const nodemailer = require('nodemailer');
const logger = require('./logger');

/**
 * Creates a nodemailer transporter from environment variables.
 * Required env vars: SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASS
 * Optional env vars: SMTP_FROM (defaults to SMTP_USER), SMTP_SECURE (defaults to 'true' if port 465)
 *
 * Returns null if SMTP is not configured so callers can fall back gracefully.
 */
const createTransport = () => {
  const { SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASS } = process.env;
  if (!SMTP_HOST || !SMTP_USER || !SMTP_PASS) {
    return null;
  }
  const port = parseInt(SMTP_PORT || '587', 10);
  const secure = process.env.SMTP_SECURE !== undefined
    ? process.env.SMTP_SECURE === 'true'
    : port === 465;

  return nodemailer.createTransport({
    host: SMTP_HOST,
    port,
    secure,
    auth: { user: SMTP_USER, pass: SMTP_PASS }
  });
};

/**
 * Send a password-reset e-mail to the given address.
 *
 * @param {string} toEmail   – recipient address
 * @param {string} resetUrl  – full URL including token query parameter
 * @returns {Promise<boolean>} true if mail was sent, false if SMTP is not configured
 */
const sendPasswordResetMail = async (toEmail, resetUrl) => {
  const transport = createTransport();
  if (!transport) {
    logger.warn(
      '[mailer] SMTP nicht konfiguriert (SMTP_HOST/SMTP_USER/SMTP_PASS fehlen). ' +
      'Reset-Link wird nur geloggt.'
    );
    return false;
  }

  const from = process.env.SMTP_FROM || process.env.SMTP_USER;

  await transport.sendMail({
    from,
    to: toEmail,
    subject: 'Passwort-Reset',
    text:
      `Sie haben einen Passwort-Reset angefordert.\n\n` +
      `Klicken Sie auf den folgenden Link (gültig für 1 Stunde):\n${resetUrl}\n\n` +
      `Falls Sie keinen Reset angefordert haben, ignorieren Sie diese Mail.`,
    html:
      `<p>Sie haben einen Passwort-Reset angefordert.</p>` +
      `<p><a href="${resetUrl}">Passwort zurücksetzen</a></p>` +
      `<p>Der Link ist 1 Stunde gültig.</p>` +
      `<p>Falls Sie keinen Reset angefordert haben, ignorieren Sie diese Mail.</p>`
  });

  return true;
};

module.exports = { sendPasswordResetMail };