// Copyright © 2014 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;

namespace CefSharp.Internals
{
    /// <summary>
    /// TaskExtension based on the following
    /// https://github.com/ChadBurggraf/parallel-extensions-extras/blob/master/Extensions/TaskExtrasExtensions.cs
    /// https://github.com/ChadBurggraf/parallel-extensions-extras/blob/ec803e58eee28c698e44f55f49c5ad6671b1aa58/Extensions/TaskCompletionSourceExtensions.cs
    /// </summary>
    public static class TaskExtensions
    {
        /// <summary>Creates a new Task that mirrors the supplied task but that will be canceled after the specified timeout.</summary>
        /// <typeparam name="TResult">Specifies the type of data contained in the task.</typeparam>
        /// <param name="task">The task.</param>
        /// <param name="timeout">The timeout.</param>
        /// <returns>The new Task that may time out.</returns>
        public static Task<TResult> WithTimeout<TResult>(this Task<TResult> task, TimeSpan timeout)
        {
            var result = new TaskCompletionSource<TResult>(task.AsyncState);
            var timer = new Timer(state => ((TaskCompletionSource<TResult>)state).TrySetCanceled(), result, timeout, TimeSpan.FromMilliseconds(-1));
            task.ContinueWith(t =>
            {
                timer.Dispose();
                result.TrySetFromTask(t);
            }, TaskContinuationOptions.ExecuteSynchronously);
            return result.Task;
        }

        /// <summary>Attempts to transfer the result of a Task to the TaskCompletionSource.</summary>
        /// <typeparam name="TResult">Specifies the type of the result.</typeparam>
        /// <param name="resultSetter">The TaskCompletionSource.</param>
        /// <param name="task">The task whose completion results should be transfered.</param>
        /// <returns>Whether the transfer could be completed.</returns>
        public static bool TrySetFromTask<TResult>(this TaskCompletionSource<TResult> resultSetter, Task task)
        {
            switch (task.Status)
            {
                case TaskStatus.RanToCompletion:
                    return resultSetter.TrySetResult(task is Task<TResult> ? ((Task<TResult>)task).Result : default(TResult));
                case TaskStatus.Faulted:
                    return resultSetter.TrySetException(task.Exception.InnerExceptions);
                case TaskStatus.Canceled:
                    return resultSetter.TrySetCanceled();
                default:
                    throw new InvalidOperationException("The task was not completed.");
            }
        }
        /// <summary>Attempts to transfer the result of a Task to the TaskCompletionSource.</summary>
        /// <typeparam name="TResult">Specifies the type of the result.</typeparam>
        /// <param name="resultSetter">The TaskCompletionSource.</param>
        /// <param name="task">The task whose completion results should be transfered.</param>
        /// <returns>Whether the transfer could be completed.</returns>
        public static bool TrySetFromTask<TResult>(this TaskCompletionSource<TResult> resultSetter, Task<TResult> task)
        {
            return TrySetFromTask(resultSetter, (Task)task);
        }

        public static Task<T> FromResult<T>(T value)
        {
            var tcs = new TaskCompletionSource<T>();
            tcs.SetResult(value);
            return tcs.Task;
        }

        public static TaskCompletionSource<TResult> WithTimeout<TResult>(this TaskCompletionSource<TResult> taskCompletionSource, TimeSpan timeout)
        {
            return WithTimeout(taskCompletionSource, timeout, null);
        }

        public static TaskCompletionSource<TResult> WithTimeout<TResult>(this TaskCompletionSource<TResult> taskCompletionSource, TimeSpan timeout, Action cancelled)
        {
            Timer timer = null;
            timer = new Timer(state =>
            {
                timer.Dispose();
                if (taskCompletionSource.Task.Status != TaskStatus.RanToCompletion)
                {
                    taskCompletionSource.TrySetCanceled();
                    if (cancelled != null)
                    {
                        cancelled();
                    }
                }
            }, null, timeout, TimeSpan.FromMilliseconds(-1));

            return taskCompletionSource;
        }

        /// <summary>
        /// Set the TaskCompletionSource in an async fashion. This prevents the Task Continuation being executed sync on the same thread
        /// This is required otherwise contintinuations will happen on CEF UI threads
        /// </summary>
        /// <typeparam name="TResult">Generic param</typeparam>
        /// <param name="taskCompletionSource">tcs</param>
        /// <param name="result">result</param>
        public static void TrySetResultAsync<TResult>(this TaskCompletionSource<TResult> taskCompletionSource, TResult result)
        {
            Task.Factory.StartNew(delegate
            { taskCompletionSource.TrySetResult(result); }, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.Default);
        }
    }
}