Shader "Unlit/OVROverlayDestRectEditor"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_SrcRectLeft("SrcRectLeft", Vector) = (0,0,1,1)
		_SrcRectRight("SrcRectRight", Vector) = (0,0,1,1)
		_DestRectLeft ("DestRectLeft", Vector) = (0,0,1,1)
		_DestRectRight("DestRectRight", Vector) = (0,0,1,1)
		_BackgroundColor("Background Color", Color) = (0.225, 0.225, 0.225, 1)
	}
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			
			#include "UnityCG.cginc"

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

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 vertex : SV_POSITION;
				float4 leftDragX : TEXCOORD1;
				float4 leftDragY : TEXCOORD2;
				float4 rightDragX : TEXCOORD3;
				float4 rightDragY : TEXCOORD4;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;

			float4 _SrcRectLeft;
			float4 _SrcRectRight;
			float4 _DestRectLeft;
			float4 _DestRectRight;

			fixed4 _BackgroundColor;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				// Add padding
				o.uv = (o.uv - 0.5) * (256.0 + 8.0) / (256.0) + 0.5;

				// left
				o.leftDragX.x = _DestRectLeft.x;
				o.leftDragY.x = _DestRectLeft.y + _DestRectLeft.w * 0.5;
				// right
				o.leftDragX.y = _DestRectLeft.x + _DestRectLeft.z;
				o.leftDragY.y = _DestRectLeft.y + _DestRectLeft.w * 0.5;
				// top
				o.leftDragX.z = _DestRectLeft.x + _DestRectLeft.z * 0.5;
				o.leftDragY.z = _DestRectLeft.y;
				// bottom
				o.leftDragX.w = _DestRectLeft.x + _DestRectLeft.z * 0.5;
				o.leftDragY.w = _DestRectLeft.y + _DestRectLeft.w;
				// right
				o.rightDragX.x = _DestRectRight.x;
				o.rightDragY.x = _DestRectRight.y + _DestRectRight.w * 0.5;
				// right
				o.rightDragX.y = _DestRectRight.x + _DestRectRight.z;
				o.rightDragY.y = _DestRectRight.y + _DestRectRight.w * 0.5;
				// top
				o.rightDragX.z = _DestRectRight.x + _DestRectRight.z * 0.5;
				o.rightDragY.z = _DestRectRight.y;
				// bottom
				o.rightDragX.w = _DestRectRight.x + _DestRectRight.z * 0.5;
				o.rightDragY.w = _DestRectRight.y + _DestRectRight.w;

				return o;
			}

			float onDrag(float2 uv, float x, float y)
			{
				const float pixelSize = 6;
				return abs(uv.x - x) < ((pixelSize / 2) / 128.0) && abs(uv.y - y) < ((pixelSize / 2) / 128.0);
			}

			float onLine(float2 uv, float4 rect)
			{
				return
					(abs(uv.x - rect.x) < (1 / 128.0) && uv.y >= rect.y && uv.y <= rect.y + rect.w) ||
					(abs(uv.x - rect.x - rect.z) < (1 / 128.0) && uv.y >= rect.y && uv.y <= rect.y + rect.w) ||
					(abs(uv.y - rect.y) < (1 / 128.0) && uv.x >= rect.x && uv.x <= rect.x + rect.z) ||
					(abs(uv.y - rect.y - rect.w) < (1 / 128.0) && uv.x >= rect.x && uv.x <= rect.x + rect.z);
			}

			float checkerboard(float2 uv)
			{
				float x = floor(uv.x * (16 + 2));
				float y = floor(uv.y * 8);

				return 2 * ((x + y) / 2.0 - floor((x + y) / 2.0));
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				float isLeftEye = i.uv < 0.5;
				float2 leftUV = float2(i.uv.x * (256.0 + 32.0) / 128.0, i.uv.y);
				float2 rightUV = float2(1 - ((1 - i.uv.x) * (256.0 + 32.0) / 128.0), i.uv.y);

				float2 uv = i.uv;
				float2 textureUV = i.uv;
				if (isLeftEye)
				{
					uv = (leftUV - _DestRectLeft.xy) / _DestRectLeft.zw;
					textureUV = uv * _SrcRectLeft.zw + _SrcRectLeft.xy;
				}
				else
				{
					uv = (rightUV - _DestRectRight.xy) / _DestRectRight.zw;
					textureUV = uv * _SrcRectRight.zw + _SrcRectRight.xy;
				}

				// sample the texture
				fixed4 col = tex2D(_MainTex, float2(textureUV.x, 1 - textureUV.y));
				
				if (uv.x < 0 || uv.x > 1 || uv.y < 0 || uv.y > 1)
				{
					col.a = 0;
				}

				col.rgb = lerp(0.41 - 0.13 * checkerboard(i.uv), col.rgb, col.a);

				if (i.uv.x < 0 || i.uv.x > 1 || i.uv.y < 0 || i.uv.y > 1 || abs(i.uv.x - 0.5) < (14 / 256.0))
				{
					col = _BackgroundColor;
				}

				// now draw clipping objects
				float left = isLeftEye && (onLine(leftUV, _DestRectLeft) ||
					onDrag(leftUV, i.leftDragX.x, i.leftDragY.x) ||
					onDrag(leftUV, i.leftDragX.y, i.leftDragY.y) ||
					onDrag(leftUV, i.leftDragX.z, i.leftDragY.z) ||
					onDrag(leftUV, i.leftDragX.w, i.leftDragY.w));

				float right = (!isLeftEye) && (onLine(rightUV, _DestRectRight) ||
					onDrag(rightUV, i.rightDragX.x, i.rightDragY.x) ||
					onDrag(rightUV, i.rightDragX.y, i.rightDragY.y) ||
					onDrag(rightUV, i.rightDragX.z, i.rightDragY.z) ||
					onDrag(rightUV, i.rightDragX.w, i.rightDragY.w));

				return lerp(col, fixed4(left, right, 0, 1), left || right);
			}
			ENDCG
		}
	}
}