/**
 * Content Security Policy middleware
 * Generates nonces for inline scripts and sets appropriate CSP headers
 */

const crypto = require('crypto');
const winston = require('winston');

// Security headers middleware (renamed from CSP middleware as it now handles more headers)
function securityMiddleware(config) {
  // If security is entirely disabled, return a no-op middleware
  if (config.security === false) {
    return function(req, res, next) { next(); };
  }
  
  // Get CSP configuration - default to enabled if not specified
  const cspEnabled = config.security && typeof config.security.csp !== 'undefined' ? 
    config.security.csp : true;
  
  // Log the CSP configuration at startup for debugging
  winston.info(`Security middleware initialized with CSP ${cspEnabled ? 'ENABLED' : 'DISABLED'}`);
  
  return function(req, res, next) {
    // Only add security headers for HTML requests
    const isHtmlRequest = req.url === '/' || req.url.match(/^\/[a-zA-Z0-9_-]+$/);
    
    if (isHtmlRequest) {
      // Add basic security headers - always applied regardless of CSP setting
      
      // 1. X-Content-Type-Options - prevents MIME-type sniffing
      res.setHeader('X-Content-Type-Options', 'nosniff');
      
      // 2. X-Frame-Options - prevents clickjacking
      res.setHeader('X-Frame-Options', 'DENY');
      
      // 3. X-XSS-Protection - legacy header, still used by some browsers
      res.setHeader('X-XSS-Protection', '1; mode=block');
      
      // 4. Referrer-Policy - controls how much referrer information is included
      res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin');
      
      // 5. Permissions-Policy - controls browser features
      res.setHeader('Permissions-Policy', 'camera=(), microphone=(), geolocation=(), interest-cohort=()');
      
      // Apply CSP headers ONLY if explicitly enabled
      if (cspEnabled === true) {
        // Generate a unique nonce for this request
        const nonce = crypto.randomBytes(16).toString('base64');
        
        // Store nonce in request object for use in HTML template
        req.cspNonce = nonce;
        
        // Build the base script sources list
        const scriptSources = ["'self'", `'nonce-${nonce}'`];
        
        // Add any additional script sources from config
        if (config.security && config.security.scriptSources && config.security.scriptSources.length > 0) {
          config.security.scriptSources.forEach(source => {
            if (source && !scriptSources.includes(source)) {
              scriptSources.push(source);
            }
          });
        }
        
        // Add unsafe-hashes if configured (for event handlers)
        if (config.security && config.security.allowUnsafeHashes) {
          scriptSources.push("'unsafe-hashes'");
        }
        
        // Create the policy - adjust based on environment
        let cspDirectives;
        
        // Development mode with potential bypass option
        if (process.env.NODE_ENV === 'development') {
          // Check if we should bypass strict CSP in development
          const bypassCSPInDev = config.security && config.security.bypassCSPInDev;
          
          if (bypassCSPInDev) {
            // Very permissive policy with unsafe-inline for development testing
            cspDirectives = [
              "default-src 'self'",
              "script-src 'self' 'unsafe-inline' 'unsafe-eval'", 
              "style-src 'self' 'unsafe-inline'",
              "img-src 'self' data:",
              "connect-src 'self'",
              "font-src 'self'"
            ];
            
            winston.debug('Using permissive development CSP policy with unsafe-inline (bypass enabled)');
          } else {
            // Standard development mode - still using nonces
            cspDirectives = [
              "default-src 'self'",
              `script-src ${scriptSources.join(' ')}`,
              "style-src 'self' 'unsafe-inline'",
              "img-src 'self' data:",
              "connect-src 'self'",
              "font-src 'self'"
            ];
            
            winston.debug('Using development CSP policy with nonces (bypass disabled)');
          }
        } else {
          // Production mode - strict policy with nonces
          cspDirectives = [
            "default-src 'self'",
            `script-src ${scriptSources.join(' ')}`,
            "style-src 'self' 'unsafe-inline'",
            "img-src 'self' data:",
            "connect-src 'self'",
            "font-src 'self'",
            "frame-ancestors 'none'",
            "base-uri 'self'",
            "form-action 'none'",
            "object-src 'none'"
          ];
          
          winston.debug(`Using strict production CSP policy with nonces${config.security.allowUnsafeHashes ? " and unsafe-hashes" : ""}`);
        }
        
        // Set the CSP header with the properly formatted policy
        res.setHeader('Content-Security-Policy', cspDirectives.join('; '));
        winston.debug('CSP header applied');
      } else {
        winston.debug('CSP is disabled by configuration - not applying CSP header');
      }
      
      // Add Cross-Origin headers only if enabled in config
      // These can be problematic for some applications, so we make them optional
      const enableCrossOriginIsolation = config.security && config.security.enableCrossOriginIsolation;
      
      if (enableCrossOriginIsolation) {
        // 6. Cross-Origin-Embedder-Policy - for cross-origin isolation
        res.setHeader('Cross-Origin-Embedder-Policy', 'require-corp');
        
        // 7. Cross-Origin-Resource-Policy - protects resources from unauthorized requests
        res.setHeader('Cross-Origin-Resource-Policy', 'same-origin');
        
        // 8. Cross-Origin-Opener-Policy - helps with cross-origin isolation
        res.setHeader('Cross-Origin-Opener-Policy', 'same-origin');
        
        winston.debug('Added Cross-Origin isolation headers');
      }
      
      // If configured, add HSTS header
      if (config.security && config.security.hsts) {
        res.setHeader('Strict-Transport-Security', 'max-age=31536000; includeSubDomains; preload');
      }
    }
    
    next();
  };
}

// Export the middleware
module.exports = securityMiddleware;