Fix archive reindex and add target dedup

backend/02-database.go

@@ -132,6 +132,12 @@ func ConnectDB(initDB bool) error {
 			inner_len INTEGER NOT NULL,
 			UNIQUE(account_id, folder, message_id)
 		)`,
+		`CREATE TABLE IF NOT EXISTS mbox_index_state(
+			account_id INTEGER NOT NULL,
+			folder TEXT NOT NULL,
+			indexed_bytes INTEGER NOT NULL DEFAULT 0,
+			UNIQUE(account_id, folder)
+		)`,
 		`CREATE TABLE IF NOT EXISTS jobs(
 			id INTEGER PRIMARY KEY AUTOINCREMENT,
 			account_id INTEGER NOT NULL REFERENCES accounts(id) ON DELETE CASCADE,
@@ -442,6 +448,23 @@ func DeleteAccount(name string) error {
 	return err
 }
 
+func FolderMap(accountID int64) (map[string]string, error) {
+	rows, err := DB.Query(`SELECT src_folder, dst_folder FROM folder_map WHERE account_id=?`, accountID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := map[string]string{}
+	for rows.Next() {
+		var src, dst string
+		if err := rows.Scan(&src, &dst); err != nil {
+			return nil, err
+		}
+		out[src] = dst
+	}
+	return out, rows.Err()
+}
+
 func ListArchiveMailboxes() ([]string, error) {
 	rows, err := DB.Query(`SELECT name FROM archive_mailboxes ORDER BY lower(name), name`)
 	if err != nil {
@@ -544,6 +567,64 @@ func SaveMboxIndex(e MboxIndexEntry) error {
 	return err
 }
 
+func ReplaceMboxIndex(accountID int64, folder string, entries []MboxIndexEntry, indexedBytes int64) error {
+	if DB == nil || accountID == 0 {
+		return nil
+	}
+	tx, err := DB.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+	if _, err := tx.Exec(`DELETE FROM mbox_index WHERE account_id=? AND folder=?`, accountID, folder); err != nil {
+		return err
+	}
+	for i, entry := range entries {
+		entry.AccountID = accountID
+		entry.Folder = folder
+		entry.Seq = i
+		if entry.MessageID == "" {
+			continue
+		}
+		if _, err := tx.Exec(`INSERT INTO mbox_index(account_id, folder, seq, message_id, subject, from_addr, date, file_offset, frame_len, inner_offset, inner_len)
+			VALUES(?,?,?,?,?,?,?,?,?,?,?)`,
+			entry.AccountID, entry.Folder, entry.Seq, entry.MessageID, entry.Subject, entry.From, entry.Date,
+			entry.FileOffset, entry.FrameLen, entry.InnerOffset, entry.InnerLen); err != nil {
+			return err
+		}
+	}
+	if _, err := tx.Exec(`INSERT INTO mbox_index_state(account_id, folder, indexed_bytes)
+		VALUES(?,?,?)
+		ON CONFLICT(account_id, folder) DO UPDATE SET indexed_bytes=excluded.indexed_bytes`,
+		accountID, folder, indexedBytes); err != nil {
+		return err
+	}
+	return tx.Commit()
+}
+
+func UpdateMboxIndexState(accountID int64, folder string, indexedBytes int64) error {
+	if DB == nil || accountID == 0 {
+		return nil
+	}
+	_, err := DB.Exec(`INSERT INTO mbox_index_state(account_id, folder, indexed_bytes)
+		VALUES(?,?,?)
+		ON CONFLICT(account_id, folder) DO UPDATE SET indexed_bytes=excluded.indexed_bytes`,
+		accountID, folder, indexedBytes)
+	return err
+}
+
+func MboxIndexedBytes(accountID int64, folder string) (int64, error) {
+	if DB == nil || accountID == 0 {
+		return 0, sql.ErrNoRows
+	}
+	var n int64
+	err := DB.QueryRow(`SELECT indexed_bytes FROM mbox_index_state WHERE account_id=? AND folder=?`, accountID, folder).Scan(&n)
+	if errors.Is(err, sql.ErrNoRows) {
+		return 0, nil
+	}
+	return n, err
+}
+
 func ListMboxIndex(accountID int64, folder string) ([]MboxIndexEntry, error) {
 	if DB == nil || accountID == 0 {
 		return nil, sql.ErrNoRows

backend/05-imap-target.go

@@ -18,6 +18,7 @@ type TargetMailbox interface {
 	Append(folder string, m RawMessage) error // mit m.Flags und m.InternalDate
 	Headers(folder string, limit, offset int) ([]MessageHeader, error)
 	FetchOne(folder string, uid uint32) (RawMessage, error)
+	DeleteUIDs(folder string, uids []uint32) error
 	Close() error
 }
 
