package imapx

import (
	"context"
	"fmt"
	"testing"
	"time"

	"github.com/emersion/go-imap/v2"
)

// seedInbox logs in as login/pass and APPENDs n minimal messages with unique
// Message-IDs into INBOX via a dedicated connection.
func seedInbox(t *testing.T, ep Endpoint, login, pass string, n int) {
	t.Helper()
	ctx := context.Background()

	c, err := Connect(ctx, ep)
	if err != nil {
		t.Fatalf("seedInbox connect: %v", err)
	}
	defer func() { _ = c.Logout().Wait() }()

	if err := c.Login(login, pass).Wait(); err != nil {
		t.Fatalf("seedInbox login: %v", err)
	}

	for i := 0; i < n; i++ {
		msg := fmt.Sprintf(
			"From: sender@localhost\r\nTo: %s\r\nSubject: seed %d\r\nMessage-Id: <seed-%d-%p@localhost>\r\n\r\nBody %d\r\n",
			login, i, i, &i, i,
		)
		buf := []byte(msg)
		appendCmd := c.Append("INBOX", int64(len(buf)), nil)
		if _, err := appendCmd.Write(buf); err != nil {
			t.Fatalf("seedInbox write %d: %v", i, err)
		}
		if err := appendCmd.Close(); err != nil {
			t.Fatalf("seedInbox close %d: %v", i, err)
		}
		if _, err := appendCmd.Wait(); err != nil {
			t.Fatalf("seedInbox append %d: %v", i, err)
		}
	}
}

// seedInboxWithDate APPENDs a single message with a given subject and a
// KNOWN IMAP internal date (via AppendOptions.Time), so the test can assert
// the date survives the copy instead of silently becoming "now" on dst.
func seedInboxWithDate(t *testing.T, ep Endpoint, login, pass, subject string, when time.Time) {
	t.Helper()
	ctx := context.Background()

	c, err := Connect(ctx, ep)
	if err != nil {
		t.Fatalf("seedInboxWithDate connect: %v", err)
	}
	defer func() { _ = c.Logout().Wait() }()

	if err := c.Login(login, pass).Wait(); err != nil {
		t.Fatalf("seedInboxWithDate login: %v", err)
	}

	msg := fmt.Sprintf(
		"From: sender@localhost\r\nTo: %s\r\nSubject: %s\r\nMessage-Id: <%s@localhost>\r\n\r\nBody\r\n",
		login, subject, subject,
	)
	buf := []byte(msg)
	appendCmd := c.Append("INBOX", int64(len(buf)), &imap.AppendOptions{Time: when})
	if _, err := appendCmd.Write(buf); err != nil {
		t.Fatalf("seedInboxWithDate write: %v", err)
	}
	if err := appendCmd.Close(); err != nil {
		t.Fatalf("seedInboxWithDate close: %v", err)
	}
	if _, err := appendCmd.Wait(); err != nil {
		t.Fatalf("seedInboxWithDate append: %v", err)
	}
}

// fetchInternalDateBySubject connects, selects INBOX and returns the
// InternalDate of the first message whose Envelope.Subject matches.
func fetchInternalDateBySubject(t *testing.T, ep Endpoint, login, pass, subject string) time.Time {
	t.Helper()
	ctx := context.Background()

	c, err := Connect(ctx, ep)
	if err != nil {
		t.Fatalf("fetchInternalDateBySubject connect: %v", err)
	}
	defer func() { _ = c.Logout().Wait() }()

	if err := c.Login(login, pass).Wait(); err != nil {
		t.Fatalf("fetchInternalDateBySubject login: %v", err)
	}

	sel, err := c.Select("INBOX", &imap.SelectOptions{ReadOnly: true}).Wait()
	if err != nil {
		t.Fatalf("fetchInternalDateBySubject select: %v", err)
	}
	if sel.NumMessages == 0 {
		t.Fatalf("fetchInternalDateBySubject: INBOX empty")
	}

	set := imap.SeqSet{imap.SeqRange{Start: 1, Stop: sel.NumMessages}}
	msgs, err := c.Fetch(set, &imap.FetchOptions{
		Envelope: true, InternalDate: true,
	}).Collect()
	if err != nil {
		t.Fatalf("fetchInternalDateBySubject fetch: %v", err)
	}

	for _, m := range msgs {
		if m.Envelope != nil && m.Envelope.Subject == subject {
			return m.InternalDate
		}
	}
	t.Fatalf("fetchInternalDateBySubject: subject %q not found among %d messages", subject, len(msgs))
	return time.Time{}
}

