using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;

namespace HT.Cloud.Code
{
	/// <summary>
	/// 队列工具类，用于另起线程处理执行类型数据
	/// </summary>
	/// <typeparam name="T"></typeparam>
	public class QueueHelper<T> : IDisposable
	{
		#region Private Field

		/// <summary>
		/// The inner queue.
		/// </summary>
		private readonly ConcurrentQueue<T> _innerQueue;

		/// <summary>
		/// The deal task.
		/// </summary>
		private readonly Task _dealTask;

		/// <summary>
		/// The flag for end thread.
		/// </summary>
		private bool _endThreadFlag = false;

		/// <summary>
		/// The auto reset event.
		/// </summary>
		private readonly AutoResetEvent _autoResetEvent = new(true);

		#endregion Private Field

		#region Public Property

		/// <summary>
		/// The deal action.
		/// </summary>
		public Action<T> DealAction { get; set; }

		#endregion Public Property

		#region Constructor

		/// <summary>
		/// Initializes a new instance of the QueueHelper`1 class.
		/// </summary>
		public QueueHelper()
		{
			this._innerQueue = new();
			this._dealTask = Task.Run(() => this.DealQueue());
		}

		/// <summary>
		/// Initializes a new instance of the QueueHelper&lt;T&gt; class.
		/// </summary>
		/// <param name="DealAction">The deal action.</param>
		public QueueHelper(Action<T> DealAction)
		{
			this.DealAction = DealAction;
			this._innerQueue = new();
			this._dealTask = Task.Run(() => this.DealQueue());
		}

		#endregion Constructor

		#region Public Method

		/// <summary>
		/// Save entity to Queue.
		/// </summary>
		/// <param name="entity">The entity what will be deal.</param>
		public bool Enqueue(T entity)
		{
			if (!this._endThreadFlag)
			{
				this._innerQueue.Enqueue(entity);
				this._autoResetEvent.Set();

				return true;
			}

			return false;
		}

		/// <summary>
		/// Disposes current instance, end the deal thread and inner queue.
		/// </summary>
		public void Dispose()
		{
			if (!this._endThreadFlag)
			{
				this._endThreadFlag = true;
				this._innerQueue.Enqueue(default);
				this._autoResetEvent.Set();

				if (!this._dealTask.IsCompleted)
					this._dealTask.Wait();

				this._dealTask.Dispose();

				this._autoResetEvent.Dispose();
				this._autoResetEvent.Close();
			}
		}

		#endregion Public Method

		#region Private Method

		/// <summary>
		/// Out Queue.
		/// </summary>
		/// <param name="entity">The init entity.</param>
		/// <returns>The entity what will be deal.</returns>
		private bool Dequeue(out T entity)
		{
			return this._innerQueue.TryDequeue(out entity);
		}

		/// <summary>
		/// Deal entity in Queue.
		/// </summary>
		private void DealQueue()
		{
			try
			{
				while (true)
				{
					if (this.Dequeue(out T entity))
					{
						if (this._endThreadFlag && Equals(entity, default(T)))
							return;

						try
						{
							this.DealAction?.Invoke(entity);
						}
						catch (Exception ex)
						{
							LogHelper.Write(ex);
						}
					}
					else
					{
						this._autoResetEvent.WaitOne();
					}
				}
			}
			catch (Exception ex)
			{
				LogHelper.Write(ex);
			}
		}

		#endregion Private Method
	}
}