const logger = require('../utils/logger');

/**
 * In-Dialog Handler - Equivalent to Kamailio's WITHINDLG route
 * Handles SIP requests within established dialogs (BYE, re-INVITE, etc.)
 */
class InDialogHandler {
  constructor(srf) {
    this.srf = srf;
  }

  /**
   * Handle media teardown for BYE/CANCEL (equivalent to kamailio.cfg:494-497)
   */
  handleMediaTeardown(req) {
    if (req.method === 'BYE' || req.method === 'CANCEL') {
      logger.info('[WITHINDLG] Media teardown for %s | Call-ID: %s', req.method, req.get('Call-ID'));
      // RTP proxy cleanup would go here
    }
  }

  /**
   * Handle media setup for ACK (equivalent to kamailio.cfg:500-502)
   */
  handleMediaSetup(req) {
    if (req.method === 'ACK') {
      logger.info('[WITHINDLG] Media setup for ACK | Call-ID: %s', req.get('Call-ID'));
      // RTP proxy setup would go here
    }
  }

  /**
   * Process loose route headers (equivalent to kamailio.cfg:506-561)
   */
  processLooseRoute(req, res) {
    const routeHeaders = req.get('Route');
    if (!routeHeaders) {
      return false;
    }

    logger.info('[WITHINDLG] Route headers processed | Call-ID: %s', req.get('Call-ID'));

    // Process Route headers to determine next hop
    const routes = Array.isArray(routeHeaders) ? routeHeaders : [routeHeaders];
    const nextRoute = routes[0];

    if (nextRoute.includes(this.srf.localAddress)) {
      // Route points back to us - check if user is registered locally
      const aor = `${req.uri.user}@${req.uri.host}`;
      const registration = this.srf.registrationHandler?.lookup(aor);

      if (registration) {
        logger.info('[WITHINDLG] Loose route resolved to local user, forwarding | Call-ID: %s', req.get('Call-ID'));
        return this.forwardToUser(req, res, registration);
      } else {
        logger.warn('[WITHINDLG] Loose route points to us but user not found locally | Call-ID: %s', req.get('Call-ID'));
        res.send(404, 'Not here');
        return true;
      }
    } else {
      // Route is to a different destination, process normally
      logger.info('[WITHINDLG] Forwarding to different destination | Call-ID: %s', req.get('Call-ID'));
      return this.forwardToDestination(req, res, nextRoute);
    }
  }

  /**
   * Forward request to registered user
   */
  async forwardToUser(req, res, registration) {
    try {
      const dlg = await this.srf.createRequest(req.method, registration.contact, {
        headers: {
          'From': req.get('From'),
          'To': req.get('To'),
          'Call-ID': req.get('Call-ID'),
          'CSeq': req.get('CSeq'),
          'Contact': req.get('Contact'),
          'Content-Type': req.get('Content-Type'),
          'Via': req.get('Via'),
          'Route': req.get('Route'),
          'Max-Forwards': req.get('Max-Forwards')
        },
        body: req.body
      });

      logger.info('[WITHINDLG] Successfully forwarded to user | Call-ID: %s', req.get('Call-ID'));

      // Send response back to originator
      res.send(200, 'OK');

      // Relay responses
      this.relayResponses(dlg, req, res);

    } catch (error) {
      logger.error('[WITHINDLG] Failed to forward to user: %s | Call-ID: %s', error.message, req.get('Call-ID'));
      res.send(500, 'Server Error');
    }
  }

  /**
   * Forward request to destination
   */
  async forwardToDestination(req, res, destination) {
    try {
      const dlg = await this.srf.createRequest(req.method, destination, {
        headers: {
          'From': req.get('From'),
          'To': req.get('To'),
          'Call-ID': req.get('Call-ID'),
          'CSeq': req.get('CSeq'),
          'Contact': req.get('Contact'),
          'Content-Type': req.get('Content-Type'),
          'Via': req.get('Via'),
          'Route': req.get('Route'),
          'Max-Forwards': req.get('Max-Forwards')
        },
        body: req.body
      });

      logger.info('[WITHINDLG] Successfully forwarded to destination | Call-ID: %s', req.get('Call-ID'));

