using System.Collections.Generic;
using UnityEditor.Graphing;
using UnityEditor.ShaderGraph;
using UnityEngine.Experimental.Rendering;
using UnityEngine.Experimental.Rendering.HDPipeline;

namespace UnityEditor.Experimental.Rendering.HDPipeline
{
    [FormerName("UnityEditor.ShaderGraph.HDPBRSubShader")]
    public class HDPBRSubShader : IPBRSubShader
    {
        Pass m_PassGBuffer = new Pass()
        {
            Name = "GBuffer",
            LightMode = "GBuffer",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_GBUFFER",
            StencilOverride = new List<string>()
            {
                "// Stencil setup for gbuffer",
                "Stencil",
                "{",
                "   WriteMask 7",       // [_StencilWriteMask]    // default: StencilMask.Lighting  (fixed at compile time)
                "   Ref  2",            // [_StencilRef]          // default: StencilLightingUsage.RegularLighting  (fixed at compile time)
                "   Comp Always",
                "   Pass Replace",
                "}"
            },
            ExtraDefines = new List<string>()
            {
                "#pragma multi_compile _ DEBUG_DISPLAY",
                "#pragma multi_compile _ LIGHTMAP_ON",
                "#pragma multi_compile _ DIRLIGHTMAP_COMBINED",
                "#pragma multi_compile _ DYNAMICLIGHTMAP_ON",
                "#pragma multi_compile _ SHADOWS_SHADOWMASK",
            },
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassGBuffer.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
                "FragInputs.worldToTangent",
                "FragInputs.positionRWS",
                "FragInputs.texCoord1",
                "FragInputs.texCoord2"
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlbedoSlotId,
                PBRMasterNode.NormalSlotId,
                PBRMasterNode.MetallicSlotId,
                PBRMasterNode.SpecularSlotId,
                PBRMasterNode.EmissionSlotId,
                PBRMasterNode.SmoothnessSlotId,
                PBRMasterNode.OcclusionSlotId,
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            }
        };

        Pass m_PassGBufferWithPrepass = new Pass()
        {
            Name = "GBufferWithPrepass",
            LightMode = "GBufferWithPrepass",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_GBUFFER",
            StencilOverride = new List<string>()
            {
                "// Stencil setup for GBufferWithPrepass",
                "Stencil",
                "{",
                "   WriteMask 7",       // _StencilWriteMask    // StencilMask.Lighting  (fixed at compile time)
                "   Ref  2",            // _StencilRef          // StencilLightingUsage.RegularLighting  (fixed at compile time)
                "   Comp Always",
                "   Pass Replace",
                "}"
            },
            ExtraDefines = new List<string>()
            {
                "#pragma multi_compile _ DEBUG_DISPLAY",
                "#pragma multi_compile _ LIGHTMAP_ON",
                "#pragma multi_compile _ DIRLIGHTMAP_COMBINED",
                "#pragma multi_compile _ DYNAMICLIGHTMAP_ON",
                "#pragma multi_compile _ SHADOWS_SHADOWMASK",
                "#define SHADERPASS_GBUFFER_BYPASS_ALPHA_TEST",
            },
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassGBuffer.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
//                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlbedoSlotId,
                PBRMasterNode.NormalSlotId,
                PBRMasterNode.MetallicSlotId,
                PBRMasterNode.SpecularSlotId,
                PBRMasterNode.EmissionSlotId,
                PBRMasterNode.SmoothnessSlotId,
                PBRMasterNode.OcclusionSlotId,
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            }
        };

        Pass m_PassMETA = new Pass()
        {
            Name = "META",
            LightMode = "Meta",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_LIGHT_TRANSPORT",
            CullOverride = "Cull Off",
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassLightTransport.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
                "AttributesMesh.normalOS",
                "AttributesMesh.tangentOS",     // Always present as we require it also in case of anisotropic lighting
                "AttributesMesh.uv0",
                "AttributesMesh.uv1",
                "AttributesMesh.color",
                "AttributesMesh.uv2",           // SHADERPASS_LIGHT_TRANSPORT always uses uv2
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlbedoSlotId,
                PBRMasterNode.NormalSlotId,
                PBRMasterNode.MetallicSlotId,
                PBRMasterNode.SpecularSlotId,
                PBRMasterNode.EmissionSlotId,
                PBRMasterNode.SmoothnessSlotId,
                PBRMasterNode.OcclusionSlotId,
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                //PBRMasterNode.PositionSlotId
            }
        };

