Compression

import compression from 'compression';
import { Request, Response, RequestHandler } from 'express';

/**
 * Default compression middleware
 * Compresses responses larger than 1KB using gzip
 */
export const compress: RequestHandler = compression({
  // Only compress responses larger than 1KB
  threshold: 1024,
  
  // Compression level (1-9, higher = more compression but slower)
  level: 6,
  
  // Filter function to decide what to compress
  filter: (req: Request, res: Response) => {
    // Don't compress if client doesn't accept it
    if (req.headers['x-no-compression']) {
      return false;
    }
    
    // Use compression's default filter (checks Accept-Encoding)
    return compression.filter(req, res);
  },
});

/**
 * Aggressive compression for bandwidth-critical applications
 * Higher compression level, lower threshold
 */
export const compressAggressive: RequestHandler = compression({
  threshold: 512,
  level: 9,
  filter: (req: Request, res: Response) => {
    if (req.headers['x-no-compression']) {
      return false;
    }
    return compression.filter(req, res);
  },
});

/**
 * Light compression for CPU-constrained servers
 * Lower compression level, higher threshold
 */
export const compressLight: RequestHandler = compression({
  threshold: 2048,
  level: 1,
  filter: (req: Request, res: Response) => {
    if (req.headers['x-no-compression']) {
      return false;
    }
    return compression.filter(req, res);
  },
});

/**
 * Skip compression for specific content types
 * Useful when serving already-compressed content (images, videos)
 */
export const compressSelectiveTypes: RequestHandler = compression({
  threshold: 1024,
  level: 6,
  filter: (req: Request, res: Response) => {
    const contentType = res.getHeader('Content-Type') as string;
    
    // Skip already-compressed formats
    const skipTypes = [
      'image/',
      'video/',
      'audio/',
      'application/zip',
      'application/gzip',
      'application/x-rar',
    ];
    
    if (contentType && skipTypes.some(type => contentType.includes(type))) {
      return false;
    }
    
    if (req.headers['x-no-compression']) {
      return false;
    }
    
    return compression.filter(req, res);
  },
});