/**
 * Reverse Proxy for Onebox
 *
 * HTTP/HTTPS reverse proxy with SNI support for multi-domain TLS
 * Uses Node.js https module for SNI via Deno's Node compatibility layer
 */

import { logger } from '../logging.ts';
import { getErrorMessage } from '../utils/error.ts';
import { OneboxDatabase } from './database.ts';
import * as nodeHttps from 'node:https';
import * as nodeHttp from 'node:http';
import type { IncomingMessage, ServerResponse } from 'node:http';
import { Buffer } from 'node:buffer';

interface IProxyRoute {
  domain: string;
  targetHost: string;
  targetPort: number;
  serviceId: number;
  containerID?: string;
}

interface ITlsConfig {
  domain: string;
  certPem: string;    // Certificate PEM content
  keyPem: string;     // Private key PEM content
}

export class OneboxReverseProxy {
  private oneboxRef: any;
  private database: OneboxDatabase;
  private routes: Map<string, IProxyRoute> = new Map();
  private httpServer: Deno.HttpServer | null = null;
  private httpsServer: nodeHttps.Server | null = null;  // Node.js HTTPS server for SNI support
  private httpPort = 80;
  private httpsPort = 443;
  private tlsConfigs: Map<string, ITlsConfig> = new Map();

  constructor(oneboxRef: any) {
    this.oneboxRef = oneboxRef;
    this.database = oneboxRef.database;
  }

  /**
   * Initialize reverse proxy
   */
  async init(): Promise<void> {
    try {
      logger.info('Reverse proxy initialized');
    } catch (error) {
      logger.error(`Failed to initialize reverse proxy: ${getErrorMessage(error)}`);
      throw error;
    }
  }

  /**
   * Start the HTTP reverse proxy server
   */
  async startHttp(port?: number): Promise<void> {
    if (this.httpServer) {
      logger.warn('HTTP reverse proxy already running');
      return;
    }

    if (port) {
      this.httpPort = port;
    }

    try {
      logger.info(`Starting HTTP reverse proxy on port ${this.httpPort}...`);

      this.httpServer = Deno.serve(
        {
          port: this.httpPort,
          hostname: '0.0.0.0',
          onListen: ({ hostname, port }) => {
            logger.success(`HTTP reverse proxy listening on http://${hostname}:${port}`);
          },
        },
        (req) => this.handleRequest(req, false)
      );

      logger.success(`HTTP reverse proxy started on port ${this.httpPort}`);
    } catch (error) {
      logger.error(`Failed to start HTTP reverse proxy: ${getErrorMessage(error)}`);
      throw error;
    }
  }

  /**
   * Start the HTTPS reverse proxy server with SNI support
   * Uses Node.js https.createServer() + addContext() for per-domain certificates
   */
  async startHttps(port?: number): Promise<void> {
    if (this.httpsServer) {
      logger.warn('HTTPS reverse proxy already running');
      return;
    }

    if (port) {
      this.httpsPort = port;
    }

    try {
      // Check if we have any TLS configs
      if (this.tlsConfigs.size === 0) {
        logger.info('No TLS certificates configured, skipping HTTPS server');
        return;
      }

      logger.info(`Starting HTTPS reverse proxy on port ${this.httpsPort} with SNI support...`);

      // Get the first certificate as default (required for server creation)
      const defaultConfig = Array.from(this.tlsConfigs.values())[0];

      // Create HTTPS server with Node.js for SNI support
      this.httpsServer = nodeHttps.createServer(
        {
          cert: defaultConfig.certPem,
          key: defaultConfig.keyPem,
        },
        (req, res) => this.handleNodeRequest(req, res, true)
      );

      // Add SNI contexts for each domain
      for (const [domain, config] of this.tlsConfigs) {
        this.httpsServer.addContext(domain, {
          cert: config.certPem,
          key: config.keyPem,
        });
        // Also add wildcard pattern for subdomains
        this.httpsServer.addContext(`*.${domain}`, {
          cert: config.certPem,
          key: config.keyPem,
        });
        logger.info(`Added SNI context for ${domain} and *.${domain}`);
      }

      // Start listening
      await new Promise<void>((resolve, reject) => {
        this.httpsServer!.listen(this.httpsPort, '0.0.0.0', () => {
          logger.success(`HTTPS reverse proxy listening on https://0.0.0.0:${this.httpsPort}`);
          resolve();
        });
        this.httpsServer!.on('error', reject);
      });

      logger.success(`HTTPS reverse proxy started on port ${this.httpsPort} with ${this.tlsConfigs.size} certificates`);
    } catch (error) {
      logger.error(`Failed to start HTTPS reverse proxy: ${getErrorMessage(error)}`);
      // Don't throw - HTTPS is optional
      logger.warn('Continuing without HTTPS support');
    }
  }

