add inline (embedded) images support

go-pkgz · Apr 24, 2022 · f81e515 · f81e515
1 parent df53159
commit f81e515
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Showing 3 changed files with 125 additions and 20 deletions.
diff --git a/README.md b/README.md
@@ -11,7 +11,10 @@ Usage example:
 ```go
 client := email.NewSender("localhost", email.ContentType("text/html"), email.Auth("user", "pass"))
 err := client.Send("<html>some content, foo bar</html>", 
-	email.Params{From: "[email protected]", To: []string{"[email protected]"}, Subject: "Hello world!", Attachments: []string{"/path/to/file1.txt", "/path/to/file2.txt"}})
+	email.Params{From: "[email protected]", To: []string{"[email protected]"}, Subject: "Hello world!", 
+		Attachments: []string{"/path/to/file1.txt", "/path/to/file2.txt"}, 
+		InlineImages: []string{"/path/to/image1.png", "/path/to/image2.png"},
+	})
 ```
 
 ## options
@@ -40,10 +43,11 @@ To send email user need to create a sender first and then use `Send` method. The
 - parameters (`email.Params`)
     ```go
     type Params struct {
-        From        string        // From email field
-        To          []string      // From email field
-        Subject     string        // Email subject
-        Attachments []string      // Attachments
+        From         string        // From email field
+        To           []string      // From email field
+        Subject      string        // Email subject
+        Attachments  []string      // Attachments
+        InlineImages []string      // Embedding directly to email body. Autogenerated Content-Id (cid) equals to file name
     }
     ```
 

diff --git a/email.go b/email.go
@@ -41,10 +41,11 @@ type Sender struct {
 
 // Params contains all user-defined parameters to send emails
 type Params struct {
-	From        string   // From email field
-	To          []string // From email field
-	Subject     string   // Email subject
-	Attachments []string // Attachments path
+	From         string   // From email field
+	To           []string // From email field
+	Subject      string   // Email subject
+	Attachments  []string // Attachments path
+	InlineImages []string // InlineImages images path
 }
 
 // Logger is used to log errors and debug messages
@@ -206,21 +207,29 @@ func (em *Sender) buildMessage(text string, params Params) (message string, err
 	message = addHeader(message, "Subject", params.Subject)
 
 	withAttachments := len(params.Attachments) > 0
+	withInlineImg := len(params.InlineImages) > 0
 
-	if em.contentType != "" || withAttachments {
+	if em.contentType != "" || withAttachments || withInlineImg {
 		message = addHeader(message, "MIME-version", "1.0")
 	}
 
 	message = addHeader(message, "Date", em.timeNow().Format(time.RFC1123Z))
 
 	buff := &bytes.Buffer{}
 	qp := quotedprintable.NewWriter(buff)
-	mp := multipart.NewWriter(buff)
-	boundary := mp.Boundary()
+	mpMixed := multipart.NewWriter(buff)
+	boundaryMixed := mpMixed.Boundary()
+	mpRelated := multipart.NewWriter(buff)
+	boundaryRelated := mpRelated.Boundary()
 
 	if withAttachments {
 		message = addHeader(message, "Content-Type", fmt.Sprintf("multipart/mixed; boundary=%q\r\n\r\n%s\r",
-			boundary, "--"+boundary))
+			boundaryMixed, "--"+boundaryMixed))
+	}
+
+	if withInlineImg {
+		message = addHeader(message, "Content-Type", fmt.Sprintf("multipart/related; boundary=%q\r\n\r\n%s\r",
+			boundaryRelated, "--"+boundaryRelated))
 	}
 
 	if em.contentType != "" {
@@ -233,9 +242,16 @@ func (em *Sender) buildMessage(text string, params Params) (message string, err
 		return "", fmt.Errorf("failed to write body: %w", err)
 	}
 
+	if withInlineImg {
+		buff.WriteString("\r\n\r\n")
+		if err := em.writeFiles(mpRelated, params.InlineImages, "inline"); err != nil {
+			return "", fmt.Errorf("failed to write inline images: %w", err)
+		}
+	}
+
 	if withAttachments {
 		buff.WriteString("\r\n\r\n")
-		if err := em.writeAttachments(mp, params.Attachments); err != nil {
+		if err := em.writeFiles(mpMixed, params.Attachments, "attachment"); err != nil {
 			return "", fmt.Errorf("failed to write attachments: %w", err)
 		}
 	}
@@ -256,8 +272,8 @@ func (em *Sender) writeBody(wc io.WriteCloser, text string) error {
 	return nil
 }
 
-func (em *Sender) writeAttachments(mp *multipart.Writer, attachments []string) error {
-	for _, attachment := range attachments {
+func (em *Sender) writeFiles(mp *multipart.Writer, files []string, disposition string) error {
+	for _, attachment := range files {
 		file, err := os.Open(filepath.Clean(attachment))
 		if err != nil {
 			return err
@@ -276,7 +292,14 @@ func (em *Sender) writeAttachments(mp *multipart.Writer, attachments []string) e
 		header := textproto.MIMEHeader{}
 		header.Set("Content-Type", http.DetectContentType(fTypeBuff)+"; name=\""+fName+"\"")
 		header.Set("Content-Transfer-Encoding", "base64")
-		header.Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", fName))
+
+		switch disposition {
+		case "attachment":
+			header.Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", fName))
+		case "inline":
+			header.Set("Content-Disposition", fmt.Sprintf("inline; filename=%q", fName))
+			header.Set("Content-ID", fmt.Sprintf("<%s>", fName))
+		}
 
 		writer, err := mp.CreatePart(header)
 		if err != nil {

diff --git a/email_test.go b/email_test.go
@@ -383,12 +383,88 @@ func TestEmail_buildMessageWithMIMEAndWrongAttachments(t *testing.T) {
 	require.Equal(t, "", msg)
 }
 
