Compression

import { FastifyInstance } from "fastify";
import compress, { FastifyCompressOptions } from "@fastify/compress";

/**
 * Default compression configuration
 */
const defaultConfig: FastifyCompressOptions = {
  // Compression method priority
  encodings: ["br", "gzip", "deflate"],
  
  // Minimum size to compress (in bytes)
  threshold: 1024, // 1KB
  
  // Brotli options (preferred for modern browsers)
  brotliOptions: {
    params: {
      // Quality: 0-11, higher = better compression but slower
      // 4 is a good balance for dynamic content
      [require("zlib").constants.BROTLI_PARAM_QUALITY]: 4,
    },
  },
  
  // Gzip options
  zlib: {
    level: 6, // 1-9, higher = better compression but slower
  },
  
  // Compress responses when Accept-Encoding header is present
  global: true,
  
  // Enable decompression of request bodies (optional)
  inflateIfDeflated: true,
  
  // Custom function to determine if response should be compressed
  customTypes: /^text\/|\+json$|\+text$|\+xml$/,
};

/**
 * Content types that should be compressed
 */
const compressibleTypes = [
  "text/html",
  "text/plain",
  "text/css",
  "text/javascript",
  "application/javascript",
  "application/json",
  "application/xml",
  "application/rss+xml",
  "image/svg+xml",
];

/**
 * Register compression middleware
 */
export async function registerCompression(
  app: FastifyInstance,
  options?: Partial<FastifyCompressOptions>
): Promise<void> {
  const config = { ...defaultConfig, ...options };
  
  await app.register(compress, config);
  
  app.log.info(
    { encodings: config.encodings, threshold: config.threshold },
    "[Compression] Configured"
  );
}

/**
 * Create route-specific compression options
 */
export function createRouteCompression(
  options: Partial<FastifyCompressOptions>
): { compress: FastifyCompressOptions } {
  return {
    compress: { ...defaultConfig, ...options },
  };
}

/**
 * Disable compression for specific routes
 */
export const noCompression = {
  compress: false as const,
};

/**
 * Compression presets for common use cases
 */
export const compressionPresets = {
  // High compression for static assets (slower but smaller)
  static: createRouteCompression({
    brotliOptions: {
      params: {
        [require("zlib").constants.BROTLI_PARAM_QUALITY]: 11,
      },
    },
    zlib: { level: 9 },
  }),
  
  // Fast compression for API responses
  api: createRouteCompression({
    brotliOptions: {
      params: {
        [require("zlib").constants.BROTLI_PARAM_QUALITY]: 4,
      },
    },
    zlib: { level: 6 },
  }),
  
  // Minimal compression for real-time data
  realtime: createRouteCompression({
    brotliOptions: {
      params: {
        [require("zlib").constants.BROTLI_PARAM_QUALITY]: 1,
      },
    },
    zlib: { level: 1 },
  }),
};

// Usage:
// await registerCompression(app);
//
// Per-route:
// app.get("/static/*", { ...compressionPresets.static }, handler);
// app.get("/stream", { ...noCompression }, streamHandler);