using UnityEngine;
using UnityEngine.InputSystem;
using UnityEngine.InputSystem.LowLevel;

namespace BaseGames.UI
{
    /// <summary>
    /// 设备检测器 —— 监听 InputSystem 的事件流，识别玩家最后使用的输入设备类型，
    /// 并通过 InputDeviceTypeEventChannelSO 广播给全局。
    ///
    /// 布置方式：挂在 UIRoot 或常驻 GameObject 上；只需存在一个实例。
    /// </summary>
    public sealed class InputDeviceDetector : MonoBehaviour
    {
        [Header("Event Channel")]
        [Tooltip("广播当前设备类型变化")]
        [SerializeField] private InputDeviceTypeEventChannelSO _onDeviceChanged;

        /// <summary>当前活跃输入设备类型，供轮询使用。</summary>
        public InputDeviceType CurrentDevice { get; private set; } = InputDeviceType.KeyboardMouse;

        private void OnEnable()
        {
            // 监听所有输入事件：每次有任何 StateEvent/DeltaStateEvent 时触发
            InputSystem.onEvent += OnInputSystemEvent;
            // 监听设备连接/断开（热插拔）
            InputSystem.onDeviceChange += OnDeviceChange;
        }

        private void OnDisable()
        {
            InputSystem.onEvent     -= OnInputSystemEvent;
            InputSystem.onDeviceChange -= OnDeviceChange;
        }

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

        private void OnInputSystemEvent(InputEventPtr eventPtr, InputDevice device)
        {
            // 只关心真实输入事件，滤掉内部状态事件
            if (!eventPtr.IsA<StateEvent>() && !eventPtr.IsA<DeltaStateEvent>()) return;

            var detected = ClassifyDevice(device);
            if (detected == CurrentDevice) return;

            CurrentDevice = detected;
            _onDeviceChanged?.Raise(CurrentDevice);
        }

        private void OnDeviceChange(InputDevice device, InputDeviceChange change)
        {
            // 当设备重新连接时重新检测（防止手柄拔插后图标仍显示手柄图标）
            if (change == InputDeviceChange.Reconnected || change == InputDeviceChange.Added)
            {
                // 保持当前 CurrentDevice 不变，等到实际输入事件再切换
            }
        }

        // ── Device Classification ─────────────────────────────────────────────

        /// <summary>
        /// 根据 InputDevice 的布局层次识别设备类型。
        /// Unity InputSystem 的设备层次：
        ///   DualShockGamepad → Gamepad → HID
        ///   XInputController → Gamepad → HID
        ///   SwitchProControllerHID → Gamepad → HID
        ///   Keyboard / Mouse
        /// </summary>
        private static InputDeviceType ClassifyDevice(InputDevice device)
        {
            if (device is Keyboard or Mouse)
                return InputDeviceType.KeyboardMouse;

            if (device is Gamepad gamepad)
            {
                var desc = gamepad.description;
                string manufacturer = desc.manufacturer ?? string.Empty;
                string product      = desc.product      ?? string.Empty;
                string interfaceName = desc.interfaceName ?? string.Empty;

                // PlayStation: DualShock 3/4 or DualSense (PS5)
                if (InputSystem.IsFirstLayoutBasedOnSecond(gamepad.layout, "DualShockGamepad")
                    || product.Contains("DualShock", System.StringComparison.OrdinalIgnoreCase)
                    || product.Contains("DualSense", System.StringComparison.OrdinalIgnoreCase)
                    || manufacturer.Contains("Sony", System.StringComparison.OrdinalIgnoreCase))
                    return InputDeviceType.PlayStationController;

                // Nintendo Switch Pro Controller / Joy-Con
                if (InputSystem.IsFirstLayoutBasedOnSecond(gamepad.layout, "SwitchProControllerHID")
                    || product.Contains("Switch", System.StringComparison.OrdinalIgnoreCase)
                    || product.Contains("Joy-Con", System.StringComparison.OrdinalIgnoreCase)
                    || manufacturer.Contains("Nintendo", System.StringComparison.OrdinalIgnoreCase))
                    return InputDeviceType.SwitchController;

                // Xbox / XInput (DirectInput 会走 HID 路径，XInput 走 XInputController)
                if (InputSystem.IsFirstLayoutBasedOnSecond(gamepad.layout, "XInputController")
                    || product.Contains("Xbox", System.StringComparison.OrdinalIgnoreCase)
                    || interfaceName.Equals("XInput", System.StringComparison.OrdinalIgnoreCase))
                    return InputDeviceType.XboxController;

                // 未知手柄 → 默认 Xbox 图标集
                return InputDeviceType.XboxController;
            }

            // 无法识别 → 键鼠
            return InputDeviceType.KeyboardMouse;
        }
    }
}