Shader "Bansonic/Sprite Outline"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        [HideInInspector] _Color ("Tint", Color) = (1,1,1,1)
        [HideInInspector] PixelSnap ("Pixel snap", Float) = 0
        [HideInInspector] _RendererColor ("RendererColor", Color) = (1,1,1,1)
        [HideInInspector] _AlphaTex ("External Alpha", 2D) = "white" {}
        [HideInInspector] _EnableExternalAlpha ("Enable External Alpha", Float) = 0

        [HDR]_OutlineColor ("Outline Color", Color) = (1,1,1,1)
        _OutlineThickness ("Outline Thickness", Range(0, 12)) = 1
        _AlphaThreshold ("Alpha Threshold", Range(0, 1)) = 0.1
        _OutlineOpacity ("Outline Opacity", Range(0, 1)) = 1
        _InnerOutline ("Inner Outline Blend", Range(0, 1)) = 0
        _SpriteAlpha ("Sprite Alpha", Range(0, 1)) = 1
    }

    SubShader
    {
        Tags
        {
            "Queue" = "Transparent"
            "RenderType" = "Transparent"
            "RenderPipeline" = "UniversalPipeline"
            "CanUseSpriteAtlas" = "True"
        }

        Blend SrcAlpha OneMinusSrcAlpha, One OneMinusSrcAlpha
        Cull Off
        ZWrite Off

        Pass
        {
            Tags { "LightMode" = "Universal2D" }

            HLSLPROGRAM
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Shaders/2D/Include/Core2D.hlsl"

            #pragma vertex SpriteVertex
            #pragma fragment SpriteFragment
            #pragma target 2.0
            #pragma multi_compile_instancing
            #pragma multi_compile _ SKINNED_SPRITE

            struct Attributes
            {
                float3 positionOS : POSITION;
                float4 color : COLOR;
                float2 uv : TEXCOORD0;
                UNITY_SKINNED_VERTEX_INPUTS
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                half4 color : COLOR;
                float2 uv : TEXCOORD0;
                UNITY_VERTEX_OUTPUT_STEREO
            };

            TEXTURE2D(_MainTex);
            SAMPLER(sampler_MainTex);
            float4 _MainTex_TexelSize;

            CBUFFER_START(UnityPerMaterial)
                half4 _Color;
                half4 _OutlineColor;
                half _OutlineThickness;
                half _AlphaThreshold;
                half _OutlineOpacity;
                half _InnerOutline;
                half _SpriteAlpha;
            CBUFFER_END

            Varyings SpriteVertex(Attributes input)
            {
                Varyings output = (Varyings)0;
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);
                UNITY_SKINNED_VERTEX_COMPUTE(input);

                SetUpSpriteInstanceProperties();
                input.positionOS = UnityFlipSprite(input.positionOS, unity_SpriteProps.xy);
                output.positionCS = TransformObjectToHClip(input.positionOS);
                output.uv = input.uv;
                output.color = input.color * _Color * unity_SpriteColor;
                return output;
            }

            half SampleAlpha(float2 uv, half4 tint)
            {
                half4 tex = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv) * tint;
                return tex.a;
            }

            half ComputeOuterMask(float2 uv, half4 tint)
            {
                float2 texel = _MainTex_TexelSize.xy * max(_OutlineThickness, 0.001h);
                half center = SampleAlpha(uv, tint);
                half maxNeighbor = 0h;

                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 1.0,  0.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2(-1.0,  0.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.0,  1.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.0, -1.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.7071,  0.7071), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2(-0.7071,  0.7071), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.7071, -0.7071), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2(-0.7071, -0.7071), tint));

                half centerMask = step(_AlphaThreshold, center);
                half neighborMask = step(_AlphaThreshold, maxNeighbor);
                return saturate(neighborMask - centerMask);
            }

            half ComputeInnerMask(float2 uv, half4 tint)
            {
                float2 texel = _MainTex_TexelSize.xy * max(_OutlineThickness, 0.001h);
                half center = SampleAlpha(uv, tint);
                half minNeighbor = 1h;

                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 1.0,  0.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2(-1.0,  0.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.0,  1.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.0, -1.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.7071,  0.7071), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2(-0.7071,  0.7071), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.7071, -0.7071), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2(-0.7071, -0.7071), tint));

                half centerMask = step(_AlphaThreshold, center);
                half neighborMask = step(_AlphaThreshold, minNeighbor);
                return saturate(centerMask - neighborMask);
            }

            half4 SpriteFragment(Varyings input) : SV_Target
            {
                half4 baseSample = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, input.uv) * input.color;
                half outerMask = ComputeOuterMask(input.uv, input.color);
                half innerMask = ComputeInnerMask(input.uv, input.color);
                half outlineMask = saturate(lerp(outerMask, max(outerMask, innerMask), _InnerOutline)) * _OutlineOpacity;

                half4 color = baseSample;
                color.rgb *= _SpriteAlpha;
                color.a *= _SpriteAlpha;

                color.rgb = lerp(color.rgb, _OutlineColor.rgb, outlineMask * _OutlineColor.a);
                color.a = saturate(color.a + outlineMask * _OutlineColor.a);
                return color;
            }
            ENDHLSL
        }

