feat: mime/multipartutil: add NewPartEmpty(), PartsSet.AddMailBody()

Author: grokify

mime/multipartutil/part.go

@@ -34,6 +34,17 @@ type Part struct {
 	BodyEncodeBase64   bool
 }
 
+func NewPartEmpty(ct string) Part {
+	p := Part{
+		Type:      PartTypeRaw,
+		HeaderRaw: textproto.MIMEHeader{},
+	}
+	if ct = strings.TrimSpace(ct); ct != "" {
+		p.HeaderRaw[hum.HeaderContentType] = []string{ct}
+	}
+	return p
+}
+
 // HeaderBodyFilepath sets Content-Disposition and Content-Type.
 func (p Part) HeaderBodyFilepath() (textproto.MIMEHeader, []byte, error) {
 	header := textproto.MIMEHeader{}

mime/multipartutil/parts_set.go

@@ -5,11 +5,22 @@ type PartsSet struct {
 	Parts       []Part
 }
 
-func NewPartsSet() PartsSet {
-	return PartsSet{Parts: []Part{}}
+func NewPartsSet(ct string) PartsSet {
+	return PartsSet{
+		ContentType: ct,
+		Parts:       []Part{}}
 }
 
-func (ms PartsSet) Builder(close bool) (MultipartBuilder, error) {
+func (ps *PartsSet) AddMailBody(textBody, htmlBody []byte) error {
+	if p, err := NewPartAlternativeOrNot(textBody, htmlBody); err != nil {
+		return err
+	} else {
+		ps.Parts = append([]Part{p}, ps.Parts...)
+		return nil
+	}
+}
+
+func (ms *PartsSet) Builder(close bool) (MultipartBuilder, error) {
 	mb := NewMultipartBuilder()
 	if len(ms.Parts) == 0 {
 		err := mb.Close()
@@ -33,7 +44,7 @@ func (ms PartsSet) Builder(close bool) (MultipartBuilder, error) {
 
 // Part returns the MultipartSimple as a Part. This can be used for
 // creating parts such as `multipart/alternative`.
-func (ms PartsSet) Part() (Part, error) {
+func (ms *PartsSet) Part() (Part, error) {
 	ct, body, err := ms.Strings()
 	if err != nil {
 		return Part{}, err
@@ -47,12 +58,16 @@ func (ms PartsSet) Part() (Part, error) {
 	}
 }
 
-func (ms PartsSet) Strings() (ctHeader, body string, err error) {
-	mb, err := ms.Builder(true)
+func (ps *PartsSet) Strings() (ctHeader, body string, err error) {
+	if len(ps.Parts) == 0 {
+		return ps.ContentType, "", nil
+	}
+
+	mb, err := ps.Builder(true)
 	if err != nil {
 		return
 	}
-	ctHeader = mb.ContentType(ms.ContentType)
+	ctHeader = mb.ContentType(ps.ContentType)
 	body = mb.String()
 	return
 }