index.js

/**
 * Application Entry Point
 *
 * This file initializes and starts the HTTP server for the application.
 * Sets up server configuration and scheduled tasks for maintenance operations.
 */

// Load configuration
import { config } from './src/config.js';
import { TIME_CONSTANTS } from './src/constants.js';

// Node core modules
import http from 'http';

// Helpers
import { helperCleanupOldScreenshots } from './src/helpers/cleanup-screenshots.js';

// Web server application
import { expressApp } from './src/app.js';

/**
 * Configure Express application settings
 * These settings are accessible via app.get('setting') throughout the application
 */
expressApp.set('env', config.server.env);
expressApp.set('port', config.server.port);
expressApp.set('host', config.server.host);

/**
 * Create HTTP server using Express application
 * This allows for future upgrades (like WebSockets) without changing the Express app
 */
const server = http.createServer(expressApp);

/**
 * Schedule screenshot cleanup task
 * Runs every hour to clean up old screenshots and prevent disk space issues
 *
 * @returns {Promise<void>} Promise that resolves when the cleanup is complete
 */
async function scheduleScreenshotCleanup() {
  try {
    const { deleted } = await helperCleanupOldScreenshots();
    if (deleted > 0) {
      console.log(
        `Scheduled cleanup: Removed ${deleted} old screenshot file${deleted !== 1 ? 's' : ''}`
      );
    }
  } catch (error) {
    console.error('Error during scheduled screenshot cleanup:', error);
  }

  // Schedule next cleanup
  setTimeout(scheduleScreenshotCleanup, TIME_CONSTANTS.ONE_HOUR_MS);
}

/**
 * Start the server and initialize scheduled tasks
 * Listens on the specified port and host
 */
server.listen(config.server.port, config.server.host, async () => {
  console.log(
    `Server started at http://${config.server.host}:${config.server.port} in ${config.server.env} mode`
  );

  // Perform initial screenshot cleanup
  try {
    const { deleted } = await helperCleanupOldScreenshots();
    if (deleted > 0) {
      console.log(
        `Initial cleanup: Removed ${deleted} old screenshot file${deleted !== 1 ? 's' : ''}`
      );
    } else {
      console.log('Initial cleanup: No old screenshot files to remove');
    }

    // Start the scheduled cleanup
    setTimeout(scheduleScreenshotCleanup, TIME_CONSTANTS.ONE_HOUR_MS);
  } catch (error) {
    console.error('Error during initial screenshot cleanup:', error);
  }
});

/**
 * Global error handling for uncaught exceptions
 * Prevents the server from crashing when unexpected errors occur
 */
process.on('uncaughtException', (error) => {
  console.error('Uncaught exception:', error);
});

/**
 * Global error handling for unhandled promise rejections
 * Prevents the server from crashing when promises are rejected without a catch handler
 */
process.on('unhandledRejection', (reason, _promise) => {
  console.error('Unhandled promise rejection:', reason);
});

/**
 * Graceful shutdown handlers
 * Ensures the server closes cleanly on termination signals
 * Allows pending requests to complete before shutting down
 */
process.on('SIGTERM', gracefulShutdown('SIGTERM'));
process.on('SIGINT', gracefulShutdown('SIGINT'));

/**
 * Graceful shutdown function
 * Closes server and exits process after completing pending connections
 *
 * @param {string} signal - The signal that triggered the shutdown
 * @returns {Function} - Signal handler function
 */
function gracefulShutdown(signal) {
  return () => {
    console.log(`${signal} received. Starting graceful shutdown...`);

    server.close(() => {
      console.log('Server closed. All connections were properly ended.');
      process.exit(0);
    });

    // Force shutdown after timeout if connections haven't closed
    setTimeout(() => {
      console.warn(
        `Forcing server shutdown after ${TIME_CONSTANTS.FORCE_SHUTDOWN_TIMEOUT_MS}ms timeout.`
      );
      process.exit(1);
    }, TIME_CONSTANTS.FORCE_SHUTDOWN_TIMEOUT_MS);
  };
}