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

[AddComponentMenu("UI/Custom/CircleHollow Image")]
[DisallowMultipleComponent]
[RequireComponent(typeof(Image))]
public class CircleHollowImage:BaseMeshEffect,ICanvasRaycastFilter {

    [SerializeField]
    Vector2 m_Center=Vector2.zero;
    public Vector2 center {
        get { return m_Center; }
        set {
            m_Center = value;
            if(this.graphic != null) {
                this.graphic.SetVerticesDirty();
            }
        }
    }

    [SerializeField]
    Vector2 m_HollowArea=new Vector2(50,50);
    public Vector2 cell {
        get { return m_HollowArea; }
        set {
            m_HollowArea = value;
            if(this.graphic != null) {
                this.graphic.SetVerticesDirty();
            }
        }
    }

    [Range(32,128)]
    [SerializeField]
    int m_Segements = 32;
    public int segements { get { return m_Segements; } }

    private Image m_Image;
    public Image image { get { return m_Image ?? (m_Image = this.AddMissingComponent<Image>()); } }

    protected List<Vector3> innerVertices;
    protected List<Vector3> outterVertices;

    protected override void Awake() {
        innerVertices = new List<Vector3>();
        outterVertices = new List<Vector3>();
    }

    public override void ModifyMesh(VertexHelper vh) {
        vh.Clear();
        innerVertices.Clear();
        outterVertices.Clear();

        var degreeDelta = (float)(2 * Mathf.PI / segements);
        var realSegements = segements;

        var width = image.rectTransform.rect.width;
        var height = image.rectTransform.rect.height;
        var outerArea = new Vector2(0.5f * width, 0.5f * height);

        // var realCenter = new Vector2(Mathf.Clamp(center.x,-width * 0.5f + cell.x,width * 0.5f - cell.x),
        //     Mathf.Clamp(center.y,-height * 0.5f + cell.y,height * 0.5f - cell.y));
        
        var realCenter = center;

        var uv = image.overrideSprite != null ? DataUtility.GetOuterUV(image.overrideSprite) : Vector4.zero;
        var uvCenterX = (uv.x + uv.z) * 0.5f;
        var uvCenterY = (uv.y + uv.w) * 0.5f;
        var uvScaleX = (uv.z - uv.x) / width;
        var uvScaleY = (uv.w - uv.y) / height;

        UIVertex uiVertex;
        var degree = Mathf.PI * 0.5f;
        var position = Vector2.zero;
        var uv0 = Vector2.zero;

        var verticeCount = 0;
        var triangleCount = 0;

        verticeCount = realSegements * 2;
        for(int i = 0;i < verticeCount;i += 2) {
            var cosA = Mathf.Cos(degree);
            var sinA = Mathf.Sin(degree);
            degree = degree - degreeDelta;

            position = new Vector3(realCenter.x + cosA * cell.x,realCenter.y + sinA * cell.y);
            uv0 = new Vector2(position.x * uvScaleX + uvCenterX,position.y * uvScaleY + uvCenterY);
            uiVertex = UIUtility.PackageUIVertex(position,uv0,image.color);
            vh.AddVert(uiVertex);
            innerVertices.Add(position);

            position = new Vector3(Mathf.Sign(cosA * 2f) * outerArea.x,Mathf.Sign(sinA * 2f) * outerArea.y);
            uv0 = new Vector2(position.x * uvScaleX + uvCenterX,position.y * uvScaleY + uvCenterY);
            uiVertex = UIUtility.PackageUIVertex(position,uv0,image.color);
            vh.AddVert(uiVertex);
            outterVertices.Add(position);
        }

        triangleCount = realSegements * 3 * 2;
        for(int i = 0,vIdx = 0;i < triangleCount - 6;i += 6,vIdx += 2) {
            vh.AddTriangle(vIdx + 1,vIdx,vIdx + 3);
            vh.AddTriangle(vIdx,vIdx + 2,vIdx + 3);
        }
        vh.AddTriangle(verticeCount - 1,verticeCount - 2,1);
        vh.AddTriangle(verticeCount - 2,0,1);

    }

    public virtual bool IsRaycastLocationValid(Vector2 screenPoint,Camera eventCamera) {
        var sprite = image.overrideSprite;
        if(sprite == null) {
            return true;
        }

        Vector2 local;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(image.rectTransform,screenPoint,eventCamera,out local);
        return Contains(local,outterVertices,innerVertices);
    }

    protected bool Contains(Vector2 p,List<Vector3> outterVertices,List<Vector3> innerVertices) {
        var crossNumber = 0;
        crossNumber += UIUtility.RayCrossingCount(p,innerVertices);
        crossNumber += UIUtility.RayCrossingCount(p,outterVertices);
        return (crossNumber & 1) == 1;
    }

}