using System;
using NUnit.Framework;
using ShrinkEventBus;

[TestFixture, NonParallelizable]
public class EventBusAllocationTests
{
    private readonly struct ProbeEvent : IShrinkEvent { }

    [Test]
    public void PublicDiagnosticsDoesNotAllocatePerPostAfterWarmup()
    {
        using var host = new ShrinkEventBusHost();
        var bus = host.CreateBus(new ShrinkBusKey("allocation", "probe"), ShrinkBusOptions.Inline());
        var calls = 0;
        using var observer = EventBus.ObserveDiagnostics(_ => calls++);
        Measure(bus);
        var allocated = Measure(bus);
        Assert.That(calls, Is.EqualTo(20000));
        Assert.That(allocated, Is.Zero);
    }

    [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.NoInlining)]
    private static long Measure(IShrinkEventBus bus)
    {
        var before = GC.GetAllocatedBytesForCurrentThread();
        for (var i = 0; i < 10000; i++) bus.Post(new ProbeEvent());
        return GC.GetAllocatedBytesForCurrentThread() - before;
    }
}