Make ResponseWriter an interface

examples/auth.go

@@ -54,7 +54,7 @@ func fingerprint(cert *x509.Certificate) string {
 	return string(b[:])
 }
 
-func profile(w *gemini.ResponseWriter, r *gemini.Request) {
+func profile(w gemini.ResponseWriter, r *gemini.Request) {
 	if r.Certificate == nil {
 		w.Status(gemini.StatusCertificateRequired)
 		return
@@ -69,7 +69,7 @@ func profile(w *gemini.ResponseWriter, r *gemini.Request) {
 	fmt.Fprintln(w, "=> /username Change username")
 }
 
-func changeUsername(w *gemini.ResponseWriter, r *gemini.Request) {
+func changeUsername(w gemini.ResponseWriter, r *gemini.Request) {
 	if r.Certificate == nil {
 		w.Status(gemini.StatusCertificateRequired)
 		return

examples/stream.go

@@ -38,7 +38,7 @@ func main() {
 }
 
 // stream writes an infinite stream to w.
-func stream(w *gemini.ResponseWriter, r *gemini.Request) {
+func stream(w gemini.ResponseWriter, r *gemini.Request) {
 	ch := make(chan string)
 	ctx, cancel := context.WithCancel(context.Background())
 

fs.go

@@ -26,7 +26,7 @@ type fsHandler struct {
 	FS
 }
 
-func (fsh fsHandler) ServeGemini(w *ResponseWriter, r *Request) {
+func (fsh fsHandler) ServeGemini(w ResponseWriter, r *Request) {
 	p := path.Clean(r.URL.Path)
 	f, err := fsh.Open(p)
 	if err != nil {
@@ -73,7 +73,7 @@ func (d Dir) Open(name string) (File, error) {
 // or directory.
 //
 // TODO: Use io/fs.FS when available.
-func ServeFile(w *ResponseWriter, fs FS, name string) {
+func ServeFile(w ResponseWriter, fs FS, name string) {
 	f, err := fs.Open(name)
 	if err != nil {
 		w.Status(StatusNotFound)

mux.go

@@ -132,7 +132,7 @@ func (mux *ServeMux) shouldRedirectRLocked(path string) bool {
 
 // ServeGemini dispatches the request to the handler whose
 // pattern most closely matches the request URL.
-func (mux *ServeMux) ServeGemini(w *ResponseWriter, r *Request) {
+func (mux *ServeMux) ServeGemini(w ResponseWriter, r *Request) {
 	path := cleanPath(r.URL.Path)
 
 	// If the given path is /tree and its handler is not registered,
@@ -202,7 +202,7 @@ func appendSorted(es []muxEntry, e muxEntry) []muxEntry {
 }
 
 // HandleFunc registers the handler function for the given pattern.
-func (mux *ServeMux) HandleFunc(pattern string, handler func(*ResponseWriter, *Request)) {
+func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
 	if handler == nil {
 		panic("gemini: nil responder")
 	}

response.go

@@ -129,8 +129,39 @@ func (b *readCloserBody) Read(p []byte) (n int, err error) {
 	return b.ReadCloser.Read(p)
 }
 
-// ResponseWriter is used to construct a Gemini response.
-type ResponseWriter struct {
+// A ResponseWriter interface is used by a Gemini handler
+// to construct a Gemini response.
+type ResponseWriter interface {
+	// Header sets the response header.
+	Header(status int, meta string)
+
+	// Status sets the response status code.
+	// It also sets the response meta to Meta(status).
+	Status(status int)
+
+	// Meta sets the response meta.
+	//
+	// For successful responses, meta should contain the media type of the response.
+	// For failure responses, meta should contain a short description of the failure.
+	// The response meta should not be greater than 1024 bytes.
+	Meta(meta string)
+
+	// Write writes data to the connection as part of the response body.
+	// If the response status does not allow for a response body, Write returns
+	// ErrBodyNotAllowed.
+	//
+	// 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.
+	//
+	// Flush writes the response header if it has not already been written.
+	// It writes a failure status code if one is not set.
+	Flush() error
+}
+
+type responseWriter struct {
 	b           *bufio.Writer
 	status      int
 	meta        string
@@ -139,41 +170,27 @@ type ResponseWriter struct {
 }
 
