#region License

// Copyright (c) 2010, ClearCanvas Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, 
// are permitted provided that the following conditions are met:
//
//    * Redistributions of source code must retain the above copyright notice, 
//      this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above copyright notice, 
//      this list of conditions and the following disclaimer in the documentation 
//      and/or other materials provided with the distribution.
//    * Neither the name of ClearCanvas Inc. nor the names of its contributors 
//      may be used to endorse or promote products derived from this software without 
//      specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, 
// OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 
// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
// OF SUCH DAMAGE.

#endregion

using System.Collections;
using System.Collections.Generic;

namespace Nullstack.ClearCanvasEx.DesktopEx.View.WpfAdapter.Utilities
{
	/// <summary>
	/// Implements an ordered set, where the order of enumeration reflects the order in which items
	/// were added to the set.  If the same item is added to the set again, it is moved to the end of the ordering.
	/// </summary>
	/// <typeparam name="T"></typeparam>
	internal class OrderedSet<T> : IEnumerable<T>
	{
		private LinkedList<T> _items;

		public OrderedSet()
		{
			_items = new LinkedList<T>();
		}

		public void Add(T item)
		{
			_items.Remove(item);
			_items.AddLast(item);
		}

		public void Remove(T item)
		{
			_items.Remove(item);
		}

		public T FirstElement
		{
			get { return _items.Count > 0 ? _items.First.Value : default(T); }
		}

		public T LastElement
		{
			get { return _items.Count > 0 ? _items.Last.Value : default(T); }
		}

		public T SecondLastElement
		{
			get { return _items.Count > 1 ? _items.Last.Previous.Value : default(T); }
		}

		public int Count
		{
			get { return _items.Count; }
		}

		#region IEnumerable<T> Members

		public IEnumerator<T> GetEnumerator()
		{
			return _items.GetEnumerator();
		}

		#endregion

		#region IEnumerable Members

		IEnumerator IEnumerable.GetEnumerator()
		{
			return _items.GetEnumerator();
		}

		#endregion
	}
}