proto: abstract formatting away and reuse formatting buffer

Author: Snawoot

handler/handler.go

@@ -30,6 +30,8 @@ func (a *BasicHMACAuthHandler) Run(input io.Reader, output io.Writer) error {
 
 	mac := hmac.NewHasher(a.Secret)
 
+	emitter := proto.NewResponseEmitter(output)
+
 	for scanner.Scan() {
 		parts := bytes.SplitN(scanner.Bytes(), []byte{' '}, 4)
 		if len(parts) < 3 {
@@ -41,9 +43,13 @@ func (a *BasicHMACAuthHandler) Run(input io.Reader, output io.Writer) error {
 		password := proto.RFC1738Unescape(parts[2])
 
 		if hmac.VerifyHMACLoginAndPassword(mac, username, password) {
-			fmt.Fprintf(output, "%s OK\n", channelID)
+			if err := emitter.EmitOK(channelID); err != nil {
+				return fmt.Errorf("response write failed: %w", err)
+			}
 		} else {
-			fmt.Fprintf(output, "%s ERR\n", channelID)
+			if err := emitter.EmitERR(channelID); err != nil {
+				return fmt.Errorf("response write failed: %w", err)
+			}
 		}
 	}
 

proto/emit.go

@@ -0,0 +1,46 @@
+package proto
+
+import (
+	"bytes"
+	"io"
+)
+
+const (
+	OK  = "OK"
+	ERR = "ERR"
+)
+
+type ResponseEmitter struct {
+	writer io.Writer
+	buffer bytes.Buffer
+}
+
+func NewResponseEmitter(writer io.Writer) *ResponseEmitter {
+	return &ResponseEmitter{
+		writer: writer,
+	}
+}
+
+func (e *ResponseEmitter) EmitOK(channelID []byte) error {
+	e.beginResponse(channelID)
+	e.buffer.WriteString(OK)
+	return e.finishResponse()
+}
+
+func (e *ResponseEmitter) EmitERR(channelID []byte) error {
+	e.beginResponse(channelID)
+	e.buffer.WriteString(ERR)
+	return e.finishResponse()
+}
+
+func (e *ResponseEmitter) beginResponse(channelID []byte) {
+	e.buffer.Reset()
+	e.buffer.Write(channelID)
+	e.buffer.WriteByte(' ')
+}
+
+func (e *ResponseEmitter) finishResponse() error {
+	e.buffer.WriteByte('\n')
+	_, err := e.buffer.WriteTo(e.writer)
+	return err
+}