// ===================================
// CORS PROXY SERVER
// ===================================
// This proxy server allows the stress testing tool to test
// production websites without CORS restrictions.

const http = require('http');
const https = require('https');
const url = require('url');
const cluster = require('cluster');
const numCPUs = require('os').cpus().length;

const fs = require('fs');
const path = require('path');

const PORT = process.env.PORT || 3000;

// Configuration
const CONFIG = {
    // Maximum request timeout (30 seconds)
    timeout: 30000,

    // Allowed origins (restrict to your stress testing tool's domain)
    // Use '*' for development, specific domain for production
    allowedOrigins: '*',

    // Maximum concurrent connections
    maxConnections: 10000, // Increased for cluster

    // User agents for rotation
    userAgents: [
        'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
        'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
        'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:121.0) Gecko/20100101 Firefox/121.0',
        'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.1 Safari/605.1.15',
        'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36'
    ]
};

// Global agents for connection pooling
const httpAgent = new http.Agent({ keepAlive: true, maxSockets: Infinity });
const httpsAgent = new https.Agent({ keepAlive: true, maxSockets: Infinity });

// Get random user agent
function getRandomUserAgent() {
    return CONFIG.userAgents[Math.floor(Math.random() * CONFIG.userAgents.length)];
}

const { exec } = require('child_process');

// Helper to get git info
const getGitInfo = () => {
    return new Promise((resolve) => {
        exec('git rev-parse --short HEAD && git log -1 --format=%cd --date=relative', (err, stdout) => {
            if (err) {
                resolve({ commit: 'Unknown', date: 'Unknown' });
                return;
            }
            const parts = stdout.trim().split('\n');
            resolve({
                commit: parts[0] || 'Unknown',
                date: parts[1] || 'Unknown'
            });
        });
    });
};

if (cluster.isMaster) {
    console.log(`Master ${process.pid} is running`);
    console.log(`Spawning ${numCPUs} workers...`);

    for (let i = 0; i < numCPUs; i++) {
        cluster.fork();
    }

    cluster.on('exit', (worker, code, signal) => {
        console.log(`Worker ${worker.process.pid} died. Respawning...`);
        cluster.fork();
    });

    // Master process only listens for SIGINT to gracefully shut down workers
    process.on('SIGINT', () => {
        console.log('\n\n🛑 Shutting down proxy server (master)...');
        for (const id in cluster.workers) {
            cluster.workers[id].kill();
        }
        process.exit(0);
    });

} else {
    // Create the proxy server
    const server = http.createServer((req, res) => {
        // Handle CORS preflight requests
        if (req.method === 'OPTIONS') {
            handleCORS(res);
            res.writeHead(200);
            res.end();
            return;
        }

        // Health check
        if (req.url === '/health' || req.url === '//health') {
            handleCORS(res);
            res.writeHead(200, { 'Content-Type': 'application/json' });
            res.end(JSON.stringify({ status: 'ok', worker: process.pid }));
            return;
        }

        // Handle Git Info request
        // Nginx proxy_pass might result in double slashes (//git-info)
        if ((req.url === '/git-info' || req.url === '//git-info') && req.method === 'GET') {
            handleCORS(res);
            getGitInfo().then(info => {
                res.writeHead(200, { 'Content-Type': 'application/json' });
                res.end(JSON.stringify(info));
            });
            return;
        }

        // Serve static files for the UI
        if (req.method === 'GET') {
            let requestPath = req.url.split('?')[0];
            let filePath = '.' + requestPath;
            if (requestPath === '/') filePath = './index.html';

            // Basic security: don't allow accessing files outside the directory or sensitive files
            const resolvedPath = path.resolve(filePath);
            const rootPath = path.resolve('.');

            if (!resolvedPath.startsWith(rootPath) || filePath.includes('..')) {
                res.writeHead(403);
                res.end('Forbidden');
                return;
            }

            fs.access(filePath, fs.constants.F_OK, (err) => {
                if (!err) {
                    const extname = path.extname(filePath).toLowerCase();
                    let contentType = 'text/html';
                    const mimeTypes = {
                        '.html': 'text/html',
                        '.js': 'text/javascript',
                        '.css': 'text/css',
                        '.png': 'image/png',
                        '.jpg': 'image/jpeg',
                        '.svg': 'image/svg+xml',
                        '.json': 'application/json'
                    };
                    contentType = mimeTypes[extname] || 'text/plain';

                    fs.readFile(filePath, (error, content) => {
                        if (!error) {
                            res.writeHead(200, { 'Content-Type': contentType });
                            res.end(content, 'utf-8');
                        } else {
                            res.writeHead(500);
                            res.end('Server Error');
                        }
                    });
                } else if (req.url === '/health' || req.url === '//health' || (req.url === '/git-info' || req.url === '//git-info')) {
                    // Handled by other logic (keep going)
                } else if (req.url === '/') {
                    // Fallback for root if index.html doesn't exist? (Unlikely)
                } else {
                    // Not a static file, maybe fall through to POST check
                }
            });

            // Special handling for health and git-info which are GET but not files
            if (req.url.includes('/health') || req.url.includes('/git-info')) {
                // Let it fall through to those handlers
            } else {
                return;
            }
        }

