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

public class DynamicLoader : MonoBehaviour
{
    public static DynamicLoader Instance;

    private void OnEnable()
    {
        Instance = this;
    }
    /// <summary>
    /// 已加载对象池
    /// </summary>
    private List<GameObject> poolLoaded;

    /// <summary>
    /// 缓存对象池
    /// </summary>
    private List<GameObject> poolCache;

    /// <summary>
    /// 待加载预设体名称列表
    /// </summary>
    public List<string> poolWillLoaded;

    /// <summary>
    /// 最大缓存数
    /// </summary>
    public int cacheMaxNum { get; set; }

    /// <summary>
    /// 通过设置层实现显示对象
    /// </summary>
    string showLayer = "Default";

    /// <summary>
    /// 通过设置层实现隐藏对象
    /// </summary>
    string hideLayer = "CacheLayer";

    int showLayerIndex;

    int hideLayerIndex;

    public string LastPos;

    // Start is called before the first frame update
    void Start()
    {
        cacheMaxNum = 10;
        poolLoaded = new List< GameObject>();
        poolCache = new List<GameObject>();
        hideLayerIndex = LayerMask.NameToLayer(hideLayer);
        showLayerIndex = LayerMask.NameToLayer(showLayer);
    }

    /// <summary>
    /// 从缓存获取要加载的对象
    /// </summary>
    /// <param name="objName">对象名</param>
    /// <returns></returns>
    GameObject GetObjectFromCache(string objName)
    {
        return poolCache.FirstOrDefault<GameObject>(obj => obj.name == objName);
    }

    /// <summary>
    /// 从已加载列表获取要加载的对象
    /// </summary>
    /// <param name="objName">对象名</param>
    /// <returns></returns>
    GameObject GetObjectFromLoaded(string objName)
    {
        return poolLoaded.FirstOrDefault<GameObject>(obj => obj.name == objName);
    }

     
    /// <summary>
    /// 加载该位置所需要的预设体
    /// </summary>
    /// <param name="preNames">预设体名称数组</param>
    public void Load(string[] preNames)
    {
        // 添加缓存数组中已存在的预设体
        List<GameObject> lstFromCache = poolCache.FindAll(obj => preNames.Contains(obj.name));
        foreach (var obj in lstFromCache)
        {
            obj.layer = showLayerIndex;
            poolLoaded.Add(obj);
            poolCache.Remove(obj);
        }

        // 移除已加载数组中不需要的预设体
        List<GameObject> lstFromLoaded = poolLoaded.FindAll(obj => !preNames.Contains(obj.name));
        foreach (var obj in lstFromLoaded)
        {
            obj.layer = hideLayerIndex;            
            poolCache.Add(obj);
            if (poolCache.Count > cacheMaxNum)
            {
                Destroy(poolCache[0]);
                poolCache.RemoveAt(0);
            }
            poolLoaded.Remove(obj);
        }

        // 加载不在场景中的预设体
        GameObject tmp = null;
        foreach (var name in preNames)
        {
            tmp = poolLoaded.FirstOrDefault(obj => obj.name == name);
            if (tmp == null)
            {
                StartCoroutine(GeneratePrefab(name));
            }
        }
    }

    IEnumerator GeneratePrefab(string name)
    {
        string parentName = name.Substring(0, name.IndexOf("_"));  // 父对象名称

        GameObject tmp = Resources.Load<GameObject>("Prefabs\\" + name);
        tmp = GameObject.Instantiate(tmp, GameObject.Find(parentName).transform);
        tmp.name = name;
        tmp.layer = showLayerIndex;
        poolLoaded.Add(tmp);

        // DataLoader.Instance.AttachOperation();

        yield return new WaitForSeconds(0.5f);
    }

}