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

namespace Streamingle.Background
{
    /// <summary>
    /// 배경 씬 로더 - 에디터/런타임 모두에서 안정적으로 동작
    /// </summary>
    public class BackgroundSceneLoader : MonoBehaviour
    {
        private static BackgroundSceneLoader _instance;
        public static BackgroundSceneLoader Instance
        {
            get
            {
                if (_instance == null)
                {
                    var go = new GameObject("[BackgroundSceneLoader]");
                    _instance = go.AddComponent<BackgroundSceneLoader>();
                    DontDestroyOnLoad(go);
                }
                return _instance;
            }
        }

        [SerializeField] private BackgroundSceneDatabase sceneDatabase;

        private Scene? _currentBackgroundScene;
        private bool _isLoading;
        private AsyncOperation _currentOperation;

        // 기존 씬 라이팅 백업
        private List<LightBackup> _originalDirectionalLights = new List<LightBackup>();
        private List<ComponentBackup> _originalNiloToonOverriders = new List<ComponentBackup>();
        private bool _hasLightingBackup;

        private class LightBackup
        {
            public Light light;
            public bool wasEnabled;
        }

        private class ComponentBackup
        {
            public MonoBehaviour component;
            public bool wasEnabled;
        }

        public event Action<BackgroundSceneInfo> OnSceneLoadStarted;
        public event Action<BackgroundSceneInfo> OnSceneLoadCompleted;
        public event Action<string> OnSceneUnloaded;
        public event Action<float> OnLoadProgress;
        public event Action<string> OnError;

        public bool IsLoading => _isLoading;
        public Scene? CurrentBackgroundScene => _currentBackgroundScene;
        public string CurrentSceneName => _currentBackgroundScene.HasValue && _currentBackgroundScene.Value.IsValid()
            ? _currentBackgroundScene.Value.name : "없음";

        public BackgroundSceneDatabase Database
        {
            get => sceneDatabase;
            set => sceneDatabase = value;
        }

        private void Awake()
        {
            if (_instance != null && _instance != this)
            {
                Destroy(gameObject);
                return;
            }

            _instance = this;
            DontDestroyOnLoad(gameObject);
        }

        private void OnDestroy()
        {
            if (_instance == this)
            {
                _instance = null;
            }
        }

        /// <summary>
        /// 현재 활성 씬의 Directional Light와 NiloToonOverrider 백업 및 비활성화
        /// </summary>
        private void BackupAndDisableOriginalLighting()
        {
            if (_hasLightingBackup) return;

            _originalDirectionalLights.Clear();
            _originalNiloToonOverriders.Clear();

            var activeScene = SceneManager.GetActiveScene();
            if (!activeScene.isLoaded) return;

            var roots = activeScene.GetRootGameObjects();
            foreach (var root in roots)
            {
                // Directional Light 찾기
                var lights = root.GetComponentsInChildren<Light>(true);
                foreach (var light in lights)
                {
                    if (light.type == LightType.Directional)
                    {
                        _originalDirectionalLights.Add(new LightBackup
                        {
                            light = light,
                            wasEnabled = light.enabled
                        });
                        light.enabled = false;
                    }
                }

                // NiloToonCharacterMainLightOverrider 찾기
                var niloToonOverriders = root.GetComponentsInChildren<MonoBehaviour>(true)
                    .Where(mb => mb != null && mb.GetType().Name == "NiloToonCharacterMainLightOverrider");
                foreach (var overrider in niloToonOverriders)
                {
                    _originalNiloToonOverriders.Add(new ComponentBackup
                    {
                        component = overrider,
                        wasEnabled = overrider.enabled
                    });
                    overrider.enabled = false;
                }
            }

            _hasLightingBackup = true;

            int lightCount = _originalDirectionalLights.Count;
            int overriderCount = _originalNiloToonOverriders.Count;
            if (lightCount > 0 || overriderCount > 0)
            {
                UnityEngine.Debug.Log($"[Runtime] 기존 씬 라이팅 비활성화: Directional Light {lightCount}개, NiloToonOverrider {overriderCount}개");
            }
        }

        /// <summary>
        /// 백업된 라이팅 복원
        /// </summary>
        private void RestoreOriginalLighting()
        {
            if (!_hasLightingBackup) return;

            foreach (var backup in _originalDirectionalLights)
            {
                if (backup.light != null)
                {
                    backup.light.enabled = backup.wasEnabled;
                }
            }

            foreach (var backup in _originalNiloToonOverriders)
            {
                if (backup.component != null)
                {
                    backup.component.enabled = backup.wasEnabled;
                }
            }

            int lightCount = _originalDirectionalLights.Count(b => b.light != null);
            int overriderCount = _originalNiloToonOverriders.Count(b => b.component != null);
            if (lightCount > 0 || overriderCount > 0)
            {
                UnityEngine.Debug.Log($"[Runtime] 기존 씬 라이팅 복원: Directional Light {lightCount}개, NiloToonOverrider {overriderCount}개");
            }

            _originalDirectionalLights.Clear();
            _originalNiloToonOverriders.Clear();
            _hasLightingBackup = false;
        }

