using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
 
namespace JC.Unity { 
    
    /**模拟鼠标-场景中需要存在EventSystem */
	public class SimulateMouse : MonoBehaviour
	{
        [SerializeField] CanvasScaler canvasScaler;
        [SerializeField] RectTransform mousePointer;
        [NonSerialized] public Action<Selectable> OnPointerEnter;
        [NonSerialized] public Action<Selectable> OnPointerClick;
		ScreenRayRaycasterUIWrapper mScreenRayRaycasterUIWrapper = new ScreenRayRaycasterUIWrapper();
 
		void Awake()
		{   
            mousePointer.anchorMin = Vector2.zero;
            mousePointer.anchorMax = Vector2.zero;
 
			if (mScreenRayRaycasterUIWrapper != null) {
                 // 把鼠标的位置传 Ray 发射位置
				mScreenRayRaycasterUIWrapper.Init(this, () => { 
                    Vector2 pos = mousePointer.anchoredPosition;
                    pos.x *= (float) Screen.width / GetScaleScreenWidth();
                    pos.y *= (float) Screen.height / GetScaleScreenHeight();
                    return pos; 
                });
			}
		}

        void OnDisable() {
            mScreenRayRaycasterUIWrapper.PressUp();
        }

        void OnEnable() {
            MakeMouseToScreenCenter();
        }

        void Update() {
            mScreenRayRaycasterUIWrapper.Update();
        }
 
		Vector2 ClampValue(Vector2 val)
		{
			val.x = val.x < 0 ? 0 : val.x;
			val.y = val.y < 0 ? 0 : val.y;

            float maxWidth = GetScaleScreenWidth();
            float maxHeight = GetScaleScreenHeight();
			val.x = val.x > maxWidth ? maxWidth : val.x;
			val.y = val.y > maxHeight ? maxHeight : val.y;
 
			return val;
		}

        #region 对外提供的接口
            public float GetScaleScreenWidth() {
                float width = Screen.width;
                if (canvasScaler.uiScaleMode == CanvasScaler.ScaleMode.ScaleWithScreenSize) {
                    if (canvasScaler.screenMatchMode == CanvasScaler.ScreenMatchMode.MatchWidthOrHeight) {
                        float height = Screen.height;
                        if (canvasScaler.matchWidthOrHeight == 1) {
                            width *= canvasScaler.referenceResolution.y / height;
                        } else if (canvasScaler.matchWidthOrHeight == 0) {
                            width = canvasScaler.referenceResolution.x;
                        }
                    }
                }
                return width;
            }
            public float GetScaleScreenHeight() {
                float height = Screen.height;
                if (canvasScaler.uiScaleMode == CanvasScaler.ScaleMode.ScaleWithScreenSize) {
                    if (canvasScaler.screenMatchMode == CanvasScaler.ScreenMatchMode.MatchWidthOrHeight) {
                        float width = Screen.width;
                        if (canvasScaler.matchWidthOrHeight == 0) {
                            height *= canvasScaler.referenceResolution.x / width;
                        } else if (canvasScaler.matchWidthOrHeight == 1) {
                            height = canvasScaler.referenceResolution.y;
                        }
                    }
                }               
                return height;
            }
            public void MoveMousePointer(Vector2 deltaPos)
            {
                if (mousePointer == null) return;
                Vector2 val = mousePointer.anchoredPosition;
                val += deltaPos;
                mousePointer.anchoredPosition = ClampValue(val);
            }
            public void SetMousePointerPosition(Vector2 pos)
            {
                if (mousePointer == null) return;
                mousePointer.position = pos;
            }
            public void ClickMousePointer()
            {
                mScreenRayRaycasterUIWrapper.Click();
            }
            public void MakeMouseToScreenCenter() {
                mousePointer.anchoredPosition = new Vector2(GetScaleScreenWidth()/2,GetScaleScreenHeight()/2);
            }
            public Selectable GetCurrentSelectable() {
                return mScreenRayRaycasterUIWrapper.m_currentSelectable;
            }

            public void onSetNullToSelectable(Selectable target)
            {
                //mScreenRayRaycasterUIWrapper.OnSelect(target);
            }
        #endregion 对外提供的接口
    }
	public class ScreenRayRaycasterUIWrapper 
	{
        public Selectable m_currentSelectable = null;
        RaycastResult m_currentRaycastResult;
 
