const dns = require('dns').promises;
const { spawn } = require('child_process');
const net = require('net');
const os = require('os');
const { logError, logDebug } = require('../../../infrastructure/logger');
const { trackRequest, trackRequestWithTiming } = require('../../../maintenance/metrics');
const { createErrorResponse } = require('../../../infrastructure/error_handler');
const { validateIP, validateDomain, sanitizeInput, validatePort } = require('../../../infrastructure/validation');
const state = require('../../../infrastructure/state');

const MIN_DIAGNOSTIC_COUNT = 1;
const MAX_DIAGNOSTIC_COUNT = 10;
const PING_TIMEOUT_MS = 30000;
const TRACEROUTE_TIMEOUT_MS = 60000;
const MAX_DIAGNOSTIC_TARGET_LENGTH = 253;

function isValidHostname(target) {
  if (!target || typeof target !== 'string') return false;
  // Accept simple hostnames/FQDNs used in local network diagnostics.
  return /^(?=.{1,253}$)(?!-)[A-Za-z0-9-]+(\.[A-Za-z0-9-]+)*\.?$/.test(target);
}

function validateDiagnosticTarget(target) {
  const sanitized = sanitizeInput(target);
  if (!sanitized || sanitized.length > MAX_DIAGNOSTIC_TARGET_LENGTH) {
    return null;
  }
  if (validateIP(sanitized) || validateDomain(sanitized) || isValidHostname(sanitized)) {
    return sanitized;
  }
  return null;
}

function normalizeCount(count) {
  const parsed = Number.parseInt(count, 10);
  if (Number.isNaN(parsed)) return 4;
  return Math.min(MAX_DIAGNOSTIC_COUNT, Math.max(MIN_DIAGNOSTIC_COUNT, parsed));
}

function runCommand(command, args, timeoutMs) {
  return new Promise((resolve, reject) => {
    const child = spawn(command, args, { timeout: timeoutMs });
    let stdout = '';
    let stderr = '';

    child.stdout.on('data', (data) => {
      stdout += data.toString();
    });

    child.stderr.on('data', (data) => {
      stderr += data.toString();
    });

    child.on('error', reject);
    child.on('close', (code, signal) => {
      resolve({ code, signal, stdout, stderr });
    });
  });
}

async function handleDiagnosticsRoutes(req, res) {
  const urlPath = req.urlPath || new URL(req.url, `https://${req.headers.host}`).pathname;
  const method = req.method;

  // POST /api/diagnostics/dns-lookup
  if (method === 'POST' && urlPath === '/api/diagnostics/dns-lookup') {
    try {
      let body = '';
      for await (const chunk of req) {
        body += chunk.toString();
      }
      const data = JSON.parse(body);
      const { domain, type = 'A' } = data;
      
      if (!domain) {
        res.writeHead(400, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'domain is required' }));
        trackRequest(urlPath, false);
        return true;
      }
      
      const startTime = Date.now();
      let results = [];
      
      try {
        switch (type.toUpperCase()) {
          case 'A':
            results = await dns.resolve4(domain);
            break;
          case 'AAAA':
            results = await dns.resolve6(domain);
            break;
          case 'MX':
            results = await dns.resolveMx(domain);
            break;
          case 'TXT':
            results = await dns.resolveTxt(domain);
            break;
          case 'NS':
            results = await dns.resolveNs(domain);
            break;
          case 'CNAME':
            results = await dns.resolveCname(domain);
            break;
          case 'SRV':
            results = await dns.resolveSrv(domain);
            break;
          case 'PTR':
            results = await dns.resolvePtr(domain);
            break;
          case 'SOA':
            results = await dns.resolveSoa(domain);
            break;
          default:
            throw new Error(`Unsupported DNS record type: ${type}`);
        }
        
        const responseTime = Date.now() - startTime;
        trackRequestWithTiming(urlPath, true, responseTime);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({
          success: true,
          domain,
          type,
          results: Array.isArray(results) ? results : [results],
          responseTime
        }));
      } catch (dnsErr) {
        const responseTime = Date.now() - startTime;
        trackRequest(urlPath, false);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({
          success: false,
          domain,
          type,
          error: dnsErr.message,
          results: [],
          responseTime
        }));
      }
    } catch (err) {
      logError('Admin', `DNS lookup failed: ${err.message}`);
      trackRequest(urlPath, false);
      const errorResponse = createErrorResponse(err, 500);
      res.writeHead(errorResponse.statusCode, errorResponse.headers);
      res.end(errorResponse.body);
    }
    return true;
  }