        /// <summary>
        /// 배경 씬 로드 (Additive)
        /// </summary>
        public void LoadScene(BackgroundSceneInfo sceneInfo, bool unloadCurrent = true)
        {
            if (sceneInfo == null)
            {
                OnError?.Invoke("씬 정보가 없습니다.");
                return;
            }

            StartCoroutine(LoadSceneCoroutine(sceneInfo, unloadCurrent));
        }

        /// <summary>
        /// 씬 경로로 로드
        /// </summary>
        public void LoadScene(string scenePath, bool unloadCurrent = true)
        {
            if (sceneDatabase == null)
            {
                OnError?.Invoke("씬 데이터베이스가 설정되지 않았습니다.");
                return;
            }

            var sceneInfo = sceneDatabase.FindByPath(scenePath);
            if (sceneInfo == null)
            {
                OnError?.Invoke($"씬을 찾을 수 없습니다: {scenePath}");
                return;
            }

            LoadScene(sceneInfo, unloadCurrent);
        }

        /// <summary>
        /// 현재 배경 씬 언로드
        /// </summary>
        public void UnloadCurrentScene()
        {
            if (_currentBackgroundScene.HasValue && _currentBackgroundScene.Value.isLoaded)
            {
                StartCoroutine(UnloadSceneCoroutine(_currentBackgroundScene.Value));
            }
        }

        private IEnumerator LoadSceneCoroutine(BackgroundSceneInfo sceneInfo, bool unloadCurrent)
        {
            if (_isLoading)
            {
                OnError?.Invoke("이미 씬을 로드 중입니다.");
                yield break;
            }

            _isLoading = true;
            OnSceneLoadStarted?.Invoke(sceneInfo);

            // 현재 씬 언로드 (새 배경 로드 시에는 라이팅 복원하지 않음)
            if (unloadCurrent && _currentBackgroundScene.HasValue && _currentBackgroundScene.Value.isLoaded)
            {
                var unloadOp = SceneManager.UnloadSceneAsync(_currentBackgroundScene.Value);
                if (unloadOp != null)
                {
                    while (!unloadOp.isDone)
                    {
                        yield return null;
                    }
                }
                OnSceneUnloaded?.Invoke(_currentBackgroundScene.Value.name);
                _currentBackgroundScene = null;
            }

            // 새 씬 로드
#if UNITY_EDITOR
            // 에디터에서는 EditorSceneManager 사용 (별도 처리 필요)
            if (!Application.isPlaying)
            {
                _isLoading = false;
                OnError?.Invoke("에디터 비플레이 모드에서는 EditorSceneManager를 사용하세요.");
                yield break;
            }
#endif

            // 씬이 빌드 세팅에 있는지 확인
            bool sceneInBuild = false;
            for (int i = 0; i < SceneManager.sceneCountInBuildSettings; i++)
            {
                string scenePath = SceneUtility.GetScenePathByBuildIndex(i);
                if (scenePath == sceneInfo.scenePath)
                {
                    sceneInBuild = true;
                    break;
                }
            }

            if (!sceneInBuild)
            {
                _isLoading = false;
                OnError?.Invoke($"씬이 빌드 세팅에 없습니다: {sceneInfo.scenePath}\n에디터에서는 Streamingle > Background Scene Loader를 사용하세요.");
                yield break;
            }

            // 기존 씬의 Directional Light와 NiloToonOverrider 비활성화
            BackupAndDisableOriginalLighting();

            _currentOperation = SceneManager.LoadSceneAsync(sceneInfo.scenePath, LoadSceneMode.Additive);

            if (_currentOperation == null)
            {
                _isLoading = false;
                RestoreOriginalLighting(); // 로드 실패 시 복원
                OnError?.Invoke($"씬 로드 실패: {sceneInfo.scenePath}");
                yield break;
            }

            while (!_currentOperation.isDone)
            {
                OnLoadProgress?.Invoke(_currentOperation.progress);
                yield return null;
            }

            // 로드된 씬 찾기
            _currentBackgroundScene = SceneManager.GetSceneByPath(sceneInfo.scenePath);

            _isLoading = false;
            _currentOperation = null;

            OnSceneLoadCompleted?.Invoke(sceneInfo);
        }

        private IEnumerator UnloadSceneCoroutine(Scene scene)
        {
            string sceneName = scene.name;

            var unloadOp = SceneManager.UnloadSceneAsync(scene);
            if (unloadOp != null)
            {
                while (!unloadOp.isDone)
                {
                    yield return null;
                }
            }

            _currentBackgroundScene = null;

            // 기존 씬의 Directional Light와 NiloToonOverrider 복원
            RestoreOriginalLighting();

            OnSceneUnloaded?.Invoke(sceneName);
        }

        /// <summary>
        /// 씬 로드 취소
        /// </summary>
        public void CancelLoad()
        {
            if (_currentOperation != null)
            {
                // Unity에서는 씬 로드 취소가 직접적으로 불가능
                // 대신 로드 완료 후 즉시 언로드
                _isLoading = false;
            }
        }
    }
}