src/Pure/System/bash.scala

clarified context for (remote) bash scripts: export variables are optional, support cwd;

/*  Title:      Pure/System/bash.scala
    Author:     Makarius

Support for GNU bash: portable external processes with propagation of
interrupts.
*/

package isabelle


import java.util.{List => JList, Map => JMap, LinkedList}
import java.io.{BufferedReader, BufferedWriter, InputStreamReader, OutputStreamWriter,
  File => JFile, IOException}
import scala.annotation.tailrec
import scala.jdk.OptionConverters._


object Bash {
  /* concrete syntax */

  private def bash_chr(c: Byte): String = {
    val ch = c.toChar
    ch match {
      case '\t' => "$'\\t'"
      case '\n' => "$'\\n'"
      case '\f' => "$'\\f'"
      case '\r' => "$'\\r'"
      case _ =>
        if (Symbol.is_ascii_letter(ch) || Symbol.is_ascii_digit(ch) || "+,-./:_".contains(ch))
          Symbol.ascii(ch)
        else if (c < 0) "$'\\x" + Integer.toHexString(256 + c) + "'"
        else if (c < 16) "$'\\x0" + Integer.toHexString(c) + "'"
        else if (c < 32 || c >= 127) "$'\\x" + Integer.toHexString(c) + "'"
        else  "\\" + ch
    }
  }

  def string(s: String): String =
    if (s == "") "\"\""
    else UTF8.bytes(s).iterator.map(bash_chr).mkString

  def strings(ss: Iterable[String]): String =
    ss.iterator.map(Bash.string).mkString(" ")


  /* process and result */

  def context(script: String,
    user_home: String = "",
    isabelle_identifier: String = "",
    cwd: Path = Path.current
  ): String = {
    if_proper(user_home,
      "export USER_HOME=" + Bash.string(user_home) + "\n") +
    if_proper(isabelle_identifier,
      "export ISABELLE_IDENTIFIER=" + Bash.string(isabelle_identifier) + "\n") +
    (if (cwd == null || cwd.is_current) "" else "cd " + quote(cwd.implode) + "\n") +
    script
  }

  private def make_description(description: String): String =
    proper_string(description) getOrElse "bash_process"

  def local_bash_process(): String =
    File.platform_path(Path.variable("ISABELLE_BASH_PROCESS"))

  def local_bash(): String =
    if (Platform.is_unix) "bash"
    else isabelle.setup.Environment.cygwin_root() + "\\bin\\bash.exe"

  def remote_bash_process(ssh: SSH.Session): String = {
    val component = Components.provide(Component_Bash_Process.home, ssh = ssh)
    val exe = Component_Bash_Process.remote_program(component)
    ssh.make_command(args_host = true, args = ssh.bash_path(exe))
  }

  type Watchdog = (Time, Process => Boolean)

  def process(script: String,
      description: String = "",
      ssh: SSH.System = SSH.Local,
      cwd: Path = Path.current,
      env: JMap[String, String] = Isabelle_System.settings(),
      redirect: Boolean = false,
      cleanup: () => Unit = () => ()): Process =
    new Process(script, description, ssh, cwd, env, redirect, cleanup)

  class Process private[Bash](
    script: String,
    description: String,
    ssh: SSH.System,
    cwd: Path,
    env: JMap[String, String],
    redirect: Boolean,
    cleanup: () => Unit
  ) {
    override def toString: String = make_description(description)

    private val proc_command: JList[String] = new LinkedList[String]

    private val winpid_file: Option[JFile] =
      if (ssh.is_local && Platform.is_windows) Some(Isabelle_System.tmp_file("bash_winpid"))
      else None
    private val winpid_script =
      winpid_file match {
        case None => ""
        case Some(file) =>
          "read < /proc/self/winpid > /dev/null 2> /dev/null\n" +
            """echo -n "$REPLY" > """ + File.bash_path(file) + "\n\n"
      }

    private val List(timing_file, script_file) =
      ssh.tmp_files(List("bash_timing", "bash_script"))

    private val timing = Synchronized[Option[Timing]](None)
    def get_timing: Timing = timing.value getOrElse Timing.zero

    ssh.write(script_file, winpid_script + script)