@@ -129,6 +130,32 @@ func (t *imapTarget) FetchOne(folder string, uid uint32) (RawMessage, error) {
 	return t.mailbox.fetchOne(folder, uid)
 }
 
+func (t *imapTarget) DeleteUIDs(folder string, uids []uint32) error {
+	if len(uids) == 0 {
+		return nil
+	}
+	if _, err := t.mailbox.c.Select(folder, nil).Wait(); err != nil {
+		return err
+	}
+	uidSet := imap.UIDSetNum(uint32sToUIDs(uids)...)
+	flags := &imap.StoreFlags{Op: imap.StoreFlagsAdd, Silent: true, Flags: []imap.Flag{imap.FlagDeleted}}
+	if err := t.mailbox.c.Store(uidSet, flags, nil).Close(); err != nil {
+		return err
+	}
+	_, err := t.mailbox.c.UIDExpunge(uidSet).Collect()
+	return err
+}
+
 func (t *imapTarget) Close() error {
 	return t.mailbox.Close()
 }
+
+func uint32sToUIDs(values []uint32) []imap.UID {
+	out := make([]imap.UID, 0, len(values))
+	for _, value := range values {
+		if value != 0 {
+			out = append(out, imap.UID(value))
+		}
+	}
+	return out
+}

backend/06-mbox.go

@@ -114,6 +114,11 @@ func mboxRecord(m RawMessage) []byte {
 
 func mboxAppendInfoFromMessage(m RawMessage, record []byte) MboxAppendInfo {
 	info := MboxAppendInfo{InnerLen: int64(len(record))}
+	parts := splitMboxRecordsWithOffsets(record)
+	if len(parts) > 0 {
+		info.InnerOffset = parts[0].Offset
+		info.InnerLen = int64(len(parts[0].Message))
+	}
 	msg, err := mail.ReadMessage(bytes.NewReader(m.Body))
 	if err != nil {
 		return info
@@ -137,6 +142,9 @@ type MboxEntry struct {
 // ReadMboxList parst die Kopfzeilen aller Mails einer mbox-Datei (fuer die
 // Nachrichtenliste). ReadMboxMessage liefert eine einzelne Mail als Rohtext.
 func ReadMboxList(path string) ([]MboxEntry, error) {
+	if err := EnsureMboxIndexed(path); err != nil {
+		return nil, err
+	}
 	if entries, ok := readMboxListFromIndex(path); ok {
 		return entries, nil
 	}
@@ -162,6 +170,9 @@ func ReadMboxList(path string) ([]MboxEntry, error) {
 }
 
 func ReadMboxMessage(path string, index int) ([]byte, error) {
+	if err := EnsureMboxIndexed(path); err != nil {
+		return nil, err
+	}
 	if raw, ok, err := readMboxMessageFromIndex(path, index); ok || err != nil {
 		return raw, err
 	}
@@ -194,6 +205,229 @@ func readMboxMessages(path string) ([][]byte, error) {
 	return readMboxMessagesBytes(b), nil
 }
 
