using System.Collections;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using BaseGames.Core;
using BaseGames.Core.Assets;
using BaseGames.Core.Events;

namespace BaseGames.UI.MainMenu
{
    /// <summary>
    /// 主菜单 UI 控制器（挂载在 Scene_MainMenu 的根 Canvas 上）。
    ///
    /// 面板结构（按 Inspector 绑定）：
    ///   ├── MainButtonsPanel  — 主按钮组（新游戏 / 继续 / 设置 / 制作团队 / 退出）
    ///   ├── SaveSlotPanel     — 存档槽选择（新游戏 & 继续共用）
    ///   ├── SettingsPanel     — 设置面板
    ///   └── CreditsPanel      — 制作团队面板
    ///
    /// 入场动画：主按钮组从下方滑入（代码驱动，无需 Animator）。
    ///
    /// 流程：
    ///   玩家选择存档槽（SaveSlotController 发布 _onSlotConfirmed）
    ///   → 关闭存档槽面板 → 发布 SceneLoadRequest（目标游戏场景）
    ///   → GameManager 响应，进入 LoadingScene 状态，显示加载画面，最终切换到 Gameplay。
    /// </summary>
    public class MainMenuController : MonoBehaviour
    {
        // ── 面板引用 ──────────────────────────────────────────────────────────

        [Header("面板")]
        [SerializeField] private CanvasGroup   _mainButtonsGroup;
        [SerializeField] private RectTransform _mainButtonsRect;   // 用于滑入动画
        [SerializeField] private GameObject    _saveSlotPanel;
        [Tooltip("存档槽面板控制器。打开前调用 SetMode 区分新游戏 / 继续语境。")]
        [SerializeField] private BaseGames.UI.Menus.SaveSlotController _saveSlotController;
        [SerializeField] private GameObject    _settingsPanel;
        [SerializeField] private GameObject    _creditsPanel;

        // ── 按钮引用 ──────────────────────────────────────────────────────────

        [Header("主菜单按钮")]
        [SerializeField] private Button _btnNewGame;
        [SerializeField] private Button _btnContinue;
        [SerializeField] private Button _btnSettings;
        [SerializeField] private Button _btnCredits;
        [SerializeField] private Button _btnQuit;

        // ── 按钮（子面板关闭）────────────────────────────────────────────────

        [Header("子面板关闭按钮（可选）")]
        [SerializeField] private Button _btnCloseSaveSlot;
        [SerializeField] private Button _btnCloseSettings;
        [SerializeField] private Button _btnCloseCredits;

        // ── 入场动画参数 ──────────────────────────────────────────────────────

        [Header("入场动画")]
        [Tooltip("按钮组初始偏移（像素，向下）")]
        [SerializeField] private float _entrySlideOffset = 80f;
        [Tooltip("入场动画持续时间（秒）")]
        [SerializeField] private float _entryDuration    = 0.55f;

        // ── 游戏场景 ──────────────────────────────────────────────────────────

        [Header("场景")]
        [Tooltip("新游戏 / 继续后进入的第一个游戏场景（Addressable Key）")]
        [SerializeField] private string _firstGameSceneKey = AddressKeys.SceneGameChapter1;

        // ── Event Channels ────────────────────────────────────────────────────

        [Header("Event Channels - Listen")]
        [SerializeField] private GameStateEventChannelSO _onGameStateChanged;
        [Tooltip("SaveSlotController 完成选槽后发布（携带槽索引）")]
        [SerializeField] private IntEventChannelSO       _onSlotConfirmed;

        [Header("Event Channels - Raise")]
        [SerializeField] private SceneLoadRequestEventChannelSO _onSceneLoadRequest;

        // ── 内部状态 ──────────────────────────────────────────────────────────

        private readonly CompositeDisposable _subs = new();
        private Vector2 _buttonsPanelOriginalPos;

        // ── 生命周期 ──────────────────────────────────────────────────────────

        private void Awake()
        {
            // 按钮绑定
            _btnNewGame? .onClick.AddListener(OnNewGameClicked);
            _btnContinue?.onClick.AddListener(OnContinueClicked);
            _btnSettings?.onClick.AddListener(OnSettingsClicked);
            _btnCredits? .onClick.AddListener(OnCreditsClicked);
            _btnQuit?    .onClick.AddListener(Application.Quit);

            _btnCloseSaveSlot?.onClick.AddListener(() => CloseSubPanel(_saveSlotPanel, _btnNewGame));
            _btnCloseSettings?.onClick.AddListener(() => CloseSubPanel(_settingsPanel, _btnSettings));
            _btnCloseCredits? .onClick.AddListener(() => CloseSubPanel(_creditsPanel,  _btnCredits));

            // 记录按钮组原始位置（供动画使用）
            if (_mainButtonsRect != null)
                _buttonsPanelOriginalPos = _mainButtonsRect.anchoredPosition;

            // 初始状态：隐藏子面板，主按钮组不可见（等待入场动画）
            SetPanel(_saveSlotPanel, false);
            SetPanel(_settingsPanel, false);
            SetPanel(_creditsPanel,  false);
            SetButtonsGroupVisible(false);

            // 刷新"继续"按钮可用性（需要至少一个有效存档）
            RefreshContinueButton();
        }

        private void OnEnable()
        {
            _onGameStateChanged?.Subscribe(HandleGameStateChanged).AddTo(_subs);
            _onSlotConfirmed?   .Subscribe(HandleSlotConfirmed).AddTo(_subs);
        }

        private void OnDisable() => _subs.Clear();

        private void Start()
        {
            // 场景初始化完成后播放入场动画
            StartCoroutine(PlayEntryAnimation());
        }

