using System.Collections;
using System.Collections.Generic;
using AK.Wwise;
using Ichni.Menu;
using Ichni.Story;
using Ichni.Story.UI;
using Ichni.UI;
using Sirenix.OdinInspector;
using SLSUtilities.WwiseAssistance;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.Serialization;

namespace Ichni
{
    public partial class MenuManager : MonoBehaviour
    {
        public static MenuManager instance;
        
        public StartUIPage startUIPage;
        public LoginPage loginPage;
        public ChapterSelectionUIPage chapterSelectionUIPage;
        public StoryUIPage storyUIPage;
        // dialogUIPage 已随旧对话系统移除；阶段 3 将接入新的 VN 对话页面引用
        public SongSelectionUIPage songSelectionUIPage;
        public TransitionUIPage transitionUIPage;
        public SettingsUIPage settingsUIPage;

        public List<string> languageList;
        public List<string> displayLanguageList;
    }
    
    public partial class MenuManager
    {
        private const string GameSceneName = "GameScene";
        private const float DefaultTransitionDelay = 0.6f;

        private Coroutine gameSceneLoadCoroutine;
        private AsyncOperation gameSceneLoadOperation;

        /// <summary>
        /// 是否已经接受了某个进入游戏的请求。
        /// 从确认进入开始便保持为 true，用于阻止按钮连点和多个入口同时发起场景切换。
        /// </summary>
        public bool isEnteringGame { get; private set; }

        /// <summary>
        /// 当前是否可以接受新的 GameScene 进入请求。
        /// GameScene 改为玩家确认后按需加载，因此不再依赖菜单启动阶段的预加载句柄。
        /// </summary>
        public bool CanBeginGame =>
            !isEnteringGame &&
            gameSceneLoadCoroutine == null &&
            gameSceneLoadOperation == null;
        
        private void Awake()
        {
            instance = this;
        }

        private void Start()
        {
            isEnteringGame = false;
            
            InformationTransistor information = InformationTransistor.instance;
            MenuReturnDestination returnDestination = information != null
                ? information.menuReturnDestination
                : MenuReturnDestination.None;

            if (returnDestination == MenuReturnDestination.SongSelection &&
                information != null && information.chapter != null &&
                information.song != null && information.difficulty != null)
            {
                startUIPage.mainCanvasGroup.gameObject.SetActive(false);
                ChapterSelectionManager.instance.currentChapter = 
                    information.chapter;
                AudioManager.SetSwitch(ChapterSelectionManager.instance.currentChapter.chapterSwitch);
                MenuInformationRecorder.instance.songSelectionRecords[
                    ChapterSelectionManager.instance.currentChapter] =
                    new SongSelectionRecord(information.song, information.difficulty);
                songSelectionUIPage.FadeIn();
            }
            else if (returnDestination == MenuReturnDestination.Story &&
                     information != null && information.chapter != null)
            {
                startUIPage.mainCanvasGroup.gameObject.SetActive(false);
                ChapterSelectionManager.instance.currentChapter = information.chapter;
                AudioManager.SetSwitch(ChapterSelectionManager.instance.currentChapter.chapterSwitch);

                // MenuScene 会在教程游玩后重新创建，必须显式重建章节故事树，
                // 不能依赖旧场景中残留的 Block 实例。
                StoryManager.instance?.OpenChapter(ChapterSelectionManager.instance.currentChapter.chapterIndex);
                storyUIPage.FadeIn();
                StoryManager.instance?.RestoreStoryAfterGameReturn();
            }

            // 返回目标是一次性运行态信息。无论是否能恢复页面，都不能让它在下次重进菜单时重复生效。
            information?.ClearMenuReturnDestination();
            
            Application.targetFrameRate = SettingsManager.instance.settingsSaveData.targetFrame;
        }
    }
    
    public partial class MenuManager
    {
        public void EnterGame()
        {
            ScheduleGameSceneLoad(ResolveCurrentReturnDestination(), 0f);
        }

        /// <summary>
        /// 按需加载 GameScene，并写入唯一的菜单返回目标。
        /// 普通选曲使用 <see cref="MenuReturnDestination.SongSelection"/>，教程使用
        /// <see cref="MenuReturnDestination.Story"/>。
        /// </summary>
        public void EnterGame(MenuReturnDestination returnDestination)
        {
            ScheduleGameSceneLoad(returnDestination, 0f);
        }

