/*  Title:      Pure/Thy/thy_header.scala

     Author:     Makarius

 Theory headers -- independent of outer syntax.

 */

 package isabelle

 import scala.collection.mutable

 import scala.util.parsing.input.{Reader, CharSequenceReader}

 import java.io.File

 object Thy_Header

 {

   val HEADER = "header"

   val THEORY = "theory"

   val IMPORTS = "imports"

   val USES = "uses"

   val BEGIN = "begin"

   val lexicon = Scan.Lexicon("%", "(", ")", ";", BEGIN, HEADER, IMPORTS, THEORY, USES)

   sealed case class Header(val name: String, val imports: List[String], val uses: List[String])

 }

 class Thy_Header(symbols: Symbol.Interpretation) extends Outer_Parse.Parser

 {

   import Thy_Header._

   /* header */

   val header: Parser[Header] =

   {

     val file_name = atom("file name", _.is_name)

     val theory_name = atom("theory name", _.is_name)

     val file =

       keyword("(") ~! (file_name ~ keyword(")")) ^^ { case _ ~ (x ~ _) => x } | file_name

     val uses = opt(keyword(USES) ~! (rep1(file))) ^^ { case None => Nil case Some(_ ~ xs) => xs }

     val args =

       theory_name ~ (keyword(IMPORTS) ~! (rep1(theory_name) ~ uses ~ keyword(BEGIN))) ^^

         { case x ~ (_ ~ (ys ~ zs ~ _)) => Header(x, ys, zs) }

     (keyword(HEADER) ~ tags) ~!

       ((doc_source ~ rep(keyword(";")) ~ keyword(THEORY) ~ tags) ~> args) ^^ { case _ ~ x => x } |

     (keyword(THEORY) ~ tags) ~! args ^^ { case _ ~ x => x }

   }

   /* read -- lazy scanning */

   def read(file: File): Header =

   {

     val token = lexicon.token(symbols, _ => false)

     val toks = new mutable.ListBuffer[Outer_Lex.Token]

     def scan_to_begin(in: Reader[Char])

     {

       token(in) match {

         case lexicon.Success(tok, rest) =>

           toks += tok

           if (!(tok.kind == Outer_Lex.Token_Kind.KEYWORD && tok.content == BEGIN))

             scan_to_begin(rest)

         case _ =>

       }

     }

     val reader = Scan.byte_reader(file)

     try { scan_to_begin(reader) } finally { reader.close }

     parse(commit(header), Outer_Lex.reader(toks.toList)) match {

       case Success(result, _) => result

       case bad => error(bad.toString)

     }

   }

 }