/*
 * LightingManager.cs
 * Authors: Mike Dapiran
 * 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 System.Collections.Generic;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using Util;

namespace tAC_Engine.Graphics
{
	/// <summary>
	/// Manages how lighting is processed
	/// </summary>
	public static class LightingManager
	{
		#region Fields

		// Reference to the current content manager
		private static ContentManager Content;

		// Struct that will hold the light or lightArray, depending on max shader value
		private static EffectParameter m_Lights;

		// A reference to the effect that will be used
		private static Effect m_Effect;

		// The color of ambient light that the shader will use
		private static Vector4 m_AmbientColor = Vector4.Zero;

		// The max shader profile that the graphics card can handle
		private static ShaderProfile maxPixelShaderProfile;

		#endregion

		#region Properties

		/// <summary>
		/// Gets/Sets the reference to the effect that will be used
		/// </summary>
		public static Effect CurrentEffect
		{
			get { return m_Effect; }
			set { m_Effect = value; }
		}

		/// <summary>
		///Gets/Sets the color of ambient light that the shader will use
		/// </summary>
		public static Vector4 AmbientColor
		{
			get { return m_AmbientColor; }
			set
			{
				m_AmbientColor = value;
				m_Effect.Parameters["ambientColor"].SetValue(m_AmbientColor);
			}
		}
		
		/// <summary>
		/// Gets/Sets the max shader profile that the graphics card can handle
		/// </summary>
		public static ShaderProfile MaxShaderVersion
		{
			get { return maxPixelShaderProfile; }
			set
			{
				maxPixelShaderProfile = value;
				if (maxPixelShaderProfile >= ShaderProfile.PS_2_0)
				{
					m_Effect = Content.Load<Effect>(AssemblyLocator.GetLocation(typeof(LightingManager).Assembly.FullName) + @"\Content\BasicShader20");
					m_Lights = m_Effect.Parameters["light"];
				}
				else if (maxPixelShaderProfile >= ShaderProfile.PS_1_1)
				{
					m_Effect = Content.Load<Effect>(AssemblyLocator.GetLocation(typeof(LightingManager).Assembly.FullName) + @"\Content\BasicShader10");
					m_Lights = m_Effect.Parameters["light"];
				}
			}
		}

		/// <summary>
		/// Gets/Sets the position of the camera
		/// </summary>
		public static Vector3 CameraPosition
		{
				get 
				{
				if(MaxShaderVersion >= ShaderProfile.PS_2_0)	
					return m_Effect.Parameters["cameraPostion"].GetValueVector3();
				else
					return Vector3.Zero;
				}

				set
				{
					if(MaxShaderVersion >= ShaderProfile.PS_2_0)
						m_Effect.Parameters["cameraPosition"].SetValue(value);
				}
		}

		#endregion

		#region Modifiers

		/// <summary>
		/// Used to change the color of a particular light
		/// </summary>
		/// <param name="p_LightNumber">The light to change</param>
		/// <param name="p_LightColor">The color of the light</param>
		public static void SetLightColor(int p_LightNumber, Vector4 p_LightColor)
		{

			if (maxPixelShaderProfile >= ShaderProfile.PS_2_0)
			{
				m_Lights.StructureMembers["color"].SetValue(p_LightColor);
			}
			else
			{
				if (p_LightNumber > 0)
					throw new IndexOutOfRangeException("Shader 1.1 supports a max of 1 one light");

				m_Lights.StructureMembers["color"].SetValue(p_LightColor);
			}
		}

		/// <summary>
		/// Used to set the position of a light
		/// </summary>
		/// <param name="p_LightNumber">The number of the light to change</param>
		/// <param name="p_LightDirection">The direciton of the light to change</param>
		public static void SetLightDirection(int p_LightNumber, Vector3 p_LightDirection)
		{

			if (maxPixelShaderProfile >= ShaderProfile.PS_2_0)
			{
				m_Lights.StructureMembers["direction"].SetValue(p_LightDirection);
			}
			else
			{
				if (p_LightNumber > 0)
					throw new InvalidOperationException("Shader 1.1 supports a max of 1 one light");

				m_Lights.StructureMembers["direction"].SetValue(p_LightDirection);
			}
		}

		/// <summary>
		/// Used to enable and disable lights
		/// </summary>
		/// <param name="p_LightNumber">The number of the light</param>
		/// <param name="p_Enabled">The new state of the light</param>
		public static void SetLightEnabled(int p_LightNumber, bool p_Enabled)
		{
			if (maxPixelShaderProfile >= ShaderProfile.PS_2_0)
			{
				m_Lights.StructureMembers["enable"].SetValue(p_Enabled);
			}
			else
			{
				if (p_LightNumber > 0)
					throw new InvalidOperationException("Shader 1.1 supports a max of 1 one light");

				m_Lights.StructureMembers["enable"].SetValue(p_Enabled);
			}
		}

		/// <summary>
		/// Sends the shader changes to the graphics card
		/// </summary>
		public static void ApplyLightChanges()
		{
			m_Effect.CommitChanges();
		}

		#endregion

		#region Initialization

		/// <summary>
		/// Needs to be called to set the game object and determine the max shader profile for the current graphics card
		/// </summary>
		/// <param name="content">Reference to the current content manager</param>
		/// <param name="graphicsDevice">Reference to the current graphics device</param>
		public static void Initialize(ContentManager content, GraphicsDevice graphicsDevice)
		{
			Content = content;
			MaxShaderVersion = graphicsDevice.GraphicsDeviceCapabilities.MaxPixelShaderProfile;
		}

		#endregion

		#region Value Returns

		/// <summary>
		/// Returns the struct that the shader uses to store the lights
		/// </summary>
		/// <param name="p_LightNumber">The number of the light to get</param>
		/// <returns></returns>
		private static EffectParameter GetLight(int p_LightNumber)
		{
			if (maxPixelShaderProfile >= ShaderProfile.PS_2_0)
			{
				try
				{
					return m_Lights.Elements[p_LightNumber];
				}
				catch (IndexOutOfRangeException)
				{
					throw new IndexOutOfRangeException("Out of range of lights");
				}
			}
			else
			{
				if (p_LightNumber > 0)
				{
					throw new InvalidOperationException("Shader 1.1 only supports a max of 1 light");
				}
				else
				{
					return m_Lights;
				}
			}
		}

		#endregion
	}
}