source: branches/RemoveBackwardsCompatibility/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/OffsetChangeMap.cs @ 18242

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
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// substantial portions of the Software.
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using ICSharpCode.AvalonEdit.Utils;
#if NREFACTORY
using ICSharpCode.NRefactory.Editor;
#endif

namespace ICSharpCode.AvalonEdit.Document
{
  /// <summary>
  /// Contains predefined offset change mapping types.
  /// </summary>
  public enum OffsetChangeMappingType
  {
    /// <summary>
    /// Normal replace.
    /// Anchors in front of the replaced region will stay in front, anchors after the replaced region will stay after.
    /// Anchors in the middle of the removed region will be deleted. If they survive deletion,
    /// they move depending on their AnchorMovementType.
    /// </summary>
    /// <remarks>
    /// This is the default implementation of DocumentChangeEventArgs when OffsetChangeMap is null,
    /// so using this option usually works without creating an OffsetChangeMap instance.
    /// This is equivalent to an OffsetChangeMap with a single entry describing the replace operation.
    /// </remarks>
    Normal,
    /// <summary>
    /// First the old text is removed, then the new text is inserted.
    /// Anchors immediately in front (or after) the replaced region may move to the other side of the insertion,
    /// depending on the AnchorMovementType.
    /// </summary>
    /// <remarks>
    /// This is implemented as an OffsetChangeMap with two entries: the removal, and the insertion.
    /// </remarks>
    RemoveAndInsert,
    /// <summary>
    /// The text is replaced character-by-character.
    /// Anchors keep their position inside the replaced text.
    /// Anchors after the replaced region will move accordingly if the replacement text has a different length than the replaced text.
    /// If the new text is shorter than the old text, anchors inside the old text that would end up behind the replacement text
    /// will be moved so that they point to the end of the replacement text.
    /// </summary>
    /// <remarks>
    /// On the OffsetChangeMap level, growing text is implemented by replacing the last character in the replaced text
    /// with itself and the additional text segment. A simple insertion of the additional text would have the undesired
    /// effect of moving anchors immediately after the replaced text into the replacement text if they used
    /// AnchorMovementStyle.BeforeInsertion.
    /// Shrinking text is implemented by removing the text segment that's too long; but in a special mode that
    /// causes anchors to always survive irrespective of their <see cref="TextAnchor.SurviveDeletion"/> setting.
    /// If the text keeps its old size, this is implemented as OffsetChangeMap.Empty.
    /// </remarks>
    CharacterReplace,
    /// <summary>
    /// Like 'Normal', but anchors with <see cref="TextAnchor.MovementType"/> = Default will stay in front of the
    /// insertion instead of being moved behind it.
    /// </summary>
    KeepAnchorBeforeInsertion
  }
  
  /// <summary>
  /// Describes a series of offset changes.
  /// </summary>
  [Serializable]
  [SuppressMessage("Microsoft.Naming", "CA1710:IdentifiersShouldHaveCorrectSuffix",
                   Justification="It's a mapping old offsets -> new offsets")]
  public sealed class OffsetChangeMap : Collection<OffsetChangeMapEntry>
  {
    /// <summary>
    /// Immutable OffsetChangeMap that is empty.
    /// </summary>
    [SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes",
                     Justification="The Empty instance is immutable")]
    public static readonly OffsetChangeMap Empty = new OffsetChangeMap(Empty<OffsetChangeMapEntry>.Array, true);
    
    /// <summary>
    /// Creates a new OffsetChangeMap with a single element.
    /// </summary>
    /// <param name="entry">The entry.</param>
    /// <returns>Returns a frozen OffsetChangeMap with a single entry.</returns>
    public static OffsetChangeMap FromSingleElement(OffsetChangeMapEntry entry)
    {
      return new OffsetChangeMap(new OffsetChangeMapEntry[] { entry }, true);
    }
    
    bool isFrozen;
    
    /// <summary>
    /// Creates a new OffsetChangeMap instance.
    /// </summary>
    public OffsetChangeMap()
    {
    }
    
    internal OffsetChangeMap(int capacity)
      : base(new List<OffsetChangeMapEntry>(capacity))
    {
    }
    
    private OffsetChangeMap(IList<OffsetChangeMapEntry> entries, bool isFrozen)
      : base(entries)
    {
      this.isFrozen = isFrozen;
    }
    
