// Copyright (c) StellaOps. Licensed under the BUSL-1.1.

using FluentAssertions;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using Microsoft.Extensions.Time.Testing;
using Moq;
using StellaOps.Eventing.Models;
using StellaOps.Eventing.Storage;
using StellaOps.HybridLogicalClock;
using Xunit;

namespace StellaOps.Eventing.Tests;

[Trait("Category", "Unit")]
public sealed class TimelineEventEmitterTests
{
    private readonly FakeTimeProvider _timeProvider;
    private readonly Mock<IHybridLogicalClock> _hlcMock;
    private readonly InMemoryTimelineEventStore _eventStore;
    private readonly IOptions<EventingOptions> _options;
    private readonly TimelineEventEmitter _emitter;

    public TimelineEventEmitterTests()
    {
        _timeProvider = new FakeTimeProvider(new DateTimeOffset(2026, 1, 7, 12, 0, 0, TimeSpan.Zero));
        _hlcMock = new Mock<IHybridLogicalClock>();
        _eventStore = new InMemoryTimelineEventStore();
        _options = Options.Create(new EventingOptions
        {
            ServiceName = "TestService",
            EngineVersion = new EngineVersionRef("TestEngine", "1.0.0", "sha256:test")
        });

        _emitter = new TimelineEventEmitter(
            _hlcMock.Object,
            _timeProvider,
            _eventStore,
            _options,
            NullLogger<TimelineEventEmitter>.Instance);
    }

    private static HlcTimestamp CreateHlc(long physicalTime, int logicalCounter, string nodeId)
    {
        return new HlcTimestamp
        {
            PhysicalTime = physicalTime,
            LogicalCounter = logicalCounter,
            NodeId = nodeId
        };
    }

    [Fact]
    public async Task EmitAsync_StoresEventWithCorrectFields()
    {
        // Arrange
        var ct = TestContext.Current.CancellationToken;
        var correlationId = "scan-abc123";
        var kind = EventKinds.Enqueue;
        var payload = new { JobId = "job-1", Status = "pending" };
        var expectedHlc = CreateHlc(1704585600000, 0, "node1");

        _hlcMock.Setup(h => h.Tick()).Returns(expectedHlc);

        // Act
        var result = await _emitter.EmitAsync(correlationId, kind, payload, ct);

        // Assert
        result.Should().NotBeNull();
        result.CorrelationId.Should().Be(correlationId);
        result.Kind.Should().Be(kind);
        result.Service.Should().Be("TestService");
        result.THlc.Should().Be(expectedHlc);
        result.TsWall.Should().Be(_timeProvider.GetUtcNow());
        result.SchemaVersion.Should().Be(1);
        result.EngineVersion.EngineName.Should().Be("TestEngine");
        result.EngineVersion.Version.Should().Be("1.0.0");
        result.PayloadDigest.Should().NotBeEmpty();
        result.EventId.Should().HaveLength(32);
    }

    [Fact]
    public async Task EmitAsync_GeneratesDeterministicEventId()
    {
        // Arrange
        var ct = TestContext.Current.CancellationToken;
        var correlationId = "scan-abc123";
        var kind = EventKinds.Execute;
        var payload = new { Step = 1 };
        var hlc = CreateHlc(1704585600000, 0, "node1");

        _hlcMock.Setup(h => h.Tick()).Returns(hlc);

        // Act
        var result1 = await _emitter.EmitAsync(correlationId, kind, payload, ct);

        // Create a second emitter with same config
        var emitter2 = new TimelineEventEmitter(
            _hlcMock.Object,
            _timeProvider,
            new InMemoryTimelineEventStore(),
            _options,
            NullLogger<TimelineEventEmitter>.Instance);

        var result2 = await emitter2.EmitAsync(correlationId, kind, payload, ct);

        // Assert - Same inputs should produce same EventId
        result1.EventId.Should().Be(result2.EventId);
    }

    [Fact]
    public async Task EmitAsync_StoresEventInStore()
    {
        // Arrange
        var ct = TestContext.Current.CancellationToken;
        var correlationId = "scan-abc123";
        var hlc = CreateHlc(1704585600000, 0, "node1");
        _hlcMock.Setup(h => h.Tick()).Returns(hlc);

        // Act
        var emitted = await _emitter.EmitAsync(correlationId, EventKinds.Enqueue, new { Test = true }, ct);

        // Assert
        var stored = await _eventStore.GetByIdAsync(emitted.EventId, ct);
        stored.Should().NotBeNull();
        stored!.EventId.Should().Be(emitted.EventId);
    }

    [Fact]
    public async Task EmitBatchAsync_StoresAllEvents()
    {
        // Arrange
        var ct = TestContext.Current.CancellationToken;
        var hlcCounter = 0;
        _hlcMock.Setup(h => h.Tick())
            .Returns(() => CreateHlc(1704585600000, hlcCounter++, "node1"));

        var pendingEvents = new[]
        {
            new PendingEvent("scan-1", EventKinds.Enqueue, new { Step = 1 }),
            new PendingEvent("scan-1", EventKinds.Execute, new { Step = 2 }),
            new PendingEvent("scan-1", EventKinds.Complete, new { Step = 3 })
        };

        // Act
        var results = await _emitter.EmitBatchAsync(pendingEvents, ct);

        // Assert
        results.Should().HaveCount(3);
        results.Select(r => r.Kind).Should().BeEquivalentTo(
            new[] { EventKinds.Enqueue, EventKinds.Execute, EventKinds.Complete });

        var stored = _eventStore.GetAll();
        stored.Should().HaveCount(3);
    }

    [Fact]
    public async Task EmitBatchAsync_EmptyBatch_ReturnsEmptyList()
    {
        // Act
        var ct = TestContext.Current.CancellationToken;
        var results = await _emitter.EmitBatchAsync(Array.Empty<PendingEvent>(), ct);

        // Assert
        results.Should().BeEmpty();
    }

    [Fact]
    public async Task EmitAsync_IncludesPayloadDigest()
    {
        // Arrange
        var ct = TestContext.Current.CancellationToken;
        var hlc = CreateHlc(1704585600000, 0, "node1");
        _hlcMock.Setup(h => h.Tick()).Returns(hlc);

        // Act
        var result = await _emitter.EmitAsync("corr-1", EventKinds.Emit, new { Data = "test" }, ct);

        // Assert
        result.PayloadDigest.Should().NotBeNull();
        result.PayloadDigest.Should().HaveCount(32); // SHA-256
    }

    [Fact]
    public async Task EmitAsync_DifferentPayloads_DifferentDigests()
    {
        // Arrange
        var ct = TestContext.Current.CancellationToken;
        var hlcCounter = 0;
        _hlcMock.Setup(h => h.Tick())
            .Returns(() => CreateHlc(1704585600000, hlcCounter++, "node1"));

        // Act
        var result1 = await _emitter.EmitAsync("corr-1", EventKinds.Emit, new { Value = 1 }, ct);
        var result2 = await _emitter.EmitAsync("corr-1", EventKinds.Emit, new { Value = 2 }, ct);

        // Assert
        result1.PayloadDigest.Should().NotBeEquivalentTo(result2.PayloadDigest);
    }
}