/**
 * Main entry point for unified email worker
 *
 * Startup sequence:
 *  1. Load configuration and domains
 *  2. Start Prometheus metrics server
 *  3. Start health check server
 *  4. Initialize UnifiedWorker
 *  5. Register signal handlers for graceful shutdown
 */

import { config, loadDomains } from './config.js';
import { log } from './logger.js';
import { startMetricsServer, type MetricsCollector } from './metrics.js';
import { startHealthServer } from './health.js';
import { UnifiedWorker } from './worker/index.js';

// ---------------------------------------------------------------------------
// Banner
// ---------------------------------------------------------------------------
function printBanner(domains: string[]): void {
  log('╔══════════════════════════════════════════════════╗');
  log('║        Unified Email Worker (TypeScript)         ║');
  log('║               Version 2.0.0                      ║');
  log('╚══════════════════════════════════════════════════╝');
  log('');
  log(`Domains (${domains.length}):`);
  for (const d of domains) {
    log(`  • ${d}`);
  }
  log('');
  log(`SMTP: ${config.smtpHost}:${config.smtpPort}`);
  log(`Internal SMTP: port ${config.internalSmtpPort}`);
  log(`Poll interval: ${config.pollInterval}s`);
  log(`Metrics: port ${config.metricsPort}`);
  log(`Health:  port ${config.healthPort}`);
  log('');
}

// ---------------------------------------------------------------------------
// Main
// ---------------------------------------------------------------------------
async function main(): Promise<void> {
  // 1. Load domains
  const domains = loadDomains();
  if (domains.length === 0) {
    log('❌ No domains configured. Set DOMAINS env var or provide DOMAINS_FILE.', 'ERROR');
    process.exit(1);
  }

  printBanner(domains);

  // 2. Metrics server
  const metrics: MetricsCollector | null = await startMetricsServer(config.metricsPort);

  // 3. Unified worker
  const worker = new UnifiedWorker(domains, metrics);

  // 4. Health server
  startHealthServer(config.healthPort, domains, () => worker.getStats());

  // 5. Signal handlers
  let shuttingDown = false;

  const shutdown = async (signal: string) => {
    if (shuttingDown) return;
    shuttingDown = true;
    log(`\n🛑 Received ${signal}. Shutting down gracefully...`);
    await worker.stop();
    log('👋 Goodbye.');
    process.exit(0);
  };

  process.on('SIGINT', () => shutdown('SIGINT'));
  process.on('SIGTERM', () => shutdown('SIGTERM'));

  // 6. Start
  await worker.start();

  // Keep alive (event loop stays open due to HTTP servers + SQS polling)
  log('✅ Worker is running. Press Ctrl+C to stop.');
}

// ---------------------------------------------------------------------------
main().catch((err) => {
  log(`💥 Fatal startup error: ${err.message ?? err}`, 'CRITICAL');
  log(err.stack ?? '', 'CRITICAL');
  process.exit(1);
});