// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Linq.Expressions;
using System.Reflection;
using Aspire.Hosting.Lifecycle;
 
namespace Aspire.Hosting.Tests;
 
[Trait("Partition", "5")]
public class AtsEventingExportsTests
{
    [Fact]
    public void TryAddEventingSubscriber_AllowsDistinctCallbacks()
    {
        var builder = DistributedApplication.CreateBuilder([]);
        var method = typeof(DistributedApplication).Assembly
            .GetType("Aspire.Hosting.Ats.EventingExports", throwOnError: true)!
            .GetMethod("TryAddEventingSubscriber", BindingFlags.Public | BindingFlags.Static)!;
        var callbackSubscriberType = method.DeclaringType!.GetNestedType("CallbackEventingSubscriber", BindingFlags.NonPublic)!;
 
        var firstSubscriber = CreateCallback(method.GetParameters()[1].ParameterType);
        var secondSubscriber = CreateCallback(method.GetParameters()[1].ParameterType);
 
        method.Invoke(null, [builder, firstSubscriber]);
        method.Invoke(null, [builder, firstSubscriber]);
        method.Invoke(null, [builder, secondSubscriber]);
 
        var subscribers = builder.Services
            .Where(descriptor => descriptor.ServiceType == typeof(IDistributedApplicationEventingSubscriber) &&
                                 descriptor.ImplementationInstance?.GetType() == callbackSubscriberType)
            .Select(descriptor => descriptor.ImplementationInstance)
            .ToList();
 
        Assert.Equal(2, subscribers.Count);
    }
 
    private static Delegate CreateCallback(Type delegateType)
    {
        var contextType = delegateType.GenericTypeArguments[0];
        var contextParameter = Expression.Parameter(contextType, "context");
        var completedTask = Expression.Property(null, typeof(Task).GetProperty(nameof(Task.CompletedTask))!);
 
        return Expression.Lambda(delegateType, completedTask, contextParameter).Compile();
    }
}