function trim(s) 
{
  while (s.substring(0,1) == ' ') 
    s = s.substring(1,s.length);
  while (s.substring(s.length-1,s.length) == ' ') 
    s = s.substring(0,s.length-1);
  return s;
}

function IsEmail(strMail)
{
	strMail = strMail.toLowerCase();
  var AtSign = strMail.indexOf("@",0);
	var Space = strMail.indexOf(" ",0);
	var Dot = strMail.indexOf(".",AtSign + 1);
	return ((strMail != "") && (AtSign >= 1) && (Dot <= strMail.length - 3) && (Dot >= AtSign+2) && (Space <= 0));
}

function IsAnInteger(strInt)
{
	var strCompare = '0123456789'
	for (var i=0;i<strInt.length;i++)
	{
		var chr = strInt.charAt(i);
		if (strCompare.indexOf(chr)==-1) return false;
	}
	return true;
}


function SetVisible(imageId, isError)
{ //show or hide ErrorImage
  var image = document.getElementById(imageId);
  try
  {
    if(image)
    {
      image.src = isError ? "images/tekstcursorError.gif" : "images/tekstcursor.gif";
    }
  }
  catch(exc)
  {
  }
}

function CheckInput(InputObject, checkError, Check, errorMessage, Control)
{ //check different kind of inputs
  var ThisCheck=true;
  var strInput = trim(InputObject.value);
  switch(Control)
    {
    case 1: //only length
      ThisCheck=(strInput.length > 0);
      break;
    case 2: //Email
      ThisCheck=IsEmail(strInput);
      break;
    case 3: //SelectBoxes
      ThisCheck=(parseInt(strInput) > 0);
      break;
    case 4: //Email if filled in
      if (strInput.length > 0) 
      {
        ThisCheck=IsEmail(strInput);
      }
      break;
    }
  if(!ThisCheck)
  {
    SetVisible(checkError,true);
    if(Check) //only firstTime error alert and focus input
    {
      alert(errorMessage);
      InputObject.focus();
    }
    return false;
  }
  //check ok; no ErrorStar 
  SetVisible(checkError,false);
  return true;
}

function CheckForm(form, errorMessage)
	{
    var check = true;
    if(!CheckInput(form.subject, "checkSubject", check, errorMessage, 3)) 
    {
      check=false;
    }
    if(!CheckInput(form.name, "checkName", check, errorMessage, 1)) 
    {
      check=false;
    }
    if(!CheckInput(form.email, "checkEmail", check, errorMessage, 4)) 
    {
      check=false;
    }
    return check;
	}