      // Send response back to originator
      res.send(200, 'OK');

      // Relay responses
      this.relayResponses(dlg, req, res);

    } catch (error) {
      logger.error('[WITHINDLG] Failed to forward to destination: %s | Call-ID: %s', error.message, req.get('Call-ID'));
      res.send(500, 'Server Error');
    }
  }

  /**
   * Relay responses between dialogs
   */
  relayResponses(uacDialog, uasReq, uasRes) {
    // Relay UAC responses back to UAS
    uacDialog.on('response', (response) => {
      uasRes.send(response.status, response.reason, response.headers);
    });

    // Handle UAS responses to UAC
    uasRes.on('response', (response) => {
      uacDialog.send(response.status, response.reason, response.headers);
    });
  }

  /**
   * Handle BYE request (equivalent to kamailio.cfg:508-511)
   */
  handleBye(req, res) {
    logger.info('[WITHINDLG] BYE request | Call-ID: %s', req.get('Call-ID'));

    // Handle media teardown
    this.handleMediaTeardown(req);

    // Process routing
    if (this.processLooseRoute(req, res)) {
      return;
    }

    // If no loose route, try to find the target user
    const aor = `${req.uri.user}@${req.uri.host}`;
    const registration = this.srf.registrationHandler?.lookup(aor);

    if (registration) {
      logger.info('[WITHINDLG] BYE: Target user found locally, forwarding | Call-ID: %s', req.get('Call-ID'));
      this.forwardToUser(req, res, registration);
    } else {
      logger.warn('[WITHINDLG] BYE: Target user not found locally | Call-ID: %s', req.get('Call-ID'));
      res.send(404, 'Not here');
    }
  }

  /**
   * Handle ACK request (equivalent to kamailio.cfg:611-621)
   */
  handleAck(req, res) {
    logger.info('[WITHINDLG] ACK request | Call-ID: %s', req.get('Call-ID'));

    // Handle media setup
    this.handleMediaSetup(req);

    // ACK is typically just absorbed
    res.send(200, 'OK');
  }

  /**
   * Handle in-dialog SUBSCRIBE (equivalent to kamailio.cfg:606-610)
   */
  handleSubscribe(req, res) {
    logger.info('[WITHINDLG] SUBSCRIBE request | Call-ID: %s', req.get('Call-ID'));
    res.send(404, 'Not here');
  }

  /**
   * Main in-dialog request handler (equivalent to kamailio.cfg:489-627)
   */
  async handleInDialog(req, res) {
    const method = req.method;
    const callId = req.get('Call-ID');

    logger.info('[WITHINDLG] %s request | Call-ID: %s', method, callId);

    // Handle media-related operations
    if (method === 'BYE' || method === 'CANCEL') {
      this.handleMediaTeardown(req);
    } else if (method === 'ACK') {
      this.handleMediaSetup(req);
    }

    // Process based on method
    switch (method) {
      case 'BYE':
        this.handleBye(req, res);
        break;

      case 'ACK':
        this.handleAck(req, res);
        break;

      case 'SUBSCRIBE':
        this.handleSubscribe(req, res);
        break;

      default:
        // For other methods, try to process Route headers
        if (!this.processLooseRoute(req, res)) {
          // No route found, try direct forwarding
          logger.info('[WITHINDLG] No route headers, forwarding to destination | Call-ID: %s', callId);
          const aor = `${req.uri.user}@${req.uri.host}`;
          const registration = this.srf.registrationHandler?.lookup(aor);

          if (registration) {
            this.forwardToUser(req, res, registration);
          } else {
            logger.warn('[WITHINDLG] No route found for %s | Call-ID: %s', method, callId);
            res.send(404, 'Not here');
          }
        }
        break;
    }
  }
}

module.exports = InDialogHandler;