using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor.ShaderGraph;
using UnityEditor.ShaderGraph.Legacy;
using static UnityEditor.Rendering.Universal.ShaderGraph.SubShaderUtils;
using static Unity.Rendering.Universal.ShaderUtils;

namespace UnityEditor.Rendering.Universal.ShaderGraph
{
    sealed class UniversalUnlitSubTarget : UniversalSubTarget, ILegacyTarget
    {
        static readonly GUID kSourceCodeGuid = new GUID("97c3f7dcb477ec842aa878573640313a"); // UniversalUnlitSubTarget.cs

        public UniversalUnlitSubTarget()
        {
            displayName = "Unlit";
        }

        protected override ShaderID shaderID => ShaderID.SG_Unlit;

        public override bool IsActive() => true;

        public override void Setup(ref TargetSetupContext context)
        {
            context.AddAssetDependency(kSourceCodeGuid, AssetCollection.Flags.SourceDependency);
            base.Setup(ref context);

            var universalRPType = typeof(UnityEngine.Rendering.Universal.UniversalRenderPipelineAsset);
            if (!context.HasCustomEditorForRenderPipeline(universalRPType))
            {
                var gui = typeof(ShaderGraphUnlitGUI);
#if HAS_VFX_GRAPH
                if (TargetsVFX())
                    gui = typeof(VFXShaderGraphUnlitGUI);
#endif
                context.AddCustomEditorForRenderPipeline(gui.FullName, universalRPType);
            }
            // Process SubShaders
            context.AddSubShader(PostProcessSubShader(SubShaders.UnlitDOTS(target, target.renderType, target.renderQueue)));
            context.AddSubShader(PostProcessSubShader(SubShaders.Unlit(target, target.renderType, target.renderQueue)));
        }

        public override void ProcessPreviewMaterial(Material material)
        {
            if (target.allowMaterialOverride)
            {
                // copy our target's default settings into the material
                // (technically not necessary since we are always recreating the material from the shader each time,
                // which will pull over the defaults from the shader definition)
                // but if that ever changes, this will ensure the defaults are set
                material.SetFloat(Property.SurfaceType, (float)target.surfaceType);
                material.SetFloat(Property.BlendMode, (float)target.alphaMode);
                material.SetFloat(Property.AlphaClip, target.alphaClip ? 1.0f : 0.0f);
                material.SetFloat(Property.CullMode, (int)target.renderFace);
                material.SetFloat(Property.CastShadows, target.castShadows ? 1.0f : 0.0f);
                material.SetFloat(Property.ZWriteControl, (float)target.zWriteControl);
                material.SetFloat(Property.ZTest, (float)target.zTestMode);
            }

            // We always need these properties regardless of whether the material is allowed to override
            // Queue control & offset enable correct automatic render queue behavior
            // Control == 0 is automatic, 1 is user-specified render queue
            material.SetFloat(Property.QueueOffset, 0.0f);
            material.SetFloat(Property.QueueControl, (float)BaseShaderGUI.QueueControl.Auto);

            // call the full unlit material setup function
            ShaderGraphUnlitGUI.UpdateMaterial(material, MaterialUpdateType.CreatedNewMaterial);
        }

        public override void GetFields(ref TargetFieldContext context)
        {
            base.GetFields(ref context);
        }

        public override void GetActiveBlocks(ref TargetActiveBlockContext context)
        {
            context.AddBlock(BlockFields.SurfaceDescription.Alpha, (target.surfaceType == SurfaceType.Transparent || target.alphaClip) || target.allowMaterialOverride);
            context.AddBlock(BlockFields.SurfaceDescription.AlphaClipThreshold, target.alphaClip || target.allowMaterialOverride);
        }

        public override void CollectShaderProperties(PropertyCollector collector, GenerationMode generationMode)
        {
            if (target.allowMaterialOverride)
            {
                collector.AddFloatProperty(Property.CastShadows, target.castShadows ? 1.0f : 0.0f);

                collector.AddFloatProperty(Property.SurfaceType, (float)target.surfaceType);
                collector.AddFloatProperty(Property.BlendMode, (float)target.alphaMode);
                collector.AddFloatProperty(Property.AlphaClip, target.alphaClip ? 1.0f : 0.0f);
                collector.AddFloatProperty(Property.SrcBlend, 1.0f);    // always set by material inspector
                collector.AddFloatProperty(Property.DstBlend, 0.0f);    // always set by material inspector
                collector.AddToggleProperty(Property.ZWrite, (target.surfaceType == SurfaceType.Opaque));
                collector.AddFloatProperty(Property.ZWriteControl, (float)target.zWriteControl);
                collector.AddFloatProperty(Property.ZTest, (float)target.zTestMode);    // ztest mode is designed to directly pass as ztest
                collector.AddFloatProperty(Property.CullMode, (float)target.renderFace);    // render face enum is designed to directly pass as a cull mode
            }

