source: trunk/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory-5.5.0/Editor/TextSourceVersionProvider.cs @ 17197

// Copyright (c) 2010-2013 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;
using System.Diagnostics;
using System.Linq;

namespace ICSharpCode.NRefactory.Editor
{
  /// <summary>
  /// Provides ITextSourceVersion instances.
  /// </summary>
  public class TextSourceVersionProvider
  {
    Version currentVersion;
    
    public TextSourceVersionProvider()
    {
      this.currentVersion = new Version(this);
    }
    
    /// <summary>
    /// Gets the current version.
    /// </summary>
    public ITextSourceVersion CurrentVersion {
      get { return currentVersion; }
    }
    
    /// <summary>
    /// Replaces the current version with a new version.
    /// </summary>
    /// <param name="change">Change from current version to new version</param>
    public void AppendChange(TextChangeEventArgs change)
    {
      if (change == null)
        throw new ArgumentNullException("change");
      currentVersion.change = change;
      currentVersion.next = new Version(currentVersion);
      currentVersion = currentVersion.next;
    }
    
    [DebuggerDisplay("Version #{id}")]
    sealed class Version : ITextSourceVersion
    {
      // Reference back to the provider.
      // Used to determine if two checkpoints belong to the same document.
      readonly TextSourceVersionProvider provider;
      // ID used for CompareAge()
      readonly int id;
      
      // the change from this version to the next version
      internal TextChangeEventArgs change;
      internal Version next;
      
      internal Version(TextSourceVersionProvider provider)
      {
        this.provider = provider;
      }
      
      internal Version(Version prev)
      {
        this.provider = prev.provider;
        this.id = unchecked( prev.id + 1 );
      }
      
      public bool BelongsToSameDocumentAs(ITextSourceVersion other)
      {
        Version o = other as Version;
        return o != null && provider == o.provider;
      }
      
      public int CompareAge(ITextSourceVersion other)
      {
        if (other == null)
          throw new ArgumentNullException("other");
        Version o = other as Version;
        if (o == null || provider != o.provider)
          throw new ArgumentException("Versions do not belong to the same document.");
        // We will allow overflows, but assume that the maximum distance between checkpoints is 2^31-1.
        // This is guaranteed on x86 because so many checkpoints don't fit into memory.
        return Math.Sign(unchecked( this.id - o.id ));
      }
      
      public IEnumerable<TextChangeEventArgs> GetChangesTo(ITextSourceVersion other)
      {
        int result = CompareAge(other);
        Version o = (Version)other;
        if (result < 0)
          return GetForwardChanges(o);
        else if (result > 0)
          return o.GetForwardChanges(this).Reverse().Select(change => change.Invert());
        else
          return EmptyList<TextChangeEventArgs>.Instance;
      }
      
      IEnumerable<TextChangeEventArgs> GetForwardChanges(Version other)
      {
        // Return changes from this(inclusive) to other(exclusive).
        for (Version node = this; node != other; node = node.next) {
          yield return node.change;
        }
      }
      
      public int MoveOffsetTo(ITextSourceVersion other, int oldOffset, AnchorMovementType movement)
      {
        int offset = oldOffset;
        foreach (var e in GetChangesTo(other)) {
          offset = e.GetNewOffset(offset, movement);
        }
        return offset;
      }
    }
  }
}