+func EnsureMboxIndexed(path string) error {
+	accountID, folder, ok := mboxIndexContext(path)
+	if !ok {
+		return nil
+	}
+	info, err := os.Stat(path)
+	if err != nil {
+		return err
+	}
+	indexed, err := MboxIndexedBytes(accountID, folder)
+	if err != nil {
+		return err
+	}
+	if indexed == info.Size() {
+		return nil
+	}
+	return ReindexMboxFile(accountID, folder, path)
+}
+
+func ReindexMboxFile(accountID int64, folder, path string) error {
+	info, err := os.Stat(path)
+	if err != nil {
+		return err
+	}
+	var entries []MboxIndexEntry
+	if strings.HasSuffix(strings.ToLower(path), ".zst") {
+		entries, err = reindexZstdMbox(path)
+	} else {
+		entries, err = reindexPlainMbox(path)
+	}
+	if err != nil {
+		return err
+	}
+	return ReplaceMboxIndex(accountID, folder, entries, info.Size())
+}
+
+func ReindexArchives(name string) error {
+	name = strings.TrimSpace(name)
+	if name == "" {
+		return fmt.Errorf("reindex ziel fehlt")
+	}
+	accounts, err := ListAccounts()
+	if err != nil {
+		return err
+	}
+	matched := 0
+	for _, account := range accounts {
+		archive := accountMboxDir(account)
+		if archive == "" {
+			continue
+		}
+		if name != "all" && !strings.EqualFold(name, account.Name) && !strings.EqualFold(name, archive) {
+			continue
+		}
+		if err := reindexAccountArchive(account); err != nil {
+			return err
+		}
+		matched++
+	}
+	if matched == 0 {
+		return fmt.Errorf("kein Konto/Archiv fuer reindex %q gefunden", name)
+	}
+	return nil
+}
+
+func reindexAccountArchive(account Account) error {
+	dir := filepath.Join(Cfg.MboxRoot, accountMboxDir(account))
+	for _, path := range archiveMboxPaths(dir) {
+		folder := folderNameFromMboxPath(path)
+		if folder == "" {
+			continue
+		}
+		if err := ReindexMboxFile(account.ID, folder, path); err != nil {
+			return fmt.Errorf("%s %s: %w", account.Name, folder, err)
+		}
+	}
+	return nil
+}
+
+func reindexPlainMbox(path string) ([]MboxIndexEntry, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	var out []MboxIndexEntry
+	for _, part := range splitMboxRecordsWithOffsets(b) {
+		entry := indexEntryFromMboxRecord(part.Message, part.Offset, int64(part.Length), 0, int64(part.Length))
+		if entry.MessageID != "" {
+			out = append(out, entry)
+		}
+	}
+	return out, nil
+}
+
+func reindexZstdMbox(path string) ([]MboxIndexEntry, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	dec, err := zstd.NewReader(nil)
+	if err != nil {
+		return nil, err
+	}
+	defer dec.Close()
+	var out []MboxIndexEntry
+	for _, frame := range splitZstdFrames(b) {
+		record, err := dec.DecodeAll(frame.Data, nil)
+		if err != nil {
+			return nil, err
+		}
+		for _, part := range splitMboxRecordsWithOffsets(record) {
+			entry := indexEntryFromMboxRecord(part.Message, frame.Offset, int64(frame.Length), part.Offset, int64(len(part.Message)))
+			if entry.MessageID != "" {
+				out = append(out, entry)
+			}
+		}
+	}
+	return out, nil
+}
+
+type mboxRecordPart struct {
+	Offset  int64
+	Length  int
+	Message []byte
+}
+
+func splitMboxRecordsWithOffsets(b []byte) []mboxRecordPart {
+	normalized := bytes.ReplaceAll(b, []byte("\r\n"), []byte("\n"))
+	lines := bytes.SplitAfter(normalized, []byte("\n"))
+	var out []mboxRecordPart
+	var cur bytes.Buffer
+	var curStart int64
+	var pos int64
+	inMsg := false
+	for _, lineWithNL := range lines {
+		line := bytes.TrimSuffix(lineWithNL, []byte("\n"))
+		if bytes.HasPrefix(line, []byte("From ")) {
+			if inMsg && cur.Len() > 0 {
+				msg := bytes.TrimRight(cur.Bytes(), "\n")
+				out = append(out, mboxRecordPart{Offset: curStart, Length: int(pos - curStart), Message: append([]byte(nil), msg...)})
+				cur.Reset()
+			}
+			inMsg = true
+			pos += int64(len(lineWithNL))
+			curStart = pos
+			continue
+		}
+		if inMsg {
+			if bytes.HasPrefix(line, []byte(">From ")) {
+				line = line[1:]
+			}
+			_, _ = cur.Write(line)
+			_ = cur.WriteByte('\n')
+		}
+		pos += int64(len(lineWithNL))
+	}
+	if inMsg && cur.Len() > 0 {
+		msg := bytes.TrimRight(cur.Bytes(), "\n")
+		out = append(out, mboxRecordPart{Offset: curStart, Length: int(pos - curStart), Message: append([]byte(nil), msg...)})
+	}
+	return out
+}
+
+type zstdFramePart struct {
+	Offset int64
+	Length int
+	Data   []byte
+}
+
+func splitZstdFrames(b []byte) []zstdFramePart {
+	magic := []byte{0x28, 0xb5, 0x2f, 0xfd}
+	var starts []int
+	for i := 0; i <= len(b)-len(magic); i++ {
+		if bytes.Equal(b[i:i+len(magic)], magic) {
+			starts = append(starts, i)
+		}
+	}
+	if len(starts) == 0 {
+		return nil
+	}
+	out := make([]zstdFramePart, 0, len(starts))
+	for i, start := range starts {
+		end := len(b)
+		if i+1 < len(starts) {
+			end = starts[i+1]
+		}
+		out = append(out, zstdFramePart{Offset: int64(start), Length: end - start, Data: b[start:end]})
+	}
+	return out
+}
+
+func indexEntryFromMboxRecord(raw []byte, fileOffset, frameLen, innerOffset, innerLen int64) MboxIndexEntry {
+	entry := MboxIndexEntry{FileOffset: fileOffset, FrameLen: frameLen, InnerOffset: innerOffset, InnerLen: innerLen}
+	msg, err := mail.ReadMessage(bytes.NewReader(raw))
+	if err != nil {
+		return entry
+	}
+	entry.MessageID = normalizeMessageID(msg.Header.Get("Message-ID"))
+	if entry.MessageID == "" {
+		entry.MessageID = messageID(raw)
+	}
+	entry.Subject = decodeHeader(msg.Header.Get("Subject"))
+	entry.From = decodeHeader(msg.Header.Get("From"))
+	entry.Date = decodeHeader(msg.Header.Get("Date"))
+	return entry
+}
+
+func unescapeMboxMessage(raw []byte) []byte {
+	raw = bytes.ReplaceAll(raw, []byte("\r\n"), []byte("\n"))
+	lines := bytes.Split(raw, []byte("\n"))
+	var b bytes.Buffer
+	for i, line := range lines {
+		if i > 0 {
+			_ = b.WriteByte('\n')
+		}
+		if bytes.HasPrefix(line, []byte(">From ")) {
+			line = line[1:]
+		}
+		_, _ = b.Write(line)
+	}
+	return bytes.TrimRight(b.Bytes(), "\n")
+}
+
 func readMboxMessagesBytes(b []byte) [][]byte {
 	b = bytes.ReplaceAll(b, []byte("\r\n"), []byte("\n"))
 	lines := bytes.Split(b, []byte("\n"))
@@ -278,11 +512,12 @@ func readMboxMessageFromIndex(path string, index int) ([]byte, bool, error) {
 	if err != nil {
 		return nil, true, err
 	}
-	msgs := readMboxMessagesBytes(record)
-	if len(msgs) == 0 {
+	start := entry.InnerOffset
+	end := entry.InnerOffset + entry.InnerLen
+	if start < 0 || end > int64(len(record)) || start >= end {
 		return nil, true, fmt.Errorf("message index out of range")
 	}
-	return msgs[0], true, nil
+	return unescapeMboxMessage(record[start:end]), true, nil
 }
 
