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

public class FragmentManager : MonoBehaviour
{
    private static readonly HashSet<string> LoadedSceneNames = new();

    // 关键：在每次进入 Play Mode（且不重启域）时，重置静态集合
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
    private static void ResetStaticState()
    {
        LoadedSceneNames.Clear();
        // 如果有其他静态字段，也在这里一并重置
    }
    
    /// <summary>
    /// 刷新场景需要列表（基于场景名称）
    /// </summary>
    /// <param name="requiredSceneNames">需要的场景名称列表（需与 Build Settings 中的名称一致，不带 .unity 扩展名）</param>
    public static void UpdateSceneRequirements(List<string> requiredSceneNames)
    {
        var toUnload = new List<string>();
        var toLoad = new List<string>();

        // 需要卸载的：当前已加载但不在 requiredSceneNames 中
        foreach (var loadedName in LoadedSceneNames)
        {
            if (!requiredSceneNames.Contains(loadedName))
                toUnload.Add(loadedName);
        }

        // 需要加载的：requiredSceneNames 中尚未加载的
        foreach (var reqName in requiredSceneNames)
        {
            if (!LoadedSceneNames.Contains(reqName))
                toLoad.Add(reqName);
        }

        UnloadScenes(toUnload);
        LoadScenes(toLoad);
    }

    /// <summary>
    /// 重置所有场景（先卸载全部，再重新加载）
    /// </summary>
    public static void ReloadAllScenes()
    {
        var scenesToReload = new List<string>(LoadedSceneNames);

        // 先卸载所有
        foreach (var sceneName in scenesToReload)
        {
            var asyncOp = SceneManager.UnloadSceneAsync(sceneName);
            if (asyncOp != null)
            {
                asyncOp.completed += _ =>
                {
                    if (LoadedSceneNames.Contains(sceneName))
                        LoadedSceneNames.Remove(sceneName);
                };
            }
            else
            {
                // 同步卸载后备（已过时，仅用于兼容）
                if (SceneManager.UnloadScene(sceneName))
                    LoadedSceneNames.Remove(sceneName);
            }
        }

        // 重新加载（注意：卸载异步，立即加载可能导致短暂重叠，但通常可接受）
        foreach (var sceneName in scenesToReload)
        {
            var asyncOp = SceneManager.LoadSceneAsync(sceneName, LoadSceneMode.Additive);
            if (asyncOp != null)
            {
                asyncOp.completed += _ =>
                {
                    var scene = SceneManager.GetSceneByName(sceneName);
                    if (scene.isLoaded && !LoadedSceneNames.Contains(sceneName))
                        LoadedSceneNames.Add(sceneName);
                };
            }
            else
            {
                // 同步加载后备
                SceneManager.LoadScene(sceneName, LoadSceneMode.Additive);
                var scene = SceneManager.GetSceneByName(sceneName);
                if (scene.isLoaded && !LoadedSceneNames.Contains(sceneName))
                    LoadedSceneNames.Add(sceneName);
            }
        }
    }

    /// <summary>
    /// 异步卸载场景列表，完成后从 LoadedSceneNames 中移除
    /// </summary>
    private static void UnloadScenes(List<string> sceneNames)
    {
        foreach (var sceneName in sceneNames)
        {
            Debug.Log("Unloading: " + sceneName);
            var asyncOp = SceneManager.UnloadSceneAsync(sceneName);
            if (asyncOp != null)
            {
                asyncOp.completed += _ =>
                {
                    if (LoadedSceneNames.Contains(sceneName))
                        LoadedSceneNames.Remove(sceneName);
                };
            }
            else
            {
                if (SceneManager.UnloadScene(sceneName))
                    LoadedSceneNames.Remove(sceneName);
            }
        }
    }

    /// <summary>
    /// 异步加载场景列表，完成后加入 LoadedSceneNames
    /// </summary>
    private static void LoadScenes(List<string> sceneNames)
    {
        foreach (var sceneName in sceneNames)
        {
            Debug.Log("Loading: " + sceneName);
            var asyncOp = SceneManager.LoadSceneAsync(sceneName, LoadSceneMode.Additive);
            if (asyncOp != null)
            {
                asyncOp.completed += _ =>
                {
                    var scene = SceneManager.GetSceneByName(sceneName);
                    if (scene.isLoaded && !LoadedSceneNames.Contains(sceneName))
                        LoadedSceneNames.Add(sceneName);
                };
            }
            else
            {
                SceneManager.LoadScene(sceneName, LoadSceneMode.Additive);
                var scene = SceneManager.GetSceneByName(sceneName);
                if (scene.isLoaded && !LoadedSceneNames.Contains(sceneName))
                    LoadedSceneNames.Add(sceneName);
            }
        }
    }
}