/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * Licensed under the Oculus SDK License Agreement (the "License");
 * you may not use the Oculus SDK except in compliance with the License,
 * which is provided at the time of installation or download, or which
 * otherwise accompanies this software in either electronic or hard copy form.
 *
 * You may obtain a copy of the License at
 *
 * https://developer.oculus.com/licenses/oculussdk/
 *
 * Unless required by applicable law or agreed to in writing, the Oculus SDK
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#if UNITY_2020_2_OR_NEWER
using System.Collections.Generic;
using System.IO;
using UnityEditor;
using UnityEngine;
using UnityEditor.AssetImporters; // AssetImporters namespace became non-experimental in 2020.2.0f1

namespace Oculus.Interaction.Editor
{
    /**
     * Asset processor that will read custom PBR properties from a Phong material description as an asset file is
     * imported. These custom properties are applied to standard lit shader properties on the material that is being
     * pre processed.
     * This is required since the Phong shader is the only one which the unity built-in FBXMaterialDescriptionPreprocessor
     * will convert to a "Standard Lit" shader when parsing an FBX file.
     * The advantage of performing this processing here, rather than leveraging custom materials in the unity package, is
     * that the Asset Import step will create a suitable material for either the URP or Builtin render pipeline.
     */
    public class PhongPbrMaterialDescriptionPostprocessor : AssetPostprocessor
    {
        private const uint Version = 2;

        // Required to be executed after every builtin unity processor to ensure the smoothness property is set properly
        private const int Order = 11;

        // Smoothness source (Albedo or Metallic map alpha)
        private static readonly int SmoothnessTextureChannelPropId = Shader.PropertyToID("_SmoothnessTextureChannel");
        private static readonly string SmoothnessTextureChannelCustomProp = "ISDK_SmoothnessTextureChannel";

        // Smoothness map and scalar properties:
        private static readonly int SmoothnessValueBrpPropId = Shader.PropertyToID("_Glossiness");
        private static readonly int SmoothnessValueUrpPropId = Shader.PropertyToID("_Smoothness");
        private static readonly int SmoothnessScaleValuePropId = Shader.PropertyToID("_GlossMapScale");
        private static readonly string SmoothnessFactorCustomProp = "ISDK_SmoothnessFactor";

        // Metallic map
        private static readonly int MetallicTexturePropId = Shader.PropertyToID("_MetallicGlossMap");
        private static readonly int MetallicValuePropId = Shader.PropertyToID("_Metallic");
        private static readonly string MetallicFactorPhongProp = "ReflectionFactor";

        // Parallax
        private static readonly int ParallaxTexturePropId = Shader.PropertyToID("_ParallaxMap");
        private static readonly int ParallaxStrengthPropId = Shader.PropertyToID("_Parallax");
        private static readonly string ParallaxCustomProp = "ISDK_HeightMap";
        private static readonly string ParallaxStrengthCustomProp = "ISDK_HeightFactor";

        // Occlusion
        private static readonly int OcclusionTexturePropId = Shader.PropertyToID("_OcclusionMap");
        private static readonly int OcclusionStrengthPropId = Shader.PropertyToID("_OcclusionStrength");
        private static readonly string OcclusionMapCustomProp = "ISDK_OcclusionMap";
        private static readonly string OcclusionStrengthCustomProp = "ISDK_OcclusionFactor";

        // Detail
        private static readonly int DetailTexturePropId = Shader.PropertyToID("_DetailMask");
        private static readonly string DetailMapCustomProp = "ISDK_DetailMap";

        public override uint GetVersion()
        {
            return Version;
        }

        public override int GetPostprocessOrder()
        {
            return Order;
        }

        public void OnPreprocessMaterialDescription(MaterialDescription description, Material material,
            AnimationClip[] clips)
        {
            // Asset Processor supports only URP and Builtin standard shaders.
            bool isBirpStandardLit = material.shader.name == "Standard";
            bool isUrpStandardLit = material.shader.name == "Universal Render Pipeline/Lit";
            if (isBirpStandardLit || isUrpStandardLit)
            {
                var lowerCaseExtension = Path.GetExtension(assetPath).ToLower();
                if (lowerCaseExtension == ".fbx" || lowerCaseExtension == ".dae" || lowerCaseExtension == ".obj" ||
                    lowerCaseExtension == ".blend" || lowerCaseExtension == ".mb" || lowerCaseExtension == ".ma" ||
                    lowerCaseExtension == ".max")
                {
                    ReadOvrPbrProperties(description, material, isUrpStandardLit);
                }
            }
        }

        private void ReadOvrPbrProperties(MaterialDescription description, Material material, bool isUrp)
        {
            if (!HasISDKProperty(description))
            {
                // Only overwrite values if an OVR property was detected. This
                // should prevent accidental conflicts with any other user defined AssetPostprocessor's
                // since we are reading from the Phong Reflection property, not a custom user defined
                // property.
                return;
            }

            Vector4 vectorProperty;
            float floatProperty;
            TexturePropertyDescription textureProperty;

            if (description.TryGetProperty(SmoothnessTextureChannelCustomProp, out floatProperty))
            {
                var isAlbedoAlphaChannel = floatProperty > float.Epsilon;
                material.SetFloat(SmoothnessTextureChannelPropId, isAlbedoAlphaChannel ? 1.0f : 0.0f);

                var isOpaque = (material.HasProperty("_Mode") && material.GetFloat("_Mode") == 0.0) ||
                               (material.HasProperty("_Surface") && material.GetFloat("_Surface") == 0.0);
                if (isAlbedoAlphaChannel && isOpaque)
                {
                    material.EnableKeyword("_SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A");
                }
            }

            if (description.TryGetProperty(SmoothnessFactorCustomProp, out floatProperty))
            {
                // Note: setting both value and scale value does not seem to cause any problems.

