/*
 * RenderQueue.cs
 * Authors:     August Zinsser
 * 
 * Copyright August Zinsser 2007
 * This program is distributed under the terms of the GNU General Public License
 */


using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Pina3D.Particles;


namespace Pina3D
{
    /// <summary>
    /// Manages a "queue" of all ColladaModels and particles to be rendered. Automatically sorts the queue for optimal render time.
    /// </summary>
    public class RenderQueue
    {
        public enum BlendMode { Alpha, Additive };

        protected Dictionary<string, List<Renderable>> mRenderables;  // Holds "subqueues" sorted by vertex type to minimize vertex delcarations
        protected List<Particle> mParticlesAlphaBlend;
        protected List<Particle> mParticlesAdditiveBlend;

        public int Count
        {
            get
            {
                int runningTotal = 0;
                foreach (KeyValuePair<string, List<Renderable>> kvp in mRenderables)
                {
                    runningTotal += kvp.Value.Count;
                }
                return runningTotal;
            }
        }


        /// <summary>
        /// Allocates internal variables
        /// </summary>
        public RenderQueue()
        {
            mRenderables = new Dictionary<string, List<Renderable>>();
            mParticlesAlphaBlend = new List<Particle>();
            mParticlesAdditiveBlend = new List<Particle>();
        }


        /// <summary>
        /// Tells each model and particle in the render queue to render itself
        /// </summary>
        public void Render()
        {
            Pina.Graphics.GraphicsDevice.RenderState.DepthBufferEnable = true;
            Pina.Graphics.GraphicsDevice.RenderState.DepthBufferWriteEnable = true;
            Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendEnable = false;
            //Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendOperation = BlendFunction.Add;
            //Pina.Graphics.GraphicsDevice.RenderState.SourceBlend = Blend.SourceAlpha;
            //Pina.Graphics.GraphicsDevice.RenderState.DestinationBlend = Blend.InverseSourceAlpha;
            //Pina.Graphics.GraphicsDevice.RenderState.SeparateAlphaBlendEnabled = false;
            foreach (KeyValuePair<string, List<Renderable>> kvp in mRenderables)
            {
                // TODO: Implement IComparable and then sort the renderables (optimization)
                // TODO: Store the sourceData of each Renderable and then render each sourceData once with a list of each Renderable's PinaState (optimization)
                // TODO: Support transparent geometry (new feature)
                for (int i = 0; i < kvp.Value.Count; i++)
                {
                    kvp.Value[i].Render();
                }
            }


            // "Quality" Alpha Blended (requires back-to-front draw order)
            //Pina.Graphics.GraphicsDevice.RenderState.DepthBufferEnable = true;
            //Pina.Graphics.GraphicsDevice.RenderState.DepthBufferWriteEnable = true;
            //Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendEnable = true;
            //Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendOperation = BlendFunction.Add;
            //Pina.Graphics.GraphicsDevice.RenderState.SourceBlend = Blend.SourceAlpha;
            //Pina.Graphics.GraphicsDevice.RenderState.DestinationBlend = Blend.InverseSourceAlpha;
            //Pina.Graphics.GraphicsDevice.RenderState.SeparateAlphaBlendEnabled = false;

            // "Fast" Alpha Blended (does NOT require back-to-front draw order, but some particles may occaisonally falsely occlude other objects. Draw them last to minimize this)
            Pina.Graphics.GraphicsDevice.RenderState.DepthBufferEnable = true;
            Pina.Graphics.GraphicsDevice.RenderState.DepthBufferWriteEnable = false;
            Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendEnable = true;
            Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendOperation = BlendFunction.Add;
            Pina.Graphics.GraphicsDevice.RenderState.SourceBlend = Blend.SourceAlpha;
            Pina.Graphics.GraphicsDevice.RenderState.DestinationBlend = Blend.InverseSourceAlpha;
            Pina.Graphics.GraphicsDevice.RenderState.SeparateAlphaBlendEnabled = false;
            for (int i = 0; i < mParticlesAlphaBlend.Count; i++)
            {
                mParticlesAlphaBlend[i].Render();
            }
            QuadRenderer.RenderAllNow();
            
            // Additive Blended
            Pina.Graphics.GraphicsDevice.RenderState.DepthBufferEnable = true;
            Pina.Graphics.GraphicsDevice.RenderState.DepthBufferWriteEnable = false;
            Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendEnable = true;
            Pina.Graphics.GraphicsDevice.RenderState.AlphaBlendOperation = BlendFunction.Add;
            Pina.Graphics.GraphicsDevice.RenderState.SourceBlend = Blend.SourceAlpha;
            Pina.Graphics.GraphicsDevice.RenderState.DestinationBlend = Blend.One;
            Pina.Graphics.GraphicsDevice.RenderState.SeparateAlphaBlendEnabled = false;
            for (int i = 0; i < mParticlesAdditiveBlend.Count; i++)
            {
                mParticlesAdditiveBlend[i].Render();
            }
            QuadRenderer.RenderAllNow();
        }


        /// <summary>
        /// Tells the specified collada model to render itself each render cycle
        /// </summary>
        /// <param name="model"></param>
        public void Add(Renderable renderable)
        {
            string vertDec = "defaultDec";
            
            // Is this a new vertex delcaration?
            if (!mRenderables.ContainsKey(vertDec))
                mRenderables.Add(vertDec, new List<Renderable>());

            // Add to the appropriate sublist
            mRenderables[vertDec].Add(renderable);
        }


        /// <summary>
        /// Tells the specified particle to render itself each render cycle
        /// </summary>
        /// <param name="particle"></param>
        public void Add(Particle particle, BlendMode blendMode)
        {
            if (blendMode == BlendMode.Alpha)
                mParticlesAlphaBlend.Add(particle);
            else
                mParticlesAdditiveBlend.Add(particle);
        }


        /// <summary>
        /// Removes the specified renderable from the render queue
        /// </summary>
        /// <returns>true if the model was found and removed, false otherwise</returns>
        public bool Remove(Renderable renderable)
        {
            string vertDec = "defaultDec";

            // Does this vertex declaration even exist?
            if (!mRenderables.ContainsKey(vertDec))
                return false;

            // Try to remove the model
            return mRenderables[vertDec].Remove(renderable);
        }


        /// <summary>
        /// Removes the specified particle from the render queue
        /// </summary>
        /// <param name="model"></param>
        /// <returns>true if the model was found and removed, false otherwise</returns>
        public bool Remove(Particle particle)
        {
            // Try to remove the particle
            if (mParticlesAlphaBlend.Contains(particle))
                return mParticlesAlphaBlend.Remove(particle);
            else
                return mParticlesAdditiveBlend.Remove(particle);
        }


        /// <summary>
        /// Removes all models and particles from the render queue
        /// </summary>
        public void Flush()
        {
            mRenderables.Clear();
            mParticlesAlphaBlend.Clear();
            mParticlesAdditiveBlend.Clear();
        }


        /// <summary>
        /// Removes particles from the render queue, but leaves models
        /// </summary>
        public void FlushParticles()
        {
            mParticlesAlphaBlend.Clear();
            mParticlesAdditiveBlend.Clear();
        }
    }
}