(*  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" [] (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;

 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 _ = 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 "Prover ready");

   in loop in_stream end));

 end;