src/Pure/Tools/server.scala

clarified argument formats: explicit Unit, allow XML.Elem as well;
tuned messages: prefer single quotes for JSON output;

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

Resident Isabelle servers.

Message formats:
  - short message (single line):
      NAME ARGUMENT
  - long message (multiple lines):
      BYTE_LENGTH
      NAME ARGUMENT

Argument formats:
  - Unit as empty string
  - XML.Elem in YXML notation
  - JSON.T in standard notation
*/

package isabelle


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


object Server
{
  /* message argument */

  object Argument
  {
    def split(msg: String): (String, String) =
    {
      val name = msg.takeWhile(c => Symbol.is_ascii_letter(c) || Symbol.is_ascii_letdig(c))
      val argument = msg.substring(name.length).dropWhile(Symbol.is_ascii_blank(_))
      (name, argument)
    }

    def print(arg: Any): String =
      arg match {
        case () => ""
        case t: XML.Elem => YXML.string_of_tree(t)
        case t: JSON.T => JSON.Format(t)
      }

    def parse(argument: String): Any =
      if (argument == "") ()
      else if (YXML.detect_elem(argument)) YXML.parse_elem(argument)
      else JSON.parse(argument, strict = false)

    def unapply(argument: String): Option[Any] =
      try { Some(parse(argument)) }
      catch { case ERROR(_) => None }
  }


  /* input command */

  object Command
  {
    type T = PartialFunction[(Server, Any), Any]

    private val table: Map[String, T] =
      Map(
        "echo" -> { case (_, t) => t },
        "help" -> { case (_, ()) => table.keySet.toList.sorted },
        "shutdown" -> { case (server, ()) => server.close(); () })

    def unapply(name: String): Option[T] = table.get(name)
  }


  /* output reply */

  object Reply extends Enumeration
  {
    val OK, ERROR, NOTE = Value

    def unapply(msg: String): Option[(Reply.Value, Any)] =
    {
      if (msg == "") None
      else {
        val (name, argument) = Argument.split(msg)
        for {
          reply <-
            try { Some(withName(name)) }
            catch { case _: NoSuchElementException => None }
          arg <- Argument.unapply(argument)
        } yield (reply, arg)
      }
    }
  }


  /* socket connection */

  object Connection
  {
    def apply(socket: Socket): Connection =
      new Connection(socket)
  }

  class Connection private(val socket: Socket)
  {
    override def toString: String = socket.toString

    def close() { socket.close }

    val in = new BufferedInputStream(socket.getInputStream)
    val out = new BufferedOutputStream(socket.getOutputStream)

    def read_message(): Option[String] =
      try {
        Bytes.read_line(in).map(_.text) match {
          case Some(Value.Int(n)) =>
            Bytes.read_block(in, n).map(bytes => Library.trim_line(bytes.text))
          case res => res
        }
      }
      catch { case _: SocketException => None }

    def write_message(msg: String)
    {
      val b = UTF8.bytes(msg)
      if (b.length > 100 || b.contains(10)) {
        out.write(UTF8.bytes((b.length + 1).toString))
        out.write(10)
      }
      out.write(b)
      out.write(10)
      try { out.flush() } catch { case _: SocketException => }
    }

    def reply(r: Server.Reply.Value, arg: Any)
    {
      val argument = Argument.print(arg)
      write_message(if (argument == "") r.toString else r.toString + " " + argument)
    }

    def reply_ok(arg: Any) { reply(Server.Reply.OK, arg) }
    def reply_error(arg: Any) { reply(Server.Reply.ERROR, arg) }
    def reply_error_message(message: String, more: (String, JSON.T)*): Unit =
      reply_error(Map("message" -> message) ++ more)

    def notify(arg: Any) { reply(Server.Reply.NOTE, arg) }
    def notify_message(message: String, more: (String, JSON.T)*): Unit =
      notify(Map("message" -> message) ++ more)
  }


  /* server info */

  sealed case class Info(name: String, port: Int, password: String)
  {
    override def toString: String =
      "server " + print_name_space(name) + "= " + print(port, password)

    def connection(): Connection =
    {
      val connection = Connection(new Socket(InetAddress.getByName("127.0.0.1"), port))
      connection.write_message(password)
      connection
    }

    def active(): Boolean =
      try {
        using(connection())(connection =>
          {
            connection.socket.setSoTimeout(2000)
            connection.read_message() == Some(Reply.OK.toString)
          })
      }
      catch {
        case _: IOException => false
        case _: SocketException => false
        case _: SocketTimeoutException => false
      }

    def console()
    {
      using(connection())(connection =>
        {
          val tty_loop =
            new TTY_Loop(
              new BufferedWriter(new OutputStreamWriter(connection.socket.getOutputStream)),
              new BufferedReader(new InputStreamReader(connection.socket.getInputStream)))
          tty_loop.join
        })
    }
  }


