/*  Title:      Pure/System/isabelle_manager.scala

    Author:     Makarius

Isabelle session manager.

*/

package isabelle

import java.io.{File, FileFilter}

class Session_Manager

{

  val ROOT_NAME = "session.root"

  def is_session_file(file: File): Boolean =

    file.isFile && file.getName == ROOT_NAME

  def is_session_dir(dir: File): Boolean =

    dir.isDirectory && (new File(dir, ROOT_NAME)).isFile

  // FIXME handle (potentially cyclic) directory graph

  private def find_sessions(reverse_prefix: List[String], reverse_sessions: List[List[String]],

    dir: File): List[List[String]] =

  {

    val (reverse_prefix1, reverse_sessions1) =

      if (is_session_dir(dir)) {

        val name = dir.getName  // FIXME from root file

        val reverse_prefix1 = name :: reverse_prefix

        val reverse_sessions1 = reverse_prefix1.reverse :: reverse_sessions

        (reverse_prefix1, reverse_sessions1)

      }

      else (reverse_prefix, reverse_sessions)

    val subdirs =

      dir.listFiles(new FileFilter { def accept(entry: File) = entry.isDirectory })

    (reverse_sessions1 /: subdirs)(find_sessions(reverse_prefix1, _, _))

  }

  def component_sessions(): List[List[String]] =

  {

    val toplevel_sessions =

      Isabelle_System.components().map(s =>

        Isabelle_System.platform_file(Path.explode(s))).filter(is_session_dir)

    ((Nil: List[List[String]]) /: toplevel_sessions)(find_sessions(Nil, _, _)).reverse

  }

}