using System.Collections.Generic;
using UnityEditor.Rendering;
using UnityEditor.Rendering.Utilities;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.HighDefinition;

namespace UnityEditor.Rendering.HighDefinition
{
    internal class ShadowKeywords
    {
        ShaderKeyword ShadowLow;
        ShaderKeyword ShadowMedium;
        ShaderKeyword ShadowHigh;

        public Dictionary<HDShadowFilteringQuality, ShaderKeyword> ShadowVariants;

        public ShadowKeywords()
        {
            ShadowLow = new ShaderKeyword("SHADOW_LOW");
            ShadowMedium = new ShaderKeyword("SHADOW_MEDIUM");
            ShadowHigh = new ShaderKeyword("SHADOW_HIGH");

            ShadowVariants = new Dictionary<HDShadowFilteringQuality, ShaderKeyword>
            {
                {HDShadowFilteringQuality.Low, ShadowLow},
                {HDShadowFilteringQuality.Medium, ShadowMedium},
                {HDShadowFilteringQuality.High, ShadowHigh},
            };
        }
    }

    abstract class BaseShaderPreprocessor
    {
        // Common keyword list
        protected ShaderKeyword m_Transparent;
        protected ShaderKeyword m_AlphaTestOn;
        protected ShaderKeyword m_DebugDisplay;
        protected ShaderKeyword m_TileLighting;
        protected ShaderKeyword m_ClusterLighting;
        protected ShaderKeyword m_LodFadeCrossFade;
        protected ShaderKeyword m_DecalsOFF;
        protected ShaderKeyword m_Decals3RT;
        protected ShaderKeyword m_Decals4RT;
        protected ShaderKeyword m_LightLayers;
        protected ShaderKeyword m_ShadowLow;
        protected ShaderKeyword m_ShadowMedium;
        protected ShaderKeyword m_ShadowHigh;
        protected ShaderKeyword m_WriteNormalBuffer;
        protected ShaderKeyword m_WriteDecalBuffer;
        protected ShaderKeyword m_WriteMSAADepth;
        protected ShaderKeyword m_SubsurfaceScattering;
        protected ShaderKeyword m_ScreenSpaceShadowOFFKeywords;
        protected ShaderKeyword m_ScreenSpaceShadowONKeywords;

        protected ShadowKeywords m_ShadowKeywords;

        protected Dictionary<HDShadowFilteringQuality, ShaderKeyword> m_ShadowVariants;

        public virtual int Priority => 0;

        public BaseShaderPreprocessor()
        {
            // NOTE: All these keyword should be automatically stripped so there's no need to handle them ourselves.
            // LIGHTMAP_ON, DIRLIGHTMAP_COMBINED, DYNAMICLIGHTMAP_ON, LIGHTMAP_SHADOW_MIXING, SHADOWS_SHADOWMASK
            // FOG_LINEAR, FOG_EXP, FOG_EXP2
            // STEREO_INSTANCING_ON, STEREO_MULTIVIEW_ON, STEREO_CUBEMAP_RENDER_ON, UNITY_SINGLE_PASS_STEREO
            // INSTANCING_ON
            m_Transparent = new ShaderKeyword("_SURFACE_TYPE_TRANSPARENT");
            m_AlphaTestOn = new ShaderKeyword("_ALPHATEST_ON");
            m_DebugDisplay = new ShaderKeyword("DEBUG_DISPLAY");
            m_TileLighting = new ShaderKeyword("USE_FPTL_LIGHTLIST");
            m_ClusterLighting = new ShaderKeyword("USE_CLUSTERED_LIGHTLIST");
            m_LodFadeCrossFade = new ShaderKeyword("LOD_FADE_CROSSFADE");
            m_DecalsOFF = new ShaderKeyword("DECALS_OFF");
            m_Decals3RT = new ShaderKeyword("DECALS_3RT");
            m_Decals4RT = new ShaderKeyword("DECALS_4RT");
            m_LightLayers = new ShaderKeyword("LIGHT_LAYERS");
            m_WriteNormalBuffer = new ShaderKeyword("WRITE_NORMAL_BUFFER");
            m_WriteDecalBuffer = new ShaderKeyword("WRITE_DECAL_BUFFER");
            m_WriteMSAADepth = new ShaderKeyword("WRITE_MSAA_DEPTH");
            m_SubsurfaceScattering = new ShaderKeyword("OUTPUT_SPLIT_LIGHTING");
            m_ScreenSpaceShadowOFFKeywords = new ShaderKeyword("SCREEN_SPACE_SHADOWS_OFF");
            m_ScreenSpaceShadowONKeywords = new ShaderKeyword("SCREEN_SPACE_SHADOWS_ON");

            m_ShadowKeywords = new ShadowKeywords();
        }

        public bool ShadersStripper(HDRenderPipelineAsset hdrpAsset, Shader shader, ShaderSnippetData snippet,
            ShaderCompilerData inputData)
        {
            return IsMaterialQualityVariantStripped(hdrpAsset, inputData) || DoShadersStripper(hdrpAsset, shader, snippet, inputData);
        }

        protected abstract bool DoShadersStripper(HDRenderPipelineAsset hdrpAsset, Shader shader, ShaderSnippetData snippet, ShaderCompilerData inputData);

        protected static bool IsMaterialQualityVariantStripped(HDRenderPipelineAsset hdrpAsset, ShaderCompilerData inputData)
        {
            var shaderMaterialLevel = inputData.shaderKeywordSet.GetMaterialQuality();
            // if there are material quality defines in this shader
            // and they don't match the material quality accepted by the hdrp asset
            if (shaderMaterialLevel != 0 && (hdrpAsset.availableMaterialQualityLevels & shaderMaterialLevel) == 0)
            {
                // then strip this variant
                return true;
            }

            return false;
        }
    }
}