using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// 子弹专用对象池 — 按 prefab.GetInstanceID() 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(单个回收)
///     BulletPool.Instance.ClearAll();        // 换炮台/切场景调用:销毁所有活跃子弹 + 清池
/// prefabID 直接用 prefab.GetInstanceID()(Unity 内部 hash,全局唯一)
/// 活跃子弹→prefabID 的映射用 Dictionary<instanceID, prefabID> 存储,不挂组件不改 name
/// </summary>
public class BulletPool : Singleton<BulletPool>
{
    // prefab.GetInstanceID() → 该 prefab 的池
    private Dictionary<int, BulletPoolData> dic = new Dictionary<int, BulletPoolData>();

    // 活跃子弹映射:子弹GameObject → prefab.GetInstanceID()
    // key 用 GameObject 本身(Unity 重载了 GetHashCode/Equals,按实例区分)
    // value 是 prefabID,回收时凭此找到对应池
    private Dictionary<GameObject, int> activeMap = new Dictionary<GameObject, int>();

    // 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 prefabID = prefab.GetInstanceID();
        GameObject obj = null;

        if (dic.TryGetValue(prefabID, out var data))
        {
            // ⭐ 循环跳过已销毁的坏对象(ClearAll 用 Destroy 延迟销毁,时序竞争中可能残留)
            while (data.poolList.Count > 0)
            {
                obj = data.GetObj();
                if (obj != null) break;       // Unity 重载 ==,能识别已 Destroy 的假 null
                obj = null;                    // 坏对象丢弃,继续取下一个
            }
        }

        if (obj != null)
        {
            // ⭐ 必须先 SetParent 再设 position:模仿 Instantiate(prefab, pos, rot, parent)
            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);
        }

        // 记录映射:子弹实例 → prefabID(回收时凭此找到对应池)
        activeMap[obj] = prefabID;
        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;

        // 取不到映射 → 非 pool 对象 → 兜底 Destroy
        if (!activeMap.TryGetValue(obj, out int prefabID) || prefabID == 0)
        {
            GameObject.Destroy(obj);
            return;
        }
        activeMap.Remove(obj);

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

        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 prefabID = prefab.GetInstanceID();

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

        for (int i = 0; i < count; i++)
        {
            var obj = GameObject.Instantiate(prefab, EnsurePoolRoot().transform);
            // 预加载的对象直接入池,不进 activeMap(它们没被"借出")
            data.PushObj(obj);
        }
    }

    /// <summary>销毁所有活跃子弹 + 清空所有池(换炮台/切场景调用)</summary>
    public void ClearAll()
    {
        // 销毁所有借出未归还的子弹
        foreach (var kv in activeMap.Keys)
        {
            if (kv != null) GameObject.Destroy(kv);
        }
        activeMap.Clear();

        // 清空所有池
        foreach (var kv in dic.Values)
            kv.Clear();
        dic.Clear();

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

    /// <summary>只销毁活跃子弹,保留池缓存(换炮台时调用:清屏但池能复用)</summary>
    public void ClearActive()
    {
        foreach (var kv in activeMap.Keys)
        {
            if (kv != null) GameObject.Destroy(kv);
        }
        activeMap.Clear();
        // ⭐ 不清 dic,池里的缓存保留,同 prefab 下次能复用
    }

    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>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);
    }
}