        // Only allow POST requests to the proxy
        if (req.method !== 'POST') {
            res.writeHead(405, { 'Content-Type': 'application/json' });
            res.end(JSON.stringify({ error: 'Method not allowed. Use POST.' }));
            return;
        }

        // Parse request body
        let body = '';
        req.on('data', chunk => {
            body += chunk.toString();
        });

        req.on('end', () => {
            try {
                const proxyRequest = JSON.parse(body);
                handleProxyRequest(proxyRequest, res);
            } catch (error) {
                res.writeHead(400, { 'Content-Type': 'application/json' });
                res.end(JSON.stringify({
                    error: 'Invalid JSON',
                    message: error.message
                }));
            }
        });
    });

    // Handle the actual proxy request
    function handleProxyRequest(proxyRequest, clientRes) {
        const { targetUrl, method = 'GET', headers = {}, body = null } = proxyRequest;

        // Validate target URL
        if (!targetUrl) {
            clientRes.writeHead(400, { 'Content-Type': 'application/json' });
            clientRes.end(JSON.stringify({ error: 'targetUrl is required' }));
            return;
        }

        let parsedUrl;
        try {
            parsedUrl = new URL(targetUrl);
        } catch (error) {
            clientRes.writeHead(400, { 'Content-Type': 'application/json' });
            clientRes.end(JSON.stringify({ error: 'Invalid URL' }));
            return;
        }

        // Determine if we need http or https and which agent to use
        const isHttps = parsedUrl.protocol === 'https:';
        const protocol = isHttps ? https : http;
        const agent = isHttps ? httpsAgent : httpAgent;

        // Prepare request options with random user agent
        const options = {
            hostname: parsedUrl.hostname,
            port: parsedUrl.port,
            path: parsedUrl.pathname + parsedUrl.search,
            method: method,
            agent: agent, // Use the global agent for connection pooling
            headers: {
                ...headers,
                'User-Agent': getRandomUserAgent(),
                'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
                'Accept-Language': 'en-US,en;q=0.5',
                'Accept-Encoding': 'gzip, deflate, br',
                'DNT': '1',
                'Connection': 'keep-alive',
                'Upgrade-Insecure-Requests': '1'
            },
            timeout: CONFIG.timeout
        };

        const startTime = Date.now();

        // Make the request to the target server
        const proxyReq = protocol.request(options, (proxyRes) => {
            const responseTime = Date.now() - startTime;

            // Collect response data
            let responseData = '';
            let responseSize = 0;
            const maxBodySize = 500000; // 500KB limit for crawler

            proxyRes.on('data', chunk => {
                responseSize += chunk.length;
                // Only collect body if under size limit (for crawler)
                if (responseSize < maxBodySize) {
                    responseData += chunk.toString();
                }
            });

            proxyRes.on('end', () => {
                // Send response back to client with CORS headers
                handleCORS(clientRes);
                clientRes.writeHead(200, { 'Content-Type': 'application/json' });

                clientRes.end(JSON.stringify({
                    success: true,
                    statusCode: proxyRes.statusCode,
                    statusMessage: proxyRes.statusMessage,
                    responseTime: responseTime,
                    headers: proxyRes.headers,
                    body: responseData, // Full body for crawler link extraction
                    bodySize: responseSize,
                    proxyWorker: process.pid // Add worker ID for debugging
                }));
            });
        });

        // Handle request errors
        proxyReq.on('error', (error) => {
            const responseTime = Date.now() - startTime;

            handleCORS(clientRes);
            clientRes.writeHead(200, { 'Content-Type': 'application/json' });

            clientRes.end(JSON.stringify({
                success: false,
                error: error.message,
                responseTime: responseTime,
                statusCode: 0
            }));
        });

        // Handle timeout
        proxyReq.on('timeout', () => {
            proxyReq.destroy();
            const responseTime = Date.now() - startTime;

            handleCORS(clientRes);
            clientRes.writeHead(200, { 'Content-Type': 'application/json' });

            clientRes.end(JSON.stringify({
                success: false,
                error: 'Request timeout',
                responseTime: responseTime,
                statusCode: 0
            }));
        });

        // Send request body if present
        if (body && method !== 'GET' && method !== 'HEAD') {
            proxyReq.write(typeof body === 'string' ? body : JSON.stringify(body));
        }

        proxyReq.end();
    }

    // Add CORS headers to response
    function handleCORS(res) {
        res.setHeader('Access-Control-Allow-Origin', CONFIG.allowedOrigins);
        res.setHeader('Access-Control-Allow-Methods', 'POST, GET, OPTIONS');
        res.setHeader('Access-Control-Allow-Headers', 'Content-Type');
    }

    // Start the server
    server.listen(PORT, () => {
        console.log(`Worker ${process.pid} running on http://localhost:${PORT}`);
    });

    // Handle server errors
    server.on('error', (error) => {
        console.error(`❌ Worker ${process.pid} server error:`, error.message);
        process.exit(1);
    });

    // Graceful shutdown for workers
    process.on('SIGINT', () => {
        console.log(`\n\n🛑 Worker ${process.pid} shutting down...`);
        server.close(() => {
            console.log(`✅ Worker ${process.pid} closed`);
            process.exit(0);
        });
    });
}