        /// <summary>
        /// 为 TutorialBlock 等非选曲入口准备上下文并播放通用转场。
        /// 运行成功后会返回 true；返回 false 时不会修改剧情变量或存档，调用方应保留原状。
        /// </summary>
        public bool TryBeginGame(ChapterSelectionUnit chapter, SongItemData song,
            DifficultyData difficulty, MenuReturnDestination returnDestination, UIPageBase sourcePage)
        {
            if (!CanBeginGame)
            {
                Debug.LogWarning("[MenuManager] 菜单已经接受其它进入请求，忽略本次 GameScene 启动请求。");
                return false;
            }

            if (InformationTransistor.instance == null || chapter == null || song == null || difficulty == null)
            {
                return false;
            }

            if (!TryReserveGameEntry())
                return false;

            if (!InformationTransistor.instance.PrepareGameLaunch(chapter, song, difficulty, returnDestination))
            {
                CancelGameEntryReservation();
                return false;
            }

            sourcePage?.FadeOut();
            transitionUIPage?.FadeIn();
            AudioManager.Post(AK.EVENTS.ENTERTOGAME);

            return ScheduleGameSceneLoad(returnDestination, DefaultTransitionDelay);
        }

        /// <summary>
        /// 在进入动画开始前预占本次场景切换。
        /// 标准 Play、快速进入和 TutorialBlock 都必须通过这里防止同一帧的重复点击。
        /// </summary>
        public bool TryReserveGameEntry()
        {
            if (!CanBeginGame)
                return false;

            isEnteringGame = true;
            return true;
        }

        /// <summary>
        /// 为已经完成自定义入场动画的入口安排 GameScene 加载。
        /// 延迟使用 realtime，确保暂停或修改 timeScale 时仍能正常进入游戏。
        /// </summary>
        public bool ScheduleCurrentGameSceneLoad(float delay = DefaultTransitionDelay)
        {
            return ScheduleGameSceneLoad(ResolveCurrentReturnDestination(), delay);
        }

        /// <summary>
        /// 在指定转场延迟后启动 GameScene 的异步加载。
        /// 这里绝不把 allowSceneActivation 设为 false：场景开始加载后会自然完成并自动激活，
        /// 避免阻塞 Localization、Addressables 和其它 Unity AsyncOperation。
        /// </summary>
        public bool ScheduleGameSceneLoad(MenuReturnDestination returnDestination, float delay)
        {
            if (gameSceneLoadCoroutine != null || gameSceneLoadOperation != null)
            {
                Debug.LogWarning("[MenuManager] GameScene 加载已经安排或正在执行，忽略重复请求。");
                return false;
            }

            if (!isEnteringGame && !TryReserveGameEntry())
                return false;

            InformationTransistor.instance?.SetMenuReturnDestination(returnDestination);
            gameSceneLoadCoroutine = StartCoroutine(
                LoadGameSceneAfterTransition(Mathf.Max(0f, delay)));
            return true;
        }

        /// <summary>
        /// 保留给既有 UnityEvent 和旧调用点的立即加载入口。
        /// 新代码通常应使用 <see cref="ScheduleCurrentGameSceneLoad"/>，把转场延迟也交给 MenuManager。
        /// </summary>
        public void EnterGameScene()
        {
            ScheduleCurrentGameSceneLoad(0f);
        }

        private IEnumerator LoadGameSceneAfterTransition(float delay)
        {
            if (delay > 0f)
                yield return new WaitForSecondsRealtime(delay);

            MenuInputManager.instance?.gameInput?.Menu.Disable();

            try
            {
                gameSceneLoadOperation = SceneManager.LoadSceneAsync(
                    GameSceneName, LoadSceneMode.Single);
            }
            catch (System.Exception exception)
            {
                Debug.LogException(exception, this);
                HandleGameSceneLoadFailure("创建 GameScene 异步加载操作时发生异常。");
                yield break;
            }

            if (gameSceneLoadOperation == null)
            {
                HandleGameSceneLoadFailure(
                    $"SceneManager.LoadSceneAsync 未能创建场景 '{GameSceneName}' 的加载操作。");
                yield break;
            }

            // 不设置 allowSceneActivation=false。长时间挂起场景激活会冻结后续 AsyncOperation，
            // 导致 Addressables String Table、AssetBundle 等资源永久停留在 0%。
            while (!gameSceneLoadOperation.isDone)
                yield return null;
        }

        private MenuReturnDestination ResolveCurrentReturnDestination()
        {
            // 剧情 SongBlock 仅在玩家确认进入指定目标歌曲后才要求返回剧情；
            // 普通选曲与从剧情入口改选其它歌曲都继续返回选曲页。
            StorySongEntryContext context = InformationTransistor.instance?.storySongEntryContext;
            return context != null && context.isActive && context.returnToStoryAfterGame
                ? MenuReturnDestination.Story
                : MenuReturnDestination.SongSelection;
        }

        private void HandleGameSceneLoadFailure(string reason)
        {
            Debug.LogError($"[MenuManager] {reason}", this);
            gameSceneLoadCoroutine = null;
            gameSceneLoadOperation = null;
            CancelGameEntryReservation();
            MenuInputManager.instance?.gameInput?.Menu.Enable();
        }

        private void CancelGameEntryReservation()
        {
            isEnteringGame = false;
        }
    }
}