 // NewResponseWriter returns a ResponseWriter that uses the provided io.Writer.
-func NewResponseWriter(w io.Writer) *ResponseWriter {
-	return &ResponseWriter{
+func NewResponseWriter(w io.Writer) ResponseWriter {
+	return &responseWriter{
 		b: bufio.NewWriter(w),
 	}
 }
 
-// Header sets the response header.
-func (w *ResponseWriter) Header(status int, meta string) {
+func (w *responseWriter) Header(status int, meta string) {
 	w.status = status
 	w.meta = meta
 }
 
-// Status sets the response status code.
-// It also sets the response meta to Meta(status).
-func (w *ResponseWriter) Status(status int) {
+func (w *responseWriter) Status(status int) {
 	w.status = status
 	w.meta = Meta(status)
 }
 
-// Meta sets the response meta.
-//
-// For successful responses, meta should contain the media type of the response.
-// For failure responses, meta should contain a short description of the failure.
-// The response meta should not be greater than 1024 bytes.
-func (w *ResponseWriter) Meta(meta string) {
+func (w *responseWriter) Meta(meta string) {
 	w.meta = meta
 }
 
-// Write writes data to the connection as part of the response body.
-// If the response status does not allow for a response body, Write returns
-// ErrBodyNotAllowed.
-//
-// Write writes the response header if it has not already been written.
-// It writes a successful status code if one is not set.
-func (w *ResponseWriter) Write(b []byte) (int, error) {
+func (w *responseWriter) Write(b []byte) (int, error) {
 	if !w.wroteHeader {
 		w.writeHeader(StatusSuccess)
 	}
@@ -183,7 +200,7 @@ func (w *ResponseWriter) Write(b []byte) (int, error) {
 	return w.b.Write(b)
 }
 
-func (w *ResponseWriter) writeHeader(defaultStatus int) {
+func (w *responseWriter) writeHeader(defaultStatus int) {
 	status := w.status
 	if status == 0 {
 		status = defaultStatus
@@ -205,11 +222,7 @@ func (w *ResponseWriter) writeHeader(defaultStatus int) {
 	w.wroteHeader = true
 }
 
-// Flush writes any buffered data to the underlying io.Writer.
-//
-// Flush writes the response header if it has not already been written.
-// It writes a failure status code if one is not set.
-func (w *ResponseWriter) Flush() error {
+func (w *responseWriter) Flush() error {
 	if !w.wroteHeader {
 		w.writeHeader(StatusTemporaryFailure)
 	}

server.go

@@ -83,7 +83,7 @@ func (s *Server) Handle(pattern string, handler Handler) {
 }
 
 // HandleFunc registers the handler function for the given pattern.
-func (s *Server) HandleFunc(pattern string, handler func(*ResponseWriter, *Request)) {
+func (s *Server) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
 	s.Handle(pattern, HandlerFunc(handler))
 }
 
@@ -258,15 +258,15 @@ func (s *Server) logf(format string, args ...interface{}) {
 // ServeGemini should write the response header and data to the ResponseWriter
 // and then return.
 type Handler interface {
-	ServeGemini(*ResponseWriter, *Request)
+	ServeGemini(ResponseWriter, *Request)
 }
 
 // The HandlerFunc type is an adapter to allow the use of ordinary functions
 // as Gemini handlers. If f is a function with the appropriate signature,
 // HandlerFunc(f) is a Handler that calls f.
-type HandlerFunc func(*ResponseWriter, *Request)
+type HandlerFunc func(ResponseWriter, *Request)
 
 // ServeGemini calls f(w, r).
-func (f HandlerFunc) ServeGemini(w *ResponseWriter, r *Request) {
+func (f HandlerFunc) ServeGemini(w ResponseWriter, r *Request) {
 	f(w, r)
 }