(*  Title:      Pure/Isar/toplevel.ML

     Author:     Markus Wenzel, TU Muenchen

 Isabelle/Isar toplevel transactions.

 *)

 signature TOPLEVEL =

 sig

   exception UNDEF

   type generic_theory

   type state

   val toplevel: state

   val is_toplevel: state -> bool

   val is_theory: state -> bool

   val is_proof: state -> bool

   val level: state -> int

   val presentation_context_of: state -> Proof.context

   val previous_context_of: state -> Proof.context option

   val context_of: state -> Proof.context

   val generic_theory_of: state -> generic_theory

   val theory_of: state -> theory

   val proof_of: state -> Proof.state

   val proof_position_of: state -> int

   val enter_proof_body: state -> Proof.state

   val print_state_context: state -> unit

   val print_state: bool -> state -> unit

   val quiet: bool Unsynchronized.ref

   val debug: bool Unsynchronized.ref

   val interact: bool Unsynchronized.ref

   val timing: bool Unsynchronized.ref

   val profiling: int Unsynchronized.ref

   val skip_proofs: bool Unsynchronized.ref

   exception TERMINATE

   exception TOPLEVEL_ERROR

   val program: (unit -> 'a) -> 'a

   type transition

   val empty: transition

   val init_of: transition -> string option

   val name_of: transition -> string

   val pos_of: transition -> Position.T

   val str_of: transition -> string

   val name: string -> transition -> transition

   val position: Position.T -> transition -> transition

   val interactive: bool -> transition -> transition

   val print: transition -> transition

   val no_timing: transition -> transition

   val init_theory: string -> (bool -> theory) -> (theory -> unit) -> transition -> transition

   val exit: transition -> transition

   val keep: (state -> unit) -> transition -> transition

   val keep': (bool -> state -> unit) -> transition -> transition

   val imperative: (unit -> unit) -> transition -> transition

   val ignored: Position.T -> transition

   val malformed: Position.T -> string -> transition

   val theory: (theory -> theory) -> transition -> transition

   val generic_theory: (generic_theory -> generic_theory) -> transition -> transition

   val theory': (bool -> theory -> theory) -> transition -> transition

   val begin_local_theory: bool -> (theory -> local_theory) -> transition -> transition

   val end_local_theory: transition -> transition

   val local_theory': xstring option -> (bool -> local_theory -> local_theory) ->

     transition -> transition

   val local_theory: xstring option -> (local_theory -> local_theory) -> transition -> transition

   val present_local_theory: xstring option -> (state -> unit) -> transition -> transition

   val local_theory_to_proof': xstring option -> (bool -> local_theory -> Proof.state) ->

     transition -> transition

   val local_theory_to_proof: xstring option -> (local_theory -> Proof.state) ->

     transition -> transition

   val theory_to_proof: (theory -> Proof.state) -> transition -> transition

   val end_proof: (bool -> Proof.state -> Proof.context) -> transition -> transition

   val forget_proof: transition -> transition

   val present_proof: (state -> unit) -> transition -> transition

   val proofs': (bool -> Proof.state -> Proof.state Seq.seq) -> transition -> transition

   val proof': (bool -> Proof.state -> Proof.state) -> transition -> transition

   val proofs: (Proof.state -> Proof.state Seq.seq) -> transition -> transition

   val proof: (Proof.state -> Proof.state) -> transition -> transition

   val actual_proof: (ProofNode.T -> ProofNode.T) -> transition -> transition

   val skip_proof: (int -> int) -> transition -> transition

   val skip_proof_to_theory: (int -> bool) -> transition -> transition

   val get_id: transition -> string option

   val put_id: string -> transition -> transition

   val unknown_theory: transition -> transition

   val unknown_proof: transition -> transition

   val unknown_context: transition -> transition

   val setmp_thread_position: transition -> ('a -> 'b) -> 'a -> 'b

   val status: transition -> Markup.T -> unit

   val error_msg: transition -> exn * string -> unit

   val add_hook: (transition -> state -> state -> unit) -> unit

   val transition: bool -> transition -> state -> (state * (exn * string) option) option

   val commit_exit: Position.T -> transition

   val command: transition -> state -> state

   val run_command: string -> transition -> state -> state option

   val excursion: (transition * transition list) list -> (transition * state) list lazy

 end;

 structure Toplevel: TOPLEVEL =

 struct

 (** toplevel state **)

 exception UNDEF = Runtime.UNDEF;

