package pagination

import (
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

type testItem struct {
	id        string
	createdAt time.Time
}

func TestPageByCursorReturnsNextCursorAndNextPage(t *testing.T) {
	now := time.Date(2026, 5, 13, 8, 0, 0, 0, time.UTC)
	items := []testItem{
		{id: "c", createdAt: now},
		{id: "b", createdAt: now.Add(-time.Minute)},
		{id: "a", createdAt: now.Add(-2 * time.Minute)},
	}
	key := func(item testItem) (time.Time, string) {
		return item.createdAt, item.id
	}

	firstPage, nextCursor, err := PageByCursor(items, 2, "", key)
	require.NoError(t, err)
	require.Len(t, firstPage, 2)
	require.NotEmpty(t, nextCursor)

	secondPage, nextCursor, err := PageByCursor(items, 2, nextCursor, key)
	require.NoError(t, err)
	require.Len(t, secondPage, 1)
	require.Empty(t, nextCursor)
	require.Equal(t, "a", secondPage[0].id)
}

func TestSortByKeyDescUsesIDAsTieBreaker(t *testing.T) {
	now := time.Date(2026, 5, 13, 8, 0, 0, 0, time.UTC)
	items := []testItem{
		{id: "a", createdAt: now},
		{id: "c", createdAt: now},
		{id: "b", createdAt: now},
	}

	SortByKeyDesc(items, func(item testItem) (time.Time, string) {
		return item.createdAt, item.id
	})

	require.Equal(t, []string{"c", "b", "a"}, []string{
		items[0].id,
		items[1].id,
		items[2].id,
	})
}