Sync all IMAP folders

backend/04-imap-source.go

@@ -66,7 +66,21 @@ type imapSource struct {
 }
 
 func (s *imapSource) Folders() ([]Folder, error) {
-	return []Folder{{Name: "INBOX", Delim: "/"}}, nil
+	boxes, err := s.c.listMailboxes()
+	if err != nil {
+		return nil, err
+	}
+	folders := make([]Folder, 0, len(boxes))
+	for _, box := range boxes {
+		if hasIMAPAttr(box.Attrs, `\Noselect`) {
+			continue
+		}
+		folders = append(folders, Folder{Name: box.Name, Attrs: box.Attrs, Delim: box.Delim})
+	}
+	if len(folders) == 0 {
+		folders = append(folders, Folder{Name: "INBOX", Delim: "/"})
+	}
+	return folders, nil
 }
 
 func (s *imapSource) Fetch(folder string) ([]RawMessage, error) {
@@ -198,6 +212,110 @@ func (c *simpleIMAP) fetchAll() ([]RawMessage, error) {
 	}
 }
 
+type imapListMailbox struct {
+	Name  string
+	Attrs []string
+	Delim string
+}
+
+func (c *simpleIMAP) listMailboxes() ([]imapListMailbox, error) {
+	tag := c.nextTag()
+	if _, err := fmt.Fprintf(c.w, "%s LIST \"\" \"*\"\r\n", tag); err != nil {
+		return nil, err
+	}
+	if err := c.w.Flush(); err != nil {
+		return nil, err
+	}
+	var out []imapListMailbox
+	for {
+		line, err := c.r.ReadString('\n')
+		if err != nil {
+			return nil, err
+		}
+		if strings.HasPrefix(line, tag+" ") {
+			if strings.Contains(line, " OK") {
+				return out, nil
+			}
+			return out, fmt.Errorf("imap list failed: %s", strings.TrimSpace(line))
+		}
+		if !strings.HasPrefix(line, "* LIST ") {
+			continue
+		}
+		if box, ok := parseListMailbox(strings.TrimSpace(line)); ok {
+			out = append(out, box)
+		}
+	}
+}
+
+func parseListMailbox(line string) (imapListMailbox, bool) {
+	rest := strings.TrimSpace(strings.TrimPrefix(line, "* LIST "))
+	if !strings.HasPrefix(rest, "(") {
+		return imapListMailbox{}, false
+	}
+	endAttrs := strings.Index(rest, ")")
+	if endAttrs < 0 {
+		return imapListMailbox{}, false
+	}
+	attrs := strings.Fields(rest[1:endAttrs])
+	rest = strings.TrimSpace(rest[endAttrs+1:])
+	delim, next, ok := parseIMAPAtomOrQuoted(rest)
+	if !ok {
+		return imapListMailbox{}, false
+	}
+	if strings.EqualFold(delim, "NIL") {
+		delim = "/"
+	}
+	rest = strings.TrimSpace(rest[next:])
+	name, _, ok := parseIMAPAtomOrQuoted(rest)
+	if !ok || name == "" {
+		return imapListMailbox{}, false
+	}
+	return imapListMailbox{Name: name, Attrs: attrs, Delim: delim}, true
+}
+
+func parseIMAPAtomOrQuoted(s string) (string, int, bool) {
+	s = strings.TrimLeft(s, " \t")
+	trimmed := len(s)
+	if s == "" {
+		return "", 0, false
+	}
+	if s[0] != '"' {
+		end := strings.IndexAny(s, " \t\r\n")
+		if end < 0 {
+			end = len(s)
+		}
+		return s[:end], trimmed - len(s) + end, true
+	}
+	var b strings.Builder
+	escaped := false
+	for i := 1; i < len(s); i++ {
+		ch := s[i]
+		if escaped {
+			b.WriteByte(ch)
+			escaped = false
+			continue
+		}
+		if ch == '\\' {
+			escaped = true
+			continue
+		}
+		if ch == '"' {
+			return b.String(), trimmed - len(s) + i + 1, true
+		}
+		b.WriteByte(ch)
+	}
+	return "", 0, false
+}
+
+func hasIMAPAttr(attrs []string, want string) bool {
+	for _, attr := range attrs {
+		if strings.EqualFold(attr, want) {
+			return true
+		}
+	}
+	return false
+}
+
 func (c *simpleIMAP) appendMessage(folder string, m RawMessage) error {
 	tag := c.nextTag()
 	flags := ""