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

public class ObjectPool
{
    #region Fields

    private GameObject _parentObject;

    private Dictionary<int, GameObject> _sourceByObjectId =
       new Dictionary<int, GameObject>();

    private Dictionary<GameObject, Stack<GameObject>> _storage =
        new Dictionary<GameObject, Stack<GameObject>>();

    #endregion


    #region Methods

    public void SetParentObject(GameObject parentObject)
    {
        _parentObject = parentObject;
    }

    public void Create(GameObject source, int count)
    {
        Stack<GameObject> objectsStack;
        bool hasStack = _storage.TryGetValue(source, out objectsStack);

        if (!hasStack)
        {
            objectsStack = new Stack<GameObject>();
            _storage[source] = objectsStack;
        }

        for (int i = 0; i < count; i++)
        {
            var pooledObject = Object.Instantiate(source) as GameObject;

            pooledObject.SetActive(false);
            pooledObject.name = source.name;

            if (_parentObject != null)
            {
                pooledObject.transform.parent = _parentObject.transform;
            }

            objectsStack.Push(pooledObject);

            int objectId = pooledObject.GetInstanceID();
            _sourceByObjectId[objectId] = source;
        }
    }

    public GameObject Get(GameObject source)
    {
        return Get(source, Vector3.zero, Quaternion.identity);
    }

    public GameObject Get(GameObject source, Vector3 initialPosition, Quaternion initialRotation)
    {
        Stack<GameObject> objectsStack;
        bool hasStack = _storage.TryGetValue(source, out objectsStack);

        if (!hasStack)
        {
            objectsStack = new Stack<GameObject>();
            _storage[source] = objectsStack;
        }

        GameObject pooledObject = null;

        if (objectsStack.Count == 0)
        {
            pooledObject = Object.Instantiate(source) as GameObject;

            pooledObject.name = source.name;

            int objectId = pooledObject.GetInstanceID();
            _sourceByObjectId[objectId] = source;
        }
        else
        {
            pooledObject = objectsStack.Pop();
            pooledObject.SetActive(true);
        }

        pooledObject.transform.parent = null;
        pooledObject.transform.position = initialPosition;
        pooledObject.transform.rotation = initialRotation;

        return pooledObject;
    }

    public void Release(GameObject releasedObject)
    {
        int objectId = releasedObject.GetInstanceID();

        GameObject source;
        bool hasSource = _sourceByObjectId.TryGetValue(objectId, out source);

        if (!hasSource)
        {
            throw new UnityException("Not found a source of pooled object.");
        }

        releasedObject.SetActive(false);

        if (_parentObject != null)
        {
            releasedObject.transform.parent = _parentObject.transform;
        }

        Stack<GameObject> objectsStack = _storage[source];
        objectsStack.Push(releasedObject);
    }

    #endregion
}