/***********************************************************************************************************************************************************************
 * File Name: withTransactionRetry.util.js
 * Type of Program: Utility
 * Description: Runs a Sequelize transaction, automatically retrying on serialization_failure
 *              (SQLSTATE 40001) — the transient "restart transaction" error CockroachDB (and
 *              Postgres SERIALIZABLE) throw when concurrent transactions can't be safely
 *              ordered. Without a retry, these surface as unhandled 500s on otherwise-correct
 *              code the moment two requests touch the same row close together.
 * Author: Kenneth Obsequio (@lash0000)
 * Date Created: Jul. 17, 2026
 ***********************************************************************************************************************************************************************
 * HOW TO USE:
 *   const { withTransactionRetry } = require('../utils/withTransactionRetry.util');
 *   const result = await withTransactionRetry(sequelize, async (t) => {
 *       await Model.upsert({...}, { transaction: t });
 *       return something;
 *   });
 ***********************************************************************************************************************************************************************/
'use strict';

const SERIALIZATION_FAILURE = '40001';
const MAX_RETRIES = 5;
const BASE_DELAY_MS = 50;

function isSerializationFailure(err) {
    return err?.parent?.code === SERIALIZATION_FAILURE || err?.original?.code === SERIALIZATION_FAILURE;
}

async function withTransactionRetry(sequelize, fn, { maxRetries = MAX_RETRIES } = {}) {
    for (let attempt = 0; ; attempt++) {
        const t = await sequelize.transaction();
        try {
            const result = await fn(t);
            await t.commit();
            return result;
        } catch (err) {
            await t.rollback();
            if (isSerializationFailure(err) && attempt < maxRetries) {
                const delay = BASE_DELAY_MS * 2 ** attempt + Math.random() * BASE_DELAY_MS;
                await new Promise((resolve) => setTimeout(resolve, delay));
                continue;
            }
            throw err;
        }
    }
}

module.exports = { withTransactionRetry, isSerializationFailure };