using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Diagnostics.Contracts;



namespace Microsoft.Research.DynamicDataDisplay.Common

{

	/// <summary>

	/// Represents a dictionary with automatic removal of old values.

	/// </summary>

	/// <typeparam name="T"></typeparam>

	public sealed class RingDictionary<T>

	{

		private int startGeneration = 0;

		private int generation;

		private readonly Dictionary<int, T> dict = new Dictionary<int, T>();

		private readonly int maxElements = 5;



		public RingDictionary(int maxElements = 5)

		{

			Contract.Assert(maxElements >= 1);



			this.maxElements = maxElements;

		}



		public int Generation

		{

			get { return generation; }

		}



		public int StartGeneration

		{

			get { return startGeneration; }

		}



		public bool ContainsValue(T value)

		{

			return dict.ContainsValue(value);

		}



		public void AddValue(T value)

		{

			Contract.Assert(value != null);



			dict.Add(generation++, value);

			Cleanup();

		}



		public int Count

		{

			get { return dict.Count; }

		}



		private void Cleanup()

		{

			while ((generation - startGeneration) > maxElements)

			{

				dict.Remove(startGeneration);

				startGeneration++;

			}

		}

	}

}