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

public class EnemyPool : MonoBehaviour 
{
	public static EnemyPool Instance;

	public Transform[] enemyPrefeb;

	private bool startGame =  false;

	private int totalEnemies = 0;
	private int killedEnemies = 0;

	private int aliveEnemies = 0;

	private static int MAX_ENEMY = 100;
	private static float SPAWING_TIME = 5; // every 5 secs

	private float _timer = SPAWING_TIME;

	List<int> toBeCreated = new List<int>();

	void Awake()
	{
		Instance = this;
	}

	void Start()
	{
	}

	public void InsertEnemy(int type,int cnt)
	{
		if ((type < 0) || (type > (enemyPrefeb.Length-1)))
		{
			Debug.LogError("type " + type + ", cannot be used. Discarding " + cnt + " enemies!");
			return;
		}

		totalEnemies += cnt;

		for(int i=0;i<cnt;i++)
		{
			// push
			toBeCreated.Add(i);
		}

		Debug.Log("adding enemy type:" + type + " " + " count: "+cnt);
	}

	public void DestroyOneEnemy(GameObject enemy)
	{
		Debug.Log("Enemy Destroyed");
		aliveEnemies--;
		killedEnemies++;
	}

	public void StartGame()
	{
		startGame = true;
	}

	void Update()
	{
		if (startGame)
		{
			_timer -= Time.deltaTime;
			if (_timer < 0) 
			{
				_timer += SPAWING_TIME;

				if (aliveEnemies < MAX_ENEMY)
				{ 
					if (toBeCreated.Count > 0)
					{
						// pop
						int type = toBeCreated[0];
						toBeCreated.RemoveAt(0);

						GameManager.CreateEnemy(enemyPrefeb[type]);

						aliveEnemies++;
					}
				}
			}
		}
	}

	public int getRemainingEnemiesToKill()
	{
		return totalEnemies - killedEnemies;
	}
}