source: branches/2929_PrioritizedGrammarEnumeration/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/TextUtilities.cs @ 15990

// Copyright (c) 2014 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.Globalization;
using System.Windows.Documents;
#if NREFACTORY
using ICSharpCode.NRefactory.Editor;
#endif

namespace ICSharpCode.AvalonEdit.Document
{
  /// <summary>
  /// Specifies the mode for getting the next caret position.
  /// </summary>
  public enum CaretPositioningMode
  {
    /// <summary>
    /// Normal positioning (stop after every grapheme)
    /// </summary>
    Normal,
    /// <summary>
    /// Stop only on word borders.
    /// </summary>
    WordBorder,
    /// <summary>
    /// Stop only at the beginning of words. This is used for Ctrl+Left/Ctrl+Right.
    /// </summary>
    WordStart,
    /// <summary>
    /// Stop only at the beginning of words, and anywhere in the middle of symbols.
    /// </summary>
    WordStartOrSymbol,
    /// <summary>
    /// Stop only on word borders, and anywhere in the middle of symbols.
    /// </summary>
    WordBorderOrSymbol,
    /// <summary>
    /// Stop between every Unicode codepoint, even within the same grapheme.
    /// This is used to implement deleting the previous grapheme when Backspace is pressed.
    /// </summary>
    EveryCodepoint
  }
  
  /// <summary>
  /// Static helper methods for working with text.
  /// </summary>
  public static partial class TextUtilities
  {
    #region GetControlCharacterName
    // the names of the first 32 ASCII characters = Unicode C0 block
    static readonly string[] c0Table = {
      "NUL", "SOH", "STX", "ETX", "EOT", "ENQ", "ACK", "BEL", "BS", "HT",
      "LF", "VT", "FF", "CR", "SO", "SI", "DLE", "DC1", "DC2", "DC3",
      "DC4", "NAK", "SYN", "ETB", "CAN", "EM", "SUB", "ESC", "FS", "GS",
      "RS", "US"
    };
    
    // DEL (ASCII 127) and
    // the names of the control characters in the C1 block (Unicode 128 to 159)
    static readonly string[] delAndC1Table = {
      "DEL",
      "PAD", "HOP", "BPH", "NBH", "IND", "NEL", "SSA", "ESA", "HTS", "HTJ",
      "VTS", "PLD", "PLU", "RI", "SS2", "SS3", "DCS", "PU1", "PU2", "STS",
      "CCH", "MW", "SPA", "EPA", "SOS", "SGCI", "SCI", "CSI", "ST", "OSC",
      "PM", "APC"
    };
    
    /// <summary>
    /// Gets the name of the control character.
    /// For unknown characters, the unicode codepoint is returned as 4-digit hexadecimal value.
    /// </summary>
    public static string GetControlCharacterName(char controlCharacter)
    {
      int num = (int)controlCharacter;
      if (num < c0Table.Length)
        return c0Table[num];
      else if (num >= 127 && num <= 159)
        return delAndC1Table[num - 127];
      else
        return num.ToString("x4", CultureInfo.InvariantCulture);
    }
    #endregion
    
    #region GetWhitespace
    /// <summary>
    /// Gets all whitespace (' ' and '\t', but no newlines) after offset.
    /// </summary>
    /// <param name="textSource">The text source.</param>
    /// <param name="offset">The offset where the whitespace starts.</param>
    /// <returns>The segment containing the whitespace.</returns>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
                                                     Justification = "WPF uses 'Whitespace'")]
    public static ISegment GetWhitespaceAfter(ITextSource textSource, int offset)
    {
      if (textSource == null)
        throw new ArgumentNullException("textSource");
      int pos;
      for (pos = offset; pos < textSource.TextLength; pos++) {
        char c = textSource.GetCharAt(pos);
        if (c != ' ' && c != '\t')
          break;
      }
      return new SimpleSegment(offset, pos - offset);
    }
    
