function isSurveyable() {
  return isSessionSurveyable() && !isUserSurveyed();
}

function isSessionSurveyable() {
  var s = Cookie.read("surveyable")
  if (!s || s.length == 0) {
    s=surveyDiceRoll().toString()
    Cookie.create("surveyable",s)
  }
  return (s == "true");
}

function surveyDiceRoll() {
  return (Math.random() <= parseFloat(system_preferences["survey:net_promoter:chance"]))
}

function showSurveyPrompt() {
  Cookie.create("surveyed","true",parseInt(system_preferences["survey:net_promoter:eligable_after"]));
  var survey_prompt = $('survey_prompt')
  var wrapper = $('body');
  if (wrapper) {
    survey_prompt.style.marginLeft = "-"+wrapper.offsetLeft+"px";
  }
  survey_popup = new Popup(survey_prompt,null,{position:'center', show_duration: 0.5});
  var objects = document.getElementsByTagName("object");
  for (var i = 0; i < objects.length; i++) {
    var obj = $(objects[i]);
    obj.hide();
  }
  survey_popup.show();
}

function isUserSurveyed() {
  return (Cookie.read("surveyed") == "true")
}