namespace HrynCo.Common.Tests;

using System.Collections.Concurrent;
using HrynCo.Common;
using FluentAssertions;
using Serilog;
using Serilog.Core;
using Serilog.Events;
using Xunit;

public sealed class ProfilerTests
{
    [Fact]
    public async Task MeasureExecutionAsync_ShouldReturnResultAndWriteStartAndEndEvents()
    {
        var sink = new CollectingSink();
        ILogger logger = new LoggerConfiguration()
            .MinimumLevel.Verbose()
            .WriteTo.Sink(sink)
            .CreateLogger();

        var profiler = new Profiler(logger);

        int result = await profiler.MeasureExecutionAsync(async () =>
        {
            await Task.Delay(1);
            return 42;
        }, "LoadItems");

        result.Should().Be(42);
        sink.Events.Count.Should().BeGreaterThan(1);
        sink.Events.Should().ContainSingle(e =>
            e.Level == LogEventLevel.Information
            && e.MessageTemplate.Text.Contains("Start", StringComparison.Ordinal)
            && e.Properties["BlockName"].ToString().Contains("LoadItems", StringComparison.Ordinal));
        sink.Events.Should().ContainSingle(e =>
            e.Level == LogEventLevel.Information
            && e.MessageTemplate.Text.Contains("End", StringComparison.Ordinal)
            && e.Properties["Measurements"].ToString().Contains("True", StringComparison.Ordinal));
    }

    [Fact]
    public async Task MeasureExecutionAsync_ActionOverload_ShouldInvokeAction()
    {
        var sink = new CollectingSink();
        ILogger logger = new LoggerConfiguration()
            .MinimumLevel.Verbose()
            .WriteTo.Sink(sink)
            .CreateLogger();

        var profiler = new Profiler(logger);
        bool invoked = false;

        await profiler.MeasureExecutionAsync(async () =>
        {
            invoked = true;
            await Task.CompletedTask;
        }, "ActionBlock");

        invoked.Should().BeTrue();
    }

    [Fact]
    public async Task MeasureExecutionAsync_ShouldLogErrorAndRethrow()
    {
        var sink = new CollectingSink();
        ILogger logger = new LoggerConfiguration()
            .MinimumLevel.Verbose()
            .WriteTo.Sink(sink)
            .CreateLogger();

        var profiler = new Profiler(logger);

        Func<Task> act = async () =>
        {
            await profiler.MeasureExecutionAsync<int>(() => throw new InvalidOperationException("boom"), "FailBlock");
        };

        await act.Should().ThrowAsync<InvalidOperationException>();
        sink.Events.Should().Contain(e =>
            e.Level == LogEventLevel.Error
            && e.MessageTemplate.Text.Contains("An error occurred", StringComparison.Ordinal));
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task MeasureExecutionAsync_WithCanceledToken_ShouldLogCancellationWithoutExceptionAndRethrow(bool actionOverload)
    {
        var sink = new CollectingSink();
        IProfiler profiler = CreateProfiler(sink);
        using var cancellation = new CancellationTokenSource();
        cancellation.Cancel();
        var exception = new OperationCanceledException(cancellation.Token);

        Func<Task> act = () => MeasureFailureAsync(profiler, actionOverload, exception, cancellation.Token);

        var assertion = await act.Should().ThrowAsync<OperationCanceledException>();
        assertion.Which.Should().BeSameAs(exception);
        sink.Events.Should().ContainSingle(e =>
            e.Level == LogEventLevel.Debug
            && e.Exception == null
            && e.MessageTemplate.Text == "{BlockName} - Canceled"
            && e.Properties["BlockName"].ToString() == "\"CanceledBlock\""
            && e.Properties["PerformanceLog"].ToString() == "True");
        sink.Events.Should().NotContain(e => e.Level == LogEventLevel.Error || e.Properties.ContainsKey("Measurements"));
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task MeasureExecutionAsync_WithCanceledToken_ShouldRecognizeTaskCanceledException(bool actionOverload)
    {
        var sink = new CollectingSink();
        IProfiler profiler = CreateProfiler(sink);
        using var cancellation = new CancellationTokenSource();
        cancellation.Cancel();
        var exception = new TaskCanceledException();

        Func<Task> act = () => MeasureFailureAsync(profiler, actionOverload, exception, cancellation.Token);

        var assertion = await act.Should().ThrowAsync<TaskCanceledException>();
        assertion.Which.Should().BeSameAs(exception);
        sink.Events.Should().ContainSingle(e => e.Level == LogEventLevel.Debug && e.Exception == null);
        sink.Events.Should().NotContain(e => e.Level == LogEventLevel.Error || e.Properties.ContainsKey("Measurements"));
    }

    [Theory]
    [InlineData(false, false)]
    [InlineData(false, true)]
    [InlineData(true, false)]
    [InlineData(true, true)]
    public async Task MeasureExecutionAsync_WithUncanceledToken_ShouldLogOperationCanceledExceptionAsError(bool actionOverload, bool tokenCanBeCanceled)
    {
        var sink = new CollectingSink();
        IProfiler profiler = CreateProfiler(sink);
        using var cancellation = new CancellationTokenSource();
        CancellationToken token = tokenCanBeCanceled ? cancellation.Token : CancellationToken.None;
        var exception = new OperationCanceledException();