 func mboxIndexContext(path string) (int64, string, bool) {

backend/06-mbox_test.go

@@ -118,3 +118,100 @@ func TestZstdMboxRoundTripAndIndexRead(t *testing.T) {
 		t.Fatalf("unexpected message body: %q", raw)
 	}
 }
+
+func TestPlainMboxPartialIndexIsRebuiltBeforeList(t *testing.T) {
+	oldCfg, oldDB := Cfg, DB
+	root := t.TempDir()
+	t.Cleanup(func() {
+		if DB != nil {
+			_ = DB.Close()
+		}
+		Cfg, DB = oldCfg, oldDB
+	})
+
+	Cfg = Config{
+		DBPath:          filepath.Join(root, "mail-graveyard.db"),
+		MboxRoot:        filepath.Join(root, "backup"),
+		MboxCompression: "none",
+	}
+	if err := ConnectDB(true); err != nil {
+		t.Fatal(err)
+	}
+	if err := SaveArchiveMailbox("archive"); err != nil {
+		t.Fatal(err)
+	}
+	if err := SaveAccount(Account{
+		Name:        "test-account",
+		SrcHost:     "source.example",
+		SrcPort:     993,
+		SrcSecurity: "tls",
+		SrcUser:     "source@example.com",
+		SrcPass:     "x",
+		DstHost:     "target.example",
+		DstPort:     993,
+		DstSecurity: "tls",
+		DstUser:     "target@example.com",
+		DstPass:     "x",
+		MboxDir:     "archive",
+		Active:      true,
+	}); err != nil {
+		t.Fatal(err)
+	}
+	account, err := GetAccount("test-account")
+	if err != nil {
+		t.Fatal(err)
+	}
+	writer, err := NewMboxWriter(filepath.Join(Cfg.MboxRoot, "archive"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	first := testRawMessage("first@example.com", "First")
+	firstInfo, err := writer.Append("INBOX", first)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := SaveMboxIndex(MboxIndexEntry{
+		AccountID:   account.ID,
+		Folder:      "INBOX",
+		MessageID:   first.MessageID,
+		Subject:     firstInfo.Subject,
+		From:        firstInfo.From,
+		Date:        firstInfo.Date,
+		FileOffset:  firstInfo.FileOffset,
+		FrameLen:    firstInfo.FrameLen,
+		InnerOffset: firstInfo.InnerOffset,
+		InnerLen:    firstInfo.InnerLen,
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := UpdateMboxIndexState(account.ID, "INBOX", firstInfo.FileOffset+firstInfo.FrameLen); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := writer.Append("INBOX", testRawMessage("second@example.com", "Second")); err != nil {
+		t.Fatal(err)
+	}
+
+	entries, err := ReadMboxList(firstInfo.Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entries) != 2 {
+		t.Fatalf("expected rebuilt full list with 2 entries, got %#v", entries)
+	}
+	if entries[0].Subject != "First" || entries[1].Subject != "Second" {
+		t.Fatalf("unexpected entries after reindex: %#v", entries)
+	}
+}
+
+func testRawMessage(id, subject string) RawMessage {
+	return RawMessage{
+		MessageID:    id,
+		InternalDate: time.Date(2026, 7, 14, 10, 11, 12, 0, time.UTC),
+		Body: []byte("Message-ID: <" + id + ">\r\n" +
+			"From: Sender <sender@example.com>\r\n" +
+			"Subject: " + subject + "\r\n" +
+			"Date: Tue, 14 Jul 2026 10:11:12 +0000\r\n" +
+			"\r\n" +
+			"Hello\r\n"),
+	}
+}

