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

namespace Smuggler
{
    public struct PBRLight
    {
        public Vector3 direction;
        public Vector3 radiance;

        public PBRLight(Vector3 direction, Vector3 radiance)
        {
            this.direction = direction;
            this.radiance = radiance;
        }
    }

    public class PBRLightCollection
    {
        readonly EffectParameter directionParam;
        readonly EffectParameter radianceParam;

        private readonly Vector3[] directions = new Vector3[PBREffect.NUM_LIGHTS];
        private readonly Vector3[] radiances = new Vector3[PBREffect.NUM_LIGHTS];

        public PBRLightCollection(EffectParameter directionParam, EffectParameter radianceParam)
        {
            this.directionParam = directionParam;
            this.radianceParam = radianceParam;
        }

        public PBRLightCollection(PBRLightCollection other)
        {
            for (int i = 0; i < PBREffect.NUM_LIGHTS; i++)
            {
                directions[i] = other.directions[i];
                radiances[i] = other.radiances[i];
            }
        }

        public PBRLight this[int index]
        {
            get
            {
                return new PBRLight(directions[index], radiances[index]);
            }

            set
            {
                directions[index] = value.direction;
                radiances[index] = value.radiance;
                directionParam.SetValue(directions);
                radianceParam.SetValue(radiances);
            }
        }
    }

    public class PBREffect : Effect
    {
        public static readonly int NUM_LIGHTS = 3;

        readonly EffectParameter viewProjectionParam;
        readonly EffectParameter sceneRotationParam;
        readonly EffectParameter eyePositionParam;
        readonly EffectParameter specularTextureLevelsParam;

        readonly EffectParameter albedoTextureParam;

        Matrix world = Matrix.Identity;
        Matrix view = Matrix.Identity;
        Matrix projection = Matrix.Identity;
        Vector3 eyePosition = Vector3.Zero;
        int specularTextureLevels = 0;

        public Matrix World
        {
            get { return world; }
            set 
            { 
                world = value;
                sceneRotationParam.SetValue(world); 
            }
        }

        public Matrix View
        {
            get { return view; }
            set 
            { 
                view = value;
                viewProjectionParam.SetValue(projection * view); 
                eyePositionParam.SetValue(Matrix.Invert(view).Backward);
            }
        }

        public Matrix Projection
        {
            get { return projection; }
            set 
            { 
                projection = value;
                viewProjectionParam.SetValue(projection * view);
            }
        }

        public PBRLightCollection Lights { get; }

        public int SpecularTextureLevels
        {
            get { return specularTextureLevels; }
            set
            {
                specularTextureLevels = value;
                specularTextureLevelsParam.SetValue(specularTextureLevels);
            }
        }

        public Texture2D AlbedoTexture
        {
            get { return albedoTextureParam.GetValueTexture2D(); }
            set { albedoTextureParam.SetValue(value); }
        }

        public PBREffect(GraphicsDevice graphicsDevice, byte[] effectCode) : base(graphicsDevice, effectCode)
        {
            viewProjectionParam = Parameters["viewProjectionMatrix"];
            sceneRotationParam  = Parameters["sceneRotationMatrix"];

            eyePositionParam = Parameters["eyePosition"];
            specularTextureLevelsParam = Parameters["specularTextureLevels"];

            Lights = new PBRLightCollection(Parameters["directions"], Parameters["radiance"]);
        }

        protected PBREffect(PBREffect cloneSource) : base(cloneSource)
        {
            viewProjectionParam = Parameters["viewProjectionMatrix"];
            sceneRotationParam  = Parameters["sceneRotationMatrix"];

            eyePositionParam = Parameters["eyePosition"];
            specularTextureLevelsParam = Parameters["specularTextureLevels"];

            World = cloneSource.World;
            View = cloneSource.View;
            Projection = cloneSource.Projection;
            Lights = new PBRLightCollection(cloneSource.Lights);
        }

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

        // FIXME: do param applications here for performance
        protected override void OnApply()
        {
            base.OnApply();
        }
    }
}