using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace Kav
{
    public class DeferredPBR_GBufferEffect : Effect, TransformEffect
    {
        EffectParameter worldParam;
        EffectParameter worldViewProjectionParam;
        EffectParameter worldInverseTransposeParam;

        EffectParameter albedoTextureParam;
        EffectParameter normalTextureParam;
        EffectParameter metallicRoughnessTextureParam;

        EffectParameter albedoParam;
        EffectParameter metallicParam;
        EffectParameter roughnessParam;

        EffectParameter vertexShaderIndexParam;
        EffectParameter shaderIndexParam;

        Matrix world = Matrix.Identity;
        Matrix view = Matrix.Identity;
        Matrix projection = Matrix.Identity;

        Vector3 albedo;
        float metallic;
        float roughness;

        bool albedoTextureEnabled = false;
        bool metallicRoughnessMapEnabled = false;
        bool normalMapEnabled = false;
        bool hardwareInstancingEnabled = false;

        EffectDirtyFlags dirtyFlags = EffectDirtyFlags.All;

        public Matrix World
        {
            get { return world; }
            set
            {
                world = value;
                dirtyFlags |= EffectDirtyFlags.World | EffectDirtyFlags.WorldViewProj;
            }
        }

        public Matrix View
        {
            get { return view; }
            set
            {
                view = value;
                dirtyFlags |= EffectDirtyFlags.WorldViewProj | EffectDirtyFlags.EyePosition;
            }
        }

        public Matrix Projection
        {
            get { return projection; }
            set
            {
                projection = value;
                dirtyFlags |= EffectDirtyFlags.WorldViewProj;
            }
        }

        public Vector3 Albedo
        {
            get { return albedo; }
            set
            {
                albedo = value;
                albedoParam.SetValue(albedo);
            }
        }

        public float Metallic
        {
            get { return metallic; }
            set
            {
                metallic = value;
                metallicParam.SetValue(metallic);
            }
        }

        public float Roughness
        {
            get { return roughness; }
            set
            {
                roughness = value;
                roughnessParam.SetValue(roughness);
            }
        }

        public Texture2D AlbedoTexture
        {
            get { return albedoTextureParam.GetValueTexture2D(); }
            set
            {
                albedoTextureParam.SetValue(value);
                albedoTextureEnabled = value != null;
                dirtyFlags |= EffectDirtyFlags.PixelShaderIndex;
            }
        }

        public Texture2D NormalTexture
        {
            get { return normalTextureParam.GetValueTexture2D(); }
            set
            {
                normalTextureParam.SetValue(value);
                normalMapEnabled = value != null;
                dirtyFlags |= EffectDirtyFlags.PixelShaderIndex;
            }
        }

        public Texture2D MetallicRoughnessTexture
        {
            get { return metallicRoughnessTextureParam.GetValueTexture2D(); }
            set
            {
                metallicRoughnessTextureParam.SetValue(value);
                metallicRoughnessMapEnabled = value != null;
                dirtyFlags |= EffectDirtyFlags.PixelShaderIndex;
            }
        }

        public bool HardwareInstancingEnabled
        {
            get { return hardwareInstancingEnabled; }
            set
            {
                if (value != hardwareInstancingEnabled)
                {
                    hardwareInstancingEnabled = value;
                    dirtyFlags |= EffectDirtyFlags.VertexShaderIndex;
                }
            }
        }

        public DeferredPBR_GBufferEffect(GraphicsDevice graphicsDevice) : base(graphicsDevice, Resources.DeferredPBR_GBufferEffect)
        {
            CacheEffectParameters();
        }

        protected DeferredPBR_GBufferEffect(DeferredPBR_GBufferEffect cloneSource) : base(cloneSource)
        {
            CacheEffectParameters();

            World = cloneSource.World;
            View = cloneSource.View;
            Projection = cloneSource.Projection;

            AlbedoTexture = cloneSource.AlbedoTexture;
            NormalTexture = cloneSource.NormalTexture;
            MetallicRoughnessTexture = cloneSource.MetallicRoughnessTexture;

            Albedo = cloneSource.Albedo;
            Metallic = cloneSource.Metallic;
            Roughness = cloneSource.Roughness;
        }

        public override Effect Clone()
        {
            return new DeferredPBR_GBufferEffect(this);
        }

        protected override void OnApply()
        {
            if ((dirtyFlags & EffectDirtyFlags.World) != 0)
            {
                worldParam.SetValue(world);

                Matrix.Invert(ref world, out Matrix worldInverse);
                Matrix.Transpose(ref worldInverse, out Matrix worldInverseTranspose);
                worldInverseTransposeParam.SetValue(worldInverseTranspose);

                dirtyFlags &= ~EffectDirtyFlags.World;
            }

            if ((dirtyFlags & EffectDirtyFlags.WorldViewProj) != 0)
            {
                Matrix.Multiply(ref world, ref view, out Matrix worldView);
                Matrix.Multiply(ref worldView, ref projection, out Matrix worldViewProj);
                worldViewProjectionParam.SetValue(worldViewProj);

                dirtyFlags &= ~EffectDirtyFlags.WorldViewProj;
            }

            if ((dirtyFlags & EffectDirtyFlags.VertexShaderIndex) != 0)
            {
                int vertexShaderIndex = 0;

                if (hardwareInstancingEnabled)
                {
                    vertexShaderIndex = 1;
                }

                vertexShaderIndexParam.SetValue(vertexShaderIndex);
            }

            if ((dirtyFlags & EffectDirtyFlags.PixelShaderIndex) != 0)
            {
                int shaderIndex = 0;

                if (albedoTextureEnabled && metallicRoughnessMapEnabled && normalMapEnabled)
                {
                    shaderIndex = 7;
                }
                else if (metallicRoughnessMapEnabled && normalMapEnabled)
                {
                    shaderIndex = 6;
                }
                else if (albedoTextureEnabled && normalMapEnabled)
                {
                    shaderIndex = 5;
                }
                else if (albedoTextureEnabled && metallicRoughnessMapEnabled)
                {
                    shaderIndex = 4;
                }
                else if (normalMapEnabled)
                {
                    shaderIndex = 3;
                }
                else if (metallicRoughnessMapEnabled)
                {
                    shaderIndex = 2;
                }
                else if (albedoTextureEnabled)
                {
                    shaderIndex = 1;
                }

                shaderIndexParam.SetValue(shaderIndex);

                dirtyFlags &= ~EffectDirtyFlags.PixelShaderIndex;
            }
        }

        void CacheEffectParameters()
        {
            worldParam = Parameters["World"];
            worldViewProjectionParam = Parameters["WorldViewProjection"];
            worldInverseTransposeParam = Parameters["WorldInverseTranspose"];

            albedoTextureParam = Parameters["AlbedoTexture"];
            normalTextureParam = Parameters["NormalTexture"];
            metallicRoughnessTextureParam = Parameters["MetallicRoughnessTexture"];

            albedoParam = Parameters["AlbedoValue"];
            metallicParam = Parameters["MetallicValue"];
            roughnessParam = Parameters["RoughnessValue"];

            shaderIndexParam = Parameters["PixelShaderIndex"];
            vertexShaderIndexParam = Parameters["VertexShaderIndex"];
        }
    }
}