/*
 * Copyright (c) 2023 Proton AG
 *
 * This file is part of ProtonVPN.
 *
 * ProtonVPN is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * ProtonVPN is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ProtonVPN.  If not, see <https://www.gnu.org/licenses/>.
 */

using System;
using System.Threading;
using System.Threading.Tasks;
using ProtonVPN.Common.Legacy.Threading;

namespace ProtonVPN.Common.Legacy.Threading.TaskQueueing;

internal class QueuedTask<TArg, TResult> : IDisposable
{
    private readonly Func<CancellationToken, Task<TResult>> _action;
    private readonly TaskCompletionSource<TResult> _completionSource;
    private readonly CancellationTokenSource _cancellationTokenSource;

    public QueuedTask(Func<CancellationToken, Task<TResult>> action, TArg arg) :
        this(action, arg, new TaskCompletionSource<TResult>(), new CancellationTokenSource())
    { }

    private QueuedTask(
        Func<CancellationToken, Task<TResult>> action,
        TArg arg,
        TaskCompletionSource<TResult> completionSource,
        CancellationTokenSource cancellationTokenSource)
    {
        _action = action;
        Arg = arg;
        _completionSource = completionSource;
        _cancellationTokenSource = cancellationTokenSource;

        Task = _completionSource.Task;
    }

    public TArg Arg { get; }

    public Task<TResult> Task { get; }

    public bool CancellationRequested => _cancellationTokenSource.IsCancellationRequested;

    public void Cancel(bool running)
    {
        if (running)
        {
            _cancellationTokenSource.Cancel();
        }
        else
        {
            _completionSource.SetCanceled();
        }
    }

    public Task Run()
    {
        return _completionSource.Wrap(() =>
        {
            var cancellationToken = _cancellationTokenSource.Token;
            cancellationToken.ThrowIfCancellationRequested();
            return _action(cancellationToken);
        });
    }

    public void Dispose()
    {
        _cancellationTokenSource.Dispose();
    }
}