    /// <summary>
    /// Gets the new offset where the specified offset moves after this document change.
    /// </summary>
    public int GetNewOffset(int offset, AnchorMovementType movementType = AnchorMovementType.Default)
    {
      IList<OffsetChangeMapEntry> items = this.Items;
      int count = items.Count;
      for (int i = 0; i < count; i++) {
        offset = items[i].GetNewOffset(offset, movementType);
      }
      return offset;
    }
    
    /// <summary>
    /// Gets whether this OffsetChangeMap is a valid explanation for the specified document change.
    /// </summary>
    public bool IsValidForDocumentChange(int offset, int removalLength, int insertionLength)
    {
      int endOffset = offset + removalLength;
      foreach (OffsetChangeMapEntry entry in this) {
        // check that ChangeMapEntry is in valid range for this document change
        if (entry.Offset < offset || entry.Offset + entry.RemovalLength > endOffset)
          return false;
        endOffset += entry.InsertionLength - entry.RemovalLength;
      }
      // check that the total delta matches
      return endOffset == offset + insertionLength;
    }
    
    /// <summary>
    /// Calculates the inverted OffsetChangeMap (used for the undo operation).
    /// </summary>
    public OffsetChangeMap Invert()
    {
      if (this == Empty)
        return this;
      OffsetChangeMap newMap = new OffsetChangeMap(this.Count);
      for (int i = this.Count - 1; i >= 0; i--) {
        OffsetChangeMapEntry entry = this[i];
        // swap InsertionLength and RemovalLength
        newMap.Add(new OffsetChangeMapEntry(entry.Offset, entry.InsertionLength, entry.RemovalLength));
      }
      return newMap;
    }
    
    /// <inheritdoc/>
    protected override void ClearItems()
    {
      CheckFrozen();
      base.ClearItems();
    }
    
    /// <inheritdoc/>
    protected override void InsertItem(int index, OffsetChangeMapEntry item)
    {
      CheckFrozen();
      base.InsertItem(index, item);
    }
    
    /// <inheritdoc/>
    protected override void RemoveItem(int index)
    {
      CheckFrozen();
      base.RemoveItem(index);
    }
    
    /// <inheritdoc/>
    protected override void SetItem(int index, OffsetChangeMapEntry item)
    {
      CheckFrozen();
      base.SetItem(index, item);
    }
    
    void CheckFrozen()
    {
      if (isFrozen)
        throw new InvalidOperationException("This instance is frozen and cannot be modified.");
    }
    
    /// <summary>
    /// Gets if this instance is frozen. Frozen instances are immutable and thus thread-safe.
    /// </summary>
    public bool IsFrozen {
      get { return isFrozen; }
    }
    
    /// <summary>
    /// Freezes this instance.
    /// </summary>
    public void Freeze()
    {
      isFrozen = true;
    }
  }
  
  /// <summary>
  /// An entry in the OffsetChangeMap.
  /// This represents the offset of a document change (either insertion or removal, not both at once).
  /// </summary>
  [Serializable]
  public struct OffsetChangeMapEntry : IEquatable<OffsetChangeMapEntry>
  {
    readonly int offset;
    
    // MSB: DefaultAnchorMovementIsBeforeInsertion
    readonly uint insertionLengthWithMovementFlag;
    
    // MSB: RemovalNeverCausesAnchorDeletion; other 31 bits: RemovalLength
    readonly uint removalLengthWithDeletionFlag;
    
    /// <summary>
    /// The offset at which the change occurs.
    /// </summary>
    public int Offset {
      get { return offset; }
    }
    
    /// <summary>
    /// The number of characters inserted.
    /// Returns 0 if this entry represents a removal.
    /// </summary>
    public int InsertionLength {
      get { return (int)(insertionLengthWithMovementFlag & 0x7fffffff); }
    }
    
    /// <summary>
    /// The number of characters removed.
    /// Returns 0 if this entry represents an insertion.
    /// </summary>
    public int RemovalLength {
      get { return (int)(removalLengthWithDeletionFlag & 0x7fffffff); }
    }
    
