(*  Title:      Pure/System/isabelle_process.ML

    Author:     Makarius

Isabelle process wrapper, based on private fifos for maximum

robustness and performance.

Startup phases:

  . raw Posix process startup with uncontrolled output on stdout/stderr

  . stdout \002: ML running

  .. stdin/stdout/stderr freely available (raw ML loop)

  .. protocol thread initialization

  ... switch to in_fifo/out_fifo channels (rendezvous via open)

  ... out_fifo INIT(pid): channels ready

  ... out_fifo STATUS(keywords)

  ... out_fifo READY: main loop ready

*)

signature ISABELLE_PROCESS =

sig

  val is_active: unit -> bool

  val add_command: string -> (string list -> unit) -> unit

  val command: string -> string list -> unit

  val crashes: exn list Synchronized.var

  val init: string -> string -> unit

end;

structure Isabelle_Process: ISABELLE_PROCESS =

struct

(* print mode *)

val isabelle_processN = "isabelle_process";

fun is_active () = Print_Mode.print_mode_active isabelle_processN;

val _ = Output.add_mode isabelle_processN Output.default_output Output.default_escape;

val _ = Markup.add_mode isabelle_processN YXML.output_markup;

(* commands *)

local

val commands =

  Synchronized.var "Isabelle_Process.commands" (Symtab.empty: (string list -> unit) Symtab.table);

in

fun add_command name cmd =

  Synchronized.change commands (fn cmds =>

   (if not (Symtab.defined cmds name) then ()

    else warning ("Redefining Isabelle process command " ^ quote name);

    Symtab.update (name, cmd) cmds));

fun command name args =

  (case Symtab.lookup (Synchronized.value commands) name of

    NONE => error ("Undefined Isabelle process command " ^ quote name)

  | SOME cmd => cmd args);

end;

(* message channels *)

local

fun chunk s = [string_of_int (size s), "\n", s];

fun message _ _ _ "" = ()

  | message mbox ch raw_props body =

      let

        val robust_props = map (pairself YXML.escape_controls) raw_props;

        val header = YXML.string_of (XML.Elem ((ch, robust_props), []));

      in Mailbox.send mbox (chunk header @ chunk body) end;

fun standard_message mbox with_serial ch body =

  message mbox ch

    ((if with_serial then cons (Markup.serialN, serial_string ()) else I)

      (Position.properties_of (Position.thread_data ()))) body;

fun message_output mbox out_stream =

  let

    fun loop receive =

      (case receive mbox of

        SOME msg =>

         (List.app (fn s => TextIO.output (out_stream, s)) msg;

          loop (Mailbox.receive_timeout (seconds 0.02)))

      | NONE => (try TextIO.flushOut out_stream; loop (SOME o Mailbox.receive)));

  in fn () => loop (SOME o Mailbox.receive) end;

in

fun setup_channels in_fifo out_fifo =

  let

    (*rendezvous*)

    val in_stream = TextIO.openIn in_fifo;

    val out_stream = TextIO.openOut out_fifo;

    val _ = TextIO.StreamIO.setBufferMode (TextIO.getOutstream TextIO.stdOut, IO.LINE_BUF);

    val _ = TextIO.StreamIO.setBufferMode (TextIO.getOutstream TextIO.stdErr, IO.LINE_BUF);

    val mbox = Mailbox.create () : string list Mailbox.T;

    val _ = Simple_Thread.fork false (message_output mbox out_stream);

  in

    Output.Private_Hooks.status_fn := standard_message mbox false "B";

    Output.Private_Hooks.report_fn := standard_message mbox false "C";

    Output.Private_Hooks.writeln_fn := standard_message mbox true "D";

    Output.Private_Hooks.tracing_fn := standard_message mbox true "E";

    Output.Private_Hooks.warning_fn := standard_message mbox true "F";

    Output.Private_Hooks.error_fn := standard_message mbox true "G";

    Output.Private_Hooks.urgent_message_fn := ! Output.Private_Hooks.writeln_fn;

    Output.Private_Hooks.prompt_fn := ignore;

    message mbox "A" [] (Session.welcome ());

    in_stream

  end;

end;

(* protocol loop -- uninterruptible *)

val crashes = Synchronized.var "Isabelle_Process.crashes" ([]: exn list);

local

fun recover crash =

  (Synchronized.change crashes (cons crash);

    warning "Recovering from Isabelle process crash -- see also Isabelle_Process.crashes");

fun read_chunk stream len =

  let

    val n =

      (case Int.fromString len of

        SOME n => n

      | NONE => error ("Isabelle process: malformed chunk header " ^ quote len));

    val chunk = TextIO.inputN (stream, n);

    val m = size chunk;

  in

    if m = n then chunk

    else error ("Isabelle process: bad chunk (" ^ string_of_int m ^ " vs. " ^ string_of_int n ^ ")")

  end;

fun read_command stream =

  (case TextIO.inputLine stream of

    NONE => raise Runtime.TERMINATE

  | SOME line => map (read_chunk stream) (space_explode "," line));

fun run_command name args =

  Runtime.debugging (command name) args

    handle exn =>

      error ("Isabelle process command failure: " ^ name ^ "\n" ^ ML_Compiler.exn_message exn);

in

fun loop stream =

  let val continue =

    (case read_command stream of

      [] => (Output.error_msg "Isabelle process: no input"; true)

    | name :: args => (run_command name args; true))

    handle Runtime.TERMINATE => false

      | exn => (Output.error_msg (ML_Compiler.exn_message exn) handle crash => recover crash; true);

  in if continue then loop stream else () end;

end;

(* init *)

fun init in_fifo out_fifo = ignore (Simple_Thread.fork false (fn () =>

  let

    val _ = OS.Process.sleep (seconds 0.5);  (*yield to raw ML toplevel*)

    val _ = Output.raw_stdout Symbol.STX;

    val _ = quick_and_dirty := true;

    val _ = Goal.parallel_proofs := 0;

    val _ = Context.set_thread_data NONE;

    val _ =

      Unsynchronized.change print_mode

        (fold (update op =)

          [Symbol.xsymbolsN, isabelle_processN, Keyword.keyword_statusN, Pretty.symbolicN]);

    val in_stream = setup_channels in_fifo out_fifo;

    val _ = Keyword.status ();

    val _ = Thy_Info.status ();

    val _ = Output.status (Markup.markup Markup.ready "process ready");

  in loop in_stream end));

end;