/*
 * Collidable.cs
 * Authors: Adam Nabinger
 * 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 Microsoft.Xna.Framework;

namespace MaritimeDefender
{
	/// <summary>
	/// Defines a class that performs checks of collision based on position and size
	/// </summary>
	public class Collidable
	{
		#region Fields

		/// <summary>
		/// Center of the Entity
		/// </summary>
		protected Vector3 mPos;

		/// <summary>
		/// Volume of the Entity
		/// </summary>
		protected Vector3 mSize;

		#endregion

		#region Properties

		/// <summary>
		/// Gets/Sets the position of the entity
		/// </summary>
		public Vector3 Position { 
			get { return mPos; }
			set { mPos = value; }
		}

		/// <summary>
		/// Gets/Sets the horizontal position
		/// </summary>
		public float X {
			get { return mPos.X; }
			set { mPos.X = value; }
		}

		/// <summary>
		/// Gets/Sets the verticle position
		/// </summary>
		public float Y { 
			get { return mPos.Y; }
			set { mPos.Y = value; }
		}

		/// <summary>
		/// Gets/Sets the layer depth
		/// </summary>
		public float Z {
			get { return mPos.Z; }
			set { mPos.Z = value; }
		}

		/// <summary>
		/// Gets/Sets the size of the entity
		/// </summary>
		public virtual Vector3 Size {
			get { return mSize; }
			set { mSize = value; }
		}

		/// <summary>
		/// Gets/Sets the X-dimension of size
		/// </summary>
		public virtual float Width { 
			get { return mSize.X; }
			set { mSize.X = value; }
		}

		/// <summary>
		/// Gets/Sets the Y-dimension of size
		/// </summary>
		public virtual float Height {
			get { return mSize.Y; }
			set { mSize.Y = value; }
		}

		/// <summary>
		/// Gets/Sets the Z-dimension of size
		/// </summary>
		public virtual float Depth {
			get { return mSize.Z; }
			set { mSize.Z = value; }
		}

		#endregion

		#region Collision

		/// <summary>
		/// Tests collision between 2 entities' bounding boxes in x and y dimensions
		/// </summary>
		/// <param name="entity1">The first object to check for collision against</param>
		/// <param name="entity2">The second object to check for collision against</param>
		/// <returns>True if collision occurs, false otherwise</returns>
		internal static bool Collides2D(Collidable entity1, Collidable entity2)
		{
			return (entity1.X + (entity1.Width * 0.5f) >= entity2.X - (entity2.Width * 0.5f) &&
			        entity1.X - (entity1.Width * 0.5f) <= entity2.X + (entity2.Width * 0.5f) &&
			        entity1.Y + (entity1.Height * 0.5f) >= entity2.Y - (entity2.Height * 0.5f) &&
			        entity1.Y - (entity1.Height * 0.5f) <= entity2.Y + (entity2.Height * 0.5f));
		}

		/// <summary>
		/// Tests collision between 2 entities' bounding boxes in 3 dimensions
		/// </summary>
		/// <param name="entity1">The first object to check for collision against</param>
		/// <param name="entity2">The second object to check for collision against</param>
		/// <returns>True if collision occurs, false otherwise</returns>
		internal static bool Collides3D(Collidable entity1, Collidable entity2)
		{
			return (entity1.X + (entity1.Width * 0.5f) >= entity2.X - (entity2.Width * 0.5f) &&
			        entity1.X - (entity1.Width * 0.5f) <= entity2.X + (entity2.Width * 0.5f) &&
			        entity1.Y + (entity1.Height * 0.5f) >= entity2.Y - (entity2.Height * 0.5f) &&
			        entity1.Y - (entity1.Height * 0.5f) <= entity2.Y + (entity2.Height * 0.5f) &&
			        entity1.Z + (entity1.Depth * 0.5f) >= entity2.Z - (entity2.Depth * 0.5f) &&
			        entity1.Z - (entity1.Depth * 0.5f) <= entity2.Z + (entity2.Depth * 0.5f));
		}

		#endregion
	}
}