using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;

/// <summary>
/// UGUIԴŲ
/// </summary>
/// <typeparam name="T"></typeparam>
public class ObjectPool<T> where T : new()
{
 private readonly Stack<T> m_Stack = new Stack<T>();
 private readonly UnityAction<T> m_ActionOnGet;
 private readonly UnityAction<T> m_ActionOnRelease;

 public int countAll { get; private set; }
 public int countActive { get { return countAll - countInactive; } }
 public int countInactive { get { return m_Stack.Count; } }

 public ObjectPool(UnityAction<T> actionOnGet, UnityAction<T> actionOnRelease)
 {
 m_ActionOnGet = actionOnGet;
 m_ActionOnRelease = actionOnRelease;
 }

 public T Get()
 {
 T element;
 if (m_Stack.Count == 0)
 {
 element = new T();
 countAll++;
 }
 else
 {
 element = m_Stack.Pop();
 }
 if (m_ActionOnGet != null)
 m_ActionOnGet(element);
 return element;
 }

 public void Release(T element)
 {
 if (m_Stack.Count > 0 && ReferenceEquals(m_Stack.Peek(), element))
 Debug.LogError("Internal error. Trying to destroy object that is already released to pool.");
 if (m_ActionOnRelease != null)
 m_ActionOnRelease(element);
 m_Stack.Push(element);
 }
}