backend/07-migrate.go

@@ -114,12 +114,17 @@ func migrateAccount(a Account, selectedFolders map[string]bool) error {
 		_ = finishJob(jobID, 0, 0, 1, "error")
 		return err
 	}
+	folderMap, err := FolderMap(a.ID)
+	if err != nil {
+		_ = finishJob(jobID, 0, 0, 1, "error")
+		return err
+	}
 	total, done, errs := 0, 0, 0
 	for _, folder := range folders {
 		if len(selectedFolders) > 0 && !selectedFolders[folder.Name] {
 			continue
 		}
-		dstFolder := MapSourceToTarget(folder.Name, folder.Attrs, folder.Delim, dst.Delim(), targets, "")
+		dstFolder := MapSourceToTarget(folder.Name, folder.Attrs, folder.Delim, dst.Delim(), targets, folderMap[folder.Name])
 		if dstFolder == "" {
 			dstFolder = folder.Name
 		}
@@ -173,6 +178,12 @@ func migrateAccount(a Account, selectedFolders map[string]bool) error {
 				log.Printf("%s %s mbox index error %s: %v", a.Name, folder.Name, m.MessageID, err)
 				return nil
 			}
+			if err := UpdateMboxIndexState(a.ID, folder.Name, appendInfo.FileOffset+appendInfo.FrameLen); err != nil {
+				errs++
+				folderErrs++
+				log.Printf("%s %s mbox index state error %s: %v", a.Name, folder.Name, m.MessageID, err)
+				return nil
+			}
 			if err := MarkCopied(a.ID, folder.Name, m.MessageID); err != nil {
 				errs++
 				folderErrs++

