import crypto from 'crypto';

/**
 * Genera un fingerprint del dispositivo basado en headers HTTP
 * @param {Object} req - Request object de Express
 * @returns {Object} Objeto con fingerprint hash y metadata del dispositivo
 */
export function generateDeviceFingerprint(req) {
  // Extraer información del dispositivo desde headers
  const userAgent = req.headers['user-agent'] || '';
  const acceptLanguage = req.headers['accept-language'] || '';
  const acceptEncoding = req.headers['accept-encoding'] || '';
  const accept = req.headers['accept'] || '';
  const connection = req.headers['connection'] || '';
  const upgradeInsecureRequests = req.headers['upgrade-insecure-requests'] || '';
  
  // IP del cliente (considerando proxies)
  const ip = req.ip || 
             req.headers['x-forwarded-for']?.split(',')[0]?.trim() || 
             req.headers['x-real-ip'] || 
             req.connection?.remoteAddress || 
             'unknown';
  
  // Crear string combinado para el hash
  const fingerprintString = [
    userAgent,
    acceptLanguage,
    acceptEncoding,
    accept,
    connection,
    upgradeInsecureRequests,
    ip
  ].join('|');
  
  // Generar hash SHA-256
  const fingerprintHash = crypto
    .createHash('sha256')
    .update(fingerprintString)
    .digest('hex');
  
  // Extraer información legible del User-Agent
  const deviceInfo = parseUserAgent(userAgent);
  
  return {
    fingerprint: fingerprintHash,
    deviceInfo: {
      ...deviceInfo,
      ip: ip,
      userAgent: userAgent.substring(0, 200), // Limitar longitud
    }
  };
}

/**
 * Parsea el User-Agent para extraer información legible
 * @param {string} userAgent - User-Agent string
 * @returns {Object} Información del dispositivo
 */
function parseUserAgent(userAgent) {
  if (!userAgent) {
    return {
      browser: 'Unknown',
      browserVersion: '',
      os: 'Unknown',
      osVersion: '',
      device: 'Unknown',
    };
  }
  
  const ua = userAgent.toLowerCase();
  
  // Detectar navegador
  let browser = 'Unknown';
  let browserVersion = '';
  
  if (ua.includes('chrome') && !ua.includes('edg') && !ua.includes('opr')) {
    browser = 'Chrome';
    const match = ua.match(/chrome\/([\d.]+)/);
    browserVersion = match ? match[1] : '';
  } else if (ua.includes('firefox')) {
    browser = 'Firefox';
    const match = ua.match(/firefox\/([\d.]+)/);
    browserVersion = match ? match[1] : '';
  } else if (ua.includes('safari') && !ua.includes('chrome')) {
    browser = 'Safari';
    const match = ua.match(/version\/([\d.]+)/);
    browserVersion = match ? match[1] : '';
  } else if (ua.includes('edg')) {
    browser = 'Edge';
    const match = ua.match(/edg\/([\d.]+)/);
    browserVersion = match ? match[1] : '';
  } else if (ua.includes('opr')) {
    browser = 'Opera';
    const match = ua.match(/opr\/([\d.]+)/);
    browserVersion = match ? match[1] : '';
  }
  
  // Detectar sistema operativo
  let os = 'Unknown';
  let osVersion = '';
  
  if (ua.includes('windows')) {
    os = 'Windows';
    if (ua.includes('windows nt 10')) osVersion = '10/11';
    else if (ua.includes('windows nt 6.3')) osVersion = '8.1';
    else if (ua.includes('windows nt 6.2')) osVersion = '8';
    else if (ua.includes('windows nt 6.1')) osVersion = '7';
  } else if (ua.includes('mac os x') || ua.includes('macintosh')) {
    os = 'macOS';
    const match = ua.match(/mac os x ([\d_]+)/);
    osVersion = match ? match[1].replace(/_/g, '.') : '';
  } else if (ua.includes('linux')) {
    os = 'Linux';
  } else if (ua.includes('android')) {
    os = 'Android';
    const match = ua.match(/android ([\d.]+)/);
    osVersion = match ? match[1] : '';
  } else if (ua.includes('ios') || ua.includes('iphone') || ua.includes('ipad')) {
    os = 'iOS';
    const match = ua.match(/os ([\d_]+)/);
    osVersion = match ? match[1].replace(/_/g, '.') : '';
  }
  
  // Detectar tipo de dispositivo
  let device = 'Desktop';
  if (ua.includes('mobile') || ua.includes('android') || ua.includes('iphone')) {
    device = 'Mobile';
  } else if (ua.includes('tablet') || ua.includes('ipad')) {
    device = 'Tablet';
  }
  
  return {
    browser,
    browserVersion,
    os,
    osVersion,
    device,
  };
}

/**
 * Genera un fingerprint desde el dashboard (cuando se envía desde el cliente)
 * @param {string} fingerprintHash - Hash del fingerprint generado en el cliente
 * @param {Object} deviceInfo - Información del dispositivo del cliente
 * @param {Object} req - Request object de Express
 * @returns {Object} Objeto con fingerprint y metadata combinada
 */
export function combineFingerprint(fingerprintHash, deviceInfo, req) {
  const serverFingerprint = generateDeviceFingerprint(req);
  
  // Si el cliente envió un fingerprint, combinarlo con el del servidor
  // Esto permite usar librerías avanzadas del cliente pero validar con servidor
  const combinedFingerprint = fingerprintHash 
    ? crypto.createHash('sha256').update(fingerprintHash + serverFingerprint.fingerprint).digest('hex')
    : serverFingerprint.fingerprint;
  
  return {
    fingerprint: combinedFingerprint,
    deviceInfo: {
      ...serverFingerprint.deviceInfo,
      ...deviceInfo, // El del cliente tiene prioridad si existe
    }
  };
}