 (* local theory wrappers *)

 type generic_theory = Context.generic;    (*theory or local_theory*)

 val loc_init = TheoryTarget.context;

 val loc_exit = LocalTheory.exit_global;

 fun loc_begin loc (Context.Theory thy) = loc_init (the_default "-" loc) thy

   | loc_begin NONE (Context.Proof lthy) = lthy

   | loc_begin (SOME loc) (Context.Proof lthy) = loc_init loc (loc_exit lthy);

 fun loc_finish _ (Context.Theory _) = Context.Theory o loc_exit

   | loc_finish NONE (Context.Proof _) = Context.Proof o LocalTheory.restore

   | loc_finish (SOME _) (Context.Proof lthy) = fn lthy' =>

       Context.Proof (LocalTheory.reinit (LocalTheory.raw_theory (K (loc_exit lthy')) lthy));

 (* datatype node *)

 datatype node =

   Theory of generic_theory * Proof.context option

     (*theory with presentation context*) |

   Proof of ProofNode.T * ((Proof.context -> generic_theory) * generic_theory)

     (*proof node, finish, original theory*) |

   SkipProof of int * (generic_theory * generic_theory);

     (*proof depth, resulting theory, original theory*)

 val theory_node = fn Theory (gthy, _) => SOME gthy | _ => NONE;

 val proof_node = fn Proof (prf, _) => SOME prf | _ => NONE;

 fun cases_node f _ (Theory (gthy, _)) = f gthy

   | cases_node _ g (Proof (prf, _)) = g (ProofNode.current prf)

   | cases_node f _ (SkipProof (_, (gthy, _))) = f gthy;

 val context_node = cases_node Context.proof_of Proof.context_of;

 (* datatype state *)

 type node_info = node * (theory -> unit);  (*node with exit operation*)

 datatype state = State of node_info option * node_info option;  (*current, previous*)

 val toplevel = State (NONE, NONE);

 fun is_toplevel (State (NONE, _)) = true

   | is_toplevel _ = false;

 fun level (State (NONE, _)) = 0

   | level (State (SOME (Theory _, _), _)) = 0

   | level (State (SOME (Proof (prf, _), _), _)) = Proof.level (ProofNode.current prf)

   | level (State (SOME (SkipProof (d, _), _), _)) = d + 1;   (*different notion of proof depth!*)

 fun str_of_state (State (NONE, _)) = "at top level"

   | str_of_state (State (SOME (Theory (Context.Theory _, _), _), _)) = "in theory mode"

   | str_of_state (State (SOME (Theory (Context.Proof _, _), _), _)) = "in local theory mode"

   | str_of_state (State (SOME (Proof _, _), _)) = "in proof mode"

   | str_of_state (State (SOME (SkipProof _, _), _)) = "in skipped proof mode";

 (* current node *)

 fun node_of (State (NONE, _)) = raise UNDEF

   | node_of (State (SOME (node, _), _)) = node;

 fun is_theory state = not (is_toplevel state) andalso is_some (theory_node (node_of state));

 fun is_proof state = not (is_toplevel state) andalso is_some (proof_node (node_of state));

 fun node_case f g state = cases_node f g (node_of state);

 fun presentation_context_of state =

   (case try node_of state of

     SOME (Theory (_, SOME ctxt)) => ctxt

   | SOME node => context_node node

   | NONE => raise UNDEF);

 fun previous_context_of (State (_, NONE)) = NONE

   | previous_context_of (State (_, SOME (prev, _))) = SOME (context_node prev);

 val context_of = node_case Context.proof_of Proof.context_of;

 val generic_theory_of = node_case I (Context.Proof o Proof.context_of);

 val theory_of = node_case Context.theory_of Proof.theory_of;

 val proof_of = node_case (fn _ => raise UNDEF) I;

 fun proof_position_of state =

   (case node_of state of

     Proof (prf, _) => ProofNode.position prf

   | _ => raise UNDEF);

 val enter_proof_body = node_case (Proof.init o Context.proof_of) Proof.enter_forward;

