//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="CancellableTask"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//     
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace StgSharp.Threading
{
    public class CancellableTask : IDisposable
    {

        private bool disposedValue;
        private CancellationTokenSource cts;
        private protected Action<CancellationToken> _startup;
        private protected Task _internalTask;

        private protected CancellableTask()
        {
            cts = new CancellationTokenSource();
        }

        private protected CancellableTask(Action<CancellationToken> action)
        {
            _internalTask = new Task(InternalAction);
            cts = new CancellationTokenSource();
        }

        public bool IsCompleted
        {
            get => _internalTask.IsCompleted;
        }

        public CancellationTokenSource Cts
        {
            get => cts;
        }

        public int Id
        {
            get => _internalTask.Id;
        }

        public void Cancel()
        {
            Cts.Cancel();
        }

        public void CancelAndWait()
        {
            Cts.Cancel();
            _internalTask.Wait();
        }

        // ~CancellableTask()
        // {
        // Dispose(disposing: false);
        // }

        public void Dispose()
        {
            Dispose(disposing:true);
            GC.SuppressFinalize(this);
        }

        public static CancellableTask Run(Action<CancellationToken> startup)
        {
            CancellableTask ret = new CancellableTask
            {
                _startup = startup
            };
            ret._internalTask = Task.Run(ret.InternalAction);
            return ret;
        }

        public void Wait()
        {
            _internalTask.Wait();
        }

        public static void WaitAll(IEnumerable<CancellableTask> tasks)
        {
            IEnumerable<Task> convertedTasks = tasks.Select<CancellableTask, Task>(
                ct => ct._internalTask);
            Task.WaitAll(convertedTasks.ToArray());
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal void InternalAction()
        {
            _startup(Cts.Token);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!disposedValue)
            {
                if (disposing)
                {
                    if (IsCompleted)
                    {
                        cts.Dispose();
                        _internalTask.Dispose();
                    } else
                    {
                        throw new InvalidOperationException(
                            "Cannot dispose a cancellable task before completed");
                    }
                }

                disposedValue = true;
            }
        }

        public static implicit operator Task(CancellableTask task)
        {
            return task._internalTask;
        }

        ~CancellableTask()
        {
            Cts.Dispose();
        }

    }
}