Synnefo » Pithos MS Client

using System;

using System.Collections.Concurrent;

using System.Collections.Generic;

using System.Diagnostics.Contracts;

using System.Linq;

using System.Text;

using System.Threading;

using System.Threading.Tasks;

namespace Pithos.Core

{

    public static class TaskExtensions

    {

        public static Task<T2> Then<T1, T2>(this Task<T1> first, Func<T1, Task<T2>> next)

        {

            if (first == null)

                throw new ArgumentNullException("first");

            if (next == null)

                throw new ArgumentNullException("next");

            Contract.EndContractBlock();

            return Then(first, next, CancellationToken.None);

        }

        public static Task Then<T1>(this Task<T1> first, Func<T1, Task> next)

        {

            if (first == null)

                throw new ArgumentNullException("first");

            if (next == null)

                throw new ArgumentNullException("next");

            Contract.EndContractBlock();

            return Then(first, next, CancellationToken.None);

        }

        public static Task<T2> Then<T1, T2>(this Task<T1> first, Func<T1, Task<T2>> next, CancellationToken cancellationToken)

        {

            if (first == null) 

                throw new ArgumentNullException("first");

            if (next == null) 

                throw new ArgumentNullException("next");

            Contract.EndContractBlock();

            Contract.Assume(TaskScheduler.Current!=null);

            var tcs = new TaskCompletionSource<T2>();

            first.ContinueWith(delegate

            {

                if (first.IsFaulted) tcs.TrySetException(first.Exception.InnerExceptions);

                else if (first.IsCanceled) tcs.TrySetCanceled();

                else

                {

                    try

                    {

                        var t = next(first.Result);

                        if (t == null) tcs.TrySetCanceled();

                        else t.ContinueWith(delegate

                        {

                            if (t.IsFaulted) tcs.TrySetException(t.Exception.InnerExceptions);

                            else if (t.IsCanceled) tcs.TrySetCanceled();

                            else tcs.TrySetResult(t.Result);

                        }, TaskContinuationOptions.ExecuteSynchronously);

                    }

                    catch (Exception exc) { tcs.TrySetException(exc); }

                }

            }, cancellationToken, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Current);

            return tcs.Task;

        }

        public static Task Then<T1>(this Task<T1> first, Func<T1, Task> next, CancellationToken cancellationToken)

        {

            if (first == null)

                throw new ArgumentNullException("first");

            if (next == null)

                throw new ArgumentNullException("next");

            Contract.EndContractBlock();

            Contract.Assume(TaskScheduler.Current != null);

            var tcs = new TaskCompletionSource<object>();

            first.ContinueWith(delegate

            {

                if (first.IsFaulted) tcs.TrySetException(first.Exception.InnerExceptions);

                else if (first.IsCanceled) tcs.TrySetCanceled();

                else

                {

                    try

                    {

                        var t = next(first.Result);

                        if (t == null) tcs.TrySetCanceled();

                        else t.ContinueWith(delegate

                        {

                            if (t.IsFaulted) tcs.TrySetException(t.Exception.InnerExceptions);

                            else if (t.IsCanceled) tcs.TrySetCanceled();

                            else tcs.TrySetResult(null);

                        }, TaskContinuationOptions.ExecuteSynchronously);

                    }

                    catch (Exception exc) { tcs.TrySetException(exc); }

                }

            }, cancellationToken, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Current);

            return tcs.Task;

        }

        public static void ReportExceptions(this Task task,Action<AggregateException> OnError,Action OnSuccess )

        {

            if (!task.IsCompleted) throw new InvalidOperationException("The task has not completed.");

            if (task.IsFaulted)             

                task.Exception.Handle(exc=>

                                          {

                                              OnError(task.Exception);

                                              return true;

                                          }); 

            else

            {

                OnSuccess();

            }

        }

        public static bool TryRemove<T>(this ObservableConcurrentCollection<T> collection,T item) where T:class

        {

            IProducerConsumerCollection<T> items= collection;

            for (var i = 0; i < items.Count; i++)

            {

                T tempItem;

                if (!items.TryTake(out tempItem)) 

                    return false;

                if (tempItem == item) 

                    return true;

                items.TryAdd(item);

            }

            return false;

        }

        public static bool TryAdd<T>(this ObservableConcurrentCollection<T> collection,T item) where T:class

        {

            if (collection==null)

                throw new ArgumentNullException("collection");

            Contract.EndContractBlock();

            if (item == null)

                return false;

            IProducerConsumerCollection<T> items= collection;            

            return items.TryAdd(item);

        }

    }

}