const config = require('config');
const logger = require('./utils/logger');
const { Srf } = require('drachtio-srf');
const RequestProcessor = require('./middleware/requestProcessor');
const RegistrationHandler = require('./routes/registration');
const InviteHandler = require('./routes/invite');
const InDialogHandler = require('./routes/indialog');

/**
 * NexusVoice SIP Border Controller - Drachtio Implementation
 *
 * This server provides equivalent functionality to the Kamailio configuration:
 * - SIP request validation and security filtering
 * - User registration and location management
 * - Call routing and media handling
 * - Integration with external systems (Asterisk, RTP proxy)
 */

class SipServer {
  constructor() {
    this.srf = new Srf();
    this.config = config;
    this.requestProcessor = new RequestProcessor(this.srf);
    this.registrationHandler = new RegistrationHandler(this.srf);
    this.inviteHandler = new InviteHandler(this.srf);
    this.inDialogHandler = new InDialogHandler(this.srf);
  }

  /**
   * Initialize the SIP server
   */
  async initialize() {
    try {
      logger.info('Initializing NexusVoice SBC...');

      // Configure SIP listening parameters
      const sipConfig = this.config.get('sip');

      // Connect to drachtio server
      await this.srf.connect({
        host: sipConfig.host,
        port: sipConfig.port,
        transport: sipConfig.transport
      });

      logger.info('Connected to drachtio server on %s:%s', sipConfig.host, sipConfig.port);

      // Setup middleware pipeline (equivalent to Kamailio's request_route)
      this.setupMiddleware();

      // Setup method-specific handlers
      this.setupMethodHandlers();

      // Setup in-dialog handlers
      this.setupInDialogHandlers();

      logger.info('NexusVoice SBC initialized successfully');
    } catch (error) {
      logger.error('Failed to initialize SBC: %s', error.message);
      throw error;
    }
  }

  /**
   * Setup the main request processing pipeline
   */
  setupMiddleware() {
    logger.info('Setting up request processing pipeline...');

    // Apply the main request processor middleware
    this.srf.use(this.requestProcessor.processRequest());

    logger.info('Request processing pipeline configured');
  }

  /**
   * Setup method-specific request handlers
   */
  setupMethodHandlers() {
    logger.info('Setting up method-specific handlers...');

    // REGISTER requests (equivalent to kamailio.cfg:186-189)
    this.srf.register((req, res) => {
      this.registrationHandler.handleRegister(req, res);
    });

    // INVITE requests (equivalent to kamailio.cfg:210-212)
    this.srf.invite((req, res) => {
      this.inviteHandler.handleInvite(req, res);
    });

    logger.info('Method-specific handlers configured');
  }

  /**
   * Setup in-dialog request handlers
   */
  setupInDialogHandlers() {
    logger.info('Setting up in-dialog handlers...');

    // Handle all in-dialog requests
    this.srf.dialog((req, res) => {
      this.inDialogHandler.handleInDialog(req, res);
    });

    logger.info('In-dialog handlers configured');
  }

  /**
   * Start the server
   */
  async start() {
    try {
      await this.initialize();
      logger.info('NexusVoice SBC started successfully');
    } catch (error) {
      logger.error('Failed to start SBC: %s', error.message);
      process.exit(1);
    }
  }

  /**
   * Graceful shutdown
   */
  async shutdown() {
    logger.info('Shutting down NexusVoice SBC...');

    try {
      await this.srf.disconnect();
      logger.info('NexusVoice SBC shutdown complete');
    } catch (error) {
      logger.error('Error during shutdown: %s', error.message);
    }
  }
}

// Create and start the server instance
const server = new SipServer();

// Handle graceful shutdown
process.on('SIGTERM', async () => {
  await server.shutdown();
  process.exit(0);
});

process.on('SIGINT', async () => {
  await server.shutdown();
  process.exit(0);
});

// Start the server
server.start().catch((error) => {
  logger.error('Failed to start server: %s', error.message);
  process.exit(1);
});

module.exports = SipServer;