        Pass
        {
            Tags { "LightMode" = "UniversalForward" }

            HLSLPROGRAM
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Shaders/2D/Include/Core2D.hlsl"

            #pragma vertex SpriteVertex
            #pragma fragment SpriteFragment
            #pragma target 2.0
            #pragma multi_compile_instancing
            #pragma multi_compile _ SKINNED_SPRITE

            struct Attributes
            {
                float3 positionOS : POSITION;
                float4 color : COLOR;
                float2 uv : TEXCOORD0;
                UNITY_SKINNED_VERTEX_INPUTS
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                half4 color : COLOR;
                float2 uv : TEXCOORD0;
                UNITY_VERTEX_OUTPUT_STEREO
            };

            TEXTURE2D(_MainTex);
            SAMPLER(sampler_MainTex);
            float4 _MainTex_TexelSize;

            CBUFFER_START(UnityPerMaterial)
                half4 _Color;
                half4 _OutlineColor;
                half _OutlineThickness;
                half _AlphaThreshold;
                half _OutlineOpacity;
                half _InnerOutline;
                half _SpriteAlpha;
            CBUFFER_END

            Varyings SpriteVertex(Attributes input)
            {
                Varyings output = (Varyings)0;
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);
                UNITY_SKINNED_VERTEX_COMPUTE(input);

                SetUpSpriteInstanceProperties();
                input.positionOS = UnityFlipSprite(input.positionOS, unity_SpriteProps.xy);
                output.positionCS = TransformObjectToHClip(input.positionOS);
                output.uv = input.uv;
                output.color = input.color * _Color * unity_SpriteColor;
                return output;
            }

            half SampleAlpha(float2 uv, half4 tint)
            {
                half4 tex = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv) * tint;
                return tex.a;
            }

            half ComputeOuterMask(float2 uv, half4 tint)
            {
                float2 texel = _MainTex_TexelSize.xy * max(_OutlineThickness, 0.001h);
                half center = SampleAlpha(uv, tint);
                half maxNeighbor = 0h;

                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 1.0,  0.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2(-1.0,  0.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.0,  1.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.0, -1.0), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.7071,  0.7071), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2(-0.7071,  0.7071), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2( 0.7071, -0.7071), tint));
                maxNeighbor = max(maxNeighbor, SampleAlpha(uv + texel * float2(-0.7071, -0.7071), tint));

                half centerMask = step(_AlphaThreshold, center);
                half neighborMask = step(_AlphaThreshold, maxNeighbor);
                return saturate(neighborMask - centerMask);
            }

            half ComputeInnerMask(float2 uv, half4 tint)
            {
                float2 texel = _MainTex_TexelSize.xy * max(_OutlineThickness, 0.001h);
                half center = SampleAlpha(uv, tint);
                half minNeighbor = 1h;

                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 1.0,  0.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2(-1.0,  0.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.0,  1.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.0, -1.0), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.7071,  0.7071), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2(-0.7071,  0.7071), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2( 0.7071, -0.7071), tint));
                minNeighbor = min(minNeighbor, SampleAlpha(uv + texel * float2(-0.7071, -0.7071), tint));

                half centerMask = step(_AlphaThreshold, center);
                half neighborMask = step(_AlphaThreshold, minNeighbor);
                return saturate(centerMask - neighborMask);
            }

            half4 SpriteFragment(Varyings input) : SV_Target
            {
                half4 baseSample = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, input.uv) * input.color;
                half outerMask = ComputeOuterMask(input.uv, input.color);
                half innerMask = ComputeInnerMask(input.uv, input.color);
                half outlineMask = saturate(lerp(outerMask, max(outerMask, innerMask), _InnerOutline)) * _OutlineOpacity;

                half4 color = baseSample;
                color.rgb *= _SpriteAlpha;
                color.a *= _SpriteAlpha;

                color.rgb = lerp(color.rgb, _OutlineColor.rgb, outlineMask * _OutlineColor.a);
                color.a = saturate(color.a + outlineMask * _OutlineColor.a);
                return color;
            }
            ENDHLSL
        }
    }

    FallBack "Sprites/Default"
}