var eCard = {
  createHref: function () {
    var to_name = $("to-name").value;
    if (!to_name) {
      alert("vul a.u.b. 'naam ontvanger' in");
      return false;
    }

    var to = $("to").value;
    if (!checkEmail(to)) {
      alert("geen geldig e-mail adres");
      return false;
    }

    var from_name = $("from-name").value;
    if (!from_name) {
      alert("vul a.u.b. 'uw naam' in");
      return false;
    }

    var message = "Beste " + to_name + ",%0A%0a" + from_name + " heeft u de onderstaande link gestuurd:%0A%0a";
    var url = getParamValue("url");
    if (url)
      message += url;
    else {
      alert("geen geldige url.")
      return false;
    }

    if ($("message").value)
      message += "%0A%0a" + escape($("message").value);

    var mailto = "mailto:" + to + "?body=" + message + "&subject=" + "Stedelijk museum e-card";

    $("sendEcard").href = mailto;
  }
}

function getParamValue(paramName) {
  //regexp van de interwebs
  paramName = paramName.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
  var regexS = "[\\?&]" + paramName + "=([^&#]*)";
  var regex = new RegExp(regexS);
  var results = regex.exec(window.location.href);
  if (results == null)
    return "";
  else
    return results[1];
}

function checkEmail(s) {  
  var filter = /^([a-zA-Z0-9_.-])+@(([a-zA-Z0-9-])+.)+([a-zA-Z0-9]{2,4})+$/;
  return filter.test(s);
}