backend/13-target-dedup.go

@@ -0,0 +1,142 @@
+package backend
+
+import (
+	"fmt"
+	"log"
+	"sort"
+	"strings"
+)
+
+type TargetDedupReport struct {
+	Account       string
+	Apply         bool
+	Folders       int
+	Groups        int
+	ExtraCopies   int
+	WithoutID     int
+	Deleted       int
+	FolderReports []TargetDedupFolderReport
+}
+
+type TargetDedupFolderReport struct {
+	Folder      string
+	Groups      int
+	ExtraCopies int
+	WithoutID   int
+	Deletes     []TargetDedupDelete
+}
+
+type TargetDedupDelete struct {
+	UID       uint32
+	MessageID string
+}
+
+func DedupTarget(name string, folders []string, apply bool) (TargetDedupReport, error) {
+	a, err := GetAccount(name)
+	if err != nil {
+		return TargetDedupReport{}, err
+	}
+	dst, err := OpenIMAPTarget(a)
+	if err != nil {
+		return TargetDedupReport{}, err
+	}
+	defer dst.Close()
+	allFolders, err := dst.Folders()
+	if err != nil {
+		return TargetDedupReport{}, err
+	}
+	selected := selectedFolderSet(folders)
+	report := TargetDedupReport{Account: name, Apply: apply}
+	for _, folder := range allFolders {
+		if len(selected) > 0 && !selected[folder.Name] {
+			continue
+		}
+		folderReport, err := dedupTargetFolder(dst, folder.Name, apply)
+		if err != nil {
+			return report, err
+		}
+		report.Folders++
+		report.Groups += folderReport.Groups
+		report.ExtraCopies += folderReport.ExtraCopies
+		report.WithoutID += folderReport.WithoutID
+		if apply {
+			report.Deleted += len(folderReport.Deletes)
+		}
+		report.FolderReports = append(report.FolderReports, folderReport)
+	}
+	log.Printf("target dedup %s apply=%v folders=%d groups=%d extra=%d candidates=%d deleted=%d without_id=%d",
+		report.Account, report.Apply, report.Folders, report.Groups, report.ExtraCopies, report.ExtraCopies, report.Deleted, report.WithoutID)
+	return report, nil
+}
+
+func dedupTargetFolder(dst TargetMailbox, folder string, apply bool) (TargetDedupFolderReport, error) {
+	report := TargetDedupFolderReport{Folder: folder}
+	byID := map[string][]uint32{}
+	for offset := 0; ; offset += mailboxListLimit {
+		headers, err := dst.Headers(folder, mailboxListLimit, offset)
+		if err != nil {
+			return report, fmt.Errorf("%s headers: %w", folder, err)
+		}
+		if len(headers) == 0 {
+			break
+		}
+		for _, header := range headers {
+			id := normalizeMessageID(header.MessageID)
+			if id == "" {
+				report.WithoutID++
+				continue
+			}
+			byID[id] = append(byID[id], header.UID)
+		}
+	}
+	var deleteUIDs []uint32
+	for id, uids := range byID {
+		if len(uids) < 2 {
+			continue
+		}
+		sort.Slice(uids, func(i, j int) bool { return uids[i] < uids[j] })
+		report.Groups++
+		report.ExtraCopies += len(uids) - 1
+		for _, uid := range uids[1:] {
+			report.Deletes = append(report.Deletes, TargetDedupDelete{UID: uid, MessageID: id})
+			deleteUIDs = append(deleteUIDs, uid)
+		}
+	}
+	sort.Slice(report.Deletes, func(i, j int) bool {
+		if report.Deletes[i].MessageID == report.Deletes[j].MessageID {
+			return report.Deletes[i].UID < report.Deletes[j].UID
+		}
+		return strings.Compare(report.Deletes[i].MessageID, report.Deletes[j].MessageID) < 0
+	})
+	if apply && len(deleteUIDs) > 0 {
+		sort.Slice(deleteUIDs, func(i, j int) bool { return deleteUIDs[i] < deleteUIDs[j] })
+		for _, del := range report.Deletes {
+			log.Printf("target dedup delete folder=%s uid=%d message_id=%s", folder, del.UID, del.MessageID)
+		}
+		if err := dst.DeleteUIDs(folder, deleteUIDs); err != nil {
+			return report, fmt.Errorf("%s delete uids: %w", folder, err)
+		}
+	}
+	if report.Groups > 0 || report.WithoutID > 0 {
+		log.Printf("target dedup folder=%s groups=%d extra=%d without_id=%d apply=%v", folder, report.Groups, report.ExtraCopies, report.WithoutID, apply)
+	}
+	return report, nil
+}
+
+func LogTargetDedupReport(report TargetDedupReport) {
+	mode := "DRY-RUN"
+	if report.Apply {
+		mode = "APPLY"
+	}
+	log.Printf("target dedup report %s account=%s folders=%d groups=%d extra=%d candidates=%d deleted=%d without_id=%d",
+		mode, report.Account, report.Folders, report.Groups, report.ExtraCopies, report.ExtraCopies, report.Deleted, report.WithoutID)
+	for _, folder := range report.FolderReports {
+		if folder.Groups == 0 && folder.WithoutID == 0 {
+			continue
+		}
+		log.Printf("target dedup report folder=%s groups=%d extra=%d without_id=%d", folder.Folder, folder.Groups, folder.ExtraCopies, folder.WithoutID)
+		for _, del := range folder.Deletes {
+			log.Printf("target dedup report candidate folder=%s uid=%d message_id=%s", folder.Folder, del.UID, del.MessageID)
+		}
+	}
+}