ILSpy/ILSpy/NavigationHistory.cs

// Copyright (c) 2011 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;

namespace ICSharpCode.ILSpy
{
	/// <summary>
	/// Stores the navigation history.
	/// </summary>
	internal sealed class NavigationHistory<T>
		where T : class, IEquatable<T>
	{
		private const double NavigationSecondsBeforeNewEntry = 0.5;

		private DateTime lastNavigationTime = DateTime.MinValue;
		T current;
		List<T> back = new List<T>();
		List<T> forward = new List<T>();

		public bool CanNavigateBack {
			get { return back.Count > 0; }
		}

		public bool CanNavigateForward {
			get { return forward.Count > 0; }
		}

		public T GoBack()
		{
			forward.Add(current);
			current = back[back.Count - 1];
			back.RemoveAt(back.Count - 1);
			return current;
		}

		public T GoForward()
		{
			back.Add(current);
			current = forward[forward.Count - 1];
			forward.RemoveAt(forward.Count - 1);
			return current;
		}

		public void RemoveAll(Predicate<T> predicate)
		{
			back.RemoveAll(predicate);
			forward.RemoveAll(predicate);
		}

		public void Clear()
		{
			back.Clear();
			forward.Clear();
		}

		public void UpdateCurrent(T node)
		{
			current = node;
		}

		public void Record(T node)
		{
			var navigationTime = DateTime.Now;
			var period = navigationTime - lastNavigationTime;

			if (period.TotalSeconds < NavigationSecondsBeforeNewEntry)
			{
				current = node;
			}
			else
			{
				if (current != null)
					back.Add(current);

				// We only store a record once, and ensure it is on the top of the stack, so we just remove the old record
				back.Remove(node);
				current = node;
			}

			forward.Clear();

			lastNavigationTime = navigationTime;
		}
	}
}