        Pass m_PassShadowCaster = new Pass()
        {
            Name = "ShadowCaster",
            LightMode = "ShadowCaster",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_SHADOWS",
            ColorMaskOverride = "ColorMask 0",
            ExtraDefines = new List<string>()
            {
                "#define USE_LEGACY_UNITY_MATRIX_VARIABLES",
            },
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassDepthOnly.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
//                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            }
        };

        Pass m_PassDepthOnly = new Pass()
        {
            Name = "DepthOnly",
            LightMode = "DepthOnly",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_DEPTH_ONLY",
            ColorMaskOverride = "ColorMask 0",
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassDepthOnly.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
//                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            }
        };

        Pass m_PassMotionVectors = new Pass()
        {
            Name = "Motion Vectors",
            LightMode = "MotionVectors",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_VELOCITY",
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassVelocity.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
                "FragInputs.positionRWS",
            },
            StencilOverride = new List<string>()
            {
                "// If velocity pass (motion vectors) is enabled we tag the stencil so it don't perform CameraMotionVelocity",
                "Stencil",
                "{",
                "   WriteMask 128",         // [_StencilWriteMaskMV]        (int) HDRenderPipeline.StencilBitMask.ObjectVelocity   // this requires us to pull in the HD Pipeline assembly...
                "   Ref 128",               // [_StencilRefMV]
                "   Comp Always",
                "   Pass Replace",
                "}"
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            },
        };

        Pass m_PassDistortion = new Pass()
        {
            Name = "Distortion",
            LightMode = "DistortionVectors",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_DISTORTION",
            BlendOverride = "Blend One One, One One",   // [_DistortionSrcBlend] [_DistortionDstBlend], [_DistortionBlurSrcBlend] [_DistortionBlurDstBlend]
            BlendOpOverride = "BlendOp Add, Add",       // Add, [_DistortionBlurBlendOp]
            ZTestOverride = "ZTest LEqual",             // [_ZTestModeDistortion]
            ZWriteOverride = "ZWrite Off",
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassDistortion.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
//                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            },
        };

        Pass m_PassTransparentDepthPrepass = new Pass()
        {
            Name = "TransparentDepthPrepass",
            LightMode = "TransparentDepthPrepass",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_DEPTH_ONLY",
            ColorMaskOverride = "ColorMask 0",
            ExtraDefines = new List<string>()
            {
                "#define CUTOFF_TRANSPARENT_DEPTH_PREPASS",
            },
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassDepthOnly.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
//                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            },
        };

        Pass m_PassTransparentBackface = new Pass()
        {
            Name = "TransparentBackface",
            LightMode = "TransparentBackface",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_FORWARD",
            CullOverride = "Cull Front",
            ExtraDefines = new List<string>()
            {
                "#pragma multi_compile _ DEBUG_DISPLAY",
                "#pragma multi_compile _ LIGHTMAP_ON",
                "#pragma multi_compile _ DIRLIGHTMAP_COMBINED",
                "#pragma multi_compile _ DYNAMICLIGHTMAP_ON",
                "#pragma multi_compile _ SHADOWS_SHADOWMASK",
                "#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS",
                "#pragma multi_compile USE_FPTL_LIGHTLIST USE_CLUSTERED_LIGHTLIST",
            },
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassForward.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
//                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlbedoSlotId,
                PBRMasterNode.NormalSlotId,
                PBRMasterNode.MetallicSlotId,
                PBRMasterNode.SpecularSlotId,
                PBRMasterNode.EmissionSlotId,
                PBRMasterNode.SmoothnessSlotId,
                PBRMasterNode.OcclusionSlotId,
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            },
        };