  /* per-user servers */

  def print_name_space(name: String): String =
    if (name == "") "" else quote(name) + " "

  def print(port: Int, password: String): String =
    "127.0.0.1:" + port + " (password " + quote(password) + ")"

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

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

  def list(db: SQLite.Database): List[Info] =
    if (db.tables.contains(Data.table.name)) {
      db.using_statement(Data.table.select())(stmt =>
        stmt.execute_query().iterator(res =>
          Info(
            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[Info] =
    list(db).find(server_info => server_info.name == name && server_info.active)

  def init(name: String = "", port: Int = 0, existing_server: Boolean = false)
    : (Info, Option[Server]) =
  {
    using(SQLite.open_database(Data.database))(db =>
      {
        db.transaction {
          Isabelle_System.bash("chmod 600 " + File.bash_path(Data.database)).check
          db.create_table(Data.table)
          list(db).filterNot(_.active).foreach(server_info =>
            db.using_statement(Data.table.delete(Data.name.where_equal(server_info.name)))(
              _.execute))
        }
        db.transaction {
          find(db, name) match {
            case Some(server_info) => (server_info, None)
            case None =>
              if (existing_server) {
                  error("Isabelle server " + print_name_space(name) + "not running")
              }

              val server = new Server(port)
              val server_info = Info(name, server.port, server.password)

              db.using_statement(Data.table.delete(Data.name.where_equal(name)))(_.execute)
              db.using_statement(Data.table.insert())(stmt =>
              {
                stmt.string(1) = server_info.name
                stmt.int(2) = server_info.port
                stmt.string(3) = server_info.password
                stmt.execute()
              })

              server.start
              (server_info, Some(server))
          }
        }
      })
  }

  def exit(name: String = ""): Boolean =
  {
    using(SQLite.open_database(Data.database))(db =>
      db.transaction {
        find(db, name) match {
          case Some(server_info) =>
            using(server_info.connection())(_.write_message("shutdown"))
            while(server_info.active) { Thread.sleep(50) }
            true
          case None => false
        }
      })
  }


  /* Isabelle tool wrapper */

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

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

  Options are:
    -C           console interaction with specified server
    -L           list servers only
    -n NAME      explicit server name
    -p PORT      explicit server port
    -s           assume existing server, no implicit startup

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

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

      if (operation_list) {
        for {
          server_info <- using(SQLite.open_database(Data.database))(list(_))
          if server_info.active
        } Output.writeln(server_info.toString, stdout = true)
      }
      else {
        val (server_info, server) = init(name, port = port, existing_server = existing_server)
        Output.writeln(server_info.toString, stdout = true)
        if (console) server_info.console()
        server.foreach(_.join)
      }
    })
}

class Server private(_port: Int)
{
  server =>

  private val server_socket = new ServerSocket(_port, 50, InetAddress.getByName("127.0.0.1"))

  def close() { server_socket.close }

  def port: Int = server_socket.getLocalPort
  val password: String = Library.UUID()

  override def toString: String = Server.print(port, password)

  private def handle(connection: Server.Connection)
  {
    connection.read_message() match {
      case Some(msg) if msg == password =>
        connection.reply_ok(())
        var finished = false
        while (!finished) {
          connection.read_message() match {
            case None => finished = true
            case Some("") =>
              connection.notify_message("Command 'help' provides list of commands")
            case Some(msg) =>
              val (name, argument) = Server.Argument.split(msg)
              name match {
                case Server.Command(cmd) =>
                  argument match {
                    case Server.Argument(arg) =>
                      if (cmd.isDefinedAt((server, arg))) {
                        Exn.capture { cmd((server, arg)) } match {
                          case Exn.Res(res) => connection.reply_ok(res)
                          case Exn.Exn(ERROR(msg)) => connection.reply_error(msg)
                          case Exn.Exn(exn) => throw exn
                        }
                      }
                      else {
                        connection.reply_error_message(
                          "Bad argument for command " + Library.single_quote(name),
                          "argument" -> argument)
                      }
                    case _ =>
                      connection.reply_error_message(
                        "Malformed argument for command " + Library.single_quote(name),
                        "argument" -> argument)
                  }
                case _ => connection.reply_error("Bad command " + Library.single_quote(name))
              }
          }
        }
      case _ =>
    }
  }

  private lazy val server_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")
              { using(Server.Connection(socket))(handle(_)) }
          case Exn.Exn(_) => finished = true
        }
      }
    }

  def start { server_thread }

  def join { server_thread.join; close() }
}