/***********************************************************************************************************************************************************************
 * File Name: email.service.js
 * Type of Program: Service
 * Description: Nodemailer-based email service.
 *              Subject + body per type are hardcoded in data/email_body.data.js —
 *              there is no admin UI or DB table. To add or change an email,
 *              edit that file directly and redeploy.
 * Author: rgrgogu, Kenneth Obsequio (@lash0000)
 * Date Created: Oct. 6, 2025
 ***********************************************************************************************************************************************************************
 * HOW TO USE:
 *   const emailService = require('../services/email.service');
 *   await emailService.sendEmail({ to: user.email, type: 'OTP', data: { otp } });
 ***********************************************************************************************************************************************************************/
const nodemailer = require('nodemailer');
const { emailTemplates } = require('../data/email_body.data');

const port = Number(process.env.SMTP_PORT);

const transporter = nodemailer.createTransport({
  host:        process.env.SMTP_HOST,
  port,
  secure:      port === 465,
  requireTLS:  port === 587,
  auth: {
    user: process.env.SMTP_USER,
    pass: process.env.SMTP_PASS,
  },
  tls: {
    rejectUnauthorized: false,
  },
});

const sendEmail = async ({ to, type, data = {} }) => {
  try {
    const templateFn = emailTemplates[type];

    if (!templateFn) {
      throw new Error(`Email template "${type}" not found`);
    }

    const { subject, html } = templateFn(data);

    return await new Promise((resolve, reject) => {
      transporter.sendMail(
        {
          from: {
            name: "STARR System",
            address: process.env.EMAIL_FROM,
          },
          to,
          subject,
          html,
        },
        (err, info) => {
          if (err) return reject(err);
          resolve(info);
        }
      );
    });
  } catch (err) {
    throw new Error(err.message);
  }
};

const ping = () => transporter.verify();

module.exports = { sendEmail, ping };