var lang = 'de';

function ErrorRequired(fieldLabel)
{
  switch (lang)
  {
  case 'de': alert('Bitte füllen Sie das Feld "' + fieldLabel +'" aus.'); break;
  case 'en': alert('Please complete the following field "' + fieldLabel +'".'); break;
  }
}

function ErrorEmail()
{
  switch (lang)
  {
  case 'de': alert("Bitte geben Sie eine gültige Email-Adresse ein."); break;
  case 'en': alert("Please enter a valid email address."); break;
  }
}

function ErrorNum()
{
  switch (lang)
  {
  case 'de': alert('Bitte geben Sie eine Nummer ein.'); break;
  case 'en': alert("Please enter a valid nummer."); break;
  }
}

function ErrorDate()
{
  switch (lang)
  {
  case 'de': alert('Bitte geben Sie ein gültiges Datum der Form TT.MM.JJJJ ein.'); break;
  case 'en': alert("Please enter a valid date"); break;
  }
}

function isEmailAddr(email)
{
  var result = false;
  var theStr = new String(email);
  var index = theStr.indexOf("@");
  if (index > 0)
  {
    var pindex = theStr.indexOf(".",index);
    if ((pindex > index+1) && (theStr.length > pindex+1))
      result = true;
  }
  return result;
}

function validRequired(formField,fieldLabel)
{
  var result = true;
  
  if (formField.value == "")
  {
    ErrorRequired(fieldLabel);
    formField.focus();
    result = false;
  }
  
  return result;
}

function validEmail(formField,fieldLabel,required)
{
  var result = true;
  
  if (required)
  {
    if (!validRequired(formField,fieldLabel))
      result = false;
  }
  if (result && (!isEmailAddr(formField.value)))
  {
    ErrorEmail();
    formField.focus();
    result = false;
  }
   
  return result;

}

function validNum(formField,fieldLabel,required)
{
  var result = true;

  if (required && !validRequired(formField,fieldLabel))
    result = false;
  
   if (result)
   {
     var num = parseInt(formField.value,10);
     if (isNaN(num))
     {
       ErrorNum();
       formField.focus();    
       result = false;
    }
  } 
  
  return result;
}

function validDate(formField,fieldLabel,required)
{
  var result = true;

  if (required && !validRequired(formField,fieldLabel))
    result = false;
  
   if (result)
   {
     var elems = formField.value.split(".");
     
     result = (elems.length == 3); // should be three components
     
     if (result)
     {
       var day   = parseInt(elems[0],10);
       var month = parseInt(elems[1],10);
       var year  = parseInt(elems[2],10);
       result = !isNaN(month) && (month > 0) && (month < 13) &&
                !isNaN(day) && (day > 0) && (day < 32) &&
                !isNaN(year) && (elems[2].length == 4);
     }
     if (!result)
     {
       ErrorDate();
       formField.focus();    
    }
  } 
  
  return result;
}