                // For smoothness texture channel = metallic alpha
                material.SetFloat(SmoothnessValueBrpPropId, floatProperty);
                // For smoothness texture channel = albedo alpha
                material.SetFloat(SmoothnessScaleValuePropId, floatProperty);
                // For smoothness on URP metallic and albedo alpha
                material.SetFloat(SmoothnessValueUrpPropId, floatProperty);
            }

            if (description.TryGetProperty(ParallaxStrengthCustomProp, out floatProperty))
            {
                material.SetFloat(ParallaxStrengthPropId, floatProperty);
            }
            if (description.TryGetProperty(OcclusionStrengthCustomProp, out floatProperty))
            {
                material.SetFloat(OcclusionStrengthPropId, floatProperty);
            }

            if (description.TryGetProperty("DiffuseColor", out vectorProperty))
            {
                // URP uses _BaseColor; BIRP uses _Color
                var materialColorProp = isUrp ? "_BaseColor" : "_Color";
                var diffuseColor = material.GetColor(materialColorProp);

                if (!description.TryGetProperty("DiffuseFactor", out float diffuseFactorProperty))
                {
                    diffuseFactorProperty = 1.0f;
                }
                diffuseColor.r = vectorProperty.x * diffuseFactorProperty;
                diffuseColor.g = vectorProperty.y * diffuseFactorProperty;
                diffuseColor.b = vectorProperty.z * diffuseFactorProperty;

                // Re-assign the diffuse color to work around incorrect color space behavior in the regular FBX importer:
                // in gamma mode, it seems to double-apply the gamma correction, so counteract one of the conversions.
                if (PlayerSettings.colorSpace == ColorSpace.Gamma)
                {
                    diffuseColor = new Color(
                        Mathf.GammaToLinearSpace(diffuseColor.r),
                        Mathf.GammaToLinearSpace(diffuseColor.g),
                        Mathf.GammaToLinearSpace(diffuseColor.b));
                }
                material.SetColor(materialColorProp, diffuseColor);
            }

            if (description.TryGetProperty(MetallicFactorPhongProp, out float metallic))
            {
                material.SetFloat(MetallicValuePropId, metallic);
            }
            if (description.TryGetProperty(MetallicFactorPhongProp, out textureProperty))
            {
                material.SetTexture(MetallicTexturePropId, textureProperty.texture);
                material.SetTextureOffset(MetallicTexturePropId, textureProperty.offset);
                material.SetTextureScale(MetallicTexturePropId, textureProperty.scale);

                // BIRP uses _METALLICGLOSSMAP ; URP uses _METALLICSPECGLOSSMAP
                material.EnableKeyword(isUrp ? "_METALLICSPECGLOSSMAP" : "_METALLICGLOSSMAP");
            }
            if (description.TryGetProperty(ParallaxCustomProp, out textureProperty))
            {
                material.SetTexture(ParallaxTexturePropId, textureProperty.texture);
                material.SetTextureOffset(ParallaxTexturePropId, textureProperty.offset);
                material.SetTextureScale(ParallaxTexturePropId, textureProperty.scale);
                material.EnableKeyword("_PARALLAXMAP");
            }
            if (description.TryGetProperty(OcclusionMapCustomProp, out textureProperty))
            {
                material.SetTexture(OcclusionTexturePropId, textureProperty.texture);
                material.SetTextureOffset(OcclusionTexturePropId, textureProperty.offset);
                material.SetTextureScale(OcclusionTexturePropId, textureProperty.scale);
            }
            if (description.TryGetProperty(DetailMapCustomProp, out textureProperty))
            {
                material.SetTexture(DetailTexturePropId, textureProperty.texture);
                material.SetTextureOffset(DetailTexturePropId, textureProperty.offset);
                material.SetTextureScale(DetailTexturePropId, textureProperty.scale);
            }


            // Apply emissive color as well as texture map, which standard doesn't do.
            if (
                description.TryGetProperty("EmissiveColor", out vectorProperty) &&
                vectorProperty.magnitude > vectorProperty.w
                || description.HasAnimationCurve("EmissiveColor.x"))
            {
                if (description.TryGetProperty("EmissiveFactor", out floatProperty))
                    vectorProperty *= floatProperty;

                Color emissiveColor = vectorProperty;
                if (PlayerSettings.colorSpace == ColorSpace.Gamma)
                {
                    // Re-assign the color to work around incorrect color space behavior in the regular FBX importer:
                    // in gamma mode, it seems to double-apply the gamma correction, so counteract one of the conversions.
                    emissiveColor = new Color(
                        Mathf.GammaToLinearSpace(emissiveColor.r),
                        Mathf.GammaToLinearSpace(emissiveColor.g),
                        Mathf.GammaToLinearSpace(emissiveColor.b));
                }
                material.SetColor("_EmissionColor", emissiveColor);
                if (floatProperty > 0.0f)
                {
                    material.EnableKeyword("_EMISSION");
                    material.globalIlluminationFlags |= MaterialGlobalIlluminationFlags.RealtimeEmissive;
                }
            }
        }

        private static bool HasISDKProperty(MaterialDescription description)
        {
            var propertyNames = new List<string>();
            description.GetFloatPropertyNames(propertyNames);
            foreach (var propertyName in propertyNames)
            {
                if (propertyName.StartsWith("ISDK_"))
                {
                    return true;
                }
            }

            return false;
        }
    }
}
#endif