        Pass m_PassForward = new Pass()
        {
            Name = "Forward",
            LightMode = "Forward",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_FORWARD",
            ExtraDefines = new List<string>()
            {
                "#pragma multi_compile _ DEBUG_DISPLAY",
                "#pragma multi_compile _ LIGHTMAP_ON",
                "#pragma multi_compile _ DIRLIGHTMAP_COMBINED",
                "#pragma multi_compile _ DYNAMICLIGHTMAP_ON",
                "#pragma multi_compile _ SHADOWS_SHADOWMASK",
                "#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS",
                "#pragma multi_compile USE_FPTL_LIGHTLIST USE_CLUSTERED_LIGHTLIST"
            },
            StencilOverride = new List<string>()
            {
                "// Stencil setup for forward",
                "Stencil",
                "{",
                "   WriteMask 7",       // [_StencilWriteMask]    // default: StencilMask.Lighting  (fixed at compile time)
                "   Ref  2",            // [_StencilRef]          // default: StencilLightingUsage.RegularLighting  (fixed at compile time)
                "   Comp Always",
                "   Pass Replace",
                "}"
            },
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassForward.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlbedoSlotId,
                PBRMasterNode.NormalSlotId,
                PBRMasterNode.MetallicSlotId,
                PBRMasterNode.SpecularSlotId,
                PBRMasterNode.EmissionSlotId,
                PBRMasterNode.SmoothnessSlotId,
                PBRMasterNode.OcclusionSlotId,
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            },
        };

        Pass m_PassTransparentDepthPostpass = new Pass()
        {
            Name = "TransparentDepthPostpass",
            LightMode = "TransparentDepthPostpass",
            TemplateName = "HDPBRPass.template",
            ShaderPassName = "SHADERPASS_DEPTH_ONLY",
            ColorMaskOverride = "ColorMask 0",
            ExtraDefines = new List<string>()
            {
                "#define CUTOFF_TRANSPARENT_DEPTH_POSTPASS",
            },
            Includes = new List<string>()
            {
                "#include \"HDRP/ShaderPass/ShaderPassDepthOnly.hlsl\"",
            },
            RequiredFields = new List<string>()
            {
//                "FragInputs.worldToTangent",
//                "FragInputs.positionRWS",
            },
            PixelShaderSlots = new List<int>()
            {
                PBRMasterNode.AlphaSlotId,
                PBRMasterNode.AlphaThresholdSlotId
            },
            VertexShaderSlots = new List<int>()
            {
                PBRMasterNode.PositionSlotId
            },
        };

        private static HashSet<string> GetActiveFieldsFromMasterNode(INode iMasterNode, Pass pass)
        {
            HashSet<string> activeFields = new HashSet<string>();

            PBRMasterNode masterNode = iMasterNode as PBRMasterNode;
            if (masterNode == null)
            {
                return activeFields;
            }

            if (masterNode.twoSided.isOn)
            {
                activeFields.Add("DoubleSided");
                if (pass.ShaderPassName != "SHADERPASS_VELOCITY")   // HACK to get around lack of a good interpolator dependency system
                {                                                   // we need to be able to build interpolators using multiple input structs
                                                                    // also: should only require isFrontFace if Normals are required...
                    activeFields.Add("DoubleSided.Mirror");         // TODO: change this depending on what kind of normal flip you want..
                    activeFields.Add("FragInputs.isFrontFace");     // will need this for determining normal flip mode
                }
            }

            switch (masterNode.model)
            {
                case PBRMasterNode.Model.Metallic:
                    break;
                case PBRMasterNode.Model.Specular:
                    activeFields.Add("Material.SpecularColor");
                    break;
                default:
                    // TODO: error!
                    break;
            }

            float constantAlpha = 0.0f;
            if (masterNode.IsSlotConnected(PBRMasterNode.AlphaThresholdSlotId) ||
                (float.TryParse(masterNode.GetSlotValue(PBRMasterNode.AlphaThresholdSlotId, GenerationMode.ForReals), out constantAlpha) && (constantAlpha > 0.0f)))
            {
                activeFields.Add("AlphaTest");
            }

            // Keywords for transparent
            // #pragma shader_feature _SURFACE_TYPE_TRANSPARENT
            if (masterNode.surfaceType != SurfaceType.Opaque)
            {
                // transparent-only defines
                activeFields.Add("SurfaceType.Transparent");

                // #pragma shader_feature _ _BLENDMODE_ALPHA _BLENDMODE_ADD _BLENDMODE_PRE_MULTIPLY
                if (masterNode.alphaMode == AlphaMode.Alpha)
                {
                    activeFields.Add("BlendMode.Alpha");
                }
                else if (masterNode.alphaMode == AlphaMode.Additive)
                {
                    activeFields.Add("BlendMode.Add");
                }
//                else if (masterNode.alphaMode == PBRMasterNode.AlphaMode.PremultiplyAlpha)            // TODO
//                {
//                    defines.AddShaderChunk("#define _BLENDMODE_PRE_MULTIPLY 1", true);
//                }
            }
            else
            {
                // opaque-only defines
            }

