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/*  Title:      Pure/Tools/server.scala
    Author:     Makarius

Resident Isabelle servers.
*/

package isabelle


import java.io.{BufferedReader, BufferedWriter, InputStreamReader, OutputStreamWriter,
  IOException}
import java.net.{Socket, ServerSocket, InetAddress}


object Server
{
  /* per-user servers */

  object Data
  {
    val database = Path.explode("$ISABELLE_HOME_USER/servers.db")

    val name = SQL.Column.string("name", primary_key = true)
    val port = SQL.Column.int("port")
    val password = SQL.Column.string("password")
    val table = SQL.Table("isabelle_servers", List(name, port, password))

    sealed case class Entry(name: String, port: Int, password: String)
    {
      def print: String =
        "server " + quote(name) + " = 127.0.0.1:" + port + " (password " + quote(password) + ")"

      def active: Boolean =
        try { (new Socket(InetAddress.getByName("127.0.0.1"), port)).close; true }
        catch { case _: IOException => false }
    }
  }

  def list(db: SQLite.Database): List[Data.Entry] =
    if (db.tables.contains(Data.table.name)) {
      db.using_statement(Data.table.select())(stmt =>
        stmt.execute_query().iterator(res =>
          Data.Entry(
            res.string(Data.name),
            res.int(Data.port),
            res.string(Data.password))).toList.sortBy(_.name))
    }
    else Nil

  def find(db: SQLite.Database, name: String): Option[Data.Entry] =
    list(db).find(entry => entry.name == name && entry.active)

  def start(name: String = "", port: Int = 0): (Data.Entry, Option[Thread]) =
  {
    using(SQLite.open_database(Data.database))(db =>
      db.transaction {
        find(db, name) match {
          case Some(entry) => (entry, None)
          case None =>
            val server = new Server(port)
            val entry = Data.Entry(name, server.port, server.password)

            Isabelle_System.bash("chmod 600 " + File.bash_path(Data.database)).check
            db.create_table(Data.table)
            db.using_statement(Data.table.delete(Data.name.where_equal(name)))(_.execute)
            db.using_statement(Data.table.insert())(stmt =>
            {
              stmt.string(1) = entry.name
              stmt.int(2) = entry.port
              stmt.string(3) = entry.password
              stmt.execute()
            })

            (entry, Some(server.thread))
        }
      })
  }

  def stop(name: String = ""): Boolean =
  {
    using(SQLite.open_database(Data.database))(db =>
      db.transaction {
        find(db, name) match {
          case Some(entry) =>
            // FIXME shutdown server
            db.using_statement(Data.table.delete(Data.name.where_equal(name)))(_.execute)
            true
          case None =>
            false
        }
      })
  }


  /* Isabelle tool wrapper */

  val isabelle_tool =
    Isabelle_Tool("server", "manage resident Isabelle servers", args =>
    {
      var operation_list = false
      var name = ""
      var port = 0

      val getopts =
        Getopts("""
Usage: isabelle server [OPTIONS]

  Options are:
    -L           list servers
    -n NAME      explicit server name
    -p PORT      explicit server port

  Manage resident Isabelle servers.
""",
          "L" -> (_ => operation_list = true),
          "n:" -> (arg => name = arg),
          "p:" -> (arg => port = Value.Int.parse(arg)))

      val more_args = getopts(args)
      if (more_args.nonEmpty) getopts.usage()

      if (operation_list) {
        for (entry <- using(SQLite.open_database(Data.database))(list(_)) if entry.active)
          Console.println(entry.print)
      }
      else {
        val (entry, thread) = start(name, port)
        Console.println(entry.print)
        thread.foreach(_.join)
      }
    })
}

class Server private(_port: Int)
{
  private val server_socket = new ServerSocket(_port, 50, InetAddress.getByName("127.0.0.1"))
  def port: Int = server_socket.getLocalPort
  def close { server_socket.close }

  val password: String = Library.UUID()

  private def handle_connection(socket: Socket)
  {
    val reader = new BufferedReader(new InputStreamReader(socket.getInputStream, UTF8.charset))
    val writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream, UTF8.charset))

    def println(s: String)
    {
      writer.write(s)
      writer.newLine()
      writer.flush()
    }

    reader.readLine() match {
      case null =>
      case bad if bad != password => println("BAD PASSWORD")
      case _ =>
        var finished = false
        while (!finished) {
          reader.readLine() match {
            case null => println("FINISHED"); finished = true
            case line => println("ECHO " + line)
          }
        }
    }
  }

  lazy val thread: Thread =
    Standard_Thread.fork("server") {
      var finished = false
      while (!finished) {
        Exn.capture(server_socket.accept) match {
          case Exn.Res(socket) =>
            Standard_Thread.fork("server_connection")
              { try { handle_connection(socket) } finally { socket.close } }
          case Exn.Exn(_) => finished = true
        }
      }
    }
}