Method Bytes

email.go:378–494

Bytes converts the Email object to a []byte representation, including all needed MIMEHeaders, boundaries, etc.

()

// Bytes converts the Email object to a []byte representation, including all needed MIMEHeaders, boundaries, etc.
func (e *Email) Bytes() ([]byte, error) {
	// TODO: better guess buffer size
	buff := bytes.NewBuffer(make([]byte, 0, 4096))

	headers, err := e.msgHeaders()
	if err != nil {
		return nil, err
	}

	htmlAttachments, otherAttachments := e.categorizeAttachments()
	if len(e.HTML) == 0 && len(htmlAttachments) > 0 {
		return nil, errors.New("there are HTML attachments, but no HTML body")
	}

	var (
		isMixed       = len(otherAttachments) > 0
		isAlternative = len(e.Text) > 0 && len(e.HTML) > 0
	)

	var w *multipart.Writer
	if isMixed || isAlternative {
		w = multipart.NewWriter(buff)
	}
	switch {
	case isMixed:
		headers.Set("Content-Type", "multipart/mixed;\r\n boundary="+w.Boundary())
	case isAlternative:
		headers.Set("Content-Type", "multipart/alternative;\r\n boundary="+w.Boundary())
	case len(e.HTML) > 0:
		headers.Set("Content-Type", "text/html; charset=UTF-8")
		headers.Set("Content-Transfer-Encoding", "quoted-printable")
	default:
		headers.Set("Content-Type", "text/plain; charset=UTF-8")
		headers.Set("Content-Transfer-Encoding", "quoted-printable")
	}
	headerToBytes(buff, headers)
	_, err = io.WriteString(buff, "\r\n")
	if err != nil {
		return nil, err
	}

	// Check to see if there is a Text or HTML field
	if len(e.Text) > 0 || len(e.HTML) > 0 {
		var subWriter *multipart.Writer

		if isMixed && isAlternative {
			// Create the multipart alternative part
			subWriter = multipart.NewWriter(buff)
			header := textproto.MIMEHeader{
				"Content-Type": {"multipart/alternative;\r\n boundary=" + subWriter.Boundary()},
			}
			if _, err := w.CreatePart(header); err != nil {
				return nil, err
			}
		} else {
			subWriter = w
		}
		// Create the body sections