From 4b87972743b36eeed42e355e1228aaaced34026a Mon Sep 17 00:00:00 2001
From: Robb Traister <rtraister@citrine.io>
Date: Tue, 2 Sep 2025 11:26:21 -0400
Subject: [PATCH 1/2] fix(fixRequestBody): support content-encoding on request
 body

---
 src/handlers/fix-request-body.ts   | 23 +++++++++++++++++++++--
 test/unit/fix-request-body.spec.ts | 17 +++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/src/handlers/fix-request-body.ts b/src/handlers/fix-request-body.ts
index cc47e68f..a92b5d31 100644
--- a/src/handlers/fix-request-body.ts
+++ b/src/handlers/fix-request-body.ts
@@ -1,5 +1,6 @@
 import type * as http from 'node:http';
 import * as querystring from 'node:querystring';
+import * as zlib from 'node:zlib';
 
 export type BodyParserLikeRequest = http.IncomingMessage & { body?: any };
 
@@ -28,8 +29,26 @@ export function fixRequestBody<TReq extends BodyParserLikeRequest = BodyParserLi
   }
 
   const writeBody = (bodyData: string) => {
-    proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
-    proxyReq.write(bodyData);
+    let proxyData: string | Buffer = bodyData;
+
+    const contentEncoding = String(proxyReq.getHeader('Content-Encoding')).toLowerCase();
+    switch (contentEncoding) {
+      case 'br':
+        proxyData = zlib.brotliCompressSync(proxyData);
+        break;
+      case 'deflate':
+        proxyData = zlib.deflateSync(proxyData);
+        break;
+      case 'gzip':
+        proxyData = zlib.gzipSync(proxyData);
+        break;
+      case 'zstd':
+        proxyData = zlib.zstdCompressSync(proxyData);
+        break;
+    }
+
+    proxyReq.setHeader('Content-Length', Buffer.byteLength(proxyData));
+    proxyReq.write(proxyData);
   };
 
   // Use if-elseif to prevent multiple writeBody/setHeader calls:
diff --git a/test/unit/fix-request-body.spec.ts b/test/unit/fix-request-body.spec.ts
index 4615c67c..254aa839 100644
--- a/test/unit/fix-request-body.spec.ts
+++ b/test/unit/fix-request-body.spec.ts
@@ -1,6 +1,7 @@
 import { ClientRequest, IncomingMessage, ServerResponse } from 'node:http';
 import { Socket } from 'node:net';
 import * as querystring from 'node:querystring';
+import * as zlib from 'node:zlib';
 
 import { BodyParserLikeRequest, fixRequestBody } from '../../src/handlers/fix-request-body';
 
@@ -213,4 +214,20 @@ describe('fixRequestBody', () => {
     expect(proxyRequest.write).toHaveBeenCalledTimes(0);
     expect(proxyRequest.destroy).toHaveBeenCalledTimes(0);
   });
+
+  it('should re-encode body when the source was encoded', () => {
+    const proxyRequest = fakeProxyRequest();
+    proxyRequest.setHeader('content-type', 'application/json; charset=utf-8');
+    proxyRequest.setHeader('content-encoding', 'gzip');
+
+    jest.spyOn(proxyRequest, 'setHeader');
+    jest.spyOn(proxyRequest, 'write');
+
+    const data = { someField: 'some value' };
+    fixRequestBody(proxyRequest, createRequestWithBody(data));
+
+    const expectedBody = zlib.gzipSync(JSON.stringify(data));
+    expect(proxyRequest.setHeader).toHaveBeenCalledWith('Content-Length', expectedBody.length);
+    expect(proxyRequest.write).toHaveBeenCalledWith(expectedBody);
+  });
 });

From b8e7462b243bb1a11d25d7dadf05f0a1671f46a6 Mon Sep 17 00:00:00 2001
From: Robb Traister <rtraister@citrine.io>
Date: Mon, 8 Sep 2025 08:40:07 -0400
Subject: [PATCH 2/2] remove experimental zstd codec

---
 src/handlers/fix-request-body.ts | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/src/handlers/fix-request-body.ts b/src/handlers/fix-request-body.ts
index a92b5d31..fc9019c7 100644
--- a/src/handlers/fix-request-body.ts
+++ b/src/handlers/fix-request-body.ts
@@ -42,9 +42,6 @@ export function fixRequestBody<TReq extends BodyParserLikeRequest = BodyParserLi
       case 'gzip':
         proxyData = zlib.gzipSync(proxyData);
         break;
-      case 'zstd':
-        proxyData = zlib.zstdCompressSync(proxyData);
-        break;
     }
 
     proxyReq.setHeader('Content-Length', Buffer.byteLength(proxyData));