Shader "DashGame/UIMask"
{
	Properties
	{
		_MainTex("Texture", 2D) = "white" {}
	}

	SubShader
	{
		Tags
		{
			"Queue" = "Transparent"
			"RenderType" = "Transparent"
			"PreviewType" = "Plane"
			"IgnoreProjector" = "True"
			"CanUseSpriteAtlas" = "True"
		}

		Cull Off
		ZWrite Off
		Lighting Off

		Blend SrcAlpha OneMinusSrcAlpha

		ZTest[unity_GUIZTestMode]

		Pass
		{
			CGPROGRAM
			
			#pragma vertex vert
			#pragma fragment frag

			#include "UnityUI.cginc"
			#include "UnityCG.cginc"

			struct appdata
			{
				float2 uv : TEXCOORD0;
				float4 color : COLOR;
				float4 vertex : POSITION;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 color : COLOR;
				float4 vertex : SV_POSITION;
				float4 screenPos : TEXCOORD1;
			};

			float _RadiusX;
			float _RadiusY;
			float2 _Center;

			float4 _MainTex_ST;
			sampler2D _MainTex;


			v2f vert(appdata v)
			{
				v2f o;

				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				o.color = v.color;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.screenPos = ComputeScreenPos(o.vertex);

				return o;
			}

			fixed4 frag(v2f i) : SV_Target
			{
				fixed4 col = tex2D(_MainTex, i.uv)*i.color;

				float AngleX = _RadiusY/4;
				float AngleY = AngleX / (_ScreenParams.y / _ScreenParams.x);

				float x = i.screenPos.x - _Center.x;
				float y = i.screenPos.y - _Center.y;

				if (abs(x) < _RadiusX && abs(y) < _RadiusY)
				{
					float2 ulo = _Center + float2(-_RadiusX, _RadiusY);
					float2 uli = ulo + float2(AngleX, -AngleY);

					float2 uro = _Center + float2(_RadiusX, _RadiusY);
					float2 uri = uro + float2(-AngleX, -AngleY);

					float2 lro = _Center + float2(_RadiusX, -_RadiusY);
					float2 lri = lro + float2(-AngleX, AngleY);

					float2 llo = _Center + float2(-_RadiusX, -_RadiusY);
					float2 lli = llo + float2(AngleX, AngleY);

					float ulix = i.screenPos.x - uli.x;
					float uliy = i.screenPos.y - uli.y;
					float ulox = i.screenPos.x - ulo.x;
					float uloy = i.screenPos.y - ulo.y;

					float urix = i.screenPos.x - uri.x;
					float uriy = i.screenPos.y -uri.y;
					float urox = i.screenPos.x - uro.x;
					float uroy = i.screenPos.y - uro.y;

					float lrix = i.screenPos.x - lri.x;
					float lriy = i.screenPos.y - lri.y;
					float lrox = i.screenPos.x - lro.x;
					float lroy = i.screenPos.y - lro.y;

					float llix = i.screenPos.x - lli.x;
					float lliy = i.screenPos.y - lli.y;
					float llox = i.screenPos.x - llo.x;
					float lloy = i.screenPos.y - llo.y;

					if(ulix < 0 && uliy > 0 && ulox > 0 && uloy < 0)
					{
						float2 vec = uli - i.screenPos;
						vec.y *= _ScreenParams.y / _ScreenParams.x;

						if (length(vec) < AngleX)
						{
							col.a = 0;
						}
					}
					else if(urix > 0 && uriy > 0 && urox < 0 && uroy < 0)
					{
						float2 vec = uri - i.screenPos;
						vec.y *= _ScreenParams.y / _ScreenParams.x;

						if (length(vec) < AngleX)
						{
							col.a = 0;
						}
					}
					else if (lrix > 0 && lriy < 0 && lrox < 0 && lroy > 0)
					{
						float2 vec = lri - i.screenPos;
						vec.y *= _ScreenParams.y / _ScreenParams.x;

						if (length(vec) < AngleX)
						{
							col.a = 0;
						}
					}
					else if (llix < 0 && lliy < 0 && llox > 0 && lloy > 0)
					{
						float2 vec = lli - i.screenPos;
						vec.y *= _ScreenParams.y / _ScreenParams.x;

						if (length(vec) < AngleX)
						{
							col.a = 0;
						}
					}
					else
					{
						col.a = 0;
					}
				}

				return col;
			}
			ENDCG
		}
	}
}