From 80df01192337181cb4a6bf2bd6d482c58da5c92c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Iv=C3=A1n=20Ovejero?= <ivov.src@gmail.com>
Date: Sun, 19 Jan 2025 15:49:04 +0100
Subject: [PATCH] fix: Prevent multiple calls to `WriteHeader` on the same
 response writer

---
 internal/api/middleware.go | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/internal/api/middleware.go b/internal/api/middleware.go
index ec5480a..c28b15c 100644
--- a/internal/api/middleware.go
+++ b/internal/api/middleware.go
@@ -152,14 +152,21 @@ type wrappedResponseWriter struct {
 	http.ResponseWriter
 	statusCode   int
 	bytesWritten int
+	wroteHeader  bool // prevent metrics middleware (using httpsnoop) from calling WriteHeader multiple times on the same response writer
 }
 
 func (rw *wrappedResponseWriter) WriteHeader(statusCode int) {
-	rw.ResponseWriter.WriteHeader(statusCode)
-	rw.statusCode = statusCode
+	if !rw.wroteHeader {
+		rw.statusCode = statusCode
+		rw.ResponseWriter.WriteHeader(statusCode)
+		rw.wroteHeader = true
+	}
 }
 
 func (rw *wrappedResponseWriter) Write(b []byte) (int, error) {
+	if !rw.wroteHeader {
+		rw.WriteHeader(http.StatusOK)
+	}
 	bytes, err := rw.ResponseWriter.Write(b)
 	rw.bytesWritten += bytes
 	return bytes, err