  // POST /api/diagnostics/ping
  if (method === 'POST' && urlPath === '/api/diagnostics/ping') {
    try {
      let body = '';
      for await (const chunk of req) {
        body += chunk.toString();
      }
      const data = JSON.parse(body);
      const { target, count = 4, stream = false } = data;
      
      const safeTarget = validateDiagnosticTarget(target);
      if (!safeTarget) {
        res.writeHead(400, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'A valid diagnostic target is required' }));
        trackRequest(urlPath, false);
        return true;
      }
      const safeCount = normalizeCount(count);
      
      // Streaming mode
      if (stream) {
        const startTime = Date.now();
        const platform = os.platform();
        const pingArgs = platform === 'win32'
          ? ['-n', safeCount.toString(), safeTarget]
          : ['-c', safeCount.toString(), safeTarget];
        const pingProcess = spawn('ping', pingArgs);
        
        // Set up streaming response
        res.writeHead(200, {
          'Content-Type': 'application/x-ndjson',
          'Transfer-Encoding': 'chunked',
          'Cache-Control': 'no-cache',
          'Connection': 'keep-alive'
        });
        
        let output = '';
        let errorOutput = '';
        
        pingProcess.stdout.on('data', (data) => {
          const text = data.toString();
          output += text;
          // Send each line as it arrives
          const lines = text.split('\n').filter(line => line.trim());
          for (const line of lines) {
            res.write(JSON.stringify({
              type: 'output',
              data: line,
              timestamp: Date.now()
            }) + '\n');
          }
        });
        
        pingProcess.stderr.on('data', (data) => {
          const text = data.toString();
          errorOutput += text;
          res.write(JSON.stringify({
            type: 'error',
            data: text,
            timestamp: Date.now()
          }) + '\n');
        });
        
        pingProcess.on('close', (code) => {
          const responseTime = Date.now() - startTime;
          const success = code === 0;
          trackRequestWithTiming(urlPath, success, responseTime);
          
          res.write(JSON.stringify({
            type: 'complete',
            success,
            exitCode: code,
            output,
            error: errorOutput || null,
            responseTime
          }) + '\n');
          res.end();
        });
        
        pingProcess.on('error', (err) => {
          res.write(JSON.stringify({
            type: 'error',
            error: err.message,
            timestamp: Date.now()
          }) + '\n');
          res.end();
          trackRequest(urlPath, false);
        });
        
        return true;
      }
      
      // Non-streaming mode (backward compatibility)
      const startTime = Date.now();
      const platform = os.platform();
      const pingArgs = platform === 'win32'
        ? ['-n', safeCount.toString(), safeTarget]
        : ['-c', safeCount.toString(), safeTarget];
      
      try {
        const { stdout, stderr, code } = await runCommand('ping', pingArgs, PING_TIMEOUT_MS);
        const responseTime = Date.now() - startTime;
        const success = code === 0;
        trackRequestWithTiming(urlPath, success, responseTime);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({
          success,
          target: safeTarget,
          count: safeCount,
          output: stdout,
          error: stderr || null,
          responseTime
        }));
      } catch (execErr) {
        const responseTime = Date.now() - startTime;
        trackRequest(urlPath, false);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({
          success: false,
          target: safeTarget,
          count: safeCount,
          output: '',
          error: execErr.message,
          responseTime
        }));
      }
    } catch (err) {
      logError('Admin', `Ping failed: ${err.message}`);
      trackRequest(urlPath, false);
      const errorResponse = createErrorResponse(err, 500);
      res.writeHead(errorResponse.statusCode, errorResponse.headers);
      res.end(errorResponse.body);
    }
    return true;
  }

