using FluentAssertions;
using Marathon.Application.Abstractions;
using Marathon.Application.Configuration;
using Marathon.Application.UseCases;
using Marathon.Domain.Entities;
using Marathon.Domain.Enums;
using Marathon.Domain.ValueObjects;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using NSubstitute;
using NSubstitute.ExceptionExtensions;

namespace Marathon.Application.Tests.UseCases;

/// <summary>
/// Unit tests for <see cref="DetectAnomaliesUseCase"/> using NSubstitute mocks.
/// </summary>
public sealed class DetectAnomaliesUseCaseTests
{
    private readonly IEventRepository    _eventRepo    = Substitute.For<IEventRepository>();
    private readonly ISnapshotRepository _snapshotRepo = Substitute.For<ISnapshotRepository>();
    private readonly IAnomalyRepository  _anomalyRepo  = Substitute.For<IAnomalyRepository>();

    private static readonly TimeSpan MoscowOffset = TimeSpan.FromHours(3);
    private static readonly DateTimeOffset BaseTime =
        new(2026, 5, 10, 18, 0, 0, MoscowOffset);

    /// <summary>Default options matching appsettings.json.</summary>
    private static IOptions<AnomalyOptions> DefaultOptions(
        int gapSeconds   = 60,
        decimal threshold = 0.30m,
        int minSnapshots = 3) =>
        Options.Create(new AnomalyOptions
        {
            SuspensionGapSeconds    = gapSeconds,
            OddsFlipThreshold       = threshold,
            MinSnapshotCount        = minSnapshots,
            DetectionIntervalSeconds = 60,
        });

    private DetectAnomaliesUseCase CreateSut(IOptions<AnomalyOptions>? opts = null) =>
        new(_eventRepo, _snapshotRepo, _anomalyRepo,
            opts ?? DefaultOptions(),
            NullLogger<DetectAnomaliesUseCase>.Instance);

    // ── Helper: build a snapshot timeline with a clear flip ───────────────────

    private static IReadOnlyList<OddsSnapshot> BuildFlipTimeline(EventId eventId)
    {
        // 4 live snapshots: first two normal, then 90s gap (>60s threshold),
        // then two with flipped odds. Rates 1.3/4.0 → 4.0/1.3 produce a large flip score.
        static OddsSnapshot MakeSnap(EventId id, DateTimeOffset at, decimal r1, decimal r2) =>
            new(id, at, OddsSource.Live,
                new List<Bet>
                {
                    new(MatchScope.Instance, BetType.Win, Side.Side1, null, new OddsRate(r1)),
                    new(MatchScope.Instance, BetType.Win, Side.Side2, null, new OddsRate(r2)),
                });

        return new[]
        {
            MakeSnap(eventId, BaseTime,                  1.3m, 4.0m),
            MakeSnap(eventId, BaseTime.AddSeconds(30),   1.3m, 4.0m),
            MakeSnap(eventId, BaseTime.AddSeconds(120),  4.0m, 1.3m), // flipped — 90 s gap
            MakeSnap(eventId, BaseTime.AddSeconds(150),  4.0m, 1.3m),
        };
    }

    // ── Test 1: Iterates events, detects, and persists new anomalies ──────────

    [Fact]
    public async Task Should_PersistNewAnomalies_When_FlipDetectedForEvent()
    {
        // Arrange
        var eventId = new EventId("11111111");
        var ev      = TestFixtures.MakeEvent(eventId.Value);

        _eventRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(new[] { ev }.ToList().AsReadOnly());

        _snapshotRepo
            .ListByEventAsync(eventId, Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(),
                Arg.Any<CancellationToken>())
            .Returns(BuildFlipTimeline(eventId));

        // No existing anomalies → dedup will not filter anything.
        _anomalyRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(Array.Empty<Anomaly>().ToList().AsReadOnly());

        var sut = CreateSut();

        // Act
        var count = await sut.ExecuteAsync(CancellationToken.None);

        // Assert
        count.Should().Be(1, "one flip was detected");
        await _anomalyRepo.Received(1).AddAsync(Arg.Any<Anomaly>(), Arg.Any<CancellationToken>());
        await _anomalyRepo.Received(1).SaveChangesAsync(Arg.Any<CancellationToken>());
    }

