using System;
using UnityEngine;
using UnityEngine.InputSystem;
using BaseGames.Core;
using BaseGames.Core.Events;
using BaseGames.Input;

namespace BaseGames.UI
{
    /// <summary>
    /// 按键图标服务实现。
    ///
    /// 职责：
    ///   1. 侦听 InputDeviceTypeEventChannelSO，更新当前图标集
    ///   2. 侦听 InputSystem.onActionChange（BoundControlsChanged），改键后刷新
    ///   3. 提供 GetActionIcon / GetActionEffectivePath，供 UI 查询
    ///   4. 在 Awake 注册自身到 ServiceLocator
    ///
    /// 布置方式：与 InputDeviceDetector 同挂在 UIRoot 上；每场景只需一个实例。
    /// </summary>
    public sealed class InputIconService : MonoBehaviour, IInputIconService
    {
        [Header("Input")]
        [SerializeField] private InputReaderSO _inputReader;

        [Header("Icon Sets — 按设备类型配置")]
        [SerializeField] private InputDeviceIconSetSO _kbMouseSet;
        [SerializeField] private InputDeviceIconSetSO _xboxSet;
        [SerializeField] private InputDeviceIconSetSO _playStationSet;
        [SerializeField] private InputDeviceIconSetSO _switchSet;

        [Header("Event Channels")]
        [SerializeField] private InputDeviceTypeEventChannelSO _onDeviceChanged;

        // ── IInputIconService ─────────────────────────────────────────────────
        public InputDeviceType CurrentDevice { get; private set; } = InputDeviceType.KeyboardMouse;
        public event Action OnIconSetChanged;

        private InputDeviceIconSetSO _activeSet;
        private readonly CompositeDisposable _subs = new();

        // ── Lifecycle ─────────────────────────────────────────────────────────
        private void Awake()
        {
            ServiceLocator.RegisterIfAbsent<IInputIconService>(this);
            _activeSet = _kbMouseSet;
        }

        private void OnEnable()
        {
            _onDeviceChanged?.Subscribe(HandleDeviceChanged).AddTo(_subs);
            // 改键后 InputSystem 会广播 BoundControlsChanged
            InputSystem.onActionChange += HandleActionChange;
        }

        private void OnDisable()
        {
            _subs.Clear();
            InputSystem.onActionChange -= HandleActionChange;
        }

        private void OnDestroy()
        {
            ServiceLocator.Unregister<IInputIconService>(this);
        }

        // ── Event Handlers ────────────────────────────────────────────────────

        private void HandleDeviceChanged(InputDeviceType deviceType)
        {
            CurrentDevice = deviceType;
            _activeSet    = deviceType switch
            {
                InputDeviceType.XboxController        => _xboxSet        ?? _kbMouseSet,
                InputDeviceType.PlayStationController => _playStationSet ?? _kbMouseSet,
                InputDeviceType.SwitchController      => _switchSet      ?? _kbMouseSet,
                _                                     => _kbMouseSet,
            };
            OnIconSetChanged?.Invoke();
        }

        private void HandleActionChange(object obj, InputActionChange change)
        {
            if (change == InputActionChange.BoundControlsChanged)
                OnIconSetChanged?.Invoke();
        }

        // ── IInputIconService impl ────────────────────────────────────────────

        public Sprite GetActionIcon(string actionName)
        {
            var path = GetActionEffectivePath(actionName);
            if (path == null || _activeSet == null) return null;
            return _activeSet.GetIcon(path);
        }

        public string GetActionEffectivePath(string actionName)
        {
            if (_inputReader == null) return null;
            var action = _inputReader.FindAction(actionName);
            if (action == null) return null;

            // 通过 binding.groups 过滤，只返回匹配当前设备控制方案的绑定路径
            string schemeFilter = GetControlSchemeForDevice(CurrentDevice);

            foreach (var binding in action.bindings)
            {
                // 跳过复合绑定的父条目（无实际路径）
                if (binding.isComposite) continue;

                // 若 binding.groups 不含当前方案，则跳过（允许空 groups 的绑定匹配所有设备）
                if (!string.IsNullOrEmpty(schemeFilter)
                    && !string.IsNullOrEmpty(binding.groups)
                    && !binding.groups.Contains(schemeFilter, StringComparison.OrdinalIgnoreCase))
                    continue;

                // effectivePath 已自动合并 overridePath（改键后的路径）
                var path = binding.effectivePath;
                if (!string.IsNullOrEmpty(path)) return path;
            }

            return null;
        }

        // ── Helpers ───────────────────────────────────────────────────────────

        /// <summary>将设备类型映射到 InputActionAsset 中配置的控制方案名称。</summary>
        private static string GetControlSchemeForDevice(InputDeviceType device) => device switch
        {
            InputDeviceType.KeyboardMouse => "Keyboard&Mouse",
            _                            => "Gamepad",          // Xbox / PS / Switch 共用 Gamepad 方案
        };
    }
}