  /**
   * Handle Node.js HTTP request and convert to fetch-style handling
   */
  private handleNodeRequest(
    req: IncomingMessage,
    res: ServerResponse,
    isHttps: boolean
  ): void {
    // Collect request body
    const chunks: Buffer[] = [];

    req.on('data', (chunk: Buffer) => {
      chunks.push(chunk);
    });

    req.on('end', async () => {
      try {
        const body = chunks.length > 0 ? Buffer.concat(chunks) : undefined;

        // Build URL from Node.js request
        const protocol = isHttps ? 'https' : 'http';
        const host = req.headers.host || 'localhost';
        const url = new URL(req.url || '/', `${protocol}://${host}`);

        // Convert Node.js headers to Headers
        const headers = new Headers();
        for (const [key, value] of Object.entries(req.headers)) {
          if (value) {
            if (Array.isArray(value)) {
              value.forEach(v => headers.append(key, v));
            } else {
              headers.set(key, value);
            }
          }
        }

        // Create fetch-style Request
        const fetchRequest = new Request(url.toString(), {
          method: req.method || 'GET',
          headers,
          body: body && req.method !== 'GET' && req.method !== 'HEAD' ? body : undefined,
        });

        // Use existing handleRequest logic
        const response = await this.handleRequest(fetchRequest, isHttps);

        // Send response back via Node.js ServerResponse
        res.statusCode = response.status;
        res.statusMessage = response.statusText;

        // Copy response headers
        response.headers.forEach((value, key) => {
          res.setHeader(key, value);
        });

        // Send response body
        if (response.body) {
          const reader = response.body.getReader();
          const pump = async () => {
            const { done, value } = await reader.read();
            if (done) {
              res.end();
              return;
            }
            res.write(value);
            await pump();
          };
          await pump();
        } else {
          res.end();
        }
      } catch (error) {
        logger.error(`Node request handler error: ${getErrorMessage(error)}`);
        res.statusCode = 502;
        res.end('Bad Gateway');
      }
    });

    req.on('error', (error) => {
      logger.error(`Node request error: ${getErrorMessage(error)}`);
      res.statusCode = 502;
      res.end('Bad Gateway');
    });
  }

  /**
   * Stop all reverse proxy servers
   */
  async stop(): Promise<void> {
    const promises: Promise<void>[] = [];

    if (this.httpServer) {
      promises.push(this.httpServer.shutdown());
      this.httpServer = null;
      logger.info('HTTP reverse proxy stopped');
    }

    if (this.httpsServer) {
      // Node.js server uses close() which accepts a callback
      promises.push(new Promise<void>((resolve, reject) => {
        this.httpsServer!.close((err) => {
          if (err) reject(err);
          else resolve();
        });
      }));
      this.httpsServer = null;
      logger.info('HTTPS reverse proxy stopped');
    }

    await Promise.all(promises);
  }

  /**
   * Check if we have a certificate for a domain (exact or wildcard match)
   */
  private hasCertificateForDomain(host: string): boolean {
    if (this.tlsConfigs.has(host)) return true;
    // Check wildcard: *.example.com covers sub.example.com
    const parts = host.split('.');
    if (parts.length >= 2) {
      const rootDomain = parts.slice(-2).join('.');
      if (this.tlsConfigs.has(rootDomain)) return true;
    }
    return false;
  }

  /**
   * Handle incoming HTTP/HTTPS request
   */
  private async handleRequest(req: Request, isHttps: boolean): Promise<Response> {
    const url = new URL(req.url);
    const host = req.headers.get('host')?.split(':')[0] || '';

    logger.debug(`Proxy request: ${req.method} ${host}${url.pathname}`);

    // HTTP to HTTPS redirect when certificate exists
    if (!isHttps && this.httpsServer !== null && this.hasCertificateForDomain(host)) {
      const httpsUrl = `https://${host}${url.pathname}${url.search}`;
      logger.debug(`Redirecting HTTP to HTTPS: ${httpsUrl}`);
      return Response.redirect(httpsUrl, 301);
    }

    // Find matching route
    const route = this.routes.get(host);

    if (!route) {
      logger.debug(`No route found for host: ${host}`);
      return new Response('Service not found', {
        status: 404,
        headers: { 'Content-Type': 'text/plain' },
      });
    }

    // Check if this is a WebSocket upgrade request
    const upgrade = req.headers.get('upgrade')?.toLowerCase();
    if (upgrade === 'websocket') {
      return await this.handleWebSocketUpgrade(req, route, isHttps);
    }

    try {
      // Build target URL
      const targetUrl = `http://${route.targetHost}:${route.targetPort}${url.pathname}${url.search}`;

      logger.debug(`Proxying to: ${targetUrl}`);

