lib/email: export the field Fields in Header

By exporting the field, this allow the caller to filter or manage the
Header Fields manually.

2 files changed, 39 insertions, 38 deletions

diff --git a/lib/email/header.go b/lib/email/header.go
index 1e0eae03..10f84b86 100644
--- a/lib/email/header.go
+++ b/lib/email/header.go
@@ -12,14 +12,15 @@ import (
 	"strings"
 )
 
-// Header represent list of fields in message.
+// Header represent header of message.
+// It contains list of field in message.
 type Header struct {
-	// fields is ordered from top to bottom, the first field in message
+	// Fields is ordered from top to bottom, the first field in message
 	// header is equal to the first element in slice.
 	//
 	// We are not using map here it to prevent the header being reordered
 	// when packing the message back into raw format.
-	fields []*Field
+	Fields []*Field
 }
 
 // ParseHeader parse the raw header from top to bottom.
@@ -59,7 +60,7 @@ func ParseHeader(raw []byte) (hdr *Header, rest []byte, err error) {
 		if hdr == nil {
 			hdr = &Header{}
 		}
-		hdr.fields = append(hdr.fields, field)
+		hdr.Fields = append(hdr.Fields, field)
 	}
 	if len(rest) == 0 {
 		return hdr, rest, nil
@@ -75,7 +76,7 @@ func (hdr *Header) addMailboxes(ft FieldType, mailboxes []byte) (err error) {
 		f, field *Field
 	)
 
-	for _, f = range hdr.fields {
+	for _, f = range hdr.Fields {
 		if f.Type == ft {
 			field = f
 			break
@@ -85,7 +86,7 @@ func (hdr *Header) addMailboxes(ft FieldType, mailboxes []byte) (err error) {
 		field = &Field{
 			Type: ft,
 		}
-		hdr.fields = append(hdr.fields, field)
+		hdr.Fields = append(hdr.Fields, field)
 		field.setName([]byte(fieldNames[ft]))
 		field.setValue(mailboxes)
 		return field.unpack()
@@ -107,7 +108,7 @@ func (hdr *Header) Boundary() string {
 // ContentType return the unpacked value of field "Content-Type", or nil if no
 // field Content-Type exist or there is an error when unpacking.
 func (hdr *Header) ContentType() *ContentType {
-	for _, f := range hdr.fields {
+	for _, f := range hdr.Fields {
 		if f.Type != FieldTypeContentType {
 			continue
 		}
@@ -129,27 +130,27 @@ func (hdr *Header) ContentType() *ContentType {
 // For example, to get the second DKIM-Signature from the top, call it with
 // "n=2", but if no second DKIM-Signature it will return nil.
 func (hdr *Header) DKIM(n int) (dkimHeader *Header) {
-	if n == 0 || len(hdr.fields) == 0 {
+	if n == 0 || len(hdr.Fields) == 0 {
 		return nil
 	}
 
 	x := 0
-	for ; x < len(hdr.fields); x++ {
-		if hdr.fields[x].Type == FieldTypeDKIMSignature {
+	for ; x < len(hdr.Fields); x++ {
+		if hdr.Fields[x].Type == FieldTypeDKIMSignature {
 			n--
 			if n == 0 {
 				break
 			}
 		}
 	}
-	if x == len(hdr.fields) {
+	if x == len(hdr.Fields) {
 		return nil
 	}
 	dkimHeader = &Header{
-		fields: make([]*Field, 0, len(hdr.fields)-x),
+		Fields: make([]*Field, 0, len(hdr.Fields)-x),
 	}
-	for ; x < len(hdr.fields); x++ {
-		dkimHeader.fields = append(dkimHeader.fields, hdr.fields[x])
+	for ; x < len(hdr.Fields); x++ {
+		dkimHeader.Fields = append(dkimHeader.Fields, hdr.Fields[x])
 	}
 
 	return dkimHeader
@@ -158,9 +159,9 @@ func (hdr *Header) DKIM(n int) (dkimHeader *Header) {
 // Filter specific field type.  If multiple fields type exist it will
 // return all of them.
 func (hdr *Header) Filter(ft FieldType) (fields []*Field) {
-	for x := len(hdr.fields) - 1; x >= 0; x-- {
-		if hdr.fields[x].Type == ft {
-			fields = append(fields, hdr.fields[x])
+	for x := len(hdr.Fields) - 1; x >= 0; x-- {
+		if hdr.Fields[x].Type == ft {
+			fields = append(fields, hdr.Fields[x])
 		}
 	}
 	return
@@ -168,9 +169,9 @@ func (hdr *Header) Filter(ft FieldType) (fields []*Field) {
 
 // ID return the Message-ID or empty if not exist.
 func (hdr *Header) ID() string {
-	for x := len(hdr.fields) - 1; x >= 0; x-- {
-		if hdr.fields[x].Type == FieldTypeMessageID {
-			return hdr.fields[x].oriValue
+	for x := len(hdr.Fields) - 1; x >= 0; x-- {
+		if hdr.Fields[x].Type == FieldTypeMessageID {
+			return hdr.Fields[x].oriValue
 		}
 	}
 	return ``
@@ -178,14 +179,14 @@ func (hdr *Header) ID() string {
 
