Shader "Hidden/EffectiveBloom"
{
    Properties
    {
        _MainTex ("EffectiveBloom", 2D) = "black" {}
    }

    SubShader
    {
        Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" }
        ZTest Always Cull Off ZWrite Off

        HLSLINCLUDE

        #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
        #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"

        #pragma prefer_hlslcc gles
        #pragma exclude_renderers d3d11_9x
        #pragma target 2.0

        struct Attributes
        {
            float4 positionOS : POSITION;
            half2 uv : TEXCOORD0;
        };

        struct Varyings
        {
            float4 positionCS : SV_POSITION;
            half2 uv : TEXCOORD0;
        };

        struct VaryingsBlur
        {
            float4 positionCS : SV_POSITION;
            half2 uv : TEXCOORD0;
        };

        TEXTURE2D(_MainTex);
        SAMPLER(sampler_MainTex);

        TEXTURE2D(_SourceTex);
        SAMPLER(sampler_SourceTex);

        CBUFFER_START(UnityPerMaterial)
            half2 _TexelSize;
            half _Intensity;
            half _Threshold;
            half3 _Curve;
            half4 _Tint;
        CBUFFER_END

        half4 BoxFilterOptimized(half2 uv)
        {
            return SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv);
        }

        half4 BoxFilter(half2 uv, half2 texelSize)
        {
            half4 sum;
            sum  = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv);
            sum += SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv + half2(texelSize.x, 0.0h));
            sum += SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv - half2(texelSize.x, 0.0h));
            sum += SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv + half2(0.0h, texelSize.y));
            return sum * 0.25h;
        }

        half4 BoxFilter2Tap(half2 uv, half2 texelSize)
        {
            half4 sum;
            sum  = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv + half2(0.5h, 0.5h) * texelSize);
            sum += SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uv - half2(0.5h, 0.5h) * texelSize);
            return sum * 0.5h;
        }

        Varyings vert_base(Attributes input)
        {
            Varyings output;
            VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
            output.positionCS = vertexInput.positionCS;
            output.uv = input.uv;
            return output;
        }

        VaryingsBlur vert_blur(Attributes input)
        {
            VaryingsBlur output;
            VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
            output.positionCS = vertexInput.positionCS;
            output.uv = input.uv;
            return output;
        }

        half4 frag_prefilter(Varyings input) : SV_Target
        {
            half4 c = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, input.uv);
            
            half contribution = _Threshold;
            
            return half4(c.rgb * contribution, c.a);
        }

        half4 frag_blur_downsample(VaryingsBlur input) : SV_Target
        {
            return BoxFilterOptimized(input.uv);
        }

        half4 frag_blur_upsample(VaryingsBlur input) : SV_Target
        {
            return BoxFilter2Tap(input.uv, _TexelSize);
        }

        half4 frag_final(VaryingsBlur input) : SV_Target
        {
            half4 bloom = BoxFilterOptimized(input.uv) * _Intensity;
            bloom.rgb *= _Tint.rgb;
            return bloom;
        }

        half4 frag_combine(VaryingsBlur input) : SV_Target
        {
            half3 bloom = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, input.uv).rgb;
            
            bloom = LinearToSRGB(bloom);
            
            bloom *= _Tint.rgb;
            
            half4 source = SAMPLE_TEXTURE2D(_SourceTex, sampler_SourceTex, input.uv);
            return half4(source.rgb + bloom, source.a);
        }

        ENDHLSL

        Pass
        {
            NAME "Prefilter"
            
            HLSLPROGRAM
            #pragma vertex vert_base
            #pragma fragment frag_prefilter
            ENDHLSL
        }

        Pass 
        {
            NAME "Downsample"
            
            HLSLPROGRAM
            #pragma vertex vert_blur
            #pragma fragment frag_blur_downsample
            ENDHLSL
        }

        Pass
        {
            NAME "Upsample"
            Blend One One
            
            HLSLPROGRAM
            #pragma vertex vert_blur
            #pragma fragment frag_blur_upsample
            ENDHLSL
        }

        Pass
        {
            NAME "Final"
            
            HLSLPROGRAM
            #pragma vertex vert_blur
            #pragma fragment frag_final
            ENDHLSL
        }

        Pass
        {
            NAME "Combine"
            
            HLSLPROGRAM
            #pragma vertex vert_blur
            #pragma fragment frag_combine
            ENDHLSL
        }
    }
}