      // Forward request to target
      const targetReq = new Request(targetUrl, {
        method: req.method,
        headers: this.forwardHeaders(req.headers, host, isHttps),
        body: req.body,
      });

      const response = await fetch(targetReq);

      // Forward response back to client
      return new Response(response.body, {
        status: response.status,
        statusText: response.statusText,
        headers: this.filterResponseHeaders(response.headers),
      });
    } catch (error) {
      logger.error(`Proxy error for ${host}: ${getErrorMessage(error)}`);
      return new Response('Bad Gateway', {
        status: 502,
        headers: { 'Content-Type': 'text/plain' },
      });
    }
  }

  /**
   * Handle WebSocket upgrade and proxy connection
   */
  private async handleWebSocketUpgrade(
    req: Request,
    route: IProxyRoute,
    isHttps: boolean
  ): Promise<Response> {
    try {
      const url = new URL(req.url);
      const targetUrl = `ws://${route.targetHost}:${route.targetPort}${url.pathname}${url.search}`;

      logger.info(`WebSocket upgrade: ${url.host} -> ${targetUrl}`);

      // Upgrade the client connection
      const { socket: clientSocket, response } = Deno.upgradeWebSocket(req);

      // Connect to backend WebSocket
      const backendSocket = new WebSocket(targetUrl);

      // Proxy messages from client to backend
      clientSocket.onmessage = (e) => {
        if (backendSocket.readyState === WebSocket.OPEN) {
          backendSocket.send(e.data);
        }
      };

      // Proxy messages from backend to client
      backendSocket.onmessage = (e) => {
        if (clientSocket.readyState === WebSocket.OPEN) {
          clientSocket.send(e.data);
        }
      };

      // Handle client close
      clientSocket.onclose = () => {
        logger.debug(`Client WebSocket closed for ${url.host}`);
        backendSocket.close();
      };

      // Handle backend close
      backendSocket.onclose = () => {
        logger.debug(`Backend WebSocket closed for ${targetUrl}`);
        clientSocket.close();
      };

      // Handle errors
      clientSocket.onerror = (e) => {
        logger.error(`Client WebSocket error: ${e}`);
        backendSocket.close();
      };

      backendSocket.onerror = (e) => {
        logger.error(`Backend WebSocket error: ${e}`);
        clientSocket.close();
      };

      return response;
    } catch (error) {
      logger.error(`WebSocket upgrade error: ${getErrorMessage(error)}`);
      return new Response('WebSocket Upgrade Failed', {
        status: 500,
        headers: { 'Content-Type': 'text/plain' },
      });
    }
  }

  /**
   * Forward request headers to target, filtering out problematic ones
   */
  private forwardHeaders(headers: Headers, originalHost: string, isHttps: boolean): Headers {
    const forwarded = new Headers();

    // Copy most headers
    for (const [key, value] of headers.entries()) {
      // Skip headers that should not be forwarded
      if (
        key.toLowerCase() === 'host' ||
        key.toLowerCase() === 'connection' ||
        key.toLowerCase() === 'keep-alive' ||
        key.toLowerCase() === 'proxy-authenticate' ||
        key.toLowerCase() === 'proxy-authorization' ||
        key.toLowerCase() === 'te' ||
        key.toLowerCase() === 'trailers' ||
        key.toLowerCase() === 'transfer-encoding' ||
        key.toLowerCase() === 'upgrade'
      ) {
        continue;
      }

      forwarded.set(key, value);
    }

    // Add X-Forwarded headers
    forwarded.set('X-Forwarded-For', headers.get('x-forwarded-for') || 'unknown');
    forwarded.set('X-Forwarded-Host', originalHost);
    forwarded.set('X-Forwarded-Proto', isHttps ? 'https' : 'http');

    return forwarded;
  }

  /**
   * Filter response headers
   */
  private filterResponseHeaders(headers: Headers): Headers {
    const filtered = new Headers();

    for (const [key, value] of headers.entries()) {
      // Skip problematic headers
      if (
        key.toLowerCase() === 'connection' ||
        key.toLowerCase() === 'keep-alive' ||
        key.toLowerCase() === 'transfer-encoding'
      ) {
        continue;
      }

      filtered.set(key, value);
    }

    return filtered;
  }

  /**
   * Add a route for a service
   */
  async addRoute(serviceId: number, domain: string, targetPort: number): Promise<void> {
    try {
      // Get container IP from Docker
      const service = this.database.getServiceByID(serviceId);
      if (!service || !service.containerID) {
        throw new Error(`Service not found or has no container: ${serviceId}`);
      }

