using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using TMPro;
using BaseGames.Core.Events;
using BaseGames.Localization;

namespace BaseGames.UI.MainMenu
{
    /// <summary>
    /// 新游戏模式（难度）选择面板，<b>数据驱动</b>：据 <see cref="NewGameModeConfigSO"/> 生成难度按钮，
    /// 经 <see cref="IUINavigator"/> 模态压栈，返回 <see cref="DifficultyLevel"/>；
    /// 点返回 / 按 ESC 取消则返回 null（由 <see cref="UIResultPanel{T}"/> 兜底）。
    /// 选中某项时在共享说明区显示其 descKey（手柄/鼠标导航通用）。
    /// 策划改 UI_NewGameModeConfig 即可增删/重排难度、改标签/说明；样式改 UI_NewGameModePanel / UI_MainMenu_Button 预制件。
    /// </summary>
    public class NewGameModeController : UIResultPanel<DifficultyLevel?>
    {
        [Header("数据表 / 选项列表")]
        [SerializeField] private NewGameModeConfigSO _config;
        [Tooltip("难度按钮的父节点（通常挂 VerticalLayoutGroup）。")]
        [SerializeField] private Transform           _container;
        [SerializeField] private MainMenuButtonView  _buttonPrefab;

        [Header("引用")]
        [SerializeField] private LocalizedText _titleText;
        [Tooltip("当前选中难度的说明文本（随选中项切换）。")]
        [SerializeField] private TMP_Text      _descText;
        [SerializeField] private Button        _btnBack;

        // 取消 / ESC / 返回默认结果：未选择。
        protected override DifficultyLevel? CancelResult => null;

        private readonly List<(MainMenuButtonView view, string descKey)> _options = new();
        private MainMenuButtonView _firstButton;
        private GameObject _lastSelected;

        private void Awake() => _btnBack?.onClick.AddListener(() => Complete(null));

        protected override void OnPanelOpen() => BuildMenu();

        /// <summary>默认焦点：第一项（通常普通难度），避免误选高难项。</summary>
        protected override GameObject ResolveFirstSelected()
            => _firstButton != null ? _firstButton.Button.gameObject
             : _btnBack != null ? _btnBack.gameObject : null;

        /// <summary>据配置重建难度按钮（public 以便编辑器预览/测试）。</summary>
        public void BuildMenu()
        {
            ClearMenu();
            if (_titleText != null && _config != null) _titleText.SetKey(_config.TitleKey);
            if (_config == null || _container == null || _buttonPrefab == null) return;

            foreach (var item in _config.Items)
            {
                var view = Instantiate(_buttonPrefab, _container);
                view.gameObject.SetActive(true);
                var level = item.level;
                view.Bind(item.labelKey, item.icon, () => Complete(level));
                _options.Add((view, item.descKey));
                if (_firstButton == null) _firstButton = view;
            }
            if (_descText != null) _descText.text = string.Empty;
            _lastSelected = null;
        }

        private void ClearMenu()
        {
            _options.Clear();
            _firstButton = null;
            if (_container == null) return;
            for (int i = _container.childCount - 1; i >= 0; i--)
            {
                var c = _container.GetChild(i).gameObject;
                if (Application.isPlaying) Destroy(c); else DestroyImmediate(c);
            }
        }

        // 显示当前选中难度的说明（轮询 EventSystem 选中项；手柄/鼠标导航通用，按钮无需额外组件）。
        private void Update()
        {
            if (_descText == null || EventSystem.current == null) return;
            var sel = EventSystem.current.currentSelectedGameObject;
            if (sel == _lastSelected) return;
            _lastSelected = sel;

            string descKey = null;
            foreach (var (view, dk) in _options)
                if (view != null && view.Button != null && view.Button.gameObject == sel) { descKey = dk; break; }
            _descText.text = string.IsNullOrEmpty(descKey)
                ? string.Empty
                : LocalizationManager.Get(descKey, LocalizationTable.UI);
        }

        /// <summary>弹出难度选择并等待结果（DifficultyLevel / null=取消）。由导航器压栈管理。</summary>
        public Task<DifficultyLevel?> ShowAsync(CancellationToken ct = default)
        {
            var nav = GetService<IUINavigator>();
            if (nav == null)
            {
                Debug.LogError("[NewGameMode] 未找到 IUINavigator 服务，无法弹出模式选择。", this);
                return Task.FromResult<DifficultyLevel?>(null);
            }
            return nav.PushForResultAsync<DifficultyLevel?>(this, ct);
        }
    }
}