config.js

/**
 * Configuration for 2G Website Compressor
 * Controls compression strategies, optimization toggles, and performance tuning
 */

module.exports = {
  // Proxy server configuration
  proxy: {
    port: 8888,
    host: '0.0.0.0',
    // SSL/TLS configuration for HTTPS MITM
    sslCaDir: './certs',
  },

  // Logging configuration
  logging: {
    level: process.env.LOG_LEVEL || 'info', // debug, info, warn, error
    format: 'json', // json or pretty
  },

  // Compression strategy configuration
  compression: {
    // Brotli compression settings (text: HTML, CSS, JS)
    brotli: {
      enabled: true,
      quality: 9, // 1-11; higher = better compression but slower. 9 = good balance
      lgwin: 22, // Brotli window size (20-24); higher = better for large files
    },
    // Gzip fallback for clients that don't support Brotli
    gzip: {
      enabled: true,
      level: 9, // 0-9; higher = better compression
    },
  },

  // HTML optimization
  html: {
    enabled: true,
    minify: true,
    // Strip these scripts (analytics, ads, tracking)
    stripScripts: [
      'google-analytics',
      'googletagmanager',
      'analytics',
      'facebook',
      'twitter',
      'instagram',
      'ads',
      'doubleclick',
      'adsense',
    ],
    // Remove these meta/link tags
    removeMetaTags: [
      'description', // Keep or remove? Keep for SEO
    ],
    // Lazy-load images by default
    lazyLoadImages: true,
    // Remove non-essential attributes
    minifyAttributes: true,
    // Remove comments and whitespace
    removeComments: true,
  },

  // Image optimization
  image: {
    enabled: true,
    // Convert to WebP (better compression)
    convertToWebP: true,
    // WebP quality setting (1-100; 50-60 for aggressive 2G optimization)
    webpQuality: 55,
    // Maximum image width (fit to phone screens: e.g., 480px for older phones)
    maxWidth: 480,
    // Maximum image height (prevent huge vertical images)
    maxHeight: 800,
    // Downscale larger images aggressively
    downscaleThreshold: 600, // If width > 600, always downscale
    // JPEG quality fallback (for devices that don't support WebP)
    jpegQuality: 60,
    // Enable progressive JPEG
    progressive: true,
  },

  // CSS optimization
  css: {
    enabled: true,
    minify: true,
    // Strip unused CSS prefixes (e.g., -webkit-, -moz-)
    stripVendorPrefixes: false, // Keep false for compatibility
  },

  // JavaScript optimization
  javascript: {
    enabled: true,
    minify: true,
    // Remove console.* statements
    removeConsole: true,
    // Remove debugger statements
    removeDebugger: true,
    // Compress variable names
    compress: true,
  },

  // Caching strategy
  cache: {
    enabled: true,
    // Use server's Cache-Control headers
    respectServerHeaders: true,
    // Default TTL for cached responses (in seconds)
    defaultTTL: 15 * 60, // 15 minutes
    // Maximum cache size (in MB)
    maxSize: 100,
    // Cache storage location
    storageDir: './cache',
  },

  // Request/Response filtering
  filtering: {
    // Domain whitelist (if empty, all domains allowed)
    domainWhitelist: [],
    // Domain blacklist (skip optimization for these)
    domainBlacklist: [
      'video.example.com', // Skip video-heavy sites
      'stream.example.com',
    ],
    // Content-Type whitelist for optimization
    contentTypesOptimize: [
      'text/html',
      'text/css',
      'text/javascript',
      'application/javascript',
      'application/x-javascript',
      'image/jpeg',
      'image/png',
      'image/gif',
      'image/webp',
    ],
    // Skip optimization for these content types
    contentTypesSkip: [
      'video/',
      'audio/',
      'application/octet-stream',
      'application/zip',
      'application/pdf',
    ],
  },

  // Performance metrics & monitoring
  metrics: {
    enabled: true,
    // Log compression ratio for each request
    logCompressionRatio: true,
    // Collect stats by domain
    collectByDomain: true,
    // Report metrics interval (seconds)
    reportInterval: 60,
  },

  // Global request/response size limits
  limits: {
    // Maximum request size to cache (MB)
    maxRequestSize: 50,
    // Maximum response size to cache (MB)
    maxResponseSize: 50,
    // Skip optimization if original size is below (KB) — efficiency threshold
    minSizeToOptimize: 0.1, // Compress everything (100 bytes+) - critical for 2G networks!
  },

  // Debug & testing
  debug: {
    enabled: process.env.DEBUG === 'true',
    // Log all requests/responses
    logAllRequests: false,
    // Save original vs. compressed to disk for analysis
    saveComparisons: false,
    comparisonDir: './debug/comparisons',
  },
};