.NET Regular Expressions Find and Replace Add-In for Visual Studio 2008

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace RegexFindAndReplace
{
    /// <summary>
    /// The MatchContextUtils class exposes several static methods that provide information about a match.
    /// </summary>
    class MatchContextUtils
    {
        const char NEW_LINE_CHARACTOR = '\n';

        /// <summary>
        /// Determines whether the specified source has multiple lines.
        /// </summary>
        /// <param name="source">The source.</param>
        /// <returns>
        /// 	<c>true</c> if the specified source has multiple lines; otherwise, <c>false</c>.
        /// </returns>
        public static bool HasMultipleLines( string source )
        {
            return GetLineCount( source ) > 0;
        }

        /// <summary>
        /// Gets the line count.
        /// </summary>
        /// <param name="source">The source.</param>
        /// <returns>The number of lines</returns>
        public static int GetLineCount( string source )
        {
            return GetLineCount( source, source.Length - 1 );
        }

        /// <summary>
        /// Gets the line count.
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="endIndex">The end index.</param>
        /// <returns>The number of lines before the end index</returns>
        public static int GetLineCount( string source, int endIndex )
        {
            int count = 1;

            if ( source != null && source.Length != 0 )
            {
                count = Regex.Matches( source.Substring( 0, endIndex ), "\n" ).Count + 1;
            }

            return count;
        }

        /// <summary>
        /// Gets the match context string.
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="startIndex">The start index.</param>
        /// <param name="endIndex">The end index.</param>
        /// <returns></returns>
        public static string GetMatchContextString( string source, int startIndex, int endIndex )
        {
            return GetMatchContextString( source, startIndex, endIndex, 0, 0 );
        }

        /// <summary>
        /// Gets the match context string.
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="startIndex">The start index.</param>
        /// <param name="endIndex">The end index.</param>
        /// <param name="matchContextBeforeLineCount">The match context before line count.</param>
        /// <param name="matchContextAfterLineCount">The match context after line count.</param>
        /// <returns></returns>
        public static string GetMatchContextString( string source, int startIndex, int endIndex, int matchContextBeforeLineCount, int matchContextAfterLineCount )
        {
            string context = string.Empty;

            int contextStartPosition = source.LastIndexOf( NEW_LINE_CHARACTOR, startIndex );

            if ( contextStartPosition < 0 )
            {
                contextStartPosition = 0;
            }

            if ( matchContextBeforeLineCount > 0 && contextStartPosition > 0 )
            {
                for ( int i = 1; i <= matchContextBeforeLineCount && contextStartPosition > 0; i++ )
                {
                    int newLinePosition = source.LastIndexOf( NEW_LINE_CHARACTOR, contextStartPosition - 1 );

                    if ( newLinePosition > 0 )
                    {
                        contextStartPosition = newLinePosition;
                    }
                    else
                    {
                        contextStartPosition = 0;
                    }
                }
            }

            int contextEndPosition = source.IndexOf( NEW_LINE_CHARACTOR, endIndex );
            
            if ( contextEndPosition < 0 )
            {
                contextEndPosition = source.Length;
            }

            if ( matchContextAfterLineCount > 0 && contextEndPosition < source.Length )
            {
                for ( int i = 1; i <= matchContextAfterLineCount && contextEndPosition < source.Length; i++ )
                {
                    int newLinePosition = source.IndexOf( NEW_LINE_CHARACTOR, contextEndPosition + 1 );

                    if ( newLinePosition > 0 )
                    {
                        contextEndPosition = newLinePosition;
                    }
                    else
                    {
                        contextEndPosition = source.Length;
                    }
                }
            }

            if ( contextStartPosition == 0 )
            {
                context = source.Substring( 0, contextEndPosition - contextStartPosition );
            }
            else
            {
                context = source.Substring( contextStartPosition + 1, contextEndPosition - contextStartPosition );
            }

            return context;
        }

        /// <summary>
        /// Gets the match context string.
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="startIndex">The start index.</param>
        /// <param name="endIndex">The end index.</param>
        /// <param name="matchContextBeforeLineCount">The match context before line count.</param>
        /// <param name="matchContextAfterLineCount">The match context after line count.</param>
        /// <returns></returns>
        public static string GetReplacementContextString( string source, int startIndex, int endIndex, string replacement, int matchContextBeforeLineCount, int matchContextAfterLineCount )
        {
            string context = string.Empty;

            int contextStartPosition = source.LastIndexOf( NEW_LINE_CHARACTOR, startIndex );

            if ( contextStartPosition < 0 )
            {
                contextStartPosition = 0;
            }

            if ( matchContextBeforeLineCount > 0 && contextStartPosition > 0 )
            {
                for ( int i = 1; i <= matchContextBeforeLineCount && contextStartPosition > 0; i++ )
                {
                    int newLinePosition = source.LastIndexOf( NEW_LINE_CHARACTOR, contextStartPosition - 1 );

                    if ( newLinePosition > 0 )
                    {
                        contextStartPosition = newLinePosition;
                    }
                    else
                    {
                        contextStartPosition = 0;
                    }
                }
            }

            int contextEndPosition = source.IndexOf( NEW_LINE_CHARACTOR, endIndex );

            if ( contextEndPosition < 0 )
            {
                contextEndPosition = source.Length;
            }

            if ( matchContextAfterLineCount > 0 && contextEndPosition < source.Length )
            {
                for ( int i = 1; i <= matchContextAfterLineCount && contextEndPosition < source.Length; i++ )
                {
                    int newLinePosition = source.IndexOf( NEW_LINE_CHARACTOR, contextEndPosition + 1 );

                    if ( newLinePosition > 0 )
                    {
                        contextEndPosition = newLinePosition;
                    }
                    else
                    {
                        contextEndPosition = source.Length;
                    }
                }
            }

            if ( contextStartPosition == 0 )
            {
                context = string.Format( "{0}{1}{2}",
                    source.Substring( 0, startIndex ),
                    replacement,
                    source.Substring( endIndex, contextEndPosition - endIndex ) );
            }
            else
            {
                context = string.Format( "{0}{1}{2}", 
                    source.Substring( contextStartPosition + 1, startIndex - contextStartPosition - 1 ),
                    replacement, 
                    source.Substring( endIndex, contextEndPosition - endIndex ) );
            }

            return context;
        }

        /// <summary>
        /// Gets the position in the specified source line.
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="absolutePosition">The absolute position.</param>
        /// <returns></returns>
        public static int GetPositionInLine( string source, int absolutePosition )
        {
            int position = 0;
            int newlinePosition = source.LastIndexOf( NEW_LINE_CHARACTOR, absolutePosition );

            if ( newlinePosition == -1 )
            {
                position = absolutePosition + 1;
            }
            else
            {
                if ( absolutePosition == newlinePosition )
                {
                    newlinePosition = source.LastIndexOf( NEW_LINE_CHARACTOR, absolutePosition - 1 );
                }

                position = absolutePosition - newlinePosition;
            }

            return position;
        }
    }
}