poor irc packet parser in scala

parser.scala

import scala.util.parsing.combinator._

class IrcParser extends RegexParsers {

/*

  RFC1459 2.3.1 Message format in 'pseudo' BNF

  <message>  ::= [':' <prefix> <SPACE> ] <command> <params> <crlf>
  <prefix>   ::= <servername> | <nick> [ '!' <user> ] [ '@' <host> ]
  <command>  ::= <letter> { <letter> } | <number> <number> <number>
  <SPACE>    ::= ' ' { ' ' }
  <params>   ::= <SPACE> [ ':' <trailing> | <middle> <params> ]

  <middle>   ::= <Any *non-empty* sequence of octets not including SPACE
  or NUL or CR or LF, the first of which may not be ':'>
  <trailing> ::= <Any, possibly *empty*, sequence of octets not including
  NUL or CR or LF>

  <crlf>     ::= CR LF

*/

  abstract class Packet
  case class Command(name: String) extends Packet
  case class Param(value: String) extends Packet
  case class ServerName(name: String) extends Packet
  case class Nickname(name: String) extends Packet
  case class UserMask(mask: String) extends Packet
  case class Message(prefix: String, command: Command, params: Param) extends Packet

  override def skipWhitespace = false;

  def uniletter:Parser[String] = regex("""\p{L}""".r);

  def number:Parser[Any] = regex("[0-9]".r);
  def crlf : Parser[Any] = regex("""\r\n""".r);
  def special:Parser[Any] = regex("""[-\[\]\\`^\{\}]""".r);
  def space:Parser[String] = regex("""[ ]{1,}""".r);

  def trailing:Parser[String] = regex("""[^\r\n]+""".r);
  def middle:Parser[String] = regex("""[^:][^\s\r\n]+""".r);

  def servername:Parser[ServerName] = regex("""[a-zA-Z0-9.\-]+""".r) ^^ (ServerName(_));
  def nick:Parser[Nickname] = regex("""(\p{L}|[0-9]|[-\[\]\\`^\{\}])+""".r) ^^ (Nickname(_));
  def user:Parser[UserMask] = regex("""\S+""".r) ^^ (UserMask(_));

  def prefix:Parser[Any] = (servername | nick ) ~ opt( '!' ~ user ) ~ opt( '@' ~ servername );

  def message:Parser[Message] = opt(':' ~ prefix ~ space) ~ command ~ params ~ crlf ^^ {
    case pfx ~ cmd ~ ps ~ crlf => pfx match {
      case Some(pfx) => new Message(pfx.toString, cmd, ps)
      case _ => new Message(null, cmd, ps)
    }
  }

  def command:Parser[Command] = regex("""[a-zA-Z]+""".r) ^^ (Command(_)) | regex("""[0-9]{3}""".r) ^^ (Command(_));

  def params:Parser[Param] = space ~ opt( ':' ~ trailing | middle ~ params ) ^^ {
    case x ~ p  => p match {
      case Some(z) => z match {
        case ':' ~ z1 => new Param(z1.toString)
        case z1 ~ z2 =>
          new Param( (if ( z1 != null ) z1.toString else null )  + (if ( z2 != null ) z2.toString else null ))
        case _ => null
      }
      case None => null
    }
  }


}