refactor: restore "First stage of access logging middleware."

This reverts commit 82651985c4.

middlewares/accesslog/capture_response_writer.go

@@ -0,0 +1,69 @@
+package accesslog
+
+import (
+	"bufio"
+	"fmt"
+	"net"
+	"net/http"
+)
+
+var (
+	_ http.ResponseWriter = &captureResponseWriter{}
+	_ http.Hijacker       = &captureResponseWriter{}
+	_ http.Flusher        = &captureResponseWriter{}
+	_ http.CloseNotifier  = &captureResponseWriter{}
+)
+
+// captureResponseWriter is a wrapper of type http.ResponseWriter
+// that tracks request status and size
+type captureResponseWriter struct {
+	rw     http.ResponseWriter
+	status int
+	size   int64
+}
+
+func (crw *captureResponseWriter) Header() http.Header {
+	return crw.rw.Header()
+}
+
+func (crw *captureResponseWriter) Write(b []byte) (int, error) {
+	if crw.status == 0 {
+		crw.status = http.StatusOK
+	}
+	size, err := crw.rw.Write(b)
+	crw.size += int64(size)
+	return size, err
+}
+
+func (crw *captureResponseWriter) WriteHeader(s int) {
+	crw.rw.WriteHeader(s)
+	crw.status = s
+}
+
+func (crw *captureResponseWriter) Flush() {
+	if f, ok := crw.rw.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
+func (crw *captureResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if h, ok := crw.rw.(http.Hijacker); ok {
+		return h.Hijack()
+	}
+	return nil, nil, fmt.Errorf("Not a hijacker: %T", crw.rw)
+}
+
+func (crw *captureResponseWriter) CloseNotify() <-chan bool {
+	if c, ok := crw.rw.(http.CloseNotifier); ok {
+		return c.CloseNotify()
+	}
+	return nil
+}
+
+func (crw *captureResponseWriter) Status() int {
+	return crw.status
+}
+
+func (crw *captureResponseWriter) Size() int64 {
+	return crw.size
+}