(*  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

   . stderr \002: ML running

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

   .. protocol thread initialization

   ... rendezvous on system channel

   ... message INIT(pid): channels ready

   ... message RAW(keywords)

   ... message RAW(ready): main loop ready

 *)

 signature ISABELLE_PROCESS =

 sig

   val is_active: unit -> bool

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

   val crashes: exn list Synchronized.var

   val init_fifos: string -> string -> unit

   val init_socket: 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;

 (* protocol commands *)

 local

 val commands =

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

 in

 fun protocol_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 run_command name args =

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

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

   | SOME cmd =>

       (Runtime.debugging cmd args handle exn =>

         error ("Isabelle process protocol failure: " ^ quote name ^ "\n" ^

           ML_Compiler.exn_message exn)));

 end;

 (* message channels *)

 local

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

 fun message do_flush mbox ch raw_props body =

   let

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

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

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

 fun standard_message mbox opt_serial ch body =

   if body = "" then ()

   else

     message false mbox ch

       ((case opt_serial of SOME i => cons (Isabelle_Markup.serialN, string_of_int i) | _ => I)

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

 fun message_output mbox channel =

   let

     fun flush () = ignore (try System_Channel.flush channel);

     fun loop receive =

       (case receive mbox of

         SOME (msg, do_flush) =>

          (List.app (fn s => System_Channel.output channel s) msg;

           if do_flush then flush () else ();

           loop (Mailbox.receive_timeout (seconds 0.02)))

       | NONE => (flush (); loop (SOME o Mailbox.receive)));

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

 in

 fun setup_channels channel =

   let

     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 * bool) Mailbox.T;

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

   in

     Output.Private_Hooks.status_fn := standard_message mbox NONE "B";

     Output.Private_Hooks.report_fn := standard_message mbox NONE "C";

     Output.Private_Hooks.writeln_fn := (fn s => standard_message mbox (SOME (serial ())) "D" s);

     Output.Private_Hooks.tracing_fn := (fn s => standard_message mbox (SOME (serial ())) "E" s);

     Output.Private_Hooks.warning_fn := (fn s => standard_message mbox (SOME (serial ())) "F" s);

     Output.Private_Hooks.error_fn := (fn (i, s) => standard_message mbox (SOME i) "G" s);

     Output.Private_Hooks.protocol_message_fn := message true mbox "H";

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

     Output.Private_Hooks.prompt_fn := ignore;

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

   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 channel len =

   let

     val n =

       (case Int.fromString len of

         SOME n => n

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

     val chunk = System_Channel.inputN channel 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 channel =

   (case System_Channel.input_line channel of

     NONE => raise Runtime.TERMINATE

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

 in

 fun loop channel =

   let val continue =

     (case read_command channel 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 channel else () end;

 end;

 (* init *)

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

   let

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

     val _ = Output.physical_stderr Symbol.STX;

     val _ = quick_and_dirty := false;

     val _ = Goal.parallel_proofs := 0;

     val _ =

       if Multithreading.max_threads_value () < 2

       then Multithreading.max_threads := 2 else ();

     val _ = Context.set_thread_data NONE;

     val _ =

       Unsynchronized.change print_mode

         (fn mode =>

           (mode @ [Syntax_Trans.no_bracketsN, Syntax_Trans.no_type_bracketsN])

           |> fold (update op =)

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

     val channel = rendezvous ();

     val _ = setup_channels channel;

     val _ = Keyword.status ();

     val _ = Thy_Info.status ();

     val _ = Output.protocol_message Isabelle_Markup.ready "";

   in loop channel end));

 fun init_fifos fifo1 fifo2 = init (fn () => System_Channel.fifo_rendezvous fifo1 fifo2);

 fun init_socket name = init (fn () => System_Channel.socket_rendezvous name);

 end;