/// <summary>
        /// Match all tags in the text with a regular expression.
        /// </summary>
        /// <param name="input">The text to be matched against.</param>
        /// <param name="handleTags">A function to interpret and transform tags.</param>
        /// <returns>Text with transformed tags.</returns>
        private static string TransformTags(string input, Func<string, string, string, string> handleTags)
        {
            var regexOptions = RegexOptions.IgnorePatternWhitespace | RegexOptions.Singleline;
            input = Regex.Replace(input, RegularExpressions.BBCodeTags, new MatchEvaluator(match =>
            {
                var originalText = match.Groups[0].Value;
                var tag = match.Groups[1].Value;
                var optionalValue = match.Groups[2].Value;
                var content = match.Groups[3].Value;
                content = TransformTags(content, handleTags);
                content = handleTags(content, optionalValue, tag) ?? originalText;
                return content;
            }), regexOptions);

            return input;
        }






        /// <summary>
        /// Find formatting tags in the text and transform them into the appropriate HTML.
        /// </summary>
        /// <param name="text">The text to be transformed.</param>
        /// <returns>A formatted string.</returns>
        public static string ConvertTagsToHtml(string text)
        {
            text = TransformTags(text, (content, optionalValue, tag) =>
                {
                    tag = tag.ToLower();

                    if (tag.Is("code"))
                        return string.Format("<pre><code>{0}</code></pre>", content);
                    else if (tag.Is("color"))
                        return string.Format("<span style='color: #{0};'>{1}</span>", optionalValue, content);
                    else if (tag.Is("img"))
                    {
                        string imageUrl = ConfirmHttp(content);
                        try
                        {
                            var client = new WebClient();
                            var stream = client.OpenRead(imageUrl);
                            var bitmap = new Bitmap(stream);
                            stream.Flush();
                            stream.Close();
                            var width = Convert.ToDecimal(bitmap.Size.Width);
                            var height = Convert.ToDecimal(bitmap.Size.Height);
                            if (width > 500m)
                            {
                                var ratio = width / 500m;
                                height = height / ratio;
                                width = 500m;
                            }
                            return string.Format("<div style='height: {0}px; width: {1}px;'><a target='_blank' href='{2}'><img style='height: {0}px; width: {1}px;' src='{2}' /></a></div>", height, width, imageUrl);
                        }
                        catch
                        {
                            return string.Format("<div><a target='_blank' href='{0}'><img src='{0}' /></a></div>", imageUrl);
                        }
                    }
                    else if (tag.Is("url"))
                        return string.Format("<a target='_blank' href='{0}'>{1}</a>", string.IsNullOrEmpty(optionalValue) ? ConfirmHttp(content) : ConfirmHttp(optionalValue), content);
                    else if (tag.Is("transmit"))
                        return string.Format("<span class='transmit'>{0}</span>", content);
                    else if (tag.Is("quote"))
                        return string.Format("<div><div class='quote'>{0}</div></div>", content);
                    else if (tag.Is("b"))
                        return string.Format("<b>{0}</b>", content);
                    else if (tag.Is("i"))
                        return string.Format("<i>{0}</i>", content);
                    else if (tag.Is("u"))
                        return string.Format("<u>{0}</u>", content);
                    else if (tag.Is("s"))
                        return string.Format("<strike>{0}</strike>", content);
                    else
                        return null;
                });

            return text;
        }