// this is based on "Linkify" from greasemonkey.mozdev.org

function linkify() {

    if (!document.evaluate) return;

    var urlRegex = /\b((?:https?|ftp|irc):\/\/(?:[^\s+\"\<\>\(\),:.]|\.(?!$|\.))+)/ig;

    var xpath = "//text()[(parent::p)]";

    var candidates = document.evaluate(xpath, document, null, XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null);

    for (var cand = null, i = 0; (cand = candidates.snapshotItem(i)); i++) {
        if (urlRegex.test(cand.nodeValue)) {
            var span = document.createElement("span");
            var source = cand.nodeValue;
            
            cand.parentNode.replaceChild(span, cand);

            urlRegex.lastIndex = 0;
            for (var match = null, lastLastIndex = 0; (match = urlRegex.exec(source)); ) {
                span.appendChild(document.createTextNode(source.substring(lastLastIndex, match.index)));
                
                var a = document.createElement("a");
                a.setAttribute("href", match[0]);
                a.appendChild(document.createTextNode(match[0]));
                span.appendChild(a);

                lastLastIndex = urlRegex.lastIndex;
            }

            span.appendChild(document.createTextNode(source.substring(lastLastIndex)));
            span.normalize();
        }
    }
}