    // ── Test 2: Deduplication — already-persisted anomaly is not re-added ─────

    [Fact]
    public async Task Should_SkipAlreadyPersistedAnomalies_When_DuplicateDetected()
    {
        // Arrange
        var eventId = new EventId("22222222");
        var ev      = TestFixtures.MakeEvent(eventId.Value);

        _eventRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(new[] { ev }.ToList().AsReadOnly());

        _snapshotRepo
            .ListByEventAsync(eventId, Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(),
                Arg.Any<CancellationToken>())
            .Returns(BuildFlipTimeline(eventId));

        // Existing anomaly with same EventId, Kind=SuspensionFlip, and DetectedAt ≈ now (within dedup window).
        var existingAnomaly = new Anomaly(
            Id:          Guid.NewGuid(),
            EventId:     eventId,
            DetectedAt:  DateTimeOffset.UtcNow.ToOffset(TimeSpan.FromHours(3)),
            Kind:        AnomalyKind.SuspensionFlip,
            Score:       0.5m,
            EvidenceJson: "{\"dummy\":true}");

        _anomalyRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(new[] { existingAnomaly }.ToList().AsReadOnly());

        var sut = CreateSut();

        // Act
        var count = await sut.ExecuteAsync(CancellationToken.None);

        // Assert
        count.Should().Be(0, "anomaly already exists — dedup prevents re-adding");
        await _anomalyRepo.DidNotReceive().AddAsync(Arg.Any<Anomaly>(), Arg.Any<CancellationToken>());
    }

    // ── Test 3: Per-event failure does not abort the cycle ────────────────────

    [Fact]
    public async Task Should_ContinueAfterPerEventFailure_And_ReturnPartialCount()
    {
        // Arrange: two events — first throws on snapshot load, second has a detectable flip.
        var ev1Id = new EventId("33333333");
        var ev2Id = new EventId("44444444");
        var ev1   = TestFixtures.MakeEvent(ev1Id.Value);
        var ev2   = TestFixtures.MakeEvent(ev2Id.Value);

        _eventRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(new[] { ev1, ev2 }.ToList().AsReadOnly());

        // Event 1 — snapshot load throws.
        _snapshotRepo
            .ListByEventAsync(ev1Id, Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(),
                Arg.Any<CancellationToken>())
            .ThrowsAsync(new InvalidOperationException("DB error for event 1"));

        // Event 2 — clean flip timeline.
        _snapshotRepo
            .ListByEventAsync(ev2Id, Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(),
                Arg.Any<CancellationToken>())
            .Returns(BuildFlipTimeline(ev2Id));

        _anomalyRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(Array.Empty<Anomaly>().ToList().AsReadOnly());

        var sut = CreateSut();

        // Act — must not throw despite event 1 failing.
        var act = async () => await sut.ExecuteAsync(CancellationToken.None);
        await act.Should().NotThrowAsync();

        var count = await sut.ExecuteAsync(CancellationToken.None);

        // Assert: event 2 succeeded — at least 1 anomaly persisted.
        count.Should().BeGreaterThan(0, "event 2 should succeed despite event 1 failure");
    }

    // ── Test 4: Returns count of new anomalies across multiple events ──────────

    [Fact]
    public async Task Should_ReturnTotalNewAnomalyCount_When_MultipleEventsHaveFlips()
    {
        // Arrange: two events, both with a flip.
        var ev1Id = new EventId("55555555");
        var ev2Id = new EventId("66666666");
        var ev1   = TestFixtures.MakeEvent(ev1Id.Value);
        var ev2   = TestFixtures.MakeEvent(ev2Id.Value);

        _eventRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(new[] { ev1, ev2 }.ToList().AsReadOnly());

        _snapshotRepo
            .ListByEventAsync(ev1Id, Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(),
                Arg.Any<CancellationToken>())
            .Returns(BuildFlipTimeline(ev1Id));

        _snapshotRepo
            .ListByEventAsync(ev2Id, Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(),
                Arg.Any<CancellationToken>())
            .Returns(BuildFlipTimeline(ev2Id));

        _anomalyRepo.ListAsync(Arg.Any<CancellationToken>())
            .Returns(Array.Empty<Anomaly>().ToList().AsReadOnly());

        var sut = CreateSut();

        // Act
        var count = await sut.ExecuteAsync(CancellationToken.None);

        // Assert
        count.Should().Be(2, "two events, one flip each → 2 new anomalies");
        await _anomalyRepo.Received(2).AddAsync(Arg.Any<Anomaly>(), Arg.Any<CancellationToken>());
    }
}