(*  Title:      Pure/System/isar.ML

    Author:     Makarius

Global state of the raw Isar read-eval-print loop.

*)

signature ISAR =

sig

  val init: unit -> unit

  val exn: unit -> (exn * string) option

  val state: unit -> Toplevel.state

  val goal: unit -> {context: Proof.context, facts: thm list, goal: thm}

  val print: unit -> unit

  val >> : Toplevel.transition -> bool

  val >>> : Toplevel.transition list -> unit

  val linear_undo: int -> unit

  val undo: int -> unit

  val kill: unit -> unit

  val kill_proof: unit -> unit

  val crashes: exn list Synchronized.var

  val toplevel_loop: TextIO.instream ->

    {init: bool, welcome: bool, sync: bool, secure: bool} -> unit

  val loop: unit -> unit

  val main: unit -> unit

end;

structure Isar: ISAR =

struct

(** TTY model -- SINGLE-THREADED! **)

(* the global state *)

type history = (Toplevel.state * Toplevel.transition) list;

  (*previous state, state transition -- regular commands only*)

local

  val global_history = Unsynchronized.ref ([]: history);

  val global_state = Unsynchronized.ref Toplevel.toplevel;

  val global_exn = Unsynchronized.ref (NONE: (exn * string) option);

in

fun edit_history count f = NAMED_CRITICAL "Isar" (fn () =>

  let

    fun edit 0 (st, hist) = (global_history := hist; global_state := st; global_exn := NONE)

      | edit n (st, hist) = edit (n - 1) (f st hist);

  in edit count (! global_state, ! global_history) end);

fun state () = ! global_state;

fun exn () = ! global_exn;

fun set_exn exn =  global_exn := exn;

end;

fun init () = edit_history 1 (K (K (Toplevel.toplevel, [])));

fun goal () = Proof.goal (Toplevel.proof_of (state ()))

  handle Toplevel.UNDEF => error "No goal present";

fun print () = Toplevel.print_state false (state ());

(* history navigation *)

local

fun find_and_undo _ [] = error "Undo history exhausted"

  | find_and_undo which ((prev, tr) :: hist) =

      if which (Toplevel.name_of tr) then (prev, hist) else find_and_undo which hist;

in

fun linear_undo n = edit_history n (K (find_and_undo (K true)));

fun undo n = edit_history n (fn st => fn hist =>

  find_and_undo (if Toplevel.is_proof st then K true else Keyword.is_theory) hist);

fun kill () = edit_history 1 (fn st => fn hist =>

  find_and_undo

    (if Toplevel.is_proof st then Keyword.is_theory else Keyword.is_theory_begin) hist);

fun kill_proof () = edit_history 1 (fn st => fn hist =>

  if Toplevel.is_proof st then find_and_undo Keyword.is_theory hist

  else raise Toplevel.UNDEF);

end;

(* interactive state transformations *)

fun op >> tr =

  (case Toplevel.transition true tr (state ()) of

    NONE => false

  | SOME (_, SOME exn_info) =>

     (set_exn (SOME exn_info);

      Toplevel.error_msg tr (ML_Compiler.exn_message (Runtime.EXCURSION_FAIL exn_info));

      true)

  | SOME (st', NONE) =>

      let

        val name = Toplevel.name_of tr;

        val _ = if Keyword.is_theory_begin name then init () else ();

        val _ =

          if Keyword.is_regular name

          then edit_history 1 (fn st => fn hist => (st', (st, tr) :: hist)) else ();

      in true end);

fun op >>> [] = ()

  | op >>> (tr :: trs) = if op >> tr then op >>> trs else ();

(* toplevel loop -- uninterruptible *)

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

local

fun raw_loop secure src =

  let

    fun check_secure () =

      (if secure then warning "Secure loop -- cannot exit to ML" else (); secure);

  in

    (case Source.get_single (Source.set_prompt Source.default_prompt src) of

      NONE => if secure then quit () else ()

    | SOME (tr, src') => if op >> tr orelse check_secure () then raw_loop secure src' else ())

    handle exn =>

      (Output.error_msg (ML_Compiler.exn_message exn)

        handle crash =>

          (Synchronized.change crashes (cons crash);

            warning "Recovering from Isar toplevel crash -- see also Isar.crashes");

        raw_loop secure src)

  end;

in

fun toplevel_loop in_stream {init = do_init, welcome, sync, secure} =

 (Context.set_thread_data NONE;

  if do_init then init () else ();

  if welcome then writeln (Session.welcome ()) else ();

  uninterruptible (fn _ => fn () => raw_loop secure (Outer_Syntax.isar in_stream sync)) ());

end;

fun loop () =

  toplevel_loop TextIO.stdIn

    {init = false, welcome = false, sync = false, secure = Secure.is_secure ()};

fun main () =

  toplevel_loop TextIO.stdIn

    {init = true, welcome = true, sync = false, secure = Secure.is_secure ()};

(** command syntax **)

local

val op >> = Scan.>>;

in

(* global history *)

val _ =

  Outer_Syntax.improper_command "init_toplevel" "init toplevel point-of-interest" Keyword.control

    (Scan.succeed (Toplevel.no_timing o Toplevel.imperative init));

val _ =

  Outer_Syntax.improper_command "linear_undo" "undo commands" Keyword.control

    (Scan.optional Parse.nat 1 >>

      (fn n => Toplevel.no_timing o Toplevel.imperative (fn () => linear_undo n)));

val _ =

  Outer_Syntax.improper_command "undo" "undo commands (skipping closed proofs)" Keyword.control

    (Scan.optional Parse.nat 1 >>

      (fn n => Toplevel.no_timing o Toplevel.imperative (fn () => undo n)));

val _ =

  Outer_Syntax.improper_command "undos_proof" "undo commands (skipping closed proofs)"

    Keyword.control

    (Scan.optional Parse.nat 1 >> (fn n => Toplevel.no_timing o

      Toplevel.keep (fn state =>

        if Toplevel.is_proof state then (undo n; print ()) else raise Toplevel.UNDEF)));

val _ =

  Outer_Syntax.improper_command "cannot_undo" "partial undo -- Proof General legacy"

    Keyword.control

    (Parse.name >>

      (fn "end" => Toplevel.no_timing o Toplevel.imperative (fn () => undo 1)

        | txt => Toplevel.imperative (fn () => error ("Cannot undo " ^ quote txt))));

val _ =

  Outer_Syntax.improper_command "kill" "kill partial proof or theory development" Keyword.control

    (Scan.succeed (Toplevel.no_timing o Toplevel.imperative kill));

end;

end;