From 44b868dae93b8999b0df87b01da140ec075197cd Mon Sep 17 00:00:00 2001
From: hallelx2 <halleluyaholudele@gmail.com>
Date: Fri, 3 Jul 2026 17:04:33 +0100
Subject: [PATCH] fix(middleware): pass through http.Flusher for SSE streaming

The request-logging, metrics, and tracing middlewares each wrap the
ResponseWriter to capture status/bytes, but none implemented
http.Flusher. Streaming handlers (/v1/answer/treewalk?stream=true,
/v1/query/stream) do w.(http.Flusher) and errored with 'response
writer does not support http.Flusher'. Add Flush() (delegating to the
wrapped writer) + Unwrap() to statusRecorder, metricsRecorder, and
tracingRecorder so flushes propagate through the whole chain and SSE
streams in real time.
---
 internal/middleware/logging.go | 12 ++++++++++++
 internal/middleware/metrics.go | 11 +++++++++++
 internal/middleware/tracing.go | 11 +++++++++++
 3 files changed, 34 insertions(+)

diff --git a/internal/middleware/logging.go b/internal/middleware/logging.go
index b1d8684..16c66c1 100644
--- a/internal/middleware/logging.go
+++ b/internal/middleware/logging.go
@@ -28,6 +28,18 @@ func (r *statusRecorder) Write(b []byte) (int, error) {
 	return n, err
 }
 
+// Flush propagates to the wrapped writer so SSE/streaming handlers can
+// flush through this middleware. Without it, w.(http.Flusher) fails and
+// streaming endpoints error out.
+func (r *statusRecorder) Flush() {
+	if f, ok := r.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
+// Unwrap exposes the wrapped writer for http.ResponseController.
+func (r *statusRecorder) Unwrap() http.ResponseWriter { return r.ResponseWriter }
+
 // AccessLog logs one structured line per HTTP request: method, path,
 // status, duration, request ID, and principal ID.
 //
diff --git a/internal/middleware/metrics.go b/internal/middleware/metrics.go
index dc59f63..46a6400 100644
--- a/internal/middleware/metrics.go
+++ b/internal/middleware/metrics.go
@@ -56,6 +56,17 @@ func (r *metricsRecorder) Write(b []byte) (int, error) {
 	return n, err
 }
 
+// Flush propagates to the wrapped writer so SSE/streaming handlers can
+// flush through the metrics middleware.
+func (r *metricsRecorder) Flush() {
+	if f, ok := r.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
+// Unwrap exposes the wrapped writer for http.ResponseController.
+func (r *metricsRecorder) Unwrap() http.ResponseWriter { return r.ResponseWriter }
+
 // normalizePath strips URL parameters to keep metric cardinality
 // bounded. Document and section IDs are replaced with a placeholder.
 func normalizePath(path string) string {
diff --git a/internal/middleware/tracing.go b/internal/middleware/tracing.go
index e0d0bff..f0005c1 100644
--- a/internal/middleware/tracing.go
+++ b/internal/middleware/tracing.go
@@ -67,6 +67,17 @@ func (r *tracingRecorder) WriteHeader(code int) {
 	r.ResponseWriter.WriteHeader(code)
 }
 
+// Flush propagates to the wrapped writer so SSE/streaming handlers can
+// flush through the tracing middleware.
+func (r *tracingRecorder) Flush() {
+	if f, ok := r.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
+// Unwrap exposes the wrapped writer for http.ResponseController.
+func (r *tracingRecorder) Unwrap() http.ResponseWriter { return r.ResponseWriter }
+
 // TraceIDFromContext extracts the trace ID string from the current span,
 // useful for correlating logs with traces.
 func TraceIDFromContext(ctx context.Context) string {