private Expression extractUrlParameter(HiddenTokenAwareTree token, String function, String text) { if (text == null) return null; if (text.length() <= function.length() + 2) return new CssString(token, "", ""); String string = text.substring(function.length() + 1, text.length() - 1); if (!URIUtils.isQuotedUrl(string)) return new CssString(token, string, ""); String quote = String.valueOf(string.charAt(0)); return new CssString(token, string.substring(1, string.length() - 1), quote); }