    /// <summary>
    /// Gets whether the removal should not cause any anchor deletions.
    /// </summary>
    public bool RemovalNeverCausesAnchorDeletion {
      get { return (removalLengthWithDeletionFlag & 0x80000000) != 0; }
    }
    
    /// <summary>
    /// Gets whether default anchor movement causes the anchor to stay in front of the caret.
    /// </summary>
    public bool DefaultAnchorMovementIsBeforeInsertion {
      get { return (insertionLengthWithMovementFlag & 0x80000000) != 0; }
    }
    
    /// <summary>
    /// Gets the new offset where the specified offset moves after this document change.
    /// </summary>
    public int GetNewOffset(int oldOffset, AnchorMovementType movementType = AnchorMovementType.Default)
    {
      int insertionLength = this.InsertionLength;
      int removalLength = this.RemovalLength;
      if (!(removalLength == 0 && oldOffset == offset)) {
        // we're getting trouble (both if statements in here would apply)
        // if there's no removal and we insert at the offset
        // -> we'd need to disambiguate by movementType, which is handled after the if
        
        // offset is before start of change: no movement
        if (oldOffset <= offset)
          return oldOffset;
        // offset is after end of change: movement by normal delta
        if (oldOffset >= offset + removalLength)
          return oldOffset + insertionLength - removalLength;
      }
      // we reach this point if
      // a) the oldOffset is inside the deleted segment
      // b) there was no removal and we insert at the caret position
      if (movementType == AnchorMovementType.AfterInsertion)
        return offset + insertionLength;
      else if (movementType == AnchorMovementType.BeforeInsertion)
        return offset;
      else
        return this.DefaultAnchorMovementIsBeforeInsertion ? offset : offset + insertionLength;
    }
    
    /// <summary>
    /// Creates a new OffsetChangeMapEntry instance.
    /// </summary>
    public OffsetChangeMapEntry(int offset, int removalLength, int insertionLength)
    {
      ThrowUtil.CheckNotNegative(offset, "offset");
      ThrowUtil.CheckNotNegative(removalLength, "removalLength");
      ThrowUtil.CheckNotNegative(insertionLength, "insertionLength");
      
      this.offset = offset;
      this.removalLengthWithDeletionFlag = (uint)removalLength;
      this.insertionLengthWithMovementFlag = (uint)insertionLength;
    }
    
    /// <summary>
    /// Creates a new OffsetChangeMapEntry instance.
    /// </summary>
    public OffsetChangeMapEntry(int offset, int removalLength, int insertionLength, bool removalNeverCausesAnchorDeletion, bool defaultAnchorMovementIsBeforeInsertion)
      : this(offset, removalLength, insertionLength)
    {
      if (removalNeverCausesAnchorDeletion)
        this.removalLengthWithDeletionFlag |= 0x80000000;
      if (defaultAnchorMovementIsBeforeInsertion)
        this.insertionLengthWithMovementFlag |= 0x80000000;
    }
    
    /// <inheritdoc/>
    public override int GetHashCode()
    {
      unchecked {
        return offset + 3559 * (int)insertionLengthWithMovementFlag + 3571 * (int)removalLengthWithDeletionFlag;
      }
    }
    
    /// <inheritdoc/>
    public override bool Equals(object obj)
    {
      return obj is OffsetChangeMapEntry && this.Equals((OffsetChangeMapEntry)obj);
    }
    
    /// <inheritdoc/>
    public bool Equals(OffsetChangeMapEntry other)
    {
      return offset == other.offset && insertionLengthWithMovementFlag == other.insertionLengthWithMovementFlag && removalLengthWithDeletionFlag == other.removalLengthWithDeletionFlag;
    }
    
    /// <summary>
    /// Tests the two entries for equality.
    /// </summary>
    public static bool operator ==(OffsetChangeMapEntry left, OffsetChangeMapEntry right)
    {
      return left.Equals(right);
    }
    
    /// <summary>
    /// Tests the two entries for inequality.
    /// </summary>
    public static bool operator !=(OffsetChangeMapEntry left, OffsetChangeMapEntry right)
    {
      return !left.Equals(right);
    }
  }
}