Merge pull request #70 from wneessen/feature/middleware-type

Introducing MiddlewareType and WriteToSkipMiddleware

msg.go

@@ -42,9 +42,14 @@ const (
 	errParseMailAddr = "failed to parse mail address %q: %w"
 )
 
+// MiddlewareType is the type description of the Middleware and needs to be returned
+// in the Middleware interface by the Type method
+type MiddlewareType string
+
 // Middleware is an interface to define a function to apply to Msg before sending
 type Middleware interface {
 	Handle(*Msg) *Msg
+	Type() MiddlewareType
 }
 
 // Msg is the mail message struct
@@ -713,6 +718,24 @@ func (m *Msg) WriteTo(w io.Writer) (int64, error) {
 	return mw.n, mw.err
 }
 
+// WriteToSkipMiddleware writes the formated Msg into a give io.Writer and satisfies
+// the io.WriteTo interface but will skip the given Middleware
+func (m *Msg) WriteToSkipMiddleware(w io.Writer, mt MiddlewareType) (int64, error) {
+	var omwl, mwl []Middleware
+	omwl = m.middlewares
+	for i := range m.middlewares {
+		if m.middlewares[i].Type() == mt {
+			continue
+		}
+		mwl = append(mwl, m.middlewares[i])
+	}
+	m.middlewares = mwl
+	mw := &msgWriter{w: w, c: m.charset, en: m.encoder}
+	mw.writeMsg(m.applyMiddlewares(m))
+	m.middlewares = omwl
+	return mw.n, mw.err
+}
+
 // Write is an alias method to WriteTo due to compatibility reasons
 func (m *Msg) Write(w io.Writer) (int64, error) {
 	return m.WriteTo(w)

msg_test.go

@@ -189,6 +189,10 @@ func (mw uppercaseMiddleware) Handle(m *Msg) *Msg {
 	return m
 }
 
+func (mw uppercaseMiddleware) Type() MiddlewareType {
+	return "uppercase"
+}
+
 type encodeMiddleware struct{}
 
 func (mw encodeMiddleware) Handle(m *Msg) *Msg {
@@ -200,6 +204,10 @@ func (mw encodeMiddleware) Handle(m *Msg) *Msg {
 	return m
 }
 
+func (mw encodeMiddleware) Type() MiddlewareType {
+	return "encode"
+}
+
 // TestNewMsgWithMiddleware tests WithMiddleware
 func TestNewMsgWithMiddleware(t *testing.T) {
 	m := NewMsg()
@@ -1584,6 +1592,38 @@ func TestMsg_WriteTo(t *testing.T) {
 	}
 }
 
+// TestMsg_WriteTo tests the WriteTo() method of the Msg
+func TestMsg_WriteToSkipMiddleware(t *testing.T) {
+	m := NewMsg(WithMiddleware(encodeMiddleware{}), WithMiddleware(uppercaseMiddleware{}))
+	m.Subject("This is a test")
+	m.SetBodyString(TypeTextPlain, "Plain")
+	wbuf := bytes.Buffer{}
+	n, err := m.WriteToSkipMiddleware(&wbuf, "uppercase")
+	if err != nil {
+		t.Errorf("WriteToSkipMiddleware() failed: %s", err)
+		return
+	}
+	if n != int64(wbuf.Len()) {
+		t.Errorf("WriteToSkipMiddleware() failed: expected written byte length: %d, got: %d", n, wbuf.Len())
+	}
+	if !strings.Contains(wbuf.String(), "Subject: This is @ test") {
+		t.Errorf("WriteToSkipMiddleware failed. Unable to find encoded subject")
+	}
+
+	wbuf2 := bytes.Buffer{}
+	n, err = m.WriteTo(&wbuf2)
+	if err != nil {
+		t.Errorf("WriteTo() failed: %s", err)
+		return
+	}
+	if n != int64(wbuf2.Len()) {
+		t.Errorf("WriteTo() failed: expected written byte length: %d, got: %d", n, wbuf2.Len())
+	}
+	if !strings.Contains(wbuf2.String(), "Subject: THIS IS @ TEST") {
+		t.Errorf("WriteToSkipMiddleware failed. Unable to find encoded and upperchase subject")
+	}
+}
+
 // TestMsg_Write tests the Write() method of the Msg
 func TestMsg_Write(t *testing.T) {
 	m := NewMsg()