Correctly handle LISTMESSAGES and STATUS commands using SeqNum instead of UID

internal/store/maildir.go

@@ -16,7 +16,8 @@ type MaildirInterface interface {
 	CreateMaildir(*Maildir) error
 	FindMaildir(account Account, name string) (Maildir, error)
 	FindMaildirs(account Account) ([]Maildir, error)
-	FindMessagesInRange(m Maildir, start, end uint64) ([]Message, error)
+	FindMessagesInRangeBySeqNum(m Maildir, start, end uint64) ([]Message, error)
+	CountMessages(m Maildir) uint64
 }
 
 type Maildir struct {
@@ -41,6 +42,14 @@ func (m *Maildir) Header(key string) (mail.Header, error) {
 	return m.filesystem.Header(key)
 }
 
+func (m *Maildir) UIDValidity() uint64 {
+	return m.uids.UIDValidity()
+}
+
+func (m *Maildir) NextUID() uint64 {
+	return m.uids.NextUID()
+}
+
 func (c *concrete) CreateMaildir(m *Maildir) error {
 	if m.directory == "" {
 		m.directory = c.buildMaildirPath(m.Account, m.Name)
@@ -130,13 +139,14 @@ func (c *concrete) buildMaildirPath(account Account, parts ...string) string {
 	return filepath.Join(bits...)
 }
 
-func (c *concrete) FindMessagesInRange(m Maildir, start, end uint64) ([]Message, error) {
+func (c *concrete) FindMessagesInRangeBySeqNum(m Maildir, start, end uint64) ([]Message, error) {
 	var out []Message
-	entries := m.uids.EntriesInRange(start, end)
+	entries := m.uids.EntriesInRangeBySeqNum(start, end)
 
 	for _, entry := range entries {
 		msg := Message{
 			UID:     entry.UID,
+			SeqNum:  entry.SeqNum,
 			Maildir: m,
 			Key:     entry.Key(),
 		}
@@ -146,3 +156,7 @@ func (c *concrete) FindMessagesInRange(m Maildir, start, end uint64) ([]Message,
 
 	return out, nil
 }
+
+func (c *concrete) CountMessages(m Maildir) uint64 {
+	return m.uids.Count()
+}

internal/store/message.go

@@ -13,6 +13,7 @@ type Message struct {
 	Maildir Maildir // maildir.name
 
 	UID      uint64
+	SeqNum   uint64
 	Key      string
 	Data     io.ReadCloser
 	hdrCache mail.Header