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

/// <summary>
/// 渐变效果 右上->左下的渐变
/// </summary>

[AddComponentMenu("UI/Effects/UIEfxGradient")]
public class UIEfxGradient : BaseMeshEffect
{
    public Color32 m_colorBottomLeft = Color.white;
    public Color32 m_colorTopRight = Color.black;

    public override void ModifyMesh(VertexHelper vh)
    {

        if (!IsActive())
        {
            return;
        }

        var count = vh.currentVertCount;
        if (count == 0)
            return;

        var vertexs = new List<UIVertex>();
        for (var i = 0; i < count; i++)
        {
            var vertex = new UIVertex();
            vh.PopulateUIVertex(ref vertex, i);
            vertexs.Add(vertex);
        }

        float posX = vertexs[0].position.x;
        float posY = vertexs[0].position.y;


        var topY = posY;
        var bottomY = posY;

        var leftX = posX;
        var rightX = posX;

        for (var i = 1; i < count; i++)
        {
            var y = vertexs[i].position.y;
            if (y > topY)
            {
                topY = y;
            }
            else if (y < bottomY)
            {
                bottomY = y;
            }

            var x = vertexs[i].position.x;
            if (x < leftX)
                leftX = x;
            else if (x > rightX)
                rightX = x;
        }

        var height = topY - bottomY;
        var weith = rightX - leftX;
        for (var i = 0; i < count; i++)
        {
            var vertex = vertexs[i];

            var color1 = Color32.Lerp(m_colorBottomLeft, m_colorTopRight, (vertex.position.y - bottomY) / height);
            var color2 = Color32.Lerp(m_colorBottomLeft, m_colorTopRight, (vertex.position.x - leftX) / weith);
            var color = Color32.Lerp(color1, color2, 0.5f);

            vertex.color = color;
            vh.SetUIVertex(vertex, i);
        }
    }
}