using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

/// <summary>
/// 矩形引导组件
/// </summary>
public class RectGuidanceController : MonoBehaviour
{
 //获取画布
 private Canvas canvas;

 /// <summary>
 /// 高亮显示的目标
 /// </summary>
 public RectTransform target;

 /// <summary>
 /// 区域范围缓存
 /// </summary>
 private Vector3[] _corners = new Vector3[4];

 /// <summary>
 /// 镂空区域中心
 /// </summary>
 private Vector4 _center;

 /// <summary>
 /// 最终的偏移值X
 /// </summary>
 private float _targetOffsetX = 0f;

 /// <summary>
 /// 最终的偏移值Y
 /// </summary>
 private float _targetOffsetY = 0f;

 /// <summary>
 /// 遮罩材质
 /// </summary>
 private Material _material;

 /// <summary>
 /// 当前的偏移值X
 /// </summary>
 private float _currentOffsetX = 0f;

 /// <summary>
 /// 当前的偏移值Y
 /// </summary>
 private float _currentOffsetY = 0f;

 /// <summary>
 /// 动画收缩时间
 /// </summary>
 private float _shrinkTime = 0.5f;

 /// <summary>
 /// 世界坐标到画布坐标的转换
 /// </summary>
 /// <param name="canvas">画布</param>
 /// <param name="world">世界坐标</param>
 /// <returns>转换后在画布的坐标</returns>
 private Vector2 WorldToCanvasPos(Canvas canvas, Vector3 world)
 {
 Vector2 position;
 RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas.transform as RectTransform, world,
 canvas.GetComponent<Camera>(), out position);
 return position;
 }

 public void SetTarget(RectTransform target)
 {
 this.target = target;
 RefreshMask();
 }

 private void RefreshMask()
 {
 canvas = GameObject.FindGameObjectWithTag("Canvas").GetComponent<Canvas>();
 //获取高亮区域四个顶点的世界坐标
 target.GetWorldCorners(_corners);
 //计算高亮显示区域咋画布中的范围
 _targetOffsetX = Vector2.Distance(WorldToCanvasPos(canvas, _corners[0]), WorldToCanvasPos(canvas, _corners[3])) / 2f;
 _targetOffsetY = Vector2.Distance(WorldToCanvasPos(canvas, _corners[0]), WorldToCanvasPos(canvas, _corners[1])) / 2f;
 //计算高亮显示区域的中心
 float x = _corners[0].x + ((_corners[3].x - _corners[0].x) / 2f);
 float y = _corners[0].y + ((_corners[1].y - _corners[0].y) / 2f);
 Vector3 centerWorld = new Vector3(x, y, 0);
 Vector2 center = WorldToCanvasPos(canvas, centerWorld);
 //设置遮罩材料中中心变量
 Vector4 centerMat = new Vector4(center.x, center.y, 0, 0);
 _material = GetComponent<Image>().material;
 _material.SetVector("_Center", centerMat);
 //计算当前偏移的初始值
 RectTransform canvasRectTransform = (canvas.transform as RectTransform);
 if (canvasRectTransform != null)
 {
 //获取画布区域的四个顶点
 canvasRectTransform.GetWorldCorners(_corners);
 //求偏移初始值
 for (int i = 0; i < _corners.Length; i++)
 {
 if (i % 2 == 0)
 _currentOffsetX = Mathf.Max(Vector3.Distance(WorldToCanvasPos(canvas, _corners[i]), center), _currentOffsetX);
 else
 _currentOffsetY = Mathf.Max(Vector3.Distance(WorldToCanvasPos(canvas, _corners[i]), center), _currentOffsetY);
 }
 }
 //设置遮罩材质中当前偏移的变量
 _material.SetFloat("_SliderX", _currentOffsetX);
 _material.SetFloat("_SliderY", _currentOffsetY);
 }

 private float _shrinkVelocityX = 0f;
 private float _shrinkVelocityY = 0f;

 private void Update()
 {
 //从当前偏移值到目标偏移值差值显示收缩动画
 float valueX = Mathf.SmoothDamp(_currentOffsetX, _targetOffsetX, ref _shrinkVelocityX, _shrinkTime);
 float valueY = Mathf.SmoothDamp(_currentOffsetY, _targetOffsetY, ref _shrinkVelocityY, _shrinkTime);
 if (!Mathf.Approximately(valueX, _currentOffsetX))
 {
 _currentOffsetX = valueX;
 _material.SetFloat("_SliderX", _currentOffsetX);
 }

 if (!Mathf.Approximately(valueY, _currentOffsetY))
 {
 _currentOffsetY = valueY;
 _material.SetFloat("_SliderY", _currentOffsetY);
 }
 }
}