// Phase 5C §14 — a simple durable worker, same pattern this codebase already uses for
// sessions.js's session sweeper and security.js's login-attempt sweeper: a plain setInterval
// poll against Postgres, no Kafka/RabbitMQ/Redis. notifications.js's claimNext() does the
// actual concurrency-safety work (FOR UPDATE SKIP LOCKED) — this file just calls it on a timer
// and hands the claimed row to the configured email provider.

const notifications = require('./notifications');
const templates = require('./email/templates');
const { getEmailProvider } = require('./email/provider');
const metrics = require('./metrics');

const POLL_MS = Number(process.env.NOTIFICATION_WORKER_POLL_MS) || 3000;

function buildAppUrl(path) {
  const origin = process.env.PUBLIC_APP_ORIGIN;
  if (!origin) return null;
  try {
    const u = new URL(origin);
    return `${u.origin}${path}`;
  } catch {
    return null; // malformed origin — treated as unconfigured, not a crash
  }
}

// Renders the right template for a queued row. Returns null (a permanent, non-retryable
// failure) if required config (PUBLIC_APP_ORIGIN for a token-bearing type) is missing — §7's
// "production should fail safely if required public-origin configuration is missing."
function renderFor(row) {
  const displayName = row.metadata?.display_name || 'there';
  if (row.notification_type === 'activation') {
    const url = buildAppUrl(`/?activate=${encodeURIComponent(row.metadata?.token || '')}`);
    if (!url || !row.metadata?.token) return null;
    return templates.activation({ displayName, programName: row.metadata?.program_name, activationUrl: url, expiresInDays: 7 });
  }
  if (row.notification_type === 'password_reset') {
    const url = buildAppUrl(`/?reset=${encodeURIComponent(row.metadata?.token || '')}`);
    if (!url || !row.metadata?.token) return null;
    return templates.passwordReset({ displayName, resetUrl: url, expiresInMinutes: 60 });
  }
  if (row.notification_type === 'enrollment_confirmation') {
    const url = buildAppUrl('/') || '/';
    return templates.enrollmentConfirmation({ displayName, programName: row.metadata?.program_name || 'your program', signInUrl: url });
  }
  if (row.notification_type === 'password_changed') {
    return templates.passwordChanged({ displayName });
  }
  // Phase 8 — registration-stage notifications. No token/public-origin dependency, so these
  // never fail on missing PUBLIC_APP_ORIGIN config the way activation/reset do.
  if (row.notification_type === 'registration_received') {
    return templates.registrationReceived({ displayName, offeringName: row.metadata?.offering_name || 'your offering' });
  }
  if (row.notification_type === 'registration_confirmed') {
    return templates.registrationConfirmed({ displayName, offeringName: row.metadata?.offering_name || 'your offering' });
  }
  if (row.notification_type === 'registration_needs_action') {
    return templates.registrationNeedsAction({ displayName, offeringName: row.metadata?.offering_name || 'your offering', reason: row.metadata?.reason });
  }
  if (row.notification_type === 'agreement_required') {
    return templates.agreementRequired({ displayName, offeringName: row.metadata?.offering_name || 'your offering', agreementTitle: row.metadata?.agreement_title || 'a required agreement' });
  }
  if (row.notification_type === 'camp_operational_update') {
    return templates.campOperationalUpdate({ displayName, offeringName: row.metadata?.offering_name || 'your offering', message: row.metadata?.message || '' });
  }
  return null;
}

async function processOne(pool) {
  const row = await notifications.claimNext(pool);
  if (!row) return false;

  const { EMAIL_PROVIDER } = require('./email/provider');
  const rendered = renderFor(row);
  if (!rendered) {
    await notifications.markFailedOrRetry(pool, row, { errorCode: 'template_or_config_error', retryable: false });
    metrics.recordNotificationAttempt(EMAIL_PROVIDER, 'failed');
    return true;
  }

  const provider = getEmailProvider();
  try {
    const result = await provider.send({
      to: row.recipient_email,
      fromName: process.env.EMAIL_FROM_NAME || 'RootNode Academy',
      fromAddress: process.env.EMAIL_FROM_ADDRESS,
      replyTo: process.env.EMAIL_REPLY_TO,
      subject: rendered.subject, text: rendered.text, html: rendered.html,
    });
    // §20 — a dev-only preview (never in production, regardless of provider) so a test/admin
    // can inspect exactly what would have been sent, including the activation/reset URL,
    // through the dedicated dev-only route — never through the normal admin notification view.
    const isProduction = process.env.COOKIE_SECURE === '1';
    const devPreview = (!isProduction && result.preview) ? result.preview : null;
    await notifications.markSent(pool, row.notification_id, result.providerMessageId, EMAIL_PROVIDER, devPreview);
    metrics.recordNotificationAttempt(EMAIL_PROVIDER, 'sent');
  } catch (e) {
    const retryable = e.errorClass !== 'permanent';
    const outcome = await notifications.markFailedOrRetry(pool, row, { errorCode: e.errorCode || 'unknown_error', retryable });
    metrics.recordNotificationAttempt(EMAIL_PROVIDER, outcome === 'retrying' ? 'retry' : 'failed');
    console.error(`[notification-worker] send failed (${row.notification_type}, ${outcome}): ${e.errorCode || e.message}`);
  }
  return true;
}

function startNotificationWorker(pool) {
  const tick = async () => {
    try {
      // Drain everything currently claimable before waiting out the next poll interval —
      // keeps a burst (e.g. a CSV import's worth of activations) from trickling out one per
      // POLL_MS when they could all go immediately.
      while (await processOne(pool)) { /* keep draining */ }
    } catch (e) {
      console.error('[notification-worker] tick failed:', e.message);
    }
  };
  const handle = setInterval(tick, POLL_MS);
  handle.unref(); // never keeps the process alive on its own, matching sessions.js's sweeper
  tick(); // don't wait a full interval for the first pass
  return handle;
}

module.exports = { startNotificationWorker, processOne, renderFor, buildAppUrl };