        // ── 入场动画 ─────────────────────────────────────────────────────────

        private IEnumerator PlayEntryAnimation()
        {
            if (_mainButtonsGroup == null) yield break;

            Vector2 startPos = _buttonsPanelOriginalPos - new Vector2(0f, _entrySlideOffset);
            if (_mainButtonsRect != null)
                _mainButtonsRect.anchoredPosition = startPos;

            float elapsed = 0f;
            while (elapsed < _entryDuration)
            {
                float t = Mathf.SmoothStep(0f, 1f, elapsed / _entryDuration);
                _mainButtonsGroup.alpha = t;
                if (_mainButtonsRect != null)
                    _mainButtonsRect.anchoredPosition = Vector2.Lerp(startPos, _buttonsPanelOriginalPos, t);
                elapsed += Time.unscaledDeltaTime;
                yield return null;
            }

            _mainButtonsGroup.alpha = 1f;
            if (_mainButtonsRect != null)
                _mainButtonsRect.anchoredPosition = _buttonsPanelOriginalPos;

            _mainButtonsGroup.interactable   = true;
            _mainButtonsGroup.blocksRaycasts = true;

            // 手柄导航：入场动画完成后将焦点置于第一个按钮
            EventSystem.current?.SetSelectedGameObject(_btnNewGame?.gameObject);
        }

        // ── 按钮回调 ─────────────────────────────────────────────────────────

        private void OnNewGameClicked()
        {
            _saveSlotController?.SetMode(BaseGames.UI.Menus.SaveSlotPanelMode.NewGame);
            OpenSubPanel(_saveSlotPanel);
        }
        private void OnContinueClicked()
        {
            _saveSlotController?.SetMode(BaseGames.UI.Menus.SaveSlotPanelMode.Continue);
            OpenSubPanel(_saveSlotPanel);
        }
        private void OnSettingsClicked() => OpenSubPanel(_settingsPanel);  // SettingsPanelController 自行设焦点
        private void OnCreditsClicked()
        {
            OpenSubPanel(_creditsPanel);
            // Credits 面板无独立控制器，打开时把焦点交给返回按钮（键盘 / 手柄可直接退出）
            if (_btnCloseCredits != null)
                EventSystem.current?.SetSelectedGameObject(_btnCloseCredits.gameObject);
        }

        /// <summary>打开子面板：禁用主按钮组交互，避免键盘/手柄导航"穿透"到背后的主菜单按钮。</summary>
        private void OpenSubPanel(GameObject panel)
        {
            SetMainButtonsInteractable(false);
            SetPanel(panel, true);
        }

        /// <summary>关闭子面板：恢复主按钮组交互，并把焦点恢复到对应主菜单按钮（导航连续性）。</summary>
        private void CloseSubPanel(GameObject panel, Button focusAfter)
        {
            SetPanel(panel, false);
            SetMainButtonsInteractable(true);
            if (focusAfter != null)
                EventSystem.current?.SetSelectedGameObject(focusAfter.gameObject);
        }

        private void SetMainButtonsInteractable(bool on)
        {
            if (_mainButtonsGroup == null) return;
            _mainButtonsGroup.interactable   = on;
            _mainButtonsGroup.blocksRaycasts = on;
        }

        // ── 存档槽确认 ───────────────────────────────────────────────────────

        private void HandleSlotConfirmed(int _)
        {
            SetPanel(_saveSlotPanel, false);

            // 继续游戏：存档已记录检查点场景时加载该场景并落在存档点出生位；
            // 否则（新游戏 / 存档尚无检查点）加载首关。
            var svc = ServiceLocator.GetOrDefault<ISaveService>();
            string checkpointScene = svc?.LastCheckpointScene;
            bool   hasCheckpoint   = !string.IsNullOrEmpty(checkpointScene);

            _onSceneLoadRequest?.Raise(new SceneLoadRequest
            {
                SceneName         = hasCheckpoint ? checkpointScene : _firstGameSceneKey,
                EntryTransitionId = hasCheckpoint ? svc.LastCheckpointSpawnId : null,
                TransitionType    = TransitionType.Scene,
                ShowLoadingScreen = true,
            });
        }

        // ── 游戏状态响应 ─────────────────────────────────────────────────────

        private void HandleGameStateChanged(GameStateId state)
        {
            bool isMainMenu = state == GameStates.MainMenu;
            // 离开 MainMenu（加载游戏中）时锁定所有交互，防止重复点击
            if (_mainButtonsGroup != null)
            {
                _mainButtonsGroup.interactable   = isMainMenu;
                _mainButtonsGroup.blocksRaycasts = isMainMenu;
            }
        }

        // ── 工具方法 ─────────────────────────────────────────────────────────

        private void RefreshContinueButton()
        {
            if (_btnContinue == null) return;

            var saveService = ServiceLocator.GetOrDefault<ISaveService>();
            bool hasAny = saveService != null
                && (saveService.HasSave(0) || saveService.HasSave(1) || saveService.HasSave(2));
            _btnContinue.interactable = hasAny;
        }

        private static void SetPanel(GameObject panel, bool active)
        {
            if (panel != null) panel.SetActive(active);
        }

        private void SetButtonsGroupVisible(bool visible)
        {
            if (_mainButtonsGroup == null) return;
            _mainButtonsGroup.alpha          = visible ? 1f : 0f;
            _mainButtonsGroup.interactable   = visible;
            _mainButtonsGroup.blocksRaycasts = visible;
        }
    }
}