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

public class DrawLine : MaskableGraphic, ICanvasRaycastFilter
{
    List<List<UIVertex>> vertexQuadList = new List<List<UIVertex>>();

    public Vector3 startPos;
    public Vector3 endPos;

    void Update()
    {
        //设定rect大小正好能圈住线
        rectTransform.position = endPos + (startPos - endPos) / 2f;
        rectTransform.sizeDelta = new Vector2(Mathf.Abs(endPos.x - startPos.x), Mathf.Abs(endPos.y - startPos.y));
    }

    public bool IsRaycastLocationValid(Vector2 sp, Camera eventCamera)
    {
        bool isEnterMesh = false;
        for (int i = 0; i < vertexQuadList.Count; i++)
        {
            if (IsContainInQuad(sp, transform.position + vertexQuadList[i][0].position, transform.position + vertexQuadList[i][1].position, transform.position + vertexQuadList[i][2].position, transform.position + vertexQuadList[i][3].position))
            {
                isEnterMesh = true;
                break;
            }
        }
        return isEnterMesh;
    }
    bool IsContainInQuad(Vector3 point, Vector3 p1, Vector3 p2, Vector3 p3, Vector3 p4)
    {
        //      p1-----p2
        //      |       |
        //      | point |
        //      |       |
        //      p4-----p3

        Vector2 p1p2 = p1 - p2;
        Vector2 p1p = p1 - point;
        Vector2 p3p4 = p3 - p4;
        Vector2 p3p = p3 - point;

        Vector2 p4p1 = p4 - p1;
        Vector2 p4p = p4 - point;
        Vector2 p2p3 = p2 - p3;
        Vector2 p2p = p2 - point;

        bool isBetweenP1P2_P3P4 = CrossAB(p1p2, p1p) * CrossAB(p3p4, p3p) > 0;
        bool isBetweenP4P1_P2P3 = CrossAB(p4p1, p4p) * CrossAB(p2p3, p2p) > 0;

        return isBetweenP1P2_P3P4 && isBetweenP4P1_P2P3;

    }
    float CrossAB(Vector2 a, Vector2 b)
    {
        return a.x * b.y - b.x * a.y;
    }

    protected override void OnPopulateMesh(VertexHelper vh)
    {
        vh.Clear(); // 清空顶点和索引数据

        for (int i = 0; i < vertexQuadList.Count; i++)
        {
            vh.AddUIVertexQuad(vertexQuadList[i].ToArray());
        }
    }
}