    /// <summary>
    /// Gets all whitespace (' ' and '\t', but no newlines) before offset.
    /// </summary>
    /// <param name="textSource">The text source.</param>
    /// <param name="offset">The offset where the whitespace ends.</param>
    /// <returns>The segment containing the whitespace.</returns>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
                                                     Justification = "WPF uses 'Whitespace'")]
    public static ISegment GetWhitespaceBefore(ITextSource textSource, int offset)
    {
      if (textSource == null)
        throw new ArgumentNullException("textSource");
      int pos;
      for (pos = offset - 1; pos >= 0; pos--) {
        char c = textSource.GetCharAt(pos);
        if (c != ' ' && c != '\t')
          break;
      }
      pos++; // go back the one character that isn't whitespace
      return new SimpleSegment(pos, offset - pos);
    }
    
    /// <summary>
    /// Gets the leading whitespace segment on the document line.
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
                                                     Justification = "WPF uses 'Whitespace'")]
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters",
                                                     Justification = "Parameter cannot be ITextSource because it must belong to the DocumentLine")]
    public static ISegment GetLeadingWhitespace(TextDocument document, DocumentLine documentLine)
    {
      if (documentLine == null)
        throw new ArgumentNullException("documentLine");
      return GetWhitespaceAfter(document, documentLine.Offset);
    }
    
    /// <summary>
    /// Gets the trailing whitespace segment on the document line.
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
                                                     Justification = "WPF uses 'Whitespace'")]
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters",
                                                     Justification = "Parameter cannot be ITextSource because it must belong to the DocumentLine")]
    public static ISegment GetTrailingWhitespace(TextDocument document, DocumentLine documentLine)
    {
      if (documentLine == null)
        throw new ArgumentNullException("documentLine");
      ISegment segment = GetWhitespaceBefore(document, documentLine.EndOffset);
      // If the whole line consists of whitespace, we consider all of it as leading whitespace,
      // so return an empty segment as trailing whitespace.
      if (segment.Offset == documentLine.Offset)
        return new SimpleSegment(documentLine.EndOffset, 0);
      else
        return segment;
    }
    #endregion
    
    #region GetSingleIndentationSegment
    /// <summary>
    /// Gets a single indentation segment starting at <paramref name="offset"/> - at most one tab
    /// or <paramref name="indentationSize"/> spaces.
    /// </summary>
    /// <param name="textSource">The text source.</param>
    /// <param name="offset">The offset where the indentation segment starts.</param>
    /// <param name="indentationSize">The size of an indentation unit. See <see cref="TextEditorOptions.IndentationSize"/>.</param>
    /// <returns>The indentation segment.
    /// If there is no indentation character at the specified <paramref name="offset"/>,
    /// an empty segment is returned.</returns>
    public static ISegment GetSingleIndentationSegment(ITextSource textSource, int offset, int indentationSize)
    {
      if (textSource == null)
        throw new ArgumentNullException("textSource");
      int pos = offset;
      while (pos < textSource.TextLength) {
        char c = textSource.GetCharAt(pos);
        if (c == '\t') {
          if (pos == offset)
            return new SimpleSegment(offset, 1);
          else
            break;
        } else if (c == ' ') {
          if (pos - offset >= indentationSize)
            break;
        } else {
          break;
        }
        // continue only if c==' ' and (pos-offset)<tabSize
        pos++;
      }
      return new SimpleSegment(offset, pos - offset);
    }
    #endregion
    
