LiveCoding.scala

import scala.util.parsing.combinator.RegexParsers

sealed trait Command
case object FlushCommand extends Command
case class LookupKey(key: String) extends Command
case class SetKey(key: String, blob: String) extends Command

object Grammar extends RegexParsers {

  val id: Parser[String] = """[a-zA-Z][a-zA-Z0-9]*""".r
  val blob = """"[^"]*"""".r
  val commandDelimiter = ";"

  def flush = "flush" ^^^ FlushCommand

  def lookupKey = "lookup" ~> id ^^ LookupKey.apply

  def setKey = "set" ~> id ~ "to" ~ blob ^^ {
    case key ~ _ ~ value => SetKey(key, value)
  }

  def command = (flush | lookupKey | setKey) <~ commandDelimiter

  def session = command *
}

Grammar.parse(Grammar.flush, "flush")
Grammar.parseAll(Grammar.lookupKey, "lookup key1")
Grammar.parse(Grammar.setKey, """set foo to "1234"""")
Grammar.parse(Grammar.command, """set foo to "1234";""")
Grammar.parseAll(Grammar.session, """flush; set foo to "1234"; lookup foo;""")