            // We always need these properties regardless of whether the material is allowed to override other shader properties.
            // Queue control & offset enable correct automatic render queue behavior.  Control == 0 is automatic, 1 is user-specified.
            // We initialize queue control to -1 to indicate to UpdateMaterial that it needs to initialize it properly on the material.
            collector.AddFloatProperty(Property.QueueOffset, 0.0f);
            collector.AddFloatProperty(Property.QueueControl, -1.0f);
        }

        public override void GetPropertiesGUI(ref TargetPropertyGUIContext context, Action onChange, Action<String> registerUndo)
        {
            var universalTarget = (target as UniversalTarget);
            universalTarget.AddDefaultMaterialOverrideGUI(ref context, onChange, registerUndo);
            universalTarget.AddDefaultSurfacePropertiesGUI(ref context, onChange, registerUndo, showReceiveShadows: false);
        }

        public bool TryUpgradeFromMasterNode(IMasterNode1 masterNode, out Dictionary<BlockFieldDescriptor, int> blockMap)
        {
            blockMap = null;
            if (!(masterNode is UnlitMasterNode1 unlitMasterNode))
                return false;

            // Set blockmap
            blockMap = new Dictionary<BlockFieldDescriptor, int>()
            {
                { BlockFields.VertexDescription.Position, 9 },
                { BlockFields.VertexDescription.Normal, 10 },
                { BlockFields.VertexDescription.Tangent, 11 },
                { BlockFields.SurfaceDescription.BaseColor, 0 },
                { BlockFields.SurfaceDescription.Alpha, 7 },
                { BlockFields.SurfaceDescription.AlphaClipThreshold, 8 },
            };

            return true;
        }

        #region SubShader
        static class SubShaders
        {
            public static SubShaderDescriptor Unlit(UniversalTarget target, string renderType, string renderQueue)
            {
                var result = new SubShaderDescriptor()
                {
                    pipelineTag = UniversalTarget.kPipelineTag,
                    customTags = UniversalTarget.kUnlitMaterialTypeTag,
                    renderType = renderType,
                    renderQueue = renderQueue,
                    generatesPreview = true,
                    passes = new PassCollection()
                };

                result.passes.Add(UnlitPasses.Forward(target));

                if (target.mayWriteDepth)
                    result.passes.Add(CorePasses.DepthOnly(target));

                result.passes.Add(CorePasses.DepthNormalOnly(target));

                if (target.castShadows || target.allowMaterialOverride)
                    result.passes.Add(CorePasses.ShadowCaster(target));

                // Currently neither of these passes (selection/picking) can be last for the game view for
                // UI shaders to render correctly. Verify [1352225] before changing this order.
                result.passes.Add(CorePasses.SceneSelection(target));
                result.passes.Add(CorePasses.ScenePicking(target));

                result.passes.Add(UnlitPasses.DepthNormalOnly(target));

                return result;
            }

            public static SubShaderDescriptor UnlitDOTS(UniversalTarget target, string renderType, string renderQueue)
            {
                var result = new SubShaderDescriptor()
                {
                    pipelineTag = UniversalTarget.kPipelineTag,
                    customTags = UniversalTarget.kUnlitMaterialTypeTag,
                    renderType = renderType,
                    renderQueue = renderQueue,
                    generatesPreview = true,
                    passes = new PassCollection()
                };

                result.passes.Add(PassVariant(UnlitPasses.Forward(target), CorePragmas.DOTSForward));

                if (target.mayWriteDepth)
                    result.passes.Add(PassVariant(CorePasses.DepthOnly(target), CorePragmas.DOTSInstanced));

                result.passes.Add(PassVariant(CorePasses.DepthNormalOnly(target), CorePragmas.DOTSInstanced));

                if (target.castShadows || target.allowMaterialOverride)
                    result.passes.Add(PassVariant(CorePasses.ShadowCaster(target), CorePragmas.DOTSInstanced));

                // Currently neither of these passes (selection/picking) can be last for the game view for
                // UI shaders to render correctly. Verify [1352225] before changing this order.
                result.passes.Add(PassVariant(CorePasses.SceneSelection(target), CorePragmas.DOTSDefault));
                result.passes.Add(PassVariant(CorePasses.ScenePicking(target), CorePragmas.DOTSDefault));

                result.passes.Add(PassVariant(UnlitPasses.DepthNormalOnly(target), CorePragmas.DOTSInstanced));

                return result;
            }
        }
        #endregion

        #region Pass
        static class UnlitPasses
        {
            public static PassDescriptor Forward(UniversalTarget target)
            {
                var result = new PassDescriptor
                {
                    // Definition
                    displayName = "Universal Forward",
                    referenceName = "SHADERPASS_UNLIT",
                    useInPreview = true,

