feat(middleware): implement response compression middleware (#325)

middleware/src/compression/compression.config.ts

@@ -0,0 +1,20 @@
+export const COMPRESSION_CONFIG = {
+  threshold: 1024, // minimum size in bytes
+  gzip: { level: 6 }, // balance speed vs size
+  brotli: { quality: 4 }, // modern browsers
+  skipTypes: [
+    /^image\//,
+    /^video\//,
+    /^audio\//,
+    /^application\/zip/,
+    /^application\/gzip/,
+  ],
+  compressibleTypes: [
+    'application/json',
+    'text/html',
+    'text/plain',
+    'application/javascript',
+    'text/css',
+    'text/xml',
+  ],
+};

middleware/src/compression/compression.middleware.ts

@@ -0,0 +1,63 @@
+import { Injectable, NestMiddleware } from '@nestjs/common';
+import { Request, Response, NextFunction } from 'express';
+import * as zlib from 'zlib';
+import { COMPRESSION_CONFIG } from './compression.config';
+
+@Injectable()
+export class CompressionMiddleware implements NestMiddleware {
+  use(req: Request, res: Response, next: NextFunction) {
+    const acceptEncoding = req.headers['accept-encoding'] || '';
+    const chunks: Buffer[] = [];
+    const originalWrite = res.write;
+    const originalEnd = res.end;
+
+    // Intercept response body
+    res.write = function (chunk: any) {
+      chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
+      return true;
+    };
+
+    res.end = function (chunk: any) {
+      if (chunk) {
+        chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
+      }
+
+      const body = Buffer.concat(chunks);
+
+      // Skip compression if too small
+      if (body.length < COMPRESSION_CONFIG.threshold) {
+        return originalEnd.call(res, body);
+      }
+
+      const contentType = res.getHeader('Content-Type') as string;
+      if (COMPRESSION_CONFIG.skipTypes.some((regex) => regex.test(contentType))) {
+        return originalEnd.call(res, body);
+      }
+
+      // Select algorithm
+      if (/\bbr\b/.test(acceptEncoding)) {
+        zlib.brotliCompress(body, { params: { [zlib.constants.BROTLI_PARAM_QUALITY]: COMPRESSION_CONFIG.brotli.quality } }, (err, compressed) => {
+          if (err) return originalEnd.call(res, body);
+          res.setHeader('Content-Encoding', 'br');
+          originalEnd.call(res, compressed);
+        });
+      } else if (/\bgzip\b/.test(acceptEncoding)) {
+        zlib.gzip(body, { level: COMPRESSION_CONFIG.gzip.level }, (err, compressed) => {
+          if (err) return originalEnd.call(res, body);
+          res.setHeader('Content-Encoding', 'gzip');
+          originalEnd.call(res, compressed);
+        });
+      } else if (/\bdeflate\b/.test(acceptEncoding)) {
+        zlib.deflate(body, (err, compressed) => {
+          if (err) return originalEnd.call(res, body);
+          res.setHeader('Content-Encoding', 'deflate');
+          originalEnd.call(res, compressed);
+        });
+      } else {
+        return originalEnd.call(res, body);
+      }
+    };
+
+    next();
+  }
+}