await queryInterface.sequelize.query(`
    ALTER TABLE approval_levels DROP COLUMN IF EXISTS tat_days;
  `);

  // Step 2: Add it back as a GENERATED STORED column
  // Formula: CEIL(tat_hours / 24.0) - rounds up to nearest day
  await queryInterface.sequelize.query(`
    ALTER TABLE approval_levels 
    ADD COLUMN tat_days INTEGER 
    GENERATED ALWAYS AS (CAST(CEIL(tat_hours / 24.0) AS INTEGER)) STORED;
  `);

  // tat_days is now auto-calculated
}

export async function down(queryInterface: QueryInterface): Promise<void> {
  // Rolling back to regular column

  // Drop the generated column
  await queryInterface.sequelize.query(`
    ALTER TABLE approval_levels DROP COLUMN IF EXISTS tat_days;
  `);

  // Add it back as a regular column (with default calculation for existing rows)
  await queryInterface.sequelize.query(`
    ALTER TABLE approval_levels 
    ADD COLUMN tat_days INTEGER;
  `);

  // Populate existing rows with calculated values
  await queryInterface.sequelize.query(`
    UPDATE approval_levels 
    SET tat_days = CAST(CEIL(tat_hours / 24.0) AS INTEGER)
    WHERE tat_days IS NULL;
  `);

  // Make it NOT NULL after populating
  await queryInterface.sequelize.query(`
    ALTER TABLE approval_levels 
    ALTER COLUMN tat_days SET NOT NULL;
  `);

  // Rolled back successfully
}