    private val ssh_file: Option[JFile] =
      ssh.ssh_session match {
        case None =>
          proc_command.add(local_bash_process())
          proc_command.add(File.platform_path(timing_file))
          proc_command.add("bash")
          proc_command.add(File.platform_path(script_file))
          None
        case Some(ssh_session) =>
          val ssh_script =
            "exec " + remote_bash_process(ssh_session) + " " +
              ssh.bash_path(timing_file) + " bash " +
              ssh.bash_path(script_file)
          val file = Isabelle_System.tmp_file("bash_ssh")
          File.write(file, ssh_script)
          proc_command.add(local_bash())
          proc_command.add(file.getPath)
          Some(file)
      }

    private val proc =
      isabelle.setup.Environment.process_builder(
        proc_command,
        if (cwd == null || cwd.is_current) null else cwd.file,
        env,
        redirect
      ).start()


    // channels

    val stdin: BufferedWriter =
      new BufferedWriter(new OutputStreamWriter(proc.getOutputStream, UTF8.charset))

    val stdout: BufferedReader =
      new BufferedReader(new InputStreamReader(proc.getInputStream, UTF8.charset))

    val stderr: BufferedReader =
      new BufferedReader(new InputStreamReader(proc.getErrorStream, UTF8.charset))


    // signals

    private val group_pid = stdout.readLine

    private def local_process_alive(pid: String): Boolean =
      ssh.is_local &&
        (for {
          p <- Value.Long.unapply(pid)
          handle <- ProcessHandle.of(p).toScala
        } yield handle.isAlive).getOrElse(false)

    private def root_process_alive(): Boolean =
      winpid_file match {
        case None => local_process_alive(group_pid)
        case Some(file) =>
          file.exists() && local_process_alive(Library.trim_line(File.read(file)))
      }

    @tailrec private def signal(s: String, count: Int = 1): Boolean = {
      count <= 0 || {
        ssh.kill_process(group_pid, s)
        val running = root_process_alive() || ssh.kill_process(group_pid, "0")
        if (running) {
          Time.seconds(if (ssh.is_local) 0.1 else 0.25).sleep()
          signal(s, count - 1)
        }
        else false
      }
    }

    def terminate(): Unit = Isabelle_Thread.try_uninterruptible {
      signal("INT", count = 7) && signal("TERM", count = 3) && signal("KILL")
      proc.destroy()
      do_cleanup()
    }

    def interrupt(): Unit = Isabelle_Thread.try_uninterruptible {
      ssh.kill_process(group_pid, "INT")
    }


    // cleanup

    private val shutdown_hook =
      Isabelle_System.create_shutdown_hook { terminate() }

    private def do_cleanup(): Unit = {
      Isabelle_System.remove_shutdown_hook(shutdown_hook)

      winpid_file.foreach(_.delete())
      ssh_file.foreach(_.delete())

      timing.change {
        case None =>
          val timing_text =
            try { ssh.read(timing_file) }
            catch { case ERROR(_) => "" }
          val t =
            Word.explode(timing_text) match {
              case List(Value.Long(elapsed), Value.Long(cpu)) =>
                Timing(Time.ms(elapsed), Time.ms(cpu), Time.zero)
              case _ => Timing.zero
            }
          Some(t)
        case some => some
      }

      ssh.delete(timing_file, script_file)

      cleanup()
    }


    // join

    def join(): Int = {
      val rc = proc.waitFor()
      do_cleanup()
      rc
    }


    // result

    def result(
      input: String = "",
      progress_stdout: String => Unit = (_: String) => (),
      progress_stderr: String => Unit = (_: String) => (),
      watchdog: Option[Watchdog] = None,
      strict: Boolean = true
    ): Process_Result = {
      val in =
        if (input.isEmpty) Future.value(stdin.close())
        else Future.thread("bash_stdin") { stdin.write(input); stdin.flush(); stdin.close(); }
      val out_lines =
        Future.thread("bash_stdout") { File.read_lines(stdout, progress_stdout) }
      val err_lines =
        Future.thread("bash_stderr") { File.read_lines(stderr, progress_stderr) }

      val watchdog_thread =
        for ((time, check) <- watchdog)
        yield {
          Future.thread("bash_watchdog") {
            while (proc.isAlive) {
              time.sleep()
              if (check(this)) interrupt()
            }
          }
        }

      val rc =
        try { join() }
        catch { case Exn.Interrupt() => terminate(); Process_Result.RC.interrupt }

      watchdog_thread.foreach(_.cancel())

      in.join
      out_lines.join
      err_lines.join

      if (strict && rc == Process_Result.RC.interrupt) throw Exn.Interrupt()

