using Microsoft.Extensions.Logging;
using ZB.MOM.WW.MxGateway.Server.Workers;
using ZB.MOM.WW.MxGateway.Tests.TestSupport;

namespace ZB.MOM.WW.MxGateway.Tests.Gateway.Workers;

/// <summary>Protects bounded teardown, fault observation, and safe diagnostic output.</summary>
public sealed class FakeWorkerDiagnosticsTests
{
    /// <summary>Repeated gateway logs remain bounded and never format sensitive state or messages.</summary>
    [Fact]
    public void Log_WhenFaultsRepeat_ReportsOnlyBoundedMetadata()
    {
        using FakeWorkerDiagnostics diagnostics = new();
        List<string> output = [];
        diagnostics.SetOutput(output.Add);
        for (int i = 0; i < 32; i++)
        {
            diagnostics.Log(LogLevel.Warning, new EventId(1), "secret-command",
                new WorkerFrameProtocolException(WorkerFrameProtocolErrorCode.InvalidEnvelope, "secret-item"),
                (state, exception) => $"{state} {exception}");
        }

        Assert.NotEmpty(output);
        Assert.InRange(output.Count, 1, 16);
        Assert.All(output, line =>
        {
            Assert.Contains("type=WorkerFrameProtocolException", line);
            Assert.Contains("code=InvalidEnvelope", line);
            Assert.DoesNotContain("secret", line);
        });
    }

    /// <summary>A late fault is observed after timeout without calling the completed output sink.</summary>
    /// <returns>The asynchronous test operation.</returns>
    [Fact]
    public async Task DrainAsync_WhenWorkerOutlivesBudget_ObservesLateFaultWithoutLateOutput()
    {
        FakeWorkerDiagnostics diagnostics = new();
        List<string> output = [];
        diagnostics.SetOutput(output.Add);
        TaskCompletionSource worker = new(TaskCreationOptions.RunContinuationsAsynchronously);
        diagnostics.Track(worker.Task);
        await diagnostics.DrainAsync(TimeSpan.Zero);
        Assert.Contains(output, line => line.Contains("source=teardown") && line.Contains("type=TimeoutException"));
        int beforeFault = output.Count;
        worker.SetException(new WorkerFrameProtocolException(WorkerFrameProtocolErrorCode.InvalidEnvelope, "secret-item"));
        await diagnostics.DrainAsync(TimeSpan.FromSeconds(5));
        Assert.Equal(beforeFault, output.Count);
    }

    /// <summary>Expected cancellation does not add fault diagnostics.</summary>
    /// <returns>The asynchronous test operation.</returns>
    [Fact]
    public async Task DrainAsync_WhenWorkerIsCancelled_DoesNotReportFault()
    {
        FakeWorkerDiagnostics diagnostics = new();
        List<string> output = [];
        diagnostics.SetOutput(output.Add);
        diagnostics.Track(Task.FromCanceled(new CancellationToken(true)));
        await diagnostics.DrainAsync(TimeSpan.FromSeconds(5));
        Assert.Empty(output);
    }

    /// <summary>An unavailable output helper cannot fault the observer or replace the primary failure.</summary>
    /// <returns>The asynchronous test operation.</returns>
    [Fact]
    public async Task DrainAsync_WhenOutputThrows_PreservesPrimaryFailure()
    {
        InvalidOperationException primary = new("primary");
        FakeWorkerDiagnostics diagnostics = new();
        diagnostics.SetOutput(_ => throw new InvalidOperationException("completed output"));
        Exception? failure = await Record.ExceptionAsync(async () =>
        {
            try
            {
                throw primary;
            }
            finally
            {
                diagnostics.Track(Task.FromException(new WorkerFrameProtocolException(
                    WorkerFrameProtocolErrorCode.InvalidEnvelope, "secret-item")));
                await diagnostics.DrainAsync(TimeSpan.FromSeconds(5));
            }
        });
        Assert.Same(primary, failure);
    }
}