    #region GetCharacterClass
    /// <summary>
    /// Gets whether the character is whitespace, part of an identifier, or line terminator.
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "c")]
    public static CharacterClass GetCharacterClass(char c)
    {
      if (c == '\r' || c == '\n')
        return CharacterClass.LineTerminator;
      if (c == '_')
        return CharacterClass.IdentifierPart;
      return GetCharacterClass(char.GetUnicodeCategory(c));
    }
    
    static CharacterClass GetCharacterClass(char highSurrogate, char lowSurrogate)
    {
      if (char.IsSurrogatePair(highSurrogate, lowSurrogate)) {
        return GetCharacterClass(char.GetUnicodeCategory(highSurrogate.ToString() + lowSurrogate.ToString(), 0));
      } else {
        // malformed surrogate pair
        return CharacterClass.Other;
      }
    }
    
    static CharacterClass GetCharacterClass(UnicodeCategory c)
    {
      switch (c) {
        case UnicodeCategory.SpaceSeparator:
        case UnicodeCategory.LineSeparator:
        case UnicodeCategory.ParagraphSeparator:
        case UnicodeCategory.Control:
          return CharacterClass.Whitespace;
        case UnicodeCategory.UppercaseLetter:
        case UnicodeCategory.LowercaseLetter:
        case UnicodeCategory.TitlecaseLetter:
        case UnicodeCategory.ModifierLetter:
        case UnicodeCategory.OtherLetter:
        case UnicodeCategory.DecimalDigitNumber:
          return CharacterClass.IdentifierPart;
        case UnicodeCategory.NonSpacingMark:
        case UnicodeCategory.SpacingCombiningMark:
        case UnicodeCategory.EnclosingMark:
          return CharacterClass.CombiningMark;
        default:
          return CharacterClass.Other;
      }
    }
    #endregion
    
    #region GetNextCaretPosition
    /// <summary>
    /// Gets the next caret position.
    /// </summary>
    /// <param name="textSource">The text source.</param>
    /// <param name="offset">The start offset inside the text source.</param>
    /// <param name="direction">The search direction (forwards or backwards).</param>
    /// <param name="mode">The mode for caret positioning.</param>
    /// <returns>The offset of the next caret position, or -1 if there is no further caret position
    /// in the text source.</returns>
    /// <remarks>
    /// This method is NOT equivalent to the actual caret movement when using VisualLine.GetNextCaretPosition.
    /// In real caret movement, there are additional caret stops at line starts and ends. This method
    /// treats linefeeds as simple whitespace.
    /// </remarks>
    public static int GetNextCaretPosition(ITextSource textSource, int offset, LogicalDirection direction, CaretPositioningMode mode)
    {
      if (textSource == null)
        throw new ArgumentNullException("textSource");
      switch (mode) {
        case CaretPositioningMode.Normal:
        case CaretPositioningMode.EveryCodepoint:
        case CaretPositioningMode.WordBorder:
        case CaretPositioningMode.WordBorderOrSymbol:
        case CaretPositioningMode.WordStart:
        case CaretPositioningMode.WordStartOrSymbol:
          break; // OK
        default:
          throw new ArgumentException("Unsupported CaretPositioningMode: " + mode, "mode");
      }
      if (direction != LogicalDirection.Backward
          && direction != LogicalDirection.Forward)
      {
        throw new ArgumentException("Invalid LogicalDirection: " + direction, "direction");
      }
      int textLength = textSource.TextLength;
      if (textLength <= 0) {
        // empty document? has a normal caret position at 0, though no word borders
        if (IsNormal(mode)) {
          if (offset > 0 && direction == LogicalDirection.Backward) return 0;
          if (offset < 0 && direction == LogicalDirection.Forward) return 0;
        }
        return -1;
      }
      while (true) {
        int nextPos = (direction == LogicalDirection.Backward) ? offset - 1 : offset + 1;
        
        // return -1 if there is no further caret position in the text source
        // we also need this to handle offset values outside the valid range
        if (nextPos < 0 || nextPos > textLength)
          return -1;
        
