import * as plugins from '../../plugins.js';
import { ForwardingHandler } from './base-handler.js';
import type { IForwardConfig } from '../config/forwarding-types.js';
import { ForwardingHandlerEvents } from '../config/forwarding-types.js';

/**
 * Handler for HTTP-only forwarding
 */
export class HttpForwardingHandler extends ForwardingHandler {
  /**
   * Create a new HTTP forwarding handler
   * @param config The forwarding configuration
   */
  constructor(config: IForwardConfig) {
    super(config);

    // Validate that this is an HTTP-only configuration
    if (config.type !== 'http-only') {
      throw new Error(`Invalid configuration type for HttpForwardingHandler: ${config.type}`);
    }
  }

  /**
   * Initialize the handler
   * HTTP handler doesn't need special initialization
   */
  public async initialize(): Promise<void> {
    // Basic initialization from parent class
    await super.initialize();
  }
  
  /**
   * Handle a raw socket connection
   * HTTP handler doesn't do much with raw sockets as it mainly processes
   * parsed HTTP requests
   */
  public handleConnection(socket: plugins.net.Socket): void {
    // For HTTP, we mainly handle parsed requests, but we can still set up
    // some basic connection tracking
    const remoteAddress = socket.remoteAddress || 'unknown';
    
    socket.on('close', (hadError) => {
      this.emit(ForwardingHandlerEvents.DISCONNECTED, {
        remoteAddress,
        hadError
      });
    });
    
    socket.on('error', (error) => {
      this.emit(ForwardingHandlerEvents.ERROR, {
        remoteAddress,
        error: error.message
      });
    });
    
    this.emit(ForwardingHandlerEvents.CONNECTED, {
      remoteAddress
    });
  }
  
  /**
   * Handle an HTTP request
   * @param req The HTTP request
   * @param res The HTTP response
   */
  public handleHttpRequest(req: plugins.http.IncomingMessage, res: plugins.http.ServerResponse): void {
    // Get the target from configuration
    const target = this.getTargetFromConfig();
    
    // Create a custom headers object with variables for substitution
    const variables = {
      clientIp: req.socket.remoteAddress || 'unknown'
    };
    
    // Prepare headers, merging with any custom headers from config
    const headers = this.applyCustomHeaders(req.headers, variables);
    
    // Create the proxy request options
    const options = {
      hostname: target.host,
      port: target.port,
      path: req.url,
      method: req.method,
      headers
    };
    
    // Create the proxy request
    const proxyReq = plugins.http.request(options, (proxyRes) => {
      // Copy status code and headers from the proxied response
      res.writeHead(proxyRes.statusCode || 500, proxyRes.headers);
      
      // Pipe the proxy response to the client response
      proxyRes.pipe(res);
      
      // Track bytes for logging
      let responseSize = 0;
      proxyRes.on('data', (chunk) => {
        responseSize += chunk.length;
      });
      
      proxyRes.on('end', () => {
        this.emit(ForwardingHandlerEvents.HTTP_RESPONSE, {
          statusCode: proxyRes.statusCode,
          headers: proxyRes.headers,
          size: responseSize
        });
      });
    });
    
    // Handle errors in the proxy request
    proxyReq.on('error', (error) => {
      this.emit(ForwardingHandlerEvents.ERROR, {
        remoteAddress: req.socket.remoteAddress,
        error: `Proxy request error: ${error.message}`
      });
      
      // Send an error response if headers haven't been sent yet
      if (!res.headersSent) {
        res.writeHead(502, { 'Content-Type': 'text/plain' });
        res.end(`Error forwarding request: ${error.message}`);
      } else {
        // Just end the response if headers have already been sent
        res.end();
      }
    });
    
    // Track request details for logging
    let requestSize = 0;
    req.on('data', (chunk) => {
      requestSize += chunk.length;
    });
    
    // Log the request
    this.emit(ForwardingHandlerEvents.HTTP_REQUEST, {
      method: req.method,
      url: req.url,
      headers: req.headers,
      remoteAddress: req.socket.remoteAddress,
      target: `${target.host}:${target.port}`
    });
    
    // Pipe the client request to the proxy request
    if (req.readable) {
      req.pipe(proxyReq);
    } else {
      proxyReq.end();
    }
  }
}