        IPointerClickHandler m_clickHandler;
        IDragHandler m_dragHandler;
 
        EventSystem m_eventSystem;
        PointerEventData m_pointerEvent;

        SimulateMouse mSimulateMouse;
        Func<Vector2> mFunPointerPos;
        private bool mIsClick = false;
        private bool mIsPress = false;
        private bool mIsDrag = false;
 
        public void Init(SimulateMouse simulateMouse, Func<Vector2> funPointerPos)
        {
            mSimulateMouse = simulateMouse;
            m_eventSystem = EventSystem.current;
            m_pointerEvent = new PointerEventData(m_eventSystem);
            m_pointerEvent.button = PointerEventData.InputButton.Left;
            mFunPointerPos = funPointerPos;
        }
 
        public void Update()
        {
            m_pointerEvent.position = mFunPointerPos.Invoke();
 
            List<RaycastResult> raycastResults = new List<RaycastResult>();
            m_eventSystem.RaycastAll(m_pointerEvent, raycastResults);
 
            // Detect selectable
            bool hasRaycastSelectable = false;
            
            if (raycastResults.Count > 0)
            {
                var result = raycastResults[0]; //只检测第一个
                var newSelectable = result.gameObject.GetComponentInParent<Selectable>();

                if (newSelectable)
                {
                    hasRaycastSelectable = true;
                    if (newSelectable != m_currentSelectable)
                    {
                        Select(newSelectable);
                        m_currentRaycastResult = result;
                    }
                }
            }

            if (!hasRaycastSelectable) 
            {
                if (m_currentSelectable)
                {
                    Select(null);
                }
            }
 
            if (m_currentSelectable)
            {
                if (m_clickHandler != null && mIsClick)
                {
                    try { mSimulateMouse.OnPointerClick?.Invoke(m_currentSelectable); }
                    catch (System.Exception e) { Debug.LogError(e.Message); } 
                    m_clickHandler.OnPointerClick(m_pointerEvent);
                    Select(null);
                }
                else if (m_dragHandler != null && mIsPress)
                {
                    mIsDrag = true;
                    m_pointerEvent.pointerPressRaycast = m_currentRaycastResult;
                    m_dragHandler.OnDrag(m_pointerEvent);
                }
            }

            mIsClick = false;
        }
        public void OnSelect(Selectable s) {
            Select(s);
        }
        void Select(Selectable s)
        {
            if (mIsDrag == true) return;
 
            // if (m_currentSelectable) { //退出选中
            //     m_currentSelectable.OnPointerExit(m_pointerEvent);
            // }

            m_currentSelectable = s;
 
            if (m_currentSelectable) {
                try { mSimulateMouse.OnPointerEnter?.Invoke(m_currentSelectable); }
                catch (System.Exception e) { Debug.LogError(e.Message); Debug.LogError(e.StackTrace); } 
                // m_currentSelectable.OnPointerEnter(m_pointerEvent); //选中
                m_clickHandler = m_currentSelectable.GetComponent<IPointerClickHandler>();
                m_dragHandler = m_currentSelectable.GetComponent<IDragHandler>();
            } else {
                m_clickHandler = null;
                m_dragHandler = null;
            }
        }

        //模拟点击
        public void Click() {
            mIsClick = true;
        }

        //模拟按下
        public void PressDown() {
            mIsClick = true;
            mIsPress = true;
            mIsDrag = false;
        }

        //模拟松开
        public void PressUp() {
            mIsClick = false;
            mIsPress = false;
            mIsDrag = false;
            Select(null);
        }
    }
}