        // check if we've run against the textSource borders.
        // a 'textSource' usually isn't the whole document, but a single VisualLineElement.
        if (nextPos == 0) {
          // at the document start, there's only a word border
          // if the first character is not whitespace
          if (IsNormal(mode) || !char.IsWhiteSpace(textSource.GetCharAt(0)))
            return nextPos;
        } else if (nextPos == textLength) {
          // at the document end, there's never a word start
          if (mode != CaretPositioningMode.WordStart && mode != CaretPositioningMode.WordStartOrSymbol) {
            // at the document end, there's only a word border
            // if the last character is not whitespace
            if (IsNormal(mode) || !char.IsWhiteSpace(textSource.GetCharAt(textLength - 1)))
              return nextPos;
          }
        } else {
          char charBefore = textSource.GetCharAt(nextPos - 1);
          char charAfter = textSource.GetCharAt(nextPos);
          // Don't stop in the middle of a surrogate pair
          if (!char.IsSurrogatePair(charBefore, charAfter)) {
            CharacterClass classBefore = GetCharacterClass(charBefore);
            CharacterClass classAfter = GetCharacterClass(charAfter);
            // get correct class for characters outside BMP:
            if (char.IsLowSurrogate(charBefore) && nextPos >= 2) {
              classBefore = GetCharacterClass(textSource.GetCharAt(nextPos - 2), charBefore);
            }
            if (char.IsHighSurrogate(charAfter) && nextPos + 1 < textLength) {
              classAfter = GetCharacterClass(charAfter, textSource.GetCharAt(nextPos + 1));
            }
            if (StopBetweenCharacters(mode, classBefore, classAfter)) {
              return nextPos;
            }
          }
        }
        // we'll have to continue searching...
        offset = nextPos;
      }
    }
    
    static bool IsNormal(CaretPositioningMode mode)
    {
      return mode == CaretPositioningMode.Normal || mode == CaretPositioningMode.EveryCodepoint;
    }
    
    static bool StopBetweenCharacters(CaretPositioningMode mode, CharacterClass charBefore, CharacterClass charAfter)
    {
      if (mode == CaretPositioningMode.EveryCodepoint)
        return true;
      // Don't stop in the middle of a grapheme
      if (charAfter == CharacterClass.CombiningMark)
        return false;
      // Stop after every grapheme in normal mode
      if (mode == CaretPositioningMode.Normal)
        return true;
      if (charBefore == charAfter) {
        if (charBefore == CharacterClass.Other &&
            (mode == CaretPositioningMode.WordBorderOrSymbol || mode == CaretPositioningMode.WordStartOrSymbol))
        {
          // With the "OrSymbol" modes, there's a word border and start between any two unknown characters
          return true;
        }
      } else {
        // this looks like a possible border
        
        // if we're looking for word starts, check that this is a word start (and not a word end)
        // if we're just checking for word borders, accept unconditionally
        if (!((mode == CaretPositioningMode.WordStart || mode == CaretPositioningMode.WordStartOrSymbol)
              && (charAfter == CharacterClass.Whitespace || charAfter == CharacterClass.LineTerminator)))
        {
          return true;
        }
      }
      return false;
    }
    #endregion
  }
  
  /// <summary>
  /// Classifies a character as whitespace, line terminator, part of an identifier, or other.
  /// </summary>
  public enum CharacterClass
  {
    /// <summary>
    /// The character is not whitespace, line terminator or part of an identifier.
    /// </summary>
    Other,
    /// <summary>
    /// The character is whitespace (but not line terminator).
    /// </summary>
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
                                                     Justification = "WPF uses 'Whitespace'")]
    Whitespace,
    /// <summary>
    /// The character can be part of an identifier (Letter, digit or underscore).
    /// </summary>
    IdentifierPart,
    /// <summary>
    /// The character is line terminator (\r or \n).
    /// </summary>
    LineTerminator,
    /// <summary>
    /// The character is a unicode combining mark that modifies the previous character.
    /// Corresponds to the Unicode designations "Mn", "Mc" and "Me".
    /// </summary>
    CombiningMark
  }
}