/*  Title:      Pure/Isar/parse.scala

    Author:     Makarius

Generic parsers for Isabelle/Isar outer syntax.

*/

package isabelle

import scala.util.parsing.combinator.Parsers

object Parse

{

  /* parsing tokens */

  trait Parser extends Parsers

  {

    type Elem = Token

    def filter_proper = true

    private def proper(in: Input): Input =

      if (in.atEnd || !in.first.is_ignored || !filter_proper) in

      else proper(in.rest)

    def token(s: String, pred: Elem => Boolean): Parser[Elem] = new Parser[Elem]

    {

      def apply(raw_input: Input) =

      {

        val in = proper(raw_input)

        if (in.atEnd) Failure(s + " expected (past end-of-file!)", in)

        else {

          val token = in.first

          if (pred(token)) Success(token, proper(in.rest))

          else

            token.text match {

              case (txt, "") =>

                Failure(s + " expected,\nbut " + txt + " was found", in)

              case (txt1, txt2) =>

                Failure(s + " expected,\nbut " + txt1 + " was found:\n" + txt2, in)

            }

        }

      }

    }

    def not_eof: Parser[Elem] = token("input token", _ => true)

    def eof: Parser[Unit] = not(not_eof)

    def atom(s: String, pred: Elem => Boolean): Parser[String] =

      token(s, pred) ^^ (_.content)

    def keyword(name: String): Parser[String] =

      atom(Token.Kind.KEYWORD.toString + " \"" + name + "\"",

        tok => tok.kind == Token.Kind.KEYWORD && tok.content == name)

    def name: Parser[String] = atom("name declaration", _.is_name)

    def xname: Parser[String] = atom("name reference", _.is_xname)

    def text: Parser[String] = atom("text", _.is_text)

    def ML_source: Parser[String] = atom("ML source", _.is_text)

    def doc_source: Parser[String] = atom("document source", _.is_text)

    def path: Parser[String] = atom("file name/path specification", _.is_name)

    private def tag_name: Parser[String] =

      atom("tag name", tok =>

          tok.kind == Token.Kind.IDENT ||

          tok.kind == Token.Kind.STRING)

    def tags: Parser[List[String]] = rep(keyword("%") ~> tag_name)

    /* wrappers */

    def parse[T](p: Parser[T], in: Token.Reader): ParseResult[T] = p(in)

    def parse_all[T](p: Parser[T], in: Token.Reader): ParseResult[T] = parse(phrase(p), in)

  }

}