(*  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 isabelle_processN: string

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

  val command: string -> string list -> unit

  val crashes: exn list Unsynchronized.ref

  val init: string -> string -> unit

end;

structure Isabelle_Process: ISABELLE_PROCESS =

struct

(* print modes *)

val isabelle_processN = "isabelle_process";

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

val _ = Markup.add_mode isabelle_processN YXML.output_markup;

(* commands *)

local

val global_commands = Unsynchronized.ref (Symtab.empty: (string list -> unit) Symtab.table);

in

fun add_command name cmd = CRITICAL (fn () =>

  Unsynchronized.change global_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 (! global_commands) name of

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

  | SOME cmd => cmd args);

end;

(* message markup *)

local

fun chunk s = string_of_int (size s) ^ "\n" ^ s;

fun message _ _ _ "" = ()

  | message out_stream 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 TextIO.output (out_stream, chunk header ^ chunk body) (*atomic output!*) end;

in

fun standard_message out_stream with_serial ch body =

  message out_stream ch

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

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

fun init_message out_stream =

  message out_stream "A" [(Markup.pidN, process_id ())] (Session.welcome ());

end;

(* channels *)

local

fun auto_flush stream =

  let

    val _ = TextIO.StreamIO.setBufferMode (TextIO.getOutstream stream, IO.BLOCK_BUF);

    fun loop () =

      (OS.Process.sleep (Time.fromMilliseconds 20); try TextIO.flushOut stream; loop ());

  in loop end;

fun rendezvous f fifo =

  let

    val path = File.platform_path (Path.explode fifo);

    val result = f fifo;  (*should block until peer is ready*)

    val _ =

      if String.isSuffix "cygwin" ml_platform then ()  (*Cygwin 1.7: no proper blocking on open*)

      else OS.FileSys.remove path;  (*prevent future access*)

  in result end;

in

fun setup_channels in_fifo out_fifo =

  let

    val in_stream = rendezvous TextIO.openIn in_fifo;

    val out_stream = rendezvous TextIO.openOut out_fifo;

    val _ = Simple_Thread.fork false (auto_flush out_stream);

    val _ = Simple_Thread.fork false (auto_flush TextIO.stdOut);

    val _ = Simple_Thread.fork false (auto_flush TextIO.stdErr);

  in

    Output.status_fn   := standard_message out_stream false "B";

    Output.report_fn   := standard_message out_stream false "C";

    Output.writeln_fn  := standard_message out_stream true "D";

    Output.tracing_fn  := standard_message out_stream true "E";

    Output.warning_fn  := standard_message out_stream true "F";

    Output.error_fn    := standard_message out_stream true "G";

    Output.priority_fn := ! Output.writeln_fn;

    Output.prompt_fn   := ignore;

    (in_stream, out_stream)

  end;

end;

(* protocol loop -- uninterruptible *)

val crashes = Unsynchronized.ref ([]: exn list);

local

fun recover crash =

  (CRITICAL (fn () => Unsynchronized.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 (Time.fromMilliseconds 500);  (*yield to raw ML toplevel*)

    val _ = Output.std_output Symbol.STX;

    val _ = quick_and_dirty := true;  (* FIXME !? *)

    val _ = Context.set_thread_data NONE;

    val _ = Unsynchronized.change print_mode

      (fold (update op =) [isabelle_processN, Keyword.keyword_statusN, Pretty.symbolicN]);

    val (in_stream, out_stream) = setup_channels in_fifo out_fifo;

    val _ = init_message out_stream;

    val _ = Keyword.status ();

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

  in loop in_stream end));

end;