'use strict';
/**
 * alert-bridge — приёмник sched webhook-алертов (универсальный outbound webhook).
 * Форматирует пейлоад sched → ntfy + email (Unisender Go, go2).
 *
 * sched шлёт: POST {version, event, task, run|schedule}, подпись
 * X-Sched-Signature-256: sha256=<hex> (HMAC-SHA256, GitHub-модель) если WEBHOOK_SECRET задан.
 *
 * Env: NTFY_URL (http://ntfy:8096), NTFY_TOPIC, WEBHOOK_SECRET,
 *      UNISENDER_API_KEY, UNISENDER_FROM, EMAIL_TO, PORT (9090)
 */
const http = require('node:http');
const crypto = require('node:crypto');

const {
  NTFY_URL = 'http://ntfy',
  NTFY_TOPIC = 'sched-alerts',
  WEBHOOK_SECRET = '',
  UNISENDER_API_KEY = '',
  UNISENDER_FROM = '',
  EMAIL_TO = '',
  PORT = '9090',
} = process.env;

const UNISENDER_ENDPOINT = process.env.UNISENDER_ENDPOINT || 'https://goapi.unisender.ru/ru/transactional/api/v1/email/send.json';

function verify(req, raw) {
  if (!WEBHOOK_SECRET) return true;
  const sig = req.headers['x-sched-signature-256'] || '';
  const expected = 'sha256=' + crypto.createHmac('sha256', WEBHOOK_SECRET).update(raw).digest('hex');
  if (sig.length !== expected.length) return false;
  return crypto.timingSafeEqual(Buffer.from(sig), Buffer.from(expected));
}

function fmt(payload) {
  const task = payload.task ?? {};
  const name = task.name ?? '?';
  if (payload.event === 'missed-slot') {
    const s = payload.schedule ?? {};
    return {
      title: `⏰ missed-slot: ${name}`,
      body: `Задача ${name} не успела на слот ${s.scheduledAt ?? '?'} (задержка ${s.delayMs ?? '?'} ms).`,
      prio: 4,
      alert: true,
    };
  }
  const status = (payload.event ?? '').replace(/^run\./, '') || '?';
  const run = payload.run ?? {};
  const err = run.error ? `\nОшибка: ${run.error}` : '';
  const failed = status === 'failed';
  return {
    title: `${failed ? '🚨' : 'ℹ️'} run.${status}: ${name}`,
    body: `Рана ${(run.id ?? '?').slice(0, 12)} · статус ${status} · attempt ${run.attempt ?? 1}${err}`,
    prio: failed ? 5 : 3,
    alert: failed,
  };
}

async function sendNtfy(m) {
  const base = NTFY_URL.replace(/\/+$/, '');
  const res = await fetch(`${base}/${encodeURIComponent(NTFY_TOPIC)}`, {
    method: 'POST',
    headers: { 'content-type': 'application/json' },
    body: JSON.stringify({
      topic: NTFY_TOPIC,
      title: m.title,
      message: m.body,
      priority: m.prio,
      tags: [m.prio >= 4 ? 'rotating_light' : 'info'],
    }),
  });
  if (!res.ok) throw new Error(`ntfy ${res.status}`);
}

async function sendEmail(m) {
  if (!UNISENDER_API_KEY || !EMAIL_TO) return { skipped: 'no UNISENDER_API_KEY/EMAIL_TO' };
  const res = await fetch(UNISENDER_ENDPOINT, {
    method: 'POST',
    headers: { 'content-type': 'application/json' },
    body: JSON.stringify({
      api_key: UNISENDER_API_KEY,
      message: {
        template_engine: 'velocity',
        body: { plaintext: m.body },
        subject: m.title,
        from_email: UNISENDER_FROM,
        from_name: 'sched-pipeline',
        recipients: [{ email: EMAIL_TO }],
      },
    }),
  });
  const text = await res.text();
  if (!res.ok) throw new Error(`unisender ${res.status}: ${text.slice(0, 200)}`);
  return text;
}

const server = http.createServer(async (req, res) => {
  const json = (code, body) => {
    const payload = JSON.stringify(body);
    res.writeHead(code, { 'content-type': 'application/json' });
    res.end(payload);
  };
  if (req.method !== 'POST' || req.url !== '/webhook') return json(404, { ok: false, error: 'not found' });

  const chunks = [];
  for await (const c of req) chunks.push(c);
  const raw = Buffer.concat(chunks);

  if (!verify(req, raw)) return json(401, { ok: false, error: 'bad signature' });

  let payload;
  try {
    payload = JSON.parse(raw.toString('utf8'));
  } catch {
    return json(400, { ok: false, error: 'bad json' });
  }

  const m = fmt(payload);
  const errs = [];
  try { await sendNtfy(m); } catch (e) { errs.push(`ntfy: ${e.message}`); }
  if (m.alert) {
    try { await sendEmail(m); } catch (e) { errs.push(`email: ${e.message}`); }
  }
  json(200, { ok: true, errors: errs });
});

server.listen(Number(PORT), '0.0.0.0', () => {
  console.log(`alert-bridge on :${PORT} (ntfy=${NTFY_URL}/${NTFY_TOPIC}, email=${EMAIL_TO ? 'on' : 'off'})`);
});