/*  Title:      Pure/Thy/thy_header.scala

    Author:     Makarius

Theory headers -- independent of outer syntax.

*/

package isabelle

import scala.annotation.tailrec

import scala.collection.mutable

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

import scala.util.matching.Regex

import java.io.File

object Thy_Header extends Parse.Parser

{

  val HEADER = "header"

  val THEORY = "theory"

  val IMPORTS = "imports"

  val USES = "uses"

  val BEGIN = "begin"

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

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

  {

    def decode_permissive_utf8: Header =

      Header(Standard_System.decode_permissive_utf8(name),

        imports.map(Standard_System.decode_permissive_utf8),

        uses.map(Standard_System.decode_permissive_utf8))

  }

  /* file name */

  def thy_path(name: String): Path = Path.basic(name).ext("thy")

  private val Thy_Path1 = new Regex("([^/]*)\\.thy")

  private val Thy_Path2 = new Regex("(.*)/([^/]*)\\.thy")

  def split_thy_path(path: String): Option[(String, String)] =

    path match {

      case Thy_Path1(name) => Some(("", name))

      case Thy_Path2(dir, name) => Some((dir, name))

      case _ => None

    }

  /* 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(reader: Reader[Char]): Header =

  {

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

    val toks = new mutable.ListBuffer[Token]

    @tailrec def scan_to_begin(in: Reader[Char])

    {

      token(in) match {

        case lexicon.Success(tok, rest) =>

          toks += tok

          if (!tok.is_begin) scan_to_begin(rest)

        case _ =>

      }

    }

    scan_to_begin(reader)

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

      case Success(result, _) => result

      case bad => error(bad.toString)

    }

  }

  def read(source: CharSequence): Header =

    read(new CharSequenceReader(source))

  def read(file: File): Header =

  {

    val reader = Scan.byte_reader(file)

    try { read(reader).decode_permissive_utf8 }

    finally { reader.close }

  }

  /* check */

  def check(name: String, source: CharSequence): Header =

  {

    val header = read(source)

    val name1 = header.name

    if (name != name1) error("Bad file name " + thy_path(name) + " for theory " + quote(name1))

    Path.explode(name)

    header

  }

}