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

[AddComponentMenu("UI/Custom/SquareHollow Image")]
[DisallowMultipleComponent]
[RequireComponent(typeof(Image))]
public class SquareHollowImage : BaseMeshEffect, ICanvasRaycastFilter
{
    [SerializeField]
    Vector2 m_Center;
    public Vector2 center {
        get { return m_Center; }
        set {
            m_Center = value;
            base.graphic.SetVerticesDirty();
        }
    }

    [SerializeField]
    Vector2 m_Cell;
    public Vector2 cell {
        get {
            return m_Cell;
        }
        set {
            m_Cell = value;
            base.graphic.SetVerticesDirty();
        }
    }

    public RectTransform rectTransform { get { return this.transform as RectTransform; } }

    private List<Vector3> innerVertices = new List<Vector3>();
    private List<Vector3> outterVertices = new List<Vector3>();

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

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

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

        var leftBottom = new Vector2(outerArea.x * -1f, outerArea.y * -1f);
        var innerArea = new Vector2(Mathf.Clamp(cell.x, 0, width), Mathf.Clamp(cell.y, 0, height));
        var innerCenter = new Vector2(Mathf.Clamp(center.x, (innerArea.x - width) * 0.5f, (width - innerArea.x) * 0.5f), Mathf.Clamp(center.y, (innerArea.y - height) * 0.5f, (height - innerArea.y) * 0.5f));

        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;

        var positions = new List<Vector3>();
        var position = Vector3.zero;
        position = new Vector3(innerCenter.x + innerArea.x * -0.5f, innerCenter.y + innerArea.y * -0.5f);
        positions.Add(position);
        innerVertices.Add(position);

        position = new Vector3(outerArea.x * -1f, outerArea.y * -1f);
        positions.Add(position);
        outterVertices.Add(position);

        position = new Vector3(innerCenter.x + innerArea.x * 0.5f, innerCenter.y + innerArea.y * -0.5f);
        positions.Add(position);
        innerVertices.Add(position);

        position = new Vector3(outerArea.x * 1f, outerArea.y * -1f);
        positions.Add(position);
        outterVertices.Add(position);

        position = new Vector3(innerCenter.x + innerArea.x * 0.5f, innerCenter.y + innerArea.y * 0.5f);
        positions.Add(position);
        innerVertices.Add(position);

        position = new Vector3(outerArea.x * 1f, outerArea.y * 1f);
        positions.Add(position);
        outterVertices.Add(position);

        position = new Vector3(innerCenter.x + innerArea.x * -0.5f, innerCenter.y + innerArea.y * 0.5f);
        positions.Add(position);
        innerVertices.Add(position);

        position = new Vector3(outerArea.x * -1f, outerArea.y * 1f);
        positions.Add(position);
        outterVertices.Add(position);

        for (int i = 0; i < positions.Count; i++)
        {
            position = positions[i];
            var uv0 = new Vector2(position.x * uvScaleX + uvCenterX, position.y * uvScaleY + uvCenterY);
            var uiVertex = UIUtility.PackageUIVertex(position, uv0, image.color);
            vh.AddVert(uiVertex);
        }

        var triangleCount = 8 * 3;
        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(8 - 1, 8 - 2, 1);
        vh.AddTriangle(8 - 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);
    }

    private 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;
    }
}