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

[AddComponentMenu("UI/Custom/Circle Image")]
[RequireComponent(typeof(Image))]
public class CircleImage : BaseMeshEffect, ICanvasRaycastFilter {

    [Range(0, 1)]
    [SerializeField]
    float m_FillPercent = 1f;
    public float fillPercent { get { return m_FillPercent; } }

    [SerializeField]
    private bool m_Reversed = false;
    public bool reversed { get { return m_Reversed; } }

    [SerializeField]
    Align m_Align = Align.Top;
    public Align align { get { return m_Align; } }

    [SerializeField]
    bool m_FullFill = true;
    public bool fullFill { get { return m_FullFill; } }

    [Range(0, 1)]
    [SerializeField]
    float m_Thickness = 0f;
    public float thickness {
        get { return m_Thickness; }
        set { m_Thickness = value; }
    }

    [Range(4, 128)]
    [SerializeField]
    int m_Segements = 30;
    public int segements { get { return m_Segements; } }

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

    private List<Vector3> innerVertices;
    private 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 = (int)(segements * fillPercent);

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

        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 * (int)align;
        var position = Vector2.zero;
        var uv0 = Vector2.zero;

        var verticeCount = 0;
        var triangleCount = 0;

        if (fullFill) {
            verticeCount = realSegements + 1;
            uv0 = new Vector2(position.x * uvScaleX + uvCenterX, position.y * uvScaleY + uvCenterY);
            uiVertex = UIUtility.PackageUIVertex(position, uv0, image.color);
            vh.AddVert(uiVertex);

            for (int i = 1; i < verticeCount; i++) {
                var cosA = Mathf.Cos(degree);
                var sinA = Mathf.Sin(degree);
                degree = reversed ? degree + degreeDelta : degree - degreeDelta;

                position = new Vector2(cosA * outerArea.x, sinA * 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;
            for (int i = 0, vIdx = 1; i < triangleCount - 3; i += 3, vIdx++) {
                vh.AddTriangle(vIdx, 0, vIdx + 1);
            }
            if (fillPercent == 1) {
                vh.AddTriangle(verticeCount - 1, 0, 1);
            }
        }
        else {
            verticeCount = realSegements * 2;
            for (int i = 0; i < verticeCount; i += 2) {
                var cosA = Mathf.Cos(degree);
                var sinA = Mathf.Sin(degree);
                degree = reversed ? degree + degreeDelta : degree - degreeDelta;

                position = new Vector3(cosA * innerArea.x, sinA * innerArea.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(cosA * outerArea.x, sinA * 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);
            }
            if (fillPercent == 1) {
                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);
    }

    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;
    }

    public enum Align {
        Top = 1,
        Left = 2,
        Bottom = 3,
        Right = 4,
    }

}