Remove SQL comments with C-Sharp

The function SQL.removeComment removes SQL comments using regular expressions.

The source code is based upon Rick Drizin's excellent work, found here, which apparently is itself based on an answer in StackOverflow that tackled removing comments from C-Sharp.

//
//    Remove comments in SQL text with regular expressions.
//
//    Based upon Rick Drizin's excellent work (https://drizin.io/Removing-comments-from-SQL-scripts/)
//    which apparently bases upon an answer in Stackoverflow (https://stackoverflow.com/questions/3524317#3524689)
//
using System;
using System.Text.RegularExpressions;

namespace tq84 {

   public class SQL {

      private static Regex noEOLchar = new Regex("[^\r\n]");

      public static string removeComments(
         string input,
         bool   removeLiterals    = false,
         bool   preservePositions = false
      )
      {

        var lineComment      = @"--(.*?)\r?\n";
        var lineCommentNoEOL = @"--(.*?)$"    ; // A line comment that has no end of line.

     //
     // Literals, bracketed identifiers and quotedIdentifiers ("object") all have the same structure:
     //     - Start character,
     //     - a number of characters (including consecutive pairs of closing
     //       characters which are counted as part of the «thing), and
     //     - the closing character
     //
        var literals             = @"('(('')|[^'])*')";          // 'John', 'O''malley''s', etc
        var bracketedIdentifiers = @"\[((\]\])|[^\]])* \]";      // [object], [ % object]] ], etc
        var quotedIdentifiers    = @"(\""((\""\"")|[^""])*\"")"; // "object", "object[]", etc - when QUOTED_IDENTIFIER is set to ON, they are identifiers, else they are literals

     //
     // The original code was for C#, but Microsoft SQL allows a nested block comments
     //     https://msdn.microsoft.com/en-us/library/ms178623.aspx
     // so we should use balancing groups
     //   -> http://weblogs.asp.net/whaggard/377025
     //
     // var blockComments = @"/\*(.*?)\*/";
     //
        var nestedBlockComments = @"/\*
                                    (?>
                                    /\*  (?<LEVEL>)     # On opening push level
                                    |
                                    \*/ (?<-LEVEL>)     # On closing pop level
                                    |
                                    (?! /\* | \*/ ) .   # Match any char unless the opening and closing strings
                                    )+                  # /* or */ in the lookahead string
                                    (?(LEVEL)(?!))      # If level exists then fail
                                    \*/";

        string noComments = Regex.Replace(input,

            nestedBlockComments    + "|" +
            lineComment            + "|" +
            lineCommentNoEOL       + "|" +
            literals               + "|" +
            bracketedIdentifiers   + "|" +
            quotedIdentifiers,

            txt => {

                if (txt.Value.StartsWith("/*")) {

                    if (preservePositions)
                    //  preserve positions and keep line-breaks
                        return noEOLchar.Replace(txt.Value, " ");

                     return "";

                }

                if (txt.Value.StartsWith("--")) {

                    if (preservePositions)
                    //  preserve positions and keep line-breaks
                        return noEOLchar.Replace(txt.Value, " ");

                    //  preserve only line-breaks
                    return noEOLchar.Replace(txt.Value, "");

                }

                if (txt.Value.StartsWith("[") || txt.Value.StartsWith("\"")) {
                //  Don't ever remove object identifiers
                    return txt.Value;
                }

                if (!removeLiterals) {
                //  Keep literal strings
                    return txt.Value;
                }


                if (preservePositions) {
                //
                //  Remove literals, but preserve positions and line-breaks
                //
                    var literalWithLineBreaks = noEOLchar.Replace(txt.Value, " ");
                    return "'" + literalWithLineBreaks.Substring(1, literalWithLineBreaks.Length - 2) + "'";
                }

                return "''";
            },
            RegexOptions.Singleline | RegexOptions.IgnorePatternWhitespace
        );

        return noComments;
      }
   }
}

set-strictMode -version latest

$src = get-content -raw SQL.cs

add-type -typeDef $src

$sqlText = @'
select
      29 + 13 as num    , -- As always: 42
     'xyz'    as literal, -- a literal
     [abc]
from
   [foo bar] join
     /* 
        comment
        comment
        comment
      
     */
    baz
    -- comment
'@

write-host ([tq84.SQL]::removeComments($sqlText))

write-host '-------------------------------------'

write-host ([tq84.SQL]::removeComments($sqlText, $true))

write-host '-------------------------------------'

write-host ([tq84.SQL]::removeComments($sqlText, $true, $true))