function isDigit( ch ) {
  return ( (ch >= '0') && (ch <= '9') );
}

function isAlpha( ch ) {
  return ( ((ch >= 'a') && (ch <= 'z')) || ((ch >= 'A') && (ch <= 'Z')) );
}

function isAlnum( ch ) {
  return ( isAlpha( ch ) || isDigit( ch ) );
}

function notIn( str1, str2 ) {
  var i = 0;
  var j = str2.length;
  for( ; i<j; i++ ) {
    var str3 =  str2.charAt(i);
    if( str1.indexOf( str3 ) != -1 )
      return false;
  }
  return true;
}

function checkUsername( username, mustBeQuoted ) {
  var i = 0;
  var j = username.length;
  if ( username.charAt(0) != '"' ) {
    if ( (username.charAt(0) <  ' ') || (username.charAt(0) >  '~')
          || !notIn( mustBeQuoted, username.charAt(0) ) )
      return false;

    for( i=1; i<j; i++ ) {
      if (((username.charAt(i) < ' ') ||
          (username.charAt(i) >  '~') ||
          !notIn(mustBeQuoted, username.charAt(i)))
          && (username.charAt(i-1) != 92) // 92 = \\ wg. IE
         )
        return false;
    }
  }
  else {
    if ( username.charAt( j-1 ) != '"' )
      return false;
    for( i=1; i<j-1; i++ ) {
      if ( ( (username.charAt(i) == '\n') || (username.charAt(i) == '\r')
            || (username.charAt(i) == '\"') )
          && (username.charAt(i-1) != 92) ) // 92 = \\ wg. IE
        return false;
    }
  }
  return true;
}

function checkNr ( nr ) {
  var i=0;
  var j=nr.length;

  if( j < 1 )
    return false;

  for( ; i<j; i++ )
    if( ( nr.charAt(i) < '0' ) || ( nr.charAt(i) > '9' ) )
      return false;

  return true;
}

function checkIpnr( ipnr ) {
  var iL=0;
  var iC=0;
  var i=0;
  var sNr = "";

  for( ; i< ipnr.length; i++ ) {
    if ( ipnr.charAt(i) == '.' ) {
      if ( !iL || (iL> 3) || parseInt( sNr,10 ) > 255 )
        return false;
      iC++;
      iL = 0;
      sNr = "";
      continue;
    }

    if ( isDigit ( ipnr.charAt(i) ) ) {
      iL++;
      sNr = sNr + ipnr.charAt(i);
      continue;
    }
    return false;
  }

  if ( parseInt( sNr,10 ) > 255 )
    return false;
  if ( ( (iC==3) && (iL>=1) && (iL<=3) ) || ( (iC==4) && (!iL) )  )
    return true;
  else
    return false;
}

function checkFqdn( fqdn ) {
  var iL=0;
  var iC=0;
  var i=fqdn.length-1;

  if ( (fqdn.charAt(0) == '.') || (fqdn.charAt(0) == '-') )
    return false;
  if ( fqdn.charAt(i) == '.' )
    i=i-1;

  for( ; i>=0; i-- ) {
    if ( fqdn.charAt(i) == '.' ) {
      if ( iL < 2 && iC < 2 )
        return false;
      if ( fqdn.charAt(i-1) == '-' )
        return false;
      iC++;
      iL = 0;
      continue;
    }

    if ( isAlnum ( fqdn.charAt(i) ) ) {
      iL++;
      continue;
    }
    if ( fqdn.charAt(i) == '-' ) {
      if ( !iL )
        return false;
      iL++;
      continue;
    }

    return false;
  }

  if ( !iC || ( iL == 1 && iC < 2 ) || ( !iL && iC==1 ) ) {
    return false;
  }

  return true;
}

function checkHostname( hostname ) {
  if ( hostname.charAt(0) == '[' ) {
    if ( hostname.charAt(hostname.length-1) != ']' )
      return false;
    var ipnr = hostname.substring( 1, hostname.length -1 );
      return checkIpnr( ipnr );
  }

  if ( hostname.charAt(0) == '#' ) {
    var nr = hostname.substring( 1, hostname.length );
    return checkNr( nr );
  }

  return checkFqdn( hostname );
}

function checkEmailAdr( address ) {
  var status = true;
  var username = "";
  var hostname = "";

  if ( address.length < 8 )
    return false;

  var seperate = address.lastIndexOf("@");
  if ( seperate == -1 )
    return false;

  username = address.substring(0, seperate );
  if ( ! checkUsername( username, "<>()[],;:@\" " ) )
    return false;

  hostname = address.substring(seperate+1, address.length );
  if ( ! checkHostname( hostname ) )
    return false;

  return true;
}

function checkEmail( email, allowFullname ) {
  var existFullname = false;
  var status = true;
  var fullname = "";
  var adress = "";
  if ( email.length < 8 )
    return false;
  var emailBegin = email.indexOf("<");
  var emailEnd = email.lastIndexOf(">");

  if ( (emailBegin == -1) && (emailEnd == -1) )
    return checkEmailAdr( email );

  if ( ( (emailBegin == -1) && (emailEnd != -1) )
      || ( (emailBegin != -1) && (emailEnd == -1) ) )
    return false;

  adress = email.substring( emailBegin+1, emailEnd );

  if ( ! checkEmailAdr( adress ) )
    return false;

  if ( email.length == adress.length + 2 )
    return true;
  else if ( ! allowFullname )
    return false;

  if ( emailEnd == email.length - 1 ) {
    if ( emailBegin == 0 )
      return true;
    if ( email.charAt( emailBegin -1 ) != ' ' )
      return false;
    fullname = email.substring( 0, emailBegin-1 );
    return checkUsername ( fullname, "<>()[],;:@\"" );
  }

  return false ;
}