Subtitlte Edit: RemoveLineBreaks (Undone)

public static string RemoveLineBreaks(string input)
        {
            const string singleWhiteSpace = " ";

            // normalize html tag e.g.: <I> => <i>
            var s = HtmlUtil.FixUpperTags(input);

            // unbreak line e.g: foo\r\nbar => foo bar
            s = s.Replace(Environment.NewLine, singleWhiteSpace);

            // ensure line was broke
            if (input.Length != s.Length)
            {
                // todo: remove!
                s = s.Replace("</i> <i>", singleWhiteSpace);
                s = s.Replace("</b> <b>", singleWhiteSpace);
                s = s.Replace("</u> <u>", singleWhiteSpace);

                var closingTag = string.Empty;

                var l = 0;
                for (int r = 0; r < s.Length; r++)
                {
                    if (s[r] == '<')
                    {
                        l = r;
                    }
                    else if (s[r] == '>' && s[l] == '<' && s[l + 1] == '/') // closing tag
                    {
                        closingTag = s.Substring(l, r - l + 1);
                        l = r + 1;
                    }
                    else if (s[r] == '>' && s[l] == '<' && closingTag.Length > 0) // opening tag (closing tag was found)
                    {
                        var openTag = s.Substring(l, r - l + 1); // todo: use span when in .net >= 6
                        // todo: check if open-tag is pair with closing-tag
                        //  - true: remove
                        //  - false: continue

                        if (openTag.IsPairWith(closingTag))
                        {
                            // todo: store the indexes that will be removed (in reverse)
                            //  - store close-tag index + len
                            //  - store open-tag index + len
                            closingTag = string.Empty;
                        }
                        // else: continue looking for matching pair
                    }
                    else if (s[r] != ' ')
                    {
                        // reset closing tag | char found that is not whitespace or start tag (start tag are handled above)
                        closingTag = string.Empty;
                    }
                }

                s = s.Replace("> ", ">");
                return s.Replace(" </", "</").FixExtraSpaces().Trim();
            }

            return input;
        }