Add optional zstd mbox archives

backend/06-mbox_test.go

@@ -0,0 +1,120 @@
+package backend
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/klauspost/compress/zstd"
+)
+
+func TestZstdMboxRoundTripAndIndexRead(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: "zstd",
+	}
+	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)
+	}
+
+	msg := RawMessage{
+		MessageID:    "zstd-test@example.com",
+		InternalDate: time.Date(2026, 7, 14, 10, 11, 12, 0, time.UTC),
+		Body: []byte("Message-ID: <zstd-test@example.com>\r\n" +
+			"From: Sender <sender@example.com>\r\n" +
+			"Subject: Zstd Test\r\n" +
+			"Date: Tue, 14 Jul 2026 10:11:12 +0000\r\n" +
+			"\r\n" +
+			"Hello\r\nFrom inside body\r\n"),
+	}
+	writer, err := NewMboxWriter(filepath.Join(Cfg.MboxRoot, "archive"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	info, err := writer.Append("INBOX", msg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := SaveMboxIndex(MboxIndexEntry{
+		AccountID:   account.ID,
+		Folder:      "INBOX",
+		MessageID:   msg.MessageID,
+		Subject:     info.Subject,
+		From:        info.From,
+		Date:        info.Date,
+		FileOffset:  info.FileOffset,
+		FrameLen:    info.FrameLen,
+		InnerOffset: info.InnerOffset,
+		InnerLen:    info.InnerLen,
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	compressed, err := os.ReadFile(info.Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	dec, err := zstd.NewReader(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dec.Close()
+	plain, err := dec.DecodeAll(compressed, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := mboxRecord(msg); !bytes.Equal(plain, want) {
+		t.Fatalf("zstd round-trip differs: got %d bytes, want %d", len(plain), len(want))
+	}
+
+	entries, err := ReadMboxList(info.Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entries) != 1 || entries[0].Index != 0 || entries[0].Subject != "Zstd Test" {
+		t.Fatalf("unexpected index list: %#v", entries)
+	}
+	raw, err := ReadMboxMessage(info.Path, entries[0].Index)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Contains(raw, []byte("Hello")) || bytes.Contains(raw, []byte(">From inside body")) {
+		t.Fatalf("unexpected message body: %q", raw)
+	}
+}