function init_webad_calculator() {
	if(!!$('frmImpressions')){
  $('frmImpressions').observe('submit', function(event) {
	  calculateInternetPrices();
	});
	}
}
function calculateInternetPrices() {
  var imp = $('txtImpressions').value;
	var budget = $('txtBudget').value;
	$('txtImpressions').value = "";
	$('txtBudget').value = "";
  if(!!imp && isNumeric(imp)) {
    updatePriceTable(imp, null);
  }
	else if(!!budget && isNumeric(budget)) {
		updatePriceTable(null, budget);
	}
  else {
    alert('Ugyldig sidevisning eller budsjett');
  }
}
function isNumeric(sText) {
  var ValidChars = "0123456789.";
  var IsNumber=true;
  var Char;
  for (i = 0; i < sText.length && IsNumber == true; i++) {
    Char = sText.charAt(i); 
    if (ValidChars.indexOf(Char) == -1) {
      IsNumber = false;
    }
  }
  return IsNumber;   
}
function updatePriceTable(imp, budget) {
	var langImp = $('langImpressions').value;
  var tr = $$('#webad_table tr');
  for (var i=0; i<tr.length; i++) {
    if(i==0) {
      td = new Element('th', {className: 'price'});
			var sup = new Element('sup');
	    sup.innerHTML = imp ? langImp : 'kroner';
	    td.innerHTML = imp ? imp : budget;
	    td.appendChild(sup);
    } else {
			var tds = tr[i].descendants();
    	var price = tds[2].innerHTML.replace(/,/, ".");
      td = new Element('td', {className: 'price'});
			var td_value = imp ? 'Kr ' + Math.round(imp * price) + ',-' : Math.round(budget / price) + ' ' + langImp;
			td.update(td_value);
    }
	  tr[i].appendChild(td);
  }
}
document.observe("dom:loaded", init_webad_calculator);