import { MigrationInterface, QueryRunner } from 'typeorm';

/**
 * Approval workflow for edits to LIVE rates. A LIVE rate is what pricing
 * charges, so it is never edited in place: the edit is filed here as PENDING
 * and the live row keeps its value until an approver applies it.
 *
 * `payload` holds the changed fields only; `previous_values` snapshots what
 * they were at submit time so the approver sees a real before→after diff.
 */
export class CreateRateChangeRequests2300000000000 implements MigrationInterface {
  name = 'CreateRateChangeRequests2300000000000';

  public async up(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.query(`
      CREATE TABLE IF NOT EXISTS freight.rate_change_requests (
        id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
        rate_id uuid NOT NULL REFERENCES freight.rates (id),
        payload jsonb NOT NULL,
        previous_values jsonb NOT NULL,
        status varchar(10) NOT NULL DEFAULT 'PENDING',
        requested_by_user_id uuid NULL,
        decided_by_user_id uuid NULL,
        decided_at timestamptz NULL,
        decision_note text NULL,
        created_at timestamptz NOT NULL DEFAULT now(),
        updated_at timestamptz NOT NULL DEFAULT now(),
        deleted_at timestamptz NULL
      )
    `);
    await queryRunner.query(`
      CREATE INDEX IF NOT EXISTS idx_rcr_status
        ON freight.rate_change_requests (status)
    `);
    // At most one pending edit per rate — two racing requests would both pass
    // validation and the second would silently overwrite the first on approval.
    await queryRunner.query(`
      CREATE UNIQUE INDEX IF NOT EXISTS uq_rcr_one_pending_per_rate
        ON freight.rate_change_requests (rate_id)
        WHERE status = 'PENDING' AND deleted_at IS NULL
    `);
  }

  public async down(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.query(`DROP TABLE IF EXISTS freight.rate_change_requests`);
  }
}