using Application.Helpers;

namespace Application.Tests;

[TestClass]
public sealed class KrxBackfillTests
{
    private static IReadOnlySet<DateOnly> NoHolidays => new HashSet<DateOnly>();

    [TestMethod]
    public async Task RunAsync_IteratesBusinessDays_RecentFirst_SkippingWeekends()
    {
        // 2025-01-06(월) ~ 2025-01-10(금) 은 평일 5일, 2025-01-11(토)/12(일) 은 주말.
        // endDate=일(12), startDate=토(11 하루 전 없음) → 창을 넓게 잡고 주말이 제외되는지 확인.
        var start = new DateOnly(2025, 1, 6);   // 월
        var end = new DateOnly(2025, 1, 12);    // 일
        var fetchedDays = new List<DateOnly>();

        var count = await KrxBackfill.RunAsync(
            existsForDate: (_, _) => Task.FromResult(false),
            fetchAndUpsertForDate: (day, _) => { fetchedDays.Add(day); return Task.CompletedTask; },
            startDate: start,
            endDate: end,
            holidays: NoHolidays,
            maxPerRun: 100,
            delayMs: 0,
            ct: CancellationToken.None);

        // 주말(11 토, 12 일) 제외 → 평일 5일 (10 금 → 6 월 순, recent-first)
        Assert.AreEqual(5, count);
        CollectionAssert.AreEqual(
            new[]
            {
                new DateOnly(2025, 1, 10),
                new DateOnly(2025, 1, 9),
                new DateOnly(2025, 1, 8),
                new DateOnly(2025, 1, 7),
                new DateOnly(2025, 1, 6)
            },
            fetchedDays,
            "endDate 부터 과거로(recent-first), 주말은 건너뛴다");
    }

    [TestMethod]
    public async Task RunAsync_SkipsHolidays()
    {
        var start = new DateOnly(2025, 1, 6);   // 월
        var end = new DateOnly(2025, 1, 10);    // 금
        var holidays = new HashSet<DateOnly> { new(2025, 1, 8) }; // 수 휴장
        var fetchedDays = new List<DateOnly>();

        var count = await KrxBackfill.RunAsync(
            existsForDate: (_, _) => Task.FromResult(false),
            fetchAndUpsertForDate: (day, _) => { fetchedDays.Add(day); return Task.CompletedTask; },
            startDate: start,
            endDate: end,
            holidays: holidays,
            maxPerRun: 100,
            delayMs: 0,
            ct: CancellationToken.None);

        Assert.AreEqual(4, count, "휴장일(8 수) 제외 → 4일");
        CollectionAssert.DoesNotContain(fetchedDays, new DateOnly(2025, 1, 8));
    }

    [TestMethod]
    public async Task RunAsync_SkipsAlreadyExistingDays_Resumable()
    {
        var start = new DateOnly(2025, 1, 6);   // 월
        var end = new DateOnly(2025, 1, 10);    // 금
        // 8 수, 9 목 은 이미 적재됨 → skip
        var existing = new HashSet<DateOnly> { new(2025, 1, 8), new(2025, 1, 9) };
        var fetchedDays = new List<DateOnly>();

        var count = await KrxBackfill.RunAsync(
            existsForDate: (day, _) => Task.FromResult(existing.Contains(day)),
            fetchAndUpsertForDate: (day, _) => { fetchedDays.Add(day); return Task.CompletedTask; },
            startDate: start,
            endDate: end,
            holidays: NoHolidays,
            maxPerRun: 100,
            delayMs: 0,
            ct: CancellationToken.None);

        Assert.AreEqual(3, count, "이미 적재된 2일 제외 → 3일 (resumable)");
        CollectionAssert.AreEqual(
            new[]
            {
                new DateOnly(2025, 1, 10),
                new DateOnly(2025, 1, 7),
                new DateOnly(2025, 1, 6)
            },
            fetchedDays);
    }

    [TestMethod]
    public async Task RunAsync_StopsAfterMaxPerRun()
    {
        // 넉넉한 창(3주) 에서 상한 3 으로 잘리는지
        var start = new DateOnly(2025, 1, 1);
        var end = new DateOnly(2025, 1, 21);
        var fetchedDays = new List<DateOnly>();

        var count = await KrxBackfill.RunAsync(
            existsForDate: (_, _) => Task.FromResult(false),
            fetchAndUpsertForDate: (day, _) => { fetchedDays.Add(day); return Task.CompletedTask; },
            startDate: start,
            endDate: end,
            holidays: NoHolidays,
            maxPerRun: 3,
            delayMs: 0,
            ct: CancellationToken.None);

        Assert.AreEqual(3, count, "maxPerRun 도달 시 즉시 멈춤");
        Assert.AreEqual(3, fetchedDays.Count);
        // recent-first: 21(화),20(월),17(금) — 18/19 는 주말
        CollectionAssert.AreEqual(
            new[]
            {
                new DateOnly(2025, 1, 21),
                new DateOnly(2025, 1, 20),
                new DateOnly(2025, 1, 17)
            },
            fetchedDays);
    }

    [TestMethod]
    public async Task RunAsync_MaxPerRunZeroOrNegative_FetchesNothing()
    {
        var fetched = 0;

        var count = await KrxBackfill.RunAsync(
            existsForDate: (_, _) => Task.FromResult(false),
            fetchAndUpsertForDate: (_, _) => { fetched++; return Task.CompletedTask; },
            startDate: new DateOnly(2025, 1, 1),
            endDate: new DateOnly(2025, 1, 31),
            holidays: NoHolidays,
            maxPerRun: 0,
            delayMs: 0,
            ct: CancellationToken.None);

        Assert.AreEqual(0, count);
        Assert.AreEqual(0, fetched, "maxPerRun<=0 이면 fetch 호출 자체가 없다");
    }

    [TestMethod]
    public async Task RunAsync_EmptyWindow_WhenStartAfterEnd_FetchesNothing()
    {
        var fetched = 0;

        var count = await KrxBackfill.RunAsync(
            existsForDate: (_, _) => Task.FromResult(false),
            fetchAndUpsertForDate: (_, _) => { fetched++; return Task.CompletedTask; },
            startDate: new DateOnly(2025, 2, 1),
            endDate: new DateOnly(2025, 1, 1), // start > end
            holidays: NoHolidays,
            maxPerRun: 100,
            delayMs: 0,
            ct: CancellationToken.None);

        Assert.AreEqual(0, count);
        Assert.AreEqual(0, fetched);
    }
}