  // POST /api/diagnostics/traceroute
  if (method === 'POST' && urlPath === '/api/diagnostics/traceroute') {
    try {
      let body = '';
      for await (const chunk of req) {
        body += chunk.toString();
      }
      const data = JSON.parse(body);
      const { target, stream = false } = data;
      
      const safeTarget = validateDiagnosticTarget(target);
      if (!safeTarget) {
        res.writeHead(400, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'A valid diagnostic target is required' }));
        trackRequest(urlPath, false);
        return true;
      }
      
      // Streaming mode
      if (stream) {
        const startTime = Date.now();
        const platform = os.platform();
        const tracerouteCmd = platform === 'win32' ? 'tracert' : 'traceroute';
        const tracerouteArgs = [safeTarget];
        const tracerouteProcess = spawn(tracerouteCmd, tracerouteArgs);
        
        // Set up streaming response
        res.writeHead(200, {
          'Content-Type': 'application/x-ndjson',
          'Transfer-Encoding': 'chunked',
          'Cache-Control': 'no-cache',
          'Connection': 'keep-alive'
        });
        
        let output = '';
        let errorOutput = '';
        
        tracerouteProcess.stdout.on('data', (data) => {
          const text = data.toString();
          output += text;
          // Send each line as it arrives
          const lines = text.split('\n').filter(line => line.trim());
          for (const line of lines) {
            res.write(JSON.stringify({
              type: 'output',
              data: line,
              timestamp: Date.now()
            }) + '\n');
          }
        });
        
        tracerouteProcess.stderr.on('data', (data) => {
          const text = data.toString();
          errorOutput += text;
          res.write(JSON.stringify({
            type: 'error',
            data: text,
            timestamp: Date.now()
          }) + '\n');
        });
        
        tracerouteProcess.on('close', (code) => {
          const responseTime = Date.now() - startTime;
          const success = code === 0;
          trackRequestWithTiming(urlPath, success, responseTime);
          
          res.write(JSON.stringify({
            type: 'complete',
            success,
            exitCode: code,
            output,
            error: errorOutput || null,
            responseTime
          }) + '\n');
          res.end();
        });
        
        tracerouteProcess.on('error', (err) => {
          res.write(JSON.stringify({
            type: 'error',
            error: err.message,
            timestamp: Date.now()
          }) + '\n');
          res.end();
          trackRequest(urlPath, false);
        });
        
        return true;
      }
      
      // Non-streaming mode (backward compatibility)
      const startTime = Date.now();
      const platform = os.platform();
      const tracerouteCmd = platform === 'win32' ? 'tracert' : 'traceroute';
      const tracerouteArgs = [safeTarget];
      
      try {
        const { stdout, stderr, code } = await runCommand(tracerouteCmd, tracerouteArgs, TRACEROUTE_TIMEOUT_MS);
        const responseTime = Date.now() - startTime;
        const success = code === 0;
        trackRequestWithTiming(urlPath, success, responseTime);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({
          success,
          target: safeTarget,
          output: stdout,
          error: stderr || null,
          responseTime
        }));
      } catch (execErr) {
        const responseTime = Date.now() - startTime;
        trackRequest(urlPath, false);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({
          success: false,
          target: safeTarget,
          output: '',
          error: execErr.message,
          responseTime
        }));
      }
    } catch (err) {
      logError('Admin', `Traceroute failed: ${err.message}`);
      trackRequest(urlPath, false);
      const errorResponse = createErrorResponse(err, 500);
      res.writeHead(errorResponse.statusCode, errorResponse.headers);
      res.end(errorResponse.body);
    }
    return true;
  }

  // POST /api/diagnostics/connection-test
  if (method === 'POST' && urlPath === '/api/diagnostics/connection-test') {
    try {
      let body = '';
      for await (const chunk of req) {
        body += chunk.toString();
      }
      const data = JSON.parse(body);
      const { domain, port } = data;
      
      if (!domain || !port) {
        res.writeHead(400, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'domain and port are required' }));
        trackRequest(urlPath, false);
        return true;
      }
      
      const startTime = Date.now();
      const safeDomain = validateDiagnosticTarget(domain);
      const safePort = Number.parseInt(port, 10);
      if (!safeDomain || !validatePort(safePort)) {
        res.writeHead(400, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'Valid domain and port are required' }));
        trackRequest(urlPath, false);
        return true;
      }
      
