(*  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;