 // PushTop put the field at the top of header.
 func (hdr *Header) PushTop(f *Field) {
-	hdr.fields = append([]*Field{f}, hdr.fields...)
+	hdr.Fields = append([]*Field{f}, hdr.Fields...)
 }
 
 // Relaxed canonicalize the header using "relaxed" algorithm and return it.
 func (hdr *Header) Relaxed() []byte {
 	var bb bytes.Buffer
 
-	for _, f := range hdr.fields {
+	for _, f := range hdr.Fields {
 		if len(f.Name) > 0 && len(f.Value) > 0 {
 			bb.Write(f.Relaxed())
 		}
@@ -213,13 +214,13 @@ func (hdr *Header) Set(ft FieldType, value []byte) (err error) {
 		return fmt.Errorf("Set: %w", err)
 	}
 
-	for x, f = range hdr.fields {
+	for x, f = range hdr.Fields {
 		if f.Type == ft {
-			hdr.fields[x] = field
+			hdr.Fields[x] = field
 			return nil
 		}
 	}
-	hdr.fields = append(hdr.fields, field)
+	hdr.Fields = append(hdr.Fields, field)
 	return nil
 }
 
@@ -227,7 +228,7 @@ func (hdr *Header) Set(ft FieldType, value []byte) (err error) {
 func (hdr *Header) Simple() []byte {
 	var bb bytes.Buffer
 
-	for _, f := range hdr.fields {
+	for _, f := range hdr.Fields {
 		if len(f.oriName) > 0 && len(f.oriValue) > 0 {
 			bb.WriteString(f.oriName)
 			bb.WriteByte(':')
@@ -240,10 +241,10 @@ func (hdr *Header) Simple() []byte {
 
 // popByName remove the field where the name match from header.
 func (hdr *Header) popByName(name string) (f *Field) {
-	for x := len(hdr.fields) - 1; x >= 0; x-- {
-		if strings.EqualFold(hdr.fields[x].Name, name) {
-			f = hdr.fields[x]
-			hdr.fields = append(hdr.fields[:x], hdr.fields[x+1:]...)
+	for x := len(hdr.Fields) - 1; x >= 0; x-- {
+		if strings.EqualFold(hdr.Fields[x].Name, name) {
+			f = hdr.Fields[x]
+			hdr.Fields = append(hdr.Fields[:x], hdr.Fields[x+1:]...)
 		}
 	}
 	return f
@@ -276,7 +277,7 @@ func (hdr *Header) WriteTo(w io.Writer) (n int64, err error) {
 		f *Field
 		m int
 	)
-	for _, f = range hdr.fields {
+	for _, f = range hdr.Fields {
 		switch f.Type {
 		case FieldTypeContentType:
 			m, err = fmt.Fprintf(w, "%s: %s\r\n", f.Name, f.contentType.String())
diff --git a/lib/email/message.go b/lib/email/message.go
index a3028267..e2570947 100644
--- a/lib/email/message.go
+++ b/lib/email/message.go
@@ -212,9 +212,9 @@ func (msg *Message) DKIMSign(pk *rsa.PrivateKey, sig *dkim.Signature) (err error
 	}
 
 	subHeader := &Header{
-		fields: make([]*Field, len(msg.Header.fields)),
+		Fields: make([]*Field, len(msg.Header.Fields)),
 	}
-	copy(subHeader.fields, msg.Header.fields)
+	copy(subHeader.Fields, msg.Header.Fields)
 
 	hh, _ := sig.Hash(msg.CanonHeader(subHeader, dkimField))
 
@@ -247,12 +247,12 @@ func (msg *Message) DKIMVerify() (*dkim.Status, error) {
 
 	// Only process the first DKIM-Signature for now.
 	subHeader := msg.Header.DKIM(1)
-	if subHeader == nil || len(subHeader.fields) == 0 {
+	if subHeader == nil || len(subHeader.Fields) == 0 {
 		msg.dkimStatus.Type = dkim.StatusNoSignature
 		return msg.dkimStatus, nil
 	}
 
-	sig, err := dkim.Parse([]byte(subHeader.fields[0].Value))
+	sig, err := dkim.Parse([]byte(subHeader.Fields[0].Value))
 
 	if sig != nil && len(sig.SDID) > 0 {
 		msg.dkimStatus.SDID = libbytes.Copy(sig.SDID)
@@ -303,7 +303,7 @@ func (msg *Message) DKIMVerify() (*dkim.Status, error) {
 		return nil, err
 	}
 
-	canonHeader := msg.CanonHeader(subHeader, subHeader.fields[0])
+	canonHeader := msg.CanonHeader(subHeader, subHeader.Fields[0])
 	hh, _ := sig.Hash(canonHeader)
 
 	err = sig.Verify(key, hh)
@@ -636,9 +636,9 @@ func (msg *Message) setDKIMHeaders(sig *dkim.Signature) {
 		return
 	}
 
-	sig.Headers = make([][]byte, 0, len(msg.Header.fields))
+	sig.Headers = make([][]byte, 0, len(msg.Header.Fields))
 
-	for _, f := range msg.Header.fields {
+	for _, f := range msg.Header.Fields {
 		sig.Headers = append(sig.Headers, []byte(f.Name))
 	}
 }