using System.Collections.Generic;
using System;
using System.Collections.Generic;

namespace TellmePdmsPluging.Core
{
    public static class SafeQueue
    {
        private static readonly object _sync = new object();
        private static Queue<ICommand> _queue;

        public static void Init()
        {
            if (_queue != null)
            {
                return;
            }

            lock (_sync)
            {
                if (_queue == null)
                {
                    _queue = new Queue<ICommand>();
                }
            }
        }

        public static void Enqueue(ICommand command)
        {
            if (command == null)
            {
                return;
            }

            Init();

            lock (_sync)
            {
                _queue.Enqueue(command);
            }
        }

        public static bool TryDequeue(out ICommand command)
        {
            Init();

            lock (_sync)
            {
                if (_queue.Count > 0)
                {
                    command = _queue.Dequeue();
                    return true;
                }
            }

            command = null;
            return false;
        }
    }

    public interface IResultCommand : ICommand
    {
        object Result { get; }
        Exception Error { get; }
        bool IsCompleted { get; }
    }
}