                    // Template
                    passTemplatePath = UniversalTarget.kUberTemplatePath,
                    sharedTemplateDirectories = UniversalTarget.kSharedTemplateDirectories,

                    // Port Mask
                    validVertexBlocks = CoreBlockMasks.Vertex,
                    validPixelBlocks = CoreBlockMasks.FragmentColorAlpha,

                    // Fields
                    structs = CoreStructCollections.Default,
                    requiredFields = UnlitRequiredFields.Unlit,
                    fieldDependencies = CoreFieldDependencies.Default,

                    // Conditional State
                    renderStates = CoreRenderStates.UberSwitchedRenderState(target),
                    pragmas = CorePragmas.Forward,
                    defines = new DefineCollection() { CoreDefines.UseFragmentFog },
                    keywords = new KeywordCollection() { UnlitKeywords.UnlitBaseKeywords },
                    includes = UnlitIncludes.Unlit,

                    // Custom Interpolator Support
                    customInterpolators = CoreCustomInterpDescriptors.Common
                };

                CorePasses.AddTargetSurfaceControlsToPass(ref result, target);

                return result;
            }

            public static PassDescriptor DepthNormalOnly(UniversalTarget target)
            {
                var result = new PassDescriptor
                {
                    // Definition
                    displayName = "DepthNormals",
                    referenceName = "SHADERPASS_DEPTHNORMALSONLY",
                    lightMode = "DepthNormalsOnly",
                    useInPreview = false,

                    // Template
                    passTemplatePath = UniversalTarget.kUberTemplatePath,
                    sharedTemplateDirectories = UniversalTarget.kSharedTemplateDirectories,

                    // Port Mask
                    validVertexBlocks = CoreBlockMasks.Vertex,
                    validPixelBlocks = UnlitBlockMasks.FragmentDepthNormals,

                    // Fields
                    structs = CoreStructCollections.Default,
                    requiredFields = UnlitRequiredFields.DepthNormalsOnly,
                    fieldDependencies = CoreFieldDependencies.Default,

                    // Conditional State
                    renderStates = CoreRenderStates.DepthNormalsOnly(target),
                    pragmas = CorePragmas.Forward,
                    defines = new DefineCollection(),
                    keywords = new KeywordCollection(),
                    includes = CoreIncludes.DepthNormalsOnly,

                    // Custom Interpolator Support
                    customInterpolators = CoreCustomInterpDescriptors.Common
                };

                CorePasses.AddTargetSurfaceControlsToPass(ref result, target);

                return result;
            }

            #region PortMasks
            static class UnlitBlockMasks
            {
                public static readonly BlockFieldDescriptor[] FragmentDepthNormals = new BlockFieldDescriptor[]
                {
                    BlockFields.SurfaceDescription.NormalWS,
                    BlockFields.SurfaceDescription.Alpha,
                    BlockFields.SurfaceDescription.AlphaClipThreshold,
                };
            }
            #endregion

            #region RequiredFields
            static class UnlitRequiredFields
            {
                public static readonly FieldCollection Unlit = new FieldCollection()
                {
                    StructFields.Varyings.positionWS,
                    StructFields.Varyings.normalWS,
                    StructFields.Varyings.viewDirectionWS,
                };

                public static readonly FieldCollection DepthNormalsOnly = new FieldCollection()
                {
                    StructFields.Varyings.normalWS,
                };
            }
            #endregion
        }
        #endregion

        #region Keywords
        static class UnlitKeywords
        {
            public static readonly KeywordCollection UnlitBaseKeywords = new KeywordCollection()
            {
                // This contain lightmaps because without a proper custom lighting solution in Shadergraph,
                // people start with the unlit then add lightmapping nodes to it.
                // If we removed lightmaps from the unlit target this would ruin a lot of peoples days.
                CoreKeywordDescriptors.StaticLightmap,
                CoreKeywordDescriptors.DirectionalLightmapCombined,
                CoreKeywordDescriptors.SampleGI,
                CoreKeywordDescriptors.DBuffer,
                CoreKeywordDescriptors.DebugDisplay,
            };
        }
        #endregion

        #region Includes
        static class UnlitIncludes
        {
            const string kUnlitPass = "Packages/com.unity.render-pipelines.universal/Editor/ShaderGraph/Includes/UnlitPass.hlsl";

            public static IncludeCollection Unlit = new IncludeCollection
            {
                // Pre-graph
                { CoreIncludes.CorePregraph },
                { CoreIncludes.ShaderGraphPregraph },
                { CoreIncludes.DBufferPregraph },

                // Post-graph
                { CoreIncludes.CorePostgraph },
                { kUnlitPass, IncludeLocation.Postgraph },
            };
        }
        #endregion
    }
}