Fix archive reindex and add target dedup

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"),
+	}
+}