+func TestEmail_buildMessageWithMIMEAndInlineImages(t *testing.T) {
+	l := &mocks.LoggerMock{LogfFunc: func(format string, args ...interface{}) {
+		fmt.Printf(format, args...)
+		fmt.Printf("\n")
+	}}
+
+	e := NewSender("localhost", ContentType("text/html"),
+		Port(2525),
+		Log(l))
+
+	msg, err := e.buildMessage("<div>this is a test mail with inline images</div><div><img src=\"cid:image.jpg\"></div>\n", Params{
+		From:         "[email protected]",
+		To:           []string{"[email protected]"},
+		Subject:      "test email with attachments",
+		InlineImages: []string{"testdata/image.jpg"},
+	})
+	require.NoError(t, err)
+	assert.Contains(t, msg, "MIME-version: 1.0", msg)
+	assert.Contains(t, msg, "Content-Type", "multipart/related; boundary=", msg)
+	assert.Contains(t, msg, "Content-Disposition: inline; filename=\"image.jpg\"", msg)
+	assert.Contains(t, msg, "Content-Id: <image.jpg>", msg)
+	assert.Contains(t, msg, "Content-Transfer-Encoding: base64", msg)
+	fData, err := os.ReadFile("testdata/image.jpg")
+	require.NoError(t, err)
+
+	b := make([]byte, base64.StdEncoding.EncodedLen(len(fData)))
+	base64.StdEncoding.Encode(b, fData)
+	assert.Contains(t, msg, string(b), msg)
+}
+
+func TestEmail_buildMessageWithMIMEAndAttachmentsAndInlineImages(t *testing.T) {
+	l := &mocks.LoggerMock{LogfFunc: func(format string, args ...interface{}) {
+		fmt.Printf(format, args...)
+		fmt.Printf("\n")
+	}}
+
+	e := NewSender("localhost", ContentType("text/html"),
+		Port(2525),
+		Log(l))
+
+	msg, err := e.buildMessage("<div>this is a test mail with inline images</div><div><img src=\"cid:image.jpg\"></div>\n", Params{
+		From:         "[email protected]",
+		To:           []string{"[email protected]"},
+		Subject:      "test email with attachments",
+		Attachments:  []string{"testdata/1.txt", "testdata/2.txt", "testdata/image.jpg"},
+		InlineImages: []string{"testdata/image.jpg"},
+	})
+	require.NoError(t, err)
+	assert.Contains(t, msg, "MIME-version: 1.0", msg)
+	assert.Contains(t, msg, "Content-Type", "multipart/mixed; boundary=", msg)
+	assert.Contains(t, msg, "Content-Disposition: attachment; filename=\"1.txt\"", msg)
+	assert.Contains(t, msg, "Content-Disposition: attachment; filename=\"2.txt\"", msg)
+	assert.Contains(t, msg, "Content-Disposition: attachment; filename=\"image.jpg\"", msg)
+	assert.Contains(t, msg, "Content-Type", "multipart/related; boundary=", msg)
+	assert.Contains(t, msg, "Content-Disposition: inline; filename=\"image.jpg\"", msg)
+	assert.Contains(t, msg, "Content-Id: <image.jpg>", msg)
+	assert.Contains(t, msg, "Content-Transfer-Encoding: base64", msg)
+
+	fData1, err := os.ReadFile("testdata/1.txt")
+	require.NoError(t, err)
+	fData2, err := os.ReadFile("testdata/2.txt")
+	require.NoError(t, err)
+	fData3, err := os.ReadFile("testdata/image.jpg")
+	require.NoError(t, err)
+
+	b1 := make([]byte, base64.StdEncoding.EncodedLen(len(fData1)))
+	base64.StdEncoding.Encode(b1, fData1)
+	b2 := make([]byte, base64.StdEncoding.EncodedLen(len(fData2)))
+	base64.StdEncoding.Encode(b2, fData2)
+	b3 := make([]byte, base64.StdEncoding.EncodedLen(len(fData3)))
+	base64.StdEncoding.Encode(b3, fData3)
+	assert.Contains(t, msg, string(b1), msg)
+	assert.Contains(t, msg, string(b2), msg)
+	assert.Contains(t, msg, string(b3), msg)
+}
+
 func TestWriteAttachmentsFailed(t *testing.T) {
 
 	e := NewSender("localhost", ContentType("text/html"))
 	wc := &fakeWriterCloser{fail: true}
 	mp := multipart.NewWriter(wc)
-	err := e.writeAttachments(mp, []string{"testdata/1.txt"})
+	err := e.writeFiles(mp, []string{"testdata/1.txt"}, "attachment")
 	require.Error(t, err)
 }
 
@@ -410,9 +486,11 @@ func TestWriteBodyFail(t *testing.T) {
 // uncomment to debug with real smtp server
 // func TestSendIntegration(t *testing.T) {
 //	client := NewSender("localhost", ContentType("text/html"), Port(2525))
-//	err := client.Send("<html>some content, foo bar</html>",
+//	err := client.Send("<html><div>some content, foo bar</div>\n<div><img src=\"cid:image.jpg\"/>\n</div></html>",
 //		Params{From: "[email protected]", To: []string{"[email protected]"}, Subject: "Hello world!",
-//			Attachments: []string{"testdata/1.txt", "testdata/2.txt", "testdata/image.jpg"}})
+//			Attachments: []string{"testdata/1.txt", "testdata/2.txt", "testdata/image.jpg"},
+//			InlineImages: []string{"testdata/image.jpg"},
+//		})
 //	require.NoError(t, err)
 //}