using System;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;

[RequireComponent(typeof(Button))]
public class UIButtonEx: Button
{
    private Button m_button;

    private enum DragState
    {
        None,
        Dragging,
        End
    }
    
    private bool _isPressed;
    private float _pressedTime;
    private bool _isCalled = false;
    private bool _isLongPressing;
    private bool _upDragCalled;
    private bool _outDragCalled;
    private DragState _curDragState;
    private Vector2 _mousePos;
    private Vector2 _lastFrameMousePos;
    private Vector2 _startDragPos;

    private const float MAX_PRESSED_TIME = 0.65f;
    private const float MIN_PRESSED_TIME = 0.2f;
    private const float MIN_DRAG_DISTANCE = 1f;
    private const float MIN_UP_DRAG_DIS = 40f;
    
    public delegate void OnLongPressCall();

    public delegate void OnPointUpCall();

    public delegate void OnStartDrag();
    public delegate void OnDrag();
    public delegate void OnEndDrag();
    public delegate void OnUpDrag();        //向上拖动

    public delegate void OnDragOut();       //向外拖动

    public delegate void OnClick();

    private OnLongPressCall _OnLongPress;
    private OnPointUpCall _OnPointUp;               //长按后抬起
    private OnStartDrag _OnStartDrag;
    private OnDrag _OnDrag;
    private OnEndDrag _OnEndDrag;
    private OnUpDrag _OnUpDrag;
    private OnDragOut _OnDragOut;
    private OnClick _OnClick;
    
    //测试代码
    private int _count = 0;

    private void Awake()
    {
        m_button = GetComponent<Button>();
    }
    
    void Update()
    {
        if (_isPressed)
        {
            _mousePos = InputManager.Instance.GetTouchPosition();
            _pressedTime += Time.deltaTime;

            //判断是否进入拖拽
            var distance = Vector2.Distance(_startDragPos, _mousePos);
            
            if (!_isLongPressing && distance > MIN_DRAG_DISTANCE && _curDragState == DragState.None)
            {
                _EnterDrag();
            }
            
            if (_IsDragging() && _lastFrameMousePos != _mousePos)
            {
                _OnDrag?.Invoke();
                if (!_upDragCalled)
                {
                    if(Math.Abs(_startDragPos.y - _mousePos.y) > MIN_UP_DRAG_DIS)
                    {
                        _OnUpDrag?.Invoke();
                        _upDragCalled = true;
                    }
                }

                if (!_outDragCalled)
                {
                    if (Vector2.Distance(_startDragPos, _mousePos) > MIN_UP_DRAG_DIS)
                    {
                        _OnDragOut?.Invoke();
                        _outDragCalled = true;
                    }
                }
            }
            
            if (_pressedTime > MAX_PRESSED_TIME && !_isCalled && !_IsDragging())
            {
                _isCalled = true;
                _isLongPressing = true;
                _OnLongPress?.Invoke();
            }

            _lastFrameMousePos = _mousePos;
        }
    }

    private bool _IsDragging()
    {
        return _curDragState == DragState.Dragging && !_isLongPressing;
    }

    private void _EnterDrag()
    {
        _curDragState = DragState.Dragging;
        _upDragCalled = false;
        _outDragCalled = false;
        _OnStartDrag?.Invoke();
    }

    private void _ExitDrag()
    {
        _curDragState = DragState.None;
        _upDragCalled = false;
        _outDragCalled = false;
        _OnEndDrag?.Invoke();
    }
    
    //按键放下和抬起
    public override void OnPointerDown(PointerEventData data)
    {
        _pressedTime = 0f;
        _isPressed = true;
        _startDragPos = InputManager.Instance.GetTouchPosition();
        _isLongPressing = false;
    }
    
    public override void OnPointerUp(PointerEventData data)
    {
        if ((_pressedTime > MIN_PRESSED_TIME && _pressedTime < MAX_PRESSED_TIME || _IsDragging()) && !_isLongPressing)
        {
            _OnPointUp?.Invoke();
        }
        else if(_pressedTime > 0)
        {
            _OnClick?.Invoke();
        }

        if (_IsDragging())
        {
            _ExitDrag();
        }
        
        _pressedTime = 0f;
        _isPressed = false;
        _isCalled = false;
        _isLongPressing = false;
        _upDragCalled = false;
        _outDragCalled = false;
    }

    
    //添加事件监听回调，外部调用接口
    public void AddLongPressListener(OnLongPressCall func)
    {
        _OnLongPress += func;
    }

    public void AddPointUpListener(OnPointUpCall func)
    {
        _OnPointUp += func;
    }

    public void AddUpDragListener(OnUpDrag func)
    {
        _OnUpDrag += func;
    }

    public void AddOutDragListener(OnDragOut func)
    {
        _OnDragOut += func;
    }
    
    public void AddClickListener(OnClick func)
    {
        _OnClick += func;
    }

    //移除事件绑定接口，外部调用
    public void RemoveAllListener()
    {
        if (m_button)
        {
            m_button.onClick.RemoveAllListeners();
        }
        
        // Delegate[] onLongPressList = OnLongPress.GetInvocationList();
        // Delegate[] onPointUpList = OnPointUp.GetInvocationList();
        // foreach (var deleg in onLongPressList)
        // {
        //     OnLongPress -= deleg as OnLongPressCall;
        // }
        // foreach (var deleg in onPointUpList)
        // {
        //     OnPointUp -= deleg as OnPointUpCall;
        // }
    }
    
    public void RemoveListener<T>(T call)
    {
        if (call is OnLongPressCall pressCall)
        {
            _OnLongPress -= pressCall;
        }
    }
}