using UnityEngine;
using UnityEngine.Events;

/// <summary>
/// 核心交互系统：射线检测 + 点击/拖拽处理。
/// 挂在主相机或专用 GameObject 上。
/// </summary>
public class InteractionSystem : MonoBehaviour
{
    [Header("射线配置")]
    [SerializeField] private Camera _mainCamera;
    [SerializeField] private LayerMask _interactableMask = ~0;
    [SerializeField] private float _maxRayDistance = 100f;

    [Header("事件 - 由 StepManager 绑定")]
    public UnityEvent<string> OnObjectClicked;   // 点击到 Tag 时触发，传 Tag
    public UnityEvent OnAnywhereClicked;          // 点击空白处触发

    [Header("拖拽配置")]
    [SerializeField] private float _dragPlaneDistance = 2f;
    [SerializeField] private float _snapDistance = 0.3f;

    private GameObject _draggedObject;
    private Vector3 _dragOffset;
    private float _dragZ;
    private bool _isDragging;

    // 考核模式序列点击
    private int _sequenceClickCount;
    private string[] _expectedSequence;

    private void Awake()
    {
        if (_mainCamera == null)
            _mainCamera = Camera.main;
    }

    private void Update()
    {
        HandleClick();
        HandleDrag();
    }

    #region 点击处理

    private void HandleClick()
    {
        if (!Input.GetMouseButtonDown(0)) return;
        if (UnityEngine.EventSystems.EventSystem.current != null &&
            UnityEngine.EventSystems.EventSystem.current.IsPointerOverGameObject())
            return;

        Ray ray = _mainCamera.ScreenPointToRay(Input.mousePosition);
        if (Physics.Raycast(ray, out RaycastHit hit, _maxRayDistance, _interactableMask))
        {
            string tag = hit.collider.tag;
            if (!string.IsNullOrEmpty(tag))
            {
                Debug.Log($"InteractionSystem: 点击到物体 Tag={tag}");
                OnObjectClicked?.Invoke(tag);
                return;
            }
        }

        OnAnywhereClicked?.Invoke();
    }

    #endregion

    #region 拖拽处理

    private void HandleDrag()
    {
        if (Input.GetMouseButtonDown(0))
        {
            if (UnityEngine.EventSystems.EventSystem.current != null &&
                UnityEngine.EventSystems.EventSystem.current.IsPointerOverGameObject())
                return;

            Ray ray = _mainCamera.ScreenPointToRay(Input.mousePosition);
            if (Physics.Raycast(ray, out RaycastHit hit, _maxRayDistance, _interactableMask))
            {
                var draggable = hit.collider.GetComponent<DraggableObject>();
                if (draggable != null && draggable.IsDraggable)
                {
                    _draggedObject = hit.collider.gameObject;
                    _dragZ = _mainCamera.WorldToScreenPoint(_draggedObject.transform.position).z;
                    _isDragging = true;
                    draggable.OnDragStart();
                }
            }
        }

        if (Input.GetMouseButton(0) && _isDragging && _draggedObject != null)
        {
            Vector3 screenPos = new Vector3(Input.mousePosition.x, Input.mousePosition.y, _dragZ);
            Vector3 worldPos = _mainCamera.ScreenToWorldPoint(screenPos);
            _draggedObject.transform.position = worldPos;
        }

        if (Input.GetMouseButtonUp(0) && _isDragging && _draggedObject != null)
        {
            var draggable = _draggedObject.GetComponent<DraggableObject>();

            if (draggable != null && draggable.SnapTarget != null)
            {
                float dist = Vector3.Distance(_draggedObject.transform.position, draggable.SnapTarget.position);
                if (dist <= _snapDistance)
                {
                    _draggedObject.transform.position = draggable.SnapTarget.position;
                    _draggedObject.transform.rotation = draggable.SnapTarget.rotation;
                    draggable.OnSnapped();
                }
            }

            draggable?.OnDragEnd();
            _draggedObject = null;
            _isDragging = false;
        }
    }

    #endregion

    #region 考核序列点击

    public void BeginSequenceCheck(string[] expectedTags)
    {
        _expectedSequence = expectedTags;
        _sequenceClickCount = 0;
    }

    public bool TrySequenceClick(string clickedTag, out bool isComplete)
    {
        isComplete = false;
        if (_expectedSequence == null || _sequenceClickCount >= _expectedSequence.Length)
            return false;

        if (clickedTag == _expectedSequence[_sequenceClickCount])
        {
            _sequenceClickCount++;
            if (_sequenceClickCount >= _expectedSequence.Length)
            {
                isComplete = true;
                _expectedSequence = null;
                return true;
            }
            return true;
        }
        return false;
    }

    /// <summary>获取当前序列已正确命中的步数（用于 proportion 计分）</summary>
    public int GetSequenceHitCount()
    {
        return _sequenceClickCount;
    }

    #endregion

    #region 公共方法

    public void SetInteractionEnabled(bool enabled)
    {
        this.enabled = enabled;
    }

    #endregion
}