// Security middleware for input validation and CSRF protection

/**
 * Input validation middleware
 * Validates common input patterns and sanitizes data
 */
function validateInput(req, res, next) {
  // Sanitize query parameters
  for (const key in req.query) {
    if (typeof req.query[key] === 'string') {
      // Remove control characters
      req.query[key] = req.query[key].replace(/[\x00-\x1F\x7F]/g, '');
      
      // Limit length
      if (req.query[key].length > 1000) {
        req.query[key] = req.query[key].substring(0, 1000);
      }
    }
  }

  // Sanitize body data for non-JSON requests
  if (req.body && typeof req.body === 'object' && !Array.isArray(req.body)) {
    for (const key in req.body) {
      if (typeof req.body[key] === 'string') {
        // Remove control characters but preserve newlines for textareas
        if (key.includes('description') || key.includes('content') || key.includes('motd')) {
          req.body[key] = req.body[key].replace(/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/g, '');
        } else {
          req.body[key] = req.body[key].replace(/[\x00-\x1F\x7F]/g, '');
        }
        
        // Limit length based on field type
        const maxLength = getMaxLengthForField(key);
        if (req.body[key].length > maxLength) {
          req.body[key] = req.body[key].substring(0, maxLength);
        }
      }
    }
  }

  next();
}

/**
 * Get maximum allowed length for different field types
 */
function getMaxLengthForField(fieldName) {
  const fieldLimits = {
    // User authentication fields
    'username': 50,
    'password': 200,
    'confirmPassword': 200,
    'currentPassword': 200,
    'newPassword': 200,
    
    // Server/world names
    'name': 100,
    'worldName': 100,
    'serverName': 200,
    
    // Text content
    'description': 2000,
    'motd': 500,
    'content': 5000,
    
    // Commands and paths
    'command': 500,
    'path': 500,
    
    // Network settings
    'bind': 100,
    'serverlist_url': 500,
    
    // Default
    'default': 200
  };

  return fieldLimits[fieldName] || fieldLimits['default'];
}

/**
 * XSS protection middleware
 * Escapes HTML in user input for specific fields
 */
function xssProtection(req, res, next) {
  if (req.body && typeof req.body === 'object') {
    // Fields that should be HTML escaped
    const fieldsToEscape = ['username', 'name', 'worldName', 'serverName', 'motd'];
    
    for (const field of fieldsToEscape) {
      if (req.body[field] && typeof req.body[field] === 'string') {
        req.body[field] = escapeHtml(req.body[field]);
      }
    }
  }
  
  next();
}

/**
 * Basic HTML escape function
 */
function escapeHtml(unsafe) {
  return unsafe
    .replace(/&/g, "&")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
    .replace(/"/g, "&quot;")
    .replace(/'/g, "&#039;");
}

/**
 * Security headers middleware (additional to helmet)
 */
function additionalSecurityHeaders(req, res, next) {
  // Prevent MIME type sniffing
  res.setHeader('X-Content-Type-Options', 'nosniff');
  
  // Prevent clickjacking
  res.setHeader('X-Frame-Options', 'DENY');
  
  // XSS protection
  res.setHeader('X-XSS-Protection', '1; mode=block');
  
  // Referrer policy
  res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin');
  
  next();
}

/**
 * Request size validation
 */
function validateRequestSize(req, res, next) {
  // Check for unusually large requests that might indicate an attack
  const contentLength = req.headers['content-length'];
  if (contentLength && parseInt(contentLength) > 50 * 1024 * 1024) { // 50MB limit
    return res.status(413).json({ error: 'Request too large' });
  }
  
  next();
}

/**
 * Path traversal protection
 */
function pathTraversalProtection(req, res, next) {
  // Check for path traversal attempts in various parameters
  const suspiciousPatterns = ['../', '..\\', '%2e%2e%2f', '%2e%2e%5c'];
  
  function checkForTraversal(obj, path = '') {
    for (const [key, value] of Object.entries(obj)) {
      if (typeof value === 'string') {
        const lowerValue = value.toLowerCase();
        for (const pattern of suspiciousPatterns) {
          if (lowerValue.includes(pattern)) {
            console.warn(`Path traversal attempt detected: ${path}${key} = ${value}`);
            return true;
          }
        }
      } else if (typeof value === 'object' && value !== null) {
        if (checkForTraversal(value, `${path}${key}.`)) {
          return true;
        }
      }
    }
    return false;
  }
  
  if ((req.query && checkForTraversal(req.query)) || 
      (req.body && checkForTraversal(req.body))) {
    return res.status(400).json({ error: 'Invalid request parameters' });
  }
  
  next();
}

module.exports = {
  validateInput,
  xssProtection,
  additionalSecurityHeaders,
  validateRequestSize,
  pathTraversalProtection,
  escapeHtml
};