// Copyright (c) 2022 .NET Foundation and Contributors. All rights reserved.

// 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 full license information.

using System;

using System.Reactive.Disposables;

using System.Threading;

namespace ReactiveUI.Testing;

/// <summary>

/// Message bus testing extensions.

/// </summary>

public static class MessageBusExtensions

{

private static readonly object mbGate = 42;

/// <summary>

/// Override the default Message Bus during the specified block.

/// </summary>

/// <typeparam name="TRet">The return type.</typeparam>

/// <param name="messageBus">The message bus to use for the block.</param>

/// <param name="block">The function to execute.</param>

/// <returns>The return value of the function.</returns>

public static TRet With<TRet>(this IMessageBus messageBus, Func<TRet> block)

{

if (block is null)

{

throw new ArgumentNullException(nameof(block));

}

using (messageBus.WithMessageBus())

{

return block();

}

}

/// <summary>

/// WithMessageBus allows you to override the default Message Bus

/// implementation until the object returned is disposed. If a

/// message bus is not specified, a default empty one is created.

/// </summary>

/// <param name="messageBus">The message bus to use, or null to create

/// a new one using the default implementation.</param>

/// <returns>An object that when disposed, restores the original

/// message bus.</returns>

public static IDisposable WithMessageBus(this IMessageBus messageBus)

{

var origMessageBus = MessageBus.Current;

Monitor.Enter(mbGate);

MessageBus.Current = messageBus;

return Disposable.Create(() =>

{

MessageBus.Current = origMessageBus;

Monitor.Exit(mbGate);

});

}

/// <summary>

/// Override the default Message Bus during the specified block.

/// </summary>

/// <param name="messageBus">The message bus to use for the block.</param>

/// <param name="block">The action to execute.</param>

public static void With(this IMessageBus messageBus, Action block)

{

if (block is null)

{

throw new ArgumentNullException(nameof(block));

}

using (messageBus.WithMessageBus())

{

block();

}

}

}