      // First resolve domain to IP
      let ip;
      try {
        const addresses = await dns.resolve4(safeDomain);
        ip = addresses[0];
      } catch (dnsErr) {
        trackRequest(urlPath, false);
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({
          success: false,
          domain: safeDomain,
          port: safePort,
          error: `DNS resolution failed: ${dnsErr.message}`,
          responseTime: Date.now() - startTime
        }));
        return true;
      }
      
      // Test TCP connection
      const testConnection = () => {
        return new Promise((resolve) => {
          const socket = new net.Socket();
          const timeout = 5000;
          let connected = false;
          
          socket.setTimeout(timeout);
          
          socket.on('connect', () => {
            connected = true;
            socket.destroy();
            resolve({ success: true, latency: Date.now() - startTime });
          });
          
          socket.on('timeout', () => {
            socket.destroy();
            resolve({ success: false, error: 'Connection timeout' });
          });
          
          socket.on('error', (err) => {
            resolve({ success: false, error: err.message });
          });
          
          socket.connect(safePort, ip);
        });
      };
      
      const result = await testConnection();
      const responseTime = Date.now() - startTime;
      
      trackRequestWithTiming(urlPath, result.success, responseTime);
      res.writeHead(200, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({
        ...result,
        domain: safeDomain,
        ip,
        port: safePort,
        responseTime
      }));
    } catch (err) {
      logError('Admin', `Connection test failed: ${err.message}`);
      trackRequest(urlPath, false);
      const errorResponse = createErrorResponse(err, 500);
      res.writeHead(errorResponse.statusCode, errorResponse.headers);
      res.end(errorResponse.body);
    }
    return true;
  }

  // GET /api/diagnostics/bandwidth
  if (method === 'GET' && urlPath === '/api/diagnostics/bandwidth') {
    try {
      const startTime = Date.now();
      const networkInterfaces = os.networkInterfaces();
      const stats = {};
      
      for (const [name, addresses] of Object.entries(networkInterfaces)) {
        if (!addresses) continue;
        let totalBytes = 0;
        let totalPackets = 0;
        
        for (const addr of addresses) {
          if (addr.family === 'IPv4' || addr.family === 'IPv6') {
            // Note: Node.js doesn't provide real-time bandwidth stats
            // This is a placeholder structure
            stats[name] = {
              name,
              addresses: addresses.map(a => ({
                address: a.address,
                netmask: a.netmask,
                family: a.family,
                mac: a.mac || 'N/A',
                internal: a.internal
              })),
              // These would need system-specific tools to get real values
              bytesReceived: 0,
              bytesSent: 0,
              packetsReceived: 0,
              packetsSent: 0
            };
          }
        }
      }
      
      const responseTime = Date.now() - startTime;
      trackRequestWithTiming(urlPath, true, responseTime);
      res.writeHead(200, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({
        interfaces: stats,
        note: 'Bandwidth statistics require system-specific tools. Interface information only.',
        responseTime
      }));
    } catch (err) {
      logError('Admin', `Bandwidth stats failed: ${err.message}`);
      trackRequest(urlPath, false);
      const errorResponse = createErrorResponse(err, 500);
      res.writeHead(errorResponse.statusCode, errorResponse.headers);
      res.end(errorResponse.body);
    }
    return true;
  }

  // GET /api/diagnostics/invites
  if (method === 'GET' && urlPath === '/api/diagnostics/invites') {
    try {
      if (!state.diagnoseInviteIssues) {
        res.writeHead(503, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'Invite diagnostics not available - system still initializing' }));
        trackRequest(urlPath, false);
        return true;
      }

      const diagnostics = state.diagnoseInviteIssues();
      res.writeHead(200, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify(diagnostics));
      trackRequest(urlPath, true);
      return true;
    } catch (err) {
      logError('DiagnosticsRoute', `Invite diagnostics error: ${err.message}`);
      res.writeHead(500, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({ error: err.message }));
      trackRequest(urlPath, false);
      return true;
    }
  }

  return false;
}

module.exports = { handleDiagnosticsRoutes };