Fix mailbox UI sorting and target layout

backend/04-imap-source.go

@@ -51,6 +51,7 @@ type SourceMailbox interface {
 	Folders() ([]Folder, error) // rekursiver Ordnerbaum
 	Count(folder string) (int, error)
 	Headers(folder string, limit, offset int) ([]MessageHeader, error)
+	AllHeaders(folder string) ([]MessageHeader, error)
 	FetchOne(folder string, uid uint32) (RawMessage, error)
 	Fetch(folder string, fn func(RawMessage) error) error // BODY[] FLAGS INTERNALDATE
 	Close() error
@@ -102,6 +103,10 @@ func (s *imapSource) Headers(folder string, limit, offset int) ([]MessageHeader,
 	return s.mailbox.fetchHeaders(folder, limit, offset)
 }
 
+func (s *imapSource) AllHeaders(folder string) ([]MessageHeader, error) {
+	return s.mailbox.fetchAllHeadersByUID(folder)
+}
+
 func (s *imapSource) FetchOne(folder string, uid uint32) (RawMessage, error) {
 	return s.mailbox.fetchOne(folder, uid)
 }
@@ -208,56 +213,25 @@ func (m *imapClientMailbox) count(folder string) (int, error) {
 }
 
 func (m *imapClientMailbox) fetchHeaders(folder string, limit, offset int) ([]MessageHeader, error) {
-	selected, err := m.c.Select(folder, &imap.SelectOptions{ReadOnly: true}).Wait()
-	if err != nil {
-		return nil, err
-	}
-	if selected.NumMessages == 0 {
-		return nil, nil
-	}
 	if limit <= 0 || limit > 200 {
 		limit = 200
 	}
 	if offset < 0 {
 		offset = 0
 	}
-	stop := int(selected.NumMessages) - offset
-	if stop <= 0 {
+	headers, err := m.fetchAllHeadersByUID(folder)
+	if err != nil {
+		return nil, err
+	}
+	sortMessageHeadersByDateDesc(headers)
+	if offset >= len(headers) {
 		return nil, nil
 	}
-	start := stop - limit + 1
-	if start < 1 {
-		start = 1
+	end := offset + limit
+	if end > len(headers) {
+		end = len(headers)
 	}
-
-	seqSet := imap.SeqSet{}
-	seqSet.AddRange(uint32(start), uint32(stop))
-	cmd := m.c.Fetch(seqSet, &imap.FetchOptions{
-		Envelope:     true,
-		Flags:        true,
-		InternalDate: true,
-		RFC822Size:   true,
-		UID:          true,
-	})
-	defer cmd.Close()
-
-	var out []MessageHeader
-	for {
-		data := cmd.Next()
-		if data == nil {
-			break
-		}
-		buf, err := data.Collect()
-		if err != nil {
-			return out, err
-		}
-		out = append(out, messageHeaderFromFetch(buf))
-	}
-	if err := cmd.Close(); err != nil {
-		return out, err
-	}
-	reverseHeaders(out)
-	return out, nil
+	return headers[offset:end], nil
 }
 
 func (m *imapClientMailbox) fetchAllHeadersByUID(folder string) ([]MessageHeader, error) {
@@ -463,6 +437,24 @@ func sortMessageHeadersByUID(headers []MessageHeader) {
 	})
 }
 
+func sortMessageHeadersByDateDesc(headers []MessageHeader) {
+	sort.SliceStable(headers, func(i, j int) bool {
+		di := headerSortDate(headers[i])
+		dj := headerSortDate(headers[j])
+		if !di.Equal(dj) {
+			return di.After(dj)
+		}
+		return headers[i].UID > headers[j].UID
+	})
+}
+
+func headerSortDate(h MessageHeader) time.Time {
+	if !h.Date.IsZero() {
+		return h.Date
+	}
+	return h.InternalDate
+}
+
 func messageIDFromFetch(buf *imapclient.FetchMessageBuffer, body []byte) string {
 	if buf != nil && buf.Envelope != nil && strings.TrimSpace(buf.Envelope.MessageID) != "" {
 		return normalizeMessageID(buf.Envelope.MessageID)