      Process_Result(rc, out_lines.join, err_lines.join, get_timing)
    }
  }


  /* server */

  object Server {
    // input messages
    private val RUN = "run"
    private val KILL = "kill"

    // output messages
    private val UUID = "uuid"
    private val INTERRUPT = "interrupt"
    private val FAILURE = "failure"
    private val RESULT = "result"

    def start(port: Int = 0, debugging: => Boolean = false): Server = {
      val server = new Server(port, debugging)
      server.start()
      server
    }
  }

  class Server private(port: Int, debugging: => Boolean)
  extends isabelle.Server.Handler(port) {
    server =>

    private val _processes = Synchronized(Map.empty[UUID.T, Bash.Process])

    override def stop(): Unit = {
      for ((_, process) <- _processes.value) process.terminate()
      super.stop()
    }

    override def handle(connection: isabelle.Server.Connection): Unit = {
      def reply(chunks: List[String]): Unit =
        try { connection.write_byte_message(chunks.map(Bytes.apply)) }
        catch { case _: IOException => }

      def reply_failure(exn: Throwable): Unit =
        reply(
          if (Exn.is_interrupt(exn)) List(Server.INTERRUPT)
          else List(Server.FAILURE, Exn.message(exn)))

      def reply_result(result: Process_Result): Unit =
        reply(
          Server.RESULT ::
          result.rc.toString ::
          result.timing.elapsed.ms.toString ::
          result.timing.cpu.ms.toString ::
          result.out_lines.length.toString ::
          result.out_lines :::
          result.err_lines)

      connection.read_byte_message().map(_.map(_.text)) match {
        case None =>

        case Some(List(Server.KILL, UUID(uuid))) =>
          if (debugging) Output.writeln("kill " + uuid)
          _processes.value.get(uuid).foreach(_.terminate())

        case Some(List(Server.RUN, script, input, cwd, putenv,
            Value.Boolean(redirect), Value.Seconds(timeout), description)) =>
          val uuid = UUID.random()

          val descr = make_description(description)
          if (debugging) {
            Output.writeln(
              "start " + quote(descr) + " (uuid=" + uuid + ", timeout=" + timeout.seconds + ")")
          }

          Exn.capture {
            Bash.process(script,
              description = description,
              cwd =
                XML.Decode.option(XML.Decode.string)(YXML.parse_body(cwd)) match {
                  case None => Path.current
                  case Some(s) => Path.explode(s)
                },
              env =
                Isabelle_System.settings(
                  XML.Decode.list(XML.Decode.pair(XML.Decode.string, XML.Decode.string))(
                    YXML.parse_body(putenv))),
              redirect= redirect)
          }
          match {
            case Exn.Exn(exn) => reply_failure(exn)
            case Exn.Res(process) =>
              _processes.change(processes => processes + (uuid -> process))
              reply(List(Server.UUID, uuid.toString))

              Isabelle_Thread.fork(name = "bash_process") {
                @volatile var is_timeout = false
                val watchdog: Option[Watchdog] =
                  if (timeout.is_zero) None else Some((timeout, _ => { is_timeout = true; true }))

                Exn.capture { process.result(input = input, watchdog = watchdog, strict = false) }
                match {
                  case Exn.Exn(exn) => reply_failure(exn)
                  case Exn.Res(res0) =>
                    val res = if (!res0.ok && is_timeout) res0.timeout_rc else res0
                    if (debugging) {
                      Output.writeln(
                        "stop " + quote(descr) + " (uuid=" + uuid + ", return_code=" + res.rc + ")")
                    }
                    reply_result(res)
                }

                _processes.change(provers => provers - uuid)
              }

              connection.await_close()
          }

        case Some(_) => reply_failure(ERROR("Bad protocol message"))
      }
    }
  }

  class Handler extends Session.Protocol_Handler {
    private var server: Server = null

    override def init(session: Session): Unit = {
      exit()
      server = Server.start(debugging = session.session_options.bool("bash_process_debugging"))
    }

    override def exit(): Unit = {
      if (server != null) {
        server.stop()
        server = null
      }
    }

    override def prover_options(options: Options): Options = {
      val address = if (server == null) "" else server.address
      val password = if (server == null) "" else server.password
      options +
        ("bash_process_address=" + address) +
        ("bash_process_password=" + password)
    }
  }
}