Move ResponseWriter.Flush to Flusher interface

examples/stream.go

@@ -39,6 +39,12 @@ func main() {
 
 // stream writes an infinite stream to w.
 func stream(w gemini.ResponseWriter, r *gemini.Request) {
+	flusher, ok := w.(gemini.Flusher)
+	if !ok {
+		w.Status(gemini.StatusTemporaryFailure)
+		return
+	}
+
 	ch := make(chan string)
 	ctx, cancel := context.WithCancel(context.Background())
 
@@ -63,7 +69,7 @@ func stream(w gemini.ResponseWriter, r *gemini.Request) {
 			break
 		}
 		fmt.Fprintln(w, s)
-		if err := w.Flush(); err != nil {
+		if err := flusher.Flush(); err != nil {
 			cancel()
 			return
 		}

response.go

@@ -156,11 +156,16 @@ type ResponseWriter interface {
 	// Write writes the response header if it has not already been written.
 	// It writes a successful status code if one is not set.
 	Write([]byte) (int, error)
+}
 
-	// Flush writes any buffered data to the underlying io.Writer.
+// The Flusher interface is implemented by ResponseWriters that allow a
+// Gemini handler to flush buffered data to the client.
 //
-	// Flush writes the response header if it has not already been written.
+// The default Gemini ResponseWriter implementation supports Flusher,
-	// It writes a failure status code if one is not set.
+// but ResponseWriter wrappers may not. Handlers should always test
+// for this ability at runtime.
+type Flusher interface {
+	// Flush sends any buffered data to the client.
 	Flush() error
 }
 
@@ -174,6 +179,10 @@ type responseWriter struct {
 
 // NewResponseWriter returns a ResponseWriter that uses the provided io.Writer.
 func NewResponseWriter(w io.Writer) ResponseWriter {
+	return newResponseWriter(w)
+}
+
+func newResponseWriter(w io.Writer) *responseWriter {
 	return &responseWriter{
 		b: bufio.NewWriter(w),
 	}

server.go

@@ -376,7 +376,7 @@ func (srv *Server) respond(conn net.Conn) {
 		conn.SetWriteDeadline(time.Now().Add(d))
 	}
 
-	w := NewResponseWriter(conn)
+	w := newResponseWriter(conn)
 
 	req, err := ReadRequest(conn)
 	if err != nil {