        Func<Task> act = () => MeasureFailureAsync(profiler, actionOverload, exception, token);

        var assertion = await act.Should().ThrowAsync<OperationCanceledException>();
        assertion.Which.Should().BeSameAs(exception);
        sink.Events.Should().ContainSingle(e => e.Level == LogEventLevel.Error && ReferenceEquals(e.Exception, exception));
        sink.Events.Should().NotContain(e => e.Level == LogEventLevel.Debug || e.Properties.ContainsKey("Measurements"));
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task MeasureExecutionAsync_WithCanceledToken_ShouldKeepOtherExceptionsAsErrors(bool actionOverload)
    {
        var sink = new CollectingSink();
        IProfiler profiler = CreateProfiler(sink);
        using var cancellation = new CancellationTokenSource();
        cancellation.Cancel();
        var exception = new InvalidOperationException("boom");

        Func<Task> act = () => MeasureFailureAsync(profiler, actionOverload, exception, cancellation.Token);

        var assertion = await act.Should().ThrowAsync<InvalidOperationException>();
        assertion.Which.Should().BeSameAs(exception);
        sink.Events.Should().ContainSingle(e => e.Level == LogEventLevel.Error && ReferenceEquals(e.Exception, exception));
        sink.Events.Should().NotContain(e => e.Level == LogEventLevel.Debug || e.Properties.ContainsKey("Measurements"));
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task MeasureExecutionAsync_WithoutToken_ShouldKeepCancellationAsError(bool actionOverload)
    {
        var sink = new CollectingSink();
        IProfiler profiler = CreateProfiler(sink);
        using var cancellation = new CancellationTokenSource();
        cancellation.Cancel();
        var exception = new OperationCanceledException(cancellation.Token);

        Func<Task> act = () => actionOverload
            ? profiler.MeasureExecutionAsync(() => Task.FromException(exception), "LegacyBlock")
            : profiler.MeasureExecutionAsync(() => Task.FromException<int>(exception), "LegacyBlock");

        var assertion = await act.Should().ThrowAsync<OperationCanceledException>();
        assertion.Which.Should().BeSameAs(exception);
        sink.Events.Should().ContainSingle(e => e.Level == LogEventLevel.Error && ReferenceEquals(e.Exception, exception));
        sink.Events.Should().NotContain(e => e.Level == LogEventLevel.Debug || e.Properties.ContainsKey("Measurements"));
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task MeasureExecutionAsync_WithCanceledToken_ShouldAllowSuccessfulWork(bool actionOverload)
    {
        var sink = new CollectingSink();
        IProfiler profiler = CreateProfiler(sink);
        using var cancellation = new CancellationTokenSource();
        cancellation.Cancel();
        bool invoked = false;

        if (actionOverload)
        {
            await profiler.MeasureExecutionAsync(() =>
            {
                invoked = true;
                return Task.CompletedTask;
            }, "SuccessBlock", cancellation.Token);
            invoked.Should().BeTrue();
        }
        else
        {
            int result = await profiler.MeasureExecutionAsync(() => Task.FromResult(42), "SuccessBlock", cancellation.Token);
            result.Should().Be(42);
        }

        sink.Events.Should().ContainSingle(e => e.Level == LogEventLevel.Information && e.Properties.ContainsKey("Measurements"));
        sink.Events.Should().NotContain(e => e.Level == LogEventLevel.Error || e.Level == LogEventLevel.Debug);
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task MeasureExecutionAsync_WithToken_ShouldSupportLegacyInterfaceImplementations(bool actionOverload)
    {
        var legacyProfiler = new LegacyProfiler();
        IProfiler profiler = legacyProfiler;
        using var cancellation = new CancellationTokenSource();
        cancellation.Cancel();
        bool invoked = false;

        if (actionOverload)
        {
            await profiler.MeasureExecutionAsync(() =>
            {
                invoked = true;
                return Task.CompletedTask;
            }, "LegacyBlock", cancellation.Token);
            invoked.Should().BeTrue();
        }
        else
        {
            int result = await profiler.MeasureExecutionAsync(() => Task.FromResult(42), "LegacyBlock", cancellation.Token);
            result.Should().Be(42);
        }

        legacyProfiler.BlockName.Should().Be("LegacyBlock");
    }

    private sealed class LegacyProfiler : IProfiler
    {
        public string? BlockName { get; private set; }

        public Task<T> MeasureExecutionAsync<T>(Func<Task<T>> function, string blockName = "")
        {
            BlockName = blockName;
            return function();
        }

        public Task MeasureExecutionAsync(Func<Task> action, string blockName = "")
        {
            BlockName = blockName;
            return action();
        }
    }

    private static IProfiler CreateProfiler(CollectingSink sink)
    {
        return new Profiler(new LoggerConfiguration()
            .MinimumLevel.Verbose()
            .WriteTo.Sink(sink)
            .CreateLogger());
    }

    private static Task MeasureFailureAsync(IProfiler profiler, bool actionOverload, Exception exception, CancellationToken cancellationToken)
    {
        return actionOverload
            ? profiler.MeasureExecutionAsync(() => Task.FromException(exception), "CanceledBlock", cancellationToken)
            : profiler.MeasureExecutionAsync(() => Task.FromException<int>(exception), "CanceledBlock", cancellationToken);
    }

    private sealed class CollectingSink : ILogEventSink
    {
        public ConcurrentQueue<LogEvent> Events { get; } = new();

        public void Emit(LogEvent logEvent)
        {
            Events.Enqueue(logEvent);
        }
    }
}