// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using MQTTnet.Internal;

namespace MQTTnet.Tests.Internal;

// ReSharper disable InconsistentNaming
[TestClass]
public sealed class AsyncEvent_Tests
{
    int _testEventAsyncCount;

    [TestMethod]
    public async Task Attach_and_Detach_Sync_And_Async_EventHandler()
    {
        var testClass = new TestClass();

        testClass.TestEventAsync += OnTestEventAsync;
        testClass.TestEvent += OnTestEvent;

        await testClass.FireEventAsync(EventArgs.Empty);
        Assert.AreEqual(2, _testEventAsyncCount);

        testClass.TestEvent -= OnTestEvent;

        await testClass.FireEventAsync(EventArgs.Empty);
        Assert.AreEqual(3, _testEventAsyncCount);

        testClass.TestEventAsync -= OnTestEventAsync;

        await testClass.FireEventAsync(EventArgs.Empty);
        Assert.AreEqual(3, _testEventAsyncCount);
    }

    [TestMethod]
    public async Task Attach_EventHandler()
    {
        var testClass = new TestClass();

        testClass.TestEventAsync += OnTestEventAsync;

        await testClass.FireEventAsync(EventArgs.Empty);

        Assert.AreEqual(1, _testEventAsyncCount);
    }

    [TestMethod]
    public async Task Attach_Sync_And_Async_EventHandler()
    {
        var testClass = new TestClass();

        testClass.TestEventAsync += OnTestEventAsync;
        testClass.TestEvent += OnTestEvent;

        await testClass.FireEventAsync(EventArgs.Empty);

        Assert.AreEqual(2, _testEventAsyncCount);
    }

    [TestMethod]
    public async Task Detach_EventHandler()
    {
        var testClass = new TestClass();

        testClass.TestEventAsync += OnTestEventAsync;
        testClass.TestEventAsync -= OnTestEventAsync;

        await testClass.FireEventAsync(EventArgs.Empty);

        Assert.AreEqual(0, _testEventAsyncCount);
    }

    [TestMethod]
    public void Has_Handlers()
    {
        var testClass = new TestClass();
        testClass.TestEventAsync += OnTestEventAsync;

        Assert.IsTrue(testClass.HasTestHandlers);
    }

    [TestMethod]
    public void No_Handlers()
    {
        var testClass = new TestClass();

        Assert.IsFalse(testClass.HasTestHandlers);
    }

    [TestMethod]
    public void Remove_Handlers()
    {
        var testClass = new TestClass();
        testClass.TestEventAsync += OnTestEventAsync;
        testClass.TestEventAsync -= OnTestEventAsync;

        Assert.IsFalse(testClass.HasTestHandlers);
    }

    void OnTestEvent(EventArgs arg)
    {
        Interlocked.Increment(ref _testEventAsyncCount);
    }

    Task OnTestEventAsync(EventArgs arg)
    {
        Interlocked.Increment(ref _testEventAsyncCount);
        return CompletedTask.Instance;
    }

    sealed class TestClass
    {
        readonly AsyncEvent<EventArgs> _testEvent = new();

        public event Action<EventArgs> TestEvent
        {
            add => _testEvent.AddHandler(value);
            remove => _testEvent.RemoveHandler(value);
        }

        public event Func<EventArgs, Task> TestEventAsync
        {
            add => _testEvent.AddHandler(value);
            remove => _testEvent.RemoveHandler(value);
        }

        public bool HasTestHandlers => _testEvent.HasHandlers;

        public Task FireEventAsync(EventArgs eventArgs)
        {
            return _testEvent.InvokeAsync(eventArgs);
        }
    }
}