      // Get container IP from Docker network, fallback to Docker DNS name
      let targetHost = 'localhost';
      try {
        const containerIP = await this.oneboxRef.docker.getContainerIP(service.containerID);
        if (containerIP) {
          targetHost = containerIP;
        } else {
          // Use Docker internal DNS name as fallback
          targetHost = `onebox-${service.name}`;
          logger.info(`Using Docker DNS name for ${service.name}: ${targetHost}`);
        }
      } catch (error) {
        logger.warn(`Could not resolve container IP for ${service.name}: ${getErrorMessage(error)}`);
        // Fall back to Docker internal DNS name
        targetHost = `onebox-${service.name}`;
      }

      const route: IProxyRoute = {
        domain,
        targetHost,
        targetPort,
        serviceId,
        containerID: service.containerID,
      };

      this.routes.set(domain, route);
      logger.success(`Added proxy route: ${domain} -> ${targetHost}:${targetPort}`);
    } catch (error) {
      logger.error(`Failed to add route for ${domain}: ${getErrorMessage(error)}`);
      throw error;
    }
  }

  /**
   * Remove a route
   */
  removeRoute(domain: string): void {
    if (this.routes.delete(domain)) {
      logger.success(`Removed proxy route: ${domain}`);
    } else {
      logger.warn(`Route not found: ${domain}`);
    }
  }

  /**
   * Get all routes
   */
  getRoutes(): IProxyRoute[] {
    return Array.from(this.routes.values());
  }

  /**
   * Reload routes from database
   */
  async reloadRoutes(): Promise<void> {
    try {
      logger.info('Reloading proxy routes...');

      this.routes.clear();

      const services = this.database.getAllServices();

      for (const service of services) {
        if (service.domain && service.status === 'running' && service.containerID) {
          await this.addRoute(service.id!, service.domain, service.port);
        }
      }

      logger.success(`Loaded ${this.routes.size} proxy routes`);
    } catch (error) {
      logger.error(`Failed to reload routes: ${getErrorMessage(error)}`);
      throw error;
    }
  }

  /**
   * Add TLS certificate for a domain (using PEM content)
   * Dynamically adds SNI context if HTTPS server is already running
   */
  addCertificate(domain: string, certPem: string, keyPem: string): void {
    if (!certPem || !keyPem) {
      logger.warn(`Cannot add certificate for ${domain}: missing PEM content`);
      return;
    }

    this.tlsConfigs.set(domain, {
      domain,
      certPem,
      keyPem,
    });

    logger.success(`Added TLS certificate for ${domain}`);

    // Dynamically add SNI context if HTTPS server is already running
    if (this.httpsServer) {
      this.httpsServer.addContext(domain, {
        cert: certPem,
        key: keyPem,
      });
      this.httpsServer.addContext(`*.${domain}`, {
        cert: certPem,
        key: keyPem,
      });
      logger.success(`Added SNI context for ${domain} and *.${domain}`);
    }
  }

  /**
   * Remove TLS certificate for a domain
   */
  removeCertificate(domain: string): void {
    if (this.tlsConfigs.delete(domain)) {
      logger.success(`Removed TLS certificate for ${domain}`);
    } else {
      logger.warn(`Certificate not found for domain: ${domain}`);
    }
  }

  /**
   * Reload TLS certificates from database
   */
  async reloadCertificates(): Promise<void> {
    try {
      logger.info('Reloading TLS certificates from database...');

      this.tlsConfigs.clear();

      const certificates = this.database.getAllSSLCertificates();

      for (const cert of certificates) {
        // Use fullchainPem for the cert (includes intermediates) and keyPem for the key
        if (cert.domain && cert.fullchainPem && cert.keyPem) {
          this.addCertificate(cert.domain, cert.fullchainPem, cert.keyPem);
        } else {
          logger.warn(`Skipping certificate for ${cert.domain}: missing PEM content`);
        }
      }

      logger.success(`Loaded ${this.tlsConfigs.size} TLS certificates`);

      // Restart HTTPS server if it was running (needed for full reload)
      if (this.httpsServer) {
        logger.info('Restarting HTTPS server with new certificates...');
        await new Promise<void>((resolve, reject) => {
          this.httpsServer!.close((err) => {
            if (err) reject(err);
            else resolve();
          });
        });
        this.httpsServer = null;
        await this.startHttps();
      }
    } catch (error) {
      logger.error(`Failed to reload certificates: ${getErrorMessage(error)}`);
      throw error;
    }
  }

  /**
   * Get status of reverse proxy
   */
  getStatus() {
    return {
      http: {
        running: this.httpServer !== null,
        port: this.httpPort,
      },
      https: {
        running: this.httpsServer !== null,
        port: this.httpsPort,
        certificates: this.tlsConfigs.size,
      },
      routes: this.routes.size,
    };
  }
}