/*
 * ParticleCPURenderer.cs
 * Authors: Brian Murphy
 * Copyright (c) 2007-2008 Cornell University

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License
  as published by the Free Software Foundation; either version 2
  of the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*/

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using tAC_Engine.Graphics.Cameras;
using TACParticleEngine.Emitters;
using Util;

namespace TACParticleEngine.Particles
{
	/// <summary>
	/// This class handles the rendering process for particle effects using CPU
	/// </summary>
	public static class ParticleCPURenderer
	{
		#region Render

		/// <summary>
		/// Handles drawing via CPU with sprite batches
		/// </summary>
		/// <param name="spriteBatch">The current sprite batch sued for drawing</param>
		/// <param name="emitter">The current emitter to draw</param>
		/// <param name="activeCamera">The current active camera</param>
		/// <param name="viewport">The The viewport in which the particles are drawn within</param>
		public static void Render(SpriteBatch spriteBatch, Emitter emitter, Camera activeCamera, Viewport viewport)
		{
			if (emitter.ParticlesDone)
			{
				return;
			}
			Texture2D text = emitter.Texture;
			if (text == null)
			{
				return;
			}
			Vector3 mForward = activeCamera.LookAt - activeCamera.Eye;
			mForward.Normalize();
			spriteBatch.Begin(emitter.mBlendEffect);
			if (emitter.mFirstActiveIndex < emitter.mFirstInactiveIndex)
			{
				for (int i = emitter.mFirstActiveIndex; i < emitter.mFirstInactiveIndex; ++i)
				{
					VertexParticle part = emitter.mVertexParticles[i];
					Vector3 mPos = viewport.Project(part.position, activeCamera.Projection, activeCamera.View, Matrix.Identity);
					float sizeValue = (float)Math.Sqrt(1d / Vector3.Multiply(Vector3.Subtract(part.position, activeCamera.Eye), mForward).Length());
					Vector2 size = part.size;
					int x = (int)(size.X * sizeValue);
					int y = (int)(size.Y * sizeValue);
					spriteBatch.Draw(text, new Rectangle((int)mPos.X - (x >> 1), (int)mPos.Y - (y >> 1), x, y), new Color(part.color));
				}
			}
			else
			{
				for (int i = emitter.mFirstActiveIndex; i < emitter.mVertexParticles.Length; ++i)
				{
					VertexParticle part = emitter.mVertexParticles[i];
					Vector3 mPos = viewport.Project(part.position, activeCamera.Projection, activeCamera.View, Matrix.Identity);
					float sizeValue = (float)Math.Sqrt(1d / Vector3.Multiply(Vector3.Subtract(part.position, activeCamera.Eye), mForward).Length());
					Vector2 size = part.size;
					int x = (int)(size.X * sizeValue);
					int y = (int)(size.Y * sizeValue);
					spriteBatch.Draw(text, new Rectangle((int)mPos.X - (x >> 1), (int)mPos.Y - (y >> 1), x, y), new Color(part.color));
				}
				for (int i = 0; i < emitter.mFirstInactiveIndex; ++i)
				{
					VertexParticle part = emitter.mVertexParticles[i];
					Vector3 mPos = viewport.Project(part.position, activeCamera.Projection, activeCamera.View, Matrix.Identity);
					float sizeValue = (float)Math.Sqrt(1d / Vector3.Multiply(Vector3.Subtract(part.position, activeCamera.Eye), mForward).Length());
					Vector2 size = part.size;
					int x = (int)(size.X * sizeValue);
					int y = (int)(size.Y * sizeValue);
					spriteBatch.Draw(text, new Rectangle((int)mPos.X - (x >> 1), (int)mPos.Y - (y >> 1), x, y), new Color(part.color));
				}
			}
			spriteBatch.End();
		}

		#endregion
	}
}