// Outbound mail via SendGrid v3 (domain-authenticated instantadpay.com).
// Key sources: SENDGRID_KEY env, else DATA_DIR/sendgrid.key in the volume.
// No key = email sign-in stays feature-flagged off in production.
const fs = require('fs');
const path = require('path');
const https = require('https');

let DATA_DIR = null;
const FROM = { email: 'no-reply@instantadpay.com', name: 'InstantAdPay' };

function init(opts) { DATA_DIR = opts.dataDir; }
function key() {
  if (process.env.SENDGRID_KEY) return process.env.SENDGRID_KEY.trim();
  try { return fs.readFileSync(path.join(DATA_DIR, 'sendgrid.key'), 'utf8').trim(); } catch (e) { return ''; }
}
function hasKey() { return !!key(); }

function send(to, subject, text) {
  return new Promise((resolve, reject) => {
    const body = JSON.stringify({
      personalizations: [{ to: [{ email: to }] }],
      from: FROM,
      subject,
      content: [{ type: 'text/plain', value: text }]
    });
    const req = https.request({ hostname: 'api.sendgrid.com', path: '/v3/mail/send', method: 'POST',
      headers: { Authorization: 'Bearer ' + key(), 'Content-Type': 'application/json',
        'Content-Length': Buffer.byteLength(body) }, timeout: 15000 },
      res => {
        let d = '';
        res.on('data', c => d += c);
        res.on('end', () => res.statusCode < 300 ? resolve(true) : reject(new Error('sendgrid ' + res.statusCode + ': ' + d.slice(0, 200))));
      });
    req.on('error', reject);
    req.on('timeout', () => req.destroy(new Error('sendgrid timeout')));
    req.end(body);
  });
}

function sendCode(to, code) {
  return send(to, code + ' is your InstantAdPay sign-in code',
    'Your sign-in code is: ' + code + '\n\n'
    + 'It works for 15 minutes. If you did not request it, ignore this email.\n\n'
    + 'InstantAdPay\nAdvertise and earn instantly. Locked in code, not promises.\nhttps://instantadpay.com');
}

module.exports = { init, hasKey, send, sendCode };