import type { Redis } from 'ioredis';
import type * as http from 'node:http';
import type * as net from 'node:net';
import { loadConfig } from './config/load.js';
import type { Config } from './config/load.js';
import { createLogger } from './observability/logger.js';
import { createMetrics, startMetricsServer } from './observability/metrics.js';
import { createPublisher, connectRedis } from './core/publish.js';
import { startServer } from './core/server.js';
import { createTeltonikaAdapter } from './adapters/teltonika/index.js';
import { AllowAllAuthority } from './adapters/teltonika/device-authority.js';

// -------------------------------------------------------------------------
// Startup: validate config (fail fast on bad env), build logger, boot server
// -------------------------------------------------------------------------

let config: Config;
try {
  config = loadConfig();
} catch (err) {
  // Config validation failures print a human-readable message and exit 1.
  // Logger is not available yet — process.stderr is the only output channel.
  process.stderr.write(`${err instanceof Error ? err.message : String(err)}\n`);
  process.exit(1);
}

const logger = createLogger({
  level: config.LOG_LEVEL,
  nodeEnv: config.NODE_ENV,
  instanceId: config.INSTANCE_ID,
});

logger.info('tcp-ingestion starting');

// Real prom-client metrics implementation (task 1.10).
const metrics = createMetrics();

// -------------------------------------------------------------------------
// Wire up the pipeline
// -------------------------------------------------------------------------

async function main(): Promise<void> {
  // 1. Connect Redis with exponential-backoff retry (3 attempts, up to 5s backoff)
  const redis = await connectRedis(config.REDIS_URL, logger);

  // 2. Build the publisher (bounded queue + XADD worker)
  const publisher = createPublisher(redis, config, logger, metrics);

  // 3. Build the Teltonika adapter (all three Phase 1 codecs registered via defaultRegistry)
  const teltonikaAdapter = createTeltonikaAdapter({
    port: config.TELTONIKA_PORT,
    deviceAuthority: new AllowAllAuthority(),
    strictDeviceAuth: config.STRICT_DEVICE_AUTH,
    // No explicit codecRegistry — createTeltonikaAdapter builds defaultRegistry
    // with codec8Handler, codec8eHandler, codec16Handler pre-registered.
  });

  // 4. Start TCP server — publisher.publish is the AdapterContext.publish impl
  const server = startServer(config.TELTONIKA_PORT, teltonikaAdapter, {
    publish: publisher.publish,
    logger,
    metrics,
  });

  // 5. Start metrics HTTP server (task 1.10).
  // readyzDeps use ioredis's synchronous `.status` field and net.Server's
  // `.listening` boolean — no I/O, so these closures are always cheap.
  const metricsServer = startMetricsServer(config.METRICS_PORT, metrics.serializeMetrics, {
    isRedisReady: () => redis.status === 'ready',
    isTcpListening: () => server.listening,
  });

  // 6. Install graceful shutdown (stub — full hardening in task 1.12)
  installGracefulShutdown({ server, metricsServer, redis, publisher, logger });

  logger.info({ port: config.TELTONIKA_PORT, metricsPort: config.METRICS_PORT }, 'tcp-ingestion ready');
}

// -------------------------------------------------------------------------
// Graceful shutdown stub — task 1.12 finalizes this
// -------------------------------------------------------------------------

type ShutdownDeps = {
  readonly server: net.Server;
  readonly metricsServer: http.Server;
  readonly redis: Redis;
  readonly publisher: { drain(timeoutMs: number): Promise<void> };
  readonly logger: ReturnType<typeof createLogger>;
};

function installGracefulShutdown(deps: ShutdownDeps): void {
  const { server, metricsServer, redis, publisher, logger: log } = deps;

  let shuttingDown = false;

  function shutdown(signal: string): void {
    if (shuttingDown) return;
    shuttingDown = true;

    log.info({ signal }, 'shutdown signal received');

    // Stop accepting new TCP connections
    server.close(() => {
      log.info('TCP server closed');
    });

    // Close the metrics HTTP server before quitting Redis so /readyz reports
    // not-ready during the drain window (task 1.12 will tighten this further).
    metricsServer.close();

    // Drain publisher queue then disconnect Redis
    publisher
      .drain(10_000)
      .then(() => redis.quit())
      .then(() => {
        log.info('graceful shutdown complete');
        process.exit(0);
      })
      .catch((err) => {
        log.error({ err }, 'error during shutdown');
        process.exit(1);
      });

    // Force exit after 15s if graceful path stalls
    setTimeout(() => {
      log.warn('forced exit after shutdown timeout');
      process.exit(1);
    }, 15_000).unref();
  }

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

// -------------------------------------------------------------------------
// Entry point
// -------------------------------------------------------------------------

main().catch((err) => {
  process.stderr.write(`Fatal startup error: ${err instanceof Error ? err.message : String(err)}\n`);
  process.exit(1);
});