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)
	}
}