            // enable dithering LOD crossfade
            // #pragma multi_compile _ LOD_FADE_CROSSFADE
            // TODO: We should have this keyword only if VelocityInGBuffer is enable, how to do that ?
            //#pragma multi_compile VELOCITYOUTPUT_OFF VELOCITYOUTPUT_ON

            return activeFields;
        }

        private static bool GenerateShaderPassLit(AbstractMaterialNode masterNode, Pass pass, GenerationMode mode, SurfaceMaterialOptions materialOptions, ShaderGenerator result, List<string> sourceAssetDependencyPaths)
        {
            // apply master node options to active fields
            HashSet<string> activeFields = GetActiveFieldsFromMasterNode(masterNode, pass);

            // use standard shader pass generation
            return HDSubShaderUtilities.GenerateShaderPass(masterNode, pass, mode, materialOptions, activeFields, result, sourceAssetDependencyPaths);
        }

        public string GetSubshader(IMasterNode iMasterNode, GenerationMode mode, List<string> sourceAssetDependencyPaths = null)
        {
            if (sourceAssetDependencyPaths != null)
            {
                // HDPBRSubShader.cs
                sourceAssetDependencyPaths.Add(AssetDatabase.GUIDToAssetPath("c4e8610eb7ce19747bb637c68acc55cd"));
                // HDSubShaderUtilities.cs
                sourceAssetDependencyPaths.Add(AssetDatabase.GUIDToAssetPath("713ced4e6eef4a44799a4dd59041484b"));
            }

            var masterNode = iMasterNode as PBRMasterNode;
            var subShader = new ShaderGenerator();
            subShader.AddShaderChunk("SubShader", true);
            subShader.AddShaderChunk("{", true);
            subShader.Indent();
            {
                SurfaceMaterialOptions materialOptions = HDSubShaderUtilities.BuildMaterialOptions(masterNode.surfaceType, masterNode.alphaMode, masterNode.twoSided.isOn);

                // Add tags at the SubShader level
                {
                    var tagsVisitor = new ShaderStringBuilder();
                    materialOptions.GetTags(tagsVisitor);
                    subShader.AddShaderChunk(tagsVisitor.ToString(), false);
                }

                // generate the necessary shader passes
                bool opaque = (masterNode.surfaceType == SurfaceType.Opaque);
                bool transparent = (masterNode.surfaceType != SurfaceType.Opaque);
                bool distortionActive = false;
                bool transparentDepthPrepassActive = transparent && false;
                bool transparentBackfaceActive = transparent && false;
                bool transparentDepthPostpassActive = transparent && false;

                if (opaque)
                {
                    GenerateShaderPassLit(masterNode, m_PassGBuffer, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                    GenerateShaderPassLit(masterNode, m_PassGBufferWithPrepass, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                }

                GenerateShaderPassLit(masterNode, m_PassMETA, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                GenerateShaderPassLit(masterNode, m_PassShadowCaster, mode, materialOptions, subShader, sourceAssetDependencyPaths);

                if (opaque)
                {
                    GenerateShaderPassLit(masterNode, m_PassDepthOnly, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                    GenerateShaderPassLit(masterNode, m_PassMotionVectors, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                }

                if (distortionActive)
                {
                    GenerateShaderPassLit(masterNode, m_PassDistortion, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                }

                if (transparentDepthPrepassActive)
                {
                    GenerateShaderPassLit(masterNode, m_PassTransparentDepthPrepass, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                }

                if (transparentBackfaceActive)
                {
                    GenerateShaderPassLit(masterNode, m_PassTransparentBackface, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                }

                GenerateShaderPassLit(masterNode, m_PassForward, mode, materialOptions, subShader, sourceAssetDependencyPaths);

                if (transparentDepthPostpassActive)
                {
                    GenerateShaderPassLit(masterNode, m_PassTransparentDepthPostpass, mode, materialOptions, subShader, sourceAssetDependencyPaths);
                }
            }
            subShader.Deindent();
            subShader.AddShaderChunk("}", true);

            return subShader.GetShaderString(0);
        }

        public bool IsPipelineCompatible(RenderPipelineAsset renderPipelineAsset)
        {
            return renderPipelineAsset is HDRenderPipelineAsset;
        }
    }
}