// TestCopyFolderPreservesInternalDate proves CopyFolder threads the source
// message's IMAP internal date through to APPEND on dst, instead of letting
// dst stamp it with "now" at APPEND time.
func TestCopyFolderPreservesInternalDate(t *testing.T) {
	ep := testEP(t)
	ctx := context.Background()

	const subject = "datecheck"
	knownTime := time.Date(2020, 1, 2, 3, 4, 5, 0, time.UTC)
	seedInboxWithDate(t, ep, "datesrc@localhost", "p", subject, knownTime)

	src, err := Connect(ctx, ep)
	if err != nil {
		t.Fatal(err)
	}
	defer func() { _ = src.Logout().Wait() }()
	if err := src.Login("datesrc@localhost", "p").Wait(); err != nil {
		t.Fatal(err)
	}

	dst, err := Connect(ctx, ep)
	if err != nil {
		t.Fatal(err)
	}
	defer func() { _ = dst.Logout().Wait() }()
	if err := dst.Login("datedst@localhost", "p").Wait(); err != nil {
		t.Fatal(err)
	}

	deps := CopyDeps{
		IsMigrated:   func(string) (bool, error) { return false, nil },
		MarkMigrated: func(_, _ string) error { return nil },
		OnProgress:   func(_, _ int) {},
	}

	r, err := CopyFolder(ctx, src, dst, "INBOX", "INBOX", deps)
	if err != nil {
		t.Fatalf("CopyFolder: %v", err)
	}
	if r.Copied != 1 {
		t.Fatalf("copied=%d want 1", r.Copied)
	}

	got := fetchInternalDateBySubject(t, ep, "datedst@localhost", "p", subject).UTC().Truncate(time.Second)
	want := knownTime.Truncate(time.Second)
	if !got.Equal(want) {
		t.Fatalf("internal date not preserved: got %v want %v", got, want)
	}
}

// Требует два ящика на greenmail. Первый запуск копирует N, второй — 0 (все skipped).
func TestCopyFolderIdempotent(t *testing.T) {
	ep := testEP(t) // plain greenmail
	ctx := context.Background()

	// подготовка: APPEND 2 письма в INBOX источника через отдельное соединение
	seedInbox(t, ep, "src@localhost", "p", 2)

	src, err := Connect(ctx, ep)
	if err != nil {
		t.Fatal(err)
	}
	defer func() { _ = src.Logout().Wait() }()
	if err := src.Login("src@localhost", "p").Wait(); err != nil {
		t.Fatal(err)
	}

	dst, err := Connect(ctx, ep)
	if err != nil {
		t.Fatal(err)
	}
	defer func() { _ = dst.Logout().Wait() }()
	if err := dst.Login("dst@localhost", "p").Wait(); err != nil {
		t.Fatal(err)
	}

	seen := map[string]bool{}
	deps := CopyDeps{
		IsMigrated:   func(k string) (bool, error) { return seen[k], nil },
		MarkMigrated: func(_, k string) error { seen[k] = true; return nil },
		OnProgress:   func(_, _ int) {},
	}

	r1, err := CopyFolder(ctx, src, dst, "INBOX", "INBOX", deps)
	if err != nil {
		t.Fatalf("run1: %v", err)
	}
	if r1.Copied != 2 {
		t.Fatalf("run1 copied=%d want 2", r1.Copied)
	}

	r2, err := CopyFolder(ctx, src, dst, "INBOX", "INBOX", deps)
	if err != nil {
		t.Fatalf("run2: %v", err)
	}
	if r2.Copied != 0 || r2.Skipped != 2 {
		t.Fatalf("run2 copied=%d skipped=%d want 0/2", r2.Copied, r2.Skipped)
	}
}