// Copyright © 2015 The CefSharp Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.

using System;

using System.Threading;

using System.Threading.Tasks;

using CefSharp.Internals.Tasks;

namespace CefSharp.Internals

{

/// <summary>

/// MethodRunnerQueue - Async Javascript Binding methods are run

/// on the ThreadPool sequentially

/// </summary>

public sealed class MethodRunnerQueue : IMethodRunnerQueue

{

//Limit to 1 task per methodRunnerQueue

//https://social.msdn.microsoft.com/Forums/vstudio/en-US/d0bcb415-fb1e-42e4-90f8-c43a088537fb/aborting-a-long-running-task-in-tpl?forum=parallelextensions

private readonly LimitedConcurrencyLevelTaskScheduler taskScheduler = new LimitedConcurrencyLevelTaskScheduler(1);

private readonly IJavascriptObjectRepositoryInternal repository;

private readonly CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();

/// <inheritdoc/>

public event EventHandler<MethodInvocationCompleteArgs> MethodInvocationComplete;

/// <summary>

/// Default constructor

/// </summary>

/// <param name="repository">javascript object repository</param>

public MethodRunnerQueue(IJavascriptObjectRepositoryInternal repository)

{

this.repository = repository;

}

/// <inheritdoc/>

public void Dispose()

{

//Cancel all tasks associated with this MethoRunnerQueue

cancellationTokenSource.Cancel();

}

/// <inheritdoc/>

public void Enqueue(MethodInvocation methodInvocation)

{

if(cancellationTokenSource.IsCancellationRequested)

{

return;

}

Task.Factory.StartNew(() =>

{

if (cancellationTokenSource.IsCancellationRequested)

{

return;

}

var result = ExecuteMethodInvocation(methodInvocation);

var handler = MethodInvocationComplete;

if (!cancellationTokenSource.Token.IsCancellationRequested && handler != null)

{

handler(this, new MethodInvocationCompleteArgs(result));

}

}, cancellationTokenSource.Token, TaskCreationOptions.HideScheduler, taskScheduler);

}

private MethodInvocationResult ExecuteMethodInvocation(MethodInvocation methodInvocation)

{

object returnValue = null;

string exception;

var success = false;

var nameConverter = repository.NameConverter;

//make sure we don't throw exceptions in the executor task

try

{

var result = repository.TryCallMethod(methodInvocation.ObjectId, methodInvocation.MethodName, methodInvocation.Parameters.ToArray());

success = result.Success;

returnValue = result.ReturnValue;

exception = result.Exception;

//We don't support Tasks by default

if (success && returnValue != null && (typeof(Task).IsAssignableFrom(returnValue.GetType())))

{

//Use StringBuilder to improve the formatting/readability of the error message

//I'm sure there's a better way I just cannot remember of the top of my head so going

//with this for now, as it's only for error scenaiors I'm not concerned about performance.

var builder = new System.Text.StringBuilder();

builder.AppendLine("Your method returned a Task which is not supported by default you must set CefSharpSettings.ConcurrentTaskExecution = true; before creating your first ChromiumWebBrowser instance.");

builder.AppendLine("This will likely change to the default at some point in the near future, subscribe to the issue link below to be notified of any changes.");

builder.AppendLine("See https://github.com/cefsharp/CefSharp/issues/2758 for more details, please report any issues you have there, make sure you have an example ready that reproduces your problem.");

success = false;

result = null;

exception = builder.ToString();

}

}

catch (Exception e)

{

exception = e.Message;

}

return new MethodInvocationResult

{

BrowserId = methodInvocation.BrowserId,

CallbackId = methodInvocation.CallbackId,

FrameId = methodInvocation.FrameId,

Message = exception,

Result = returnValue,

Success = success,

NameConverter = nameConverter

};

}

}

}