using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// 子弹专用对象池 — 按 prefab 实例ID 分桶,与鱼的 Pool 完全隔离
/// 用法:
///     var go = BulletPool.Instance.Get(prefab, pos, rot, parent);
///     BulletPool.Instance.Return(go);   // 代替 Destroy
/// </summary>
public class BulletPool : Singleton<BulletPool>
{
    // prefab.GetInstanceID() → 该 prefab 的池
    private Dictionary<int, BulletPoolData> dic = new Dictionary<int, BulletPoolData>();

    // 每个池子的最大缓存数(超出直接 Destroy,防止内存膨胀)
    private const int MaxCachePerPrefab = 200;

    // 池子根节点(隐藏在场景里)
    private GameObject poolRoot;

    /// <summary>从池中取一个子弹(池空则 Instantiate)</summary>
    public GameObject Get(GameObject prefab, Vector3 position, Quaternion rotation, Transform parent)
    {
        if (prefab == null) return null;

        int id = prefab.GetInstanceID();
        GameObject obj;

        if (dic.TryGetValue(id, out var data) && data.poolList.Count > 0)
        {
            obj = data.GetObj();
            // ⭐ 必须先 SetParent 再设 position:模仿 Instantiate(prefab, pos, rot, parent)
            // 若先设 position 再 SetParent(parent, false),localPosition 会保持,
            // 换 parent 后世界位置偏移 → 子弹从错误位置飞出
            obj.transform.SetParent(parent, false);
            obj.transform.position = position;
            obj.transform.rotation = rotation;
            obj.SetActive(true);
        }
        else
        {
            obj = GameObject.Instantiate(prefab, position, rotation, parent);
            obj.SetActive(true);
        }

        // 确保挂上 tracker 记录 prefabID(回收时凭此找到对应池)
        var tracker = obj.GetComponent<BulletPoolTracker>();
        if (tracker == null)
            tracker = obj.AddComponent<BulletPoolTracker>();
        tracker.prefabID = id;

        return obj;
    }

    /// <summary>无 parent 重载</summary>
    public GameObject Get(GameObject prefab, Vector3 position, Quaternion rotation)
    {
        return Get(prefab, position, rotation, null);
    }

    /// <summary>回收子弹到池(超容量则 Destroy)</summary>
    public void Return(GameObject obj)
    {
        if (obj == null) return;

        var tracker = obj.GetComponent<BulletPoolTracker>();
        int id = tracker != null ? tracker.prefabID : 0;

        // 取不到 id → 兜底 Destroy(非池内对象)
        if (id == 0)
        {
            GameObject.Destroy(obj);
            return;
        }

        if (!dic.TryGetValue(id, out var data))
            dic[id] = data = new BulletPoolData(EnsurePoolRoot().transform, id);

        if (data.poolList.Count >= MaxCachePerPrefab)
        {
            GameObject.Destroy(obj);
            return;
        }

        // 重置子弹状态(若有 BullitMove 组件)
        var bm = obj.GetComponent<BullitMove>();
        if (bm != null) bm.ResetState();

        data.PushObj(obj);
    }

    /// <summary>预加载 N 个某 prefab 到池</summary>
    public void Preload(GameObject prefab, int count)
    {
        if (prefab == null || count <= 0) return;
        int id = prefab.GetInstanceID();

        if (!dic.TryGetValue(id, out var data))
            dic[id] = data = new BulletPoolData(EnsurePoolRoot().transform, id);

        for (int i = 0; i < count; i++)
        {
            var obj = GameObject.Instantiate(prefab, EnsurePoolRoot().transform);
            var tracker = obj.GetComponent<BulletPoolTracker>();
            if (tracker == null)
                tracker = obj.AddComponent<BulletPoolTracker>();
            tracker.prefabID = id;
            data.PushObj(obj);
        }
    }

    /// <summary>清理所有子弹池(切场景时调用)</summary>
    public void Clear()
    {
        foreach (var kv in dic.Values)
            kv.Clear();
        dic.Clear();

        if (poolRoot != null)
        {
            GameObject.Destroy(poolRoot);
            poolRoot = null;
        }
    }

    private GameObject EnsurePoolRoot()
    {
        if (poolRoot == null)
        {
            poolRoot = new GameObject("[BulletPool]");
            poolRoot.SetActive(false);  // 池根节点隐藏,池内对象跟随隐藏
        }
        return poolRoot;
    }
}

/// <summary>挂在池内对象上,记录所属 prefabID(回收时凭此找到对应池)</summary>
public class BulletPoolTracker : MonoBehaviour
{
    public int prefabID;
}

/// <summary>单个 prefab 的子弹池数据</summary>
public class BulletPoolData
{
    public Transform fatherObj;
    public List<GameObject> poolList;

    public BulletPoolData(Transform root, int id)
    {
        fatherObj = new GameObject("bulletPool_" + id).transform;
        fatherObj.SetParent(root, false);
        poolList = new List<GameObject>();
    }

    public void PushObj(GameObject obj)
    {
        if (obj == null) return;
        poolList.Add(obj);
        obj.transform.SetParent(fatherObj, false);
        obj.SetActive(false);
    }

    public GameObject GetObj()
    {
        GameObject obj = poolList[poolList.Count - 1];
        poolList.RemoveAt(poolList.Count - 1);
        return obj;
    }

    public void Clear()
    {
        foreach (var obj in poolList)
        {
            if (obj != null) GameObject.Destroy(obj);
        }
        poolList.Clear();

        if (fatherObj != null)
            GameObject.Destroy(fatherObj.gameObject);
    }
}