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

namespace TBL.CSharp.Utilities
{
    /// <summary>
    /// 对象池
    /// </summary>
    public class ObjectPool<T> where T : new()
    {
        /// <summary>
        /// 对象集合
        /// </summary>
        private readonly Queue<T> _set = new Queue<T>();

        /// <summary>
        /// 全局对象
        /// </summary>
        public static readonly ObjectPool<T> Global = new ObjectPool<T>();

        /// <summary>
        /// 剩余对象计数
        /// </summary>
        public int RemainCount => _set.Count;

        /// <summary>
        /// 回收池对象
        /// </summary>
        public void Recycle(T instance)
        {
            Debug.Assert(instance != null);
            _set.Enqueue(instance);
        }

        /// <summary>
        /// 预分配
        /// </summary>
        public void Preallocate(int size)
        {
            for (var i = 0; i < size; i++)
                _set.Enqueue(new T());
        }

        /// <summary>
        /// 获取一个池对象
        /// <para>注意手动初始化和清理</para>
        /// </summary>
        public T Use()
        {
            return _set.Count > 0
                ? _set.Dequeue()
                : new T();
        }

        /// <summary>
        /// 清空池对象
        /// </summary>
        public void Clear()
        {
            _set.Clear();
        }
    }
}