 (* print state *)

 val pretty_context = LocalTheory.pretty o Context.cases (TheoryTarget.init NONE) I;

 fun print_state_context state =

   (case try node_of state of

     NONE => []

   | SOME (Theory (gthy, _)) => pretty_context gthy

   | SOME (Proof (_, (_, gthy))) => pretty_context gthy

   | SOME (SkipProof (_, (gthy, _))) => pretty_context gthy)

   |> Pretty.chunks |> Pretty.writeln;

 fun print_state prf_only state =

   (case try node_of state of

     NONE => []

   | SOME (Theory (gthy, _)) => if prf_only then [] else pretty_context gthy

   | SOME (Proof (prf, _)) =>

       Proof.pretty_state (ProofNode.position prf) (ProofNode.current prf)

   | SOME (SkipProof (d, _)) => [Pretty.str ("skipped proof: depth " ^ string_of_int d)])

   |> Pretty.markup_chunks Markup.state |> Pretty.writeln;

 (** toplevel transitions **)

 val quiet = Unsynchronized.ref false;

 val debug = Output.debugging;

 val interact = Unsynchronized.ref false;

 val timing = Output.timing;

 val profiling = Unsynchronized.ref 0;

 val skip_proofs = Unsynchronized.ref false;

 exception TERMINATE = Runtime.TERMINATE;

 exception EXCURSION_FAIL = Runtime.EXCURSION_FAIL;

 exception TOPLEVEL_ERROR = Runtime.TOPLEVEL_ERROR;

 fun program f =

  (f

   |> Runtime.controlled_execution

   |> Runtime.toplevel_error ML_Compiler.exn_message) ();

 (* node transactions -- maintaining stable checkpoints *)

 exception FAILURE of state * exn;

 local

 fun reset_presentation (Theory (gthy, _)) = Theory (gthy, NONE)

   | reset_presentation node = node;

 fun is_draft_theory (Theory (gthy, _)) = Context.is_draft (Context.theory_of gthy)

   | is_draft_theory _ = false;

 fun is_stale state = Context.is_stale (theory_of state) handle Runtime.UNDEF => false;

 fun stale_error NONE = SOME (ERROR "Stale theory encountered after successful execution!")

   | stale_error some = some;

 fun map_theory f (Theory (gthy, ctxt)) =

       Theory (Context.mapping f (LocalTheory.raw_theory f) gthy, ctxt)

   | map_theory _ node = node;

 in

 fun apply_transaction f g (node, exit) =

   let

     val _ = is_draft_theory node andalso error "Illegal draft theory in toplevel state";

     val cont_node = reset_presentation node;

     val back_node = map_theory (Theory.checkpoint o Theory.copy) cont_node;

     fun state_error e nd = (State (SOME (nd, exit), SOME (node, exit)), e);

     val (result, err) =

       cont_node

       |> Runtime.controlled_execution f

       |> map_theory Theory.checkpoint

       |> state_error NONE

       handle exn => state_error (SOME exn) cont_node;

     val (result', err') =

       if is_stale result then state_error (stale_error err) back_node

       else (result, err);

   in

     (case err' of

       NONE => tap g result'

     | SOME exn => raise FAILURE (result', exn))

   end;

 end;

 (* primitive transitions *)

 datatype trans =

   Init of string * (bool -> theory) * (theory -> unit) | (*theory name, init, exit*)

   Exit |                                         (*formal exit of theory -- without committing*)

   CommitExit |                                   (*exit and commit final theory*)

   Keep of bool -> state -> unit |                (*peek at state*)

   Transaction of (bool -> node -> node) * (state -> unit);  (*node transaction and presentation*)

 local

 fun apply_tr int (Init (_, f, exit)) (State (NONE, _)) =

       State (SOME (Theory (Context.Theory (Theory.checkpoint (f int)), NONE), exit), NONE)

   | apply_tr _ Exit (State (prev as SOME (Theory (Context.Theory _, _), _), _)) =

       State (NONE, prev)

   | apply_tr _ CommitExit (State (NONE, SOME (Theory (Context.Theory thy, _), exit))) =

       (Runtime.controlled_execution exit thy; toplevel)

   | apply_tr int (Keep f) state =

       Runtime.controlled_execution (fn x => tap (f int) x) state

   | apply_tr int (Transaction (f, g)) (State (SOME state, _)) =

       apply_transaction (fn x => f int x) g state

   | apply_tr _ _ _ = raise UNDEF;

 fun apply_union _ [] state = raise FAILURE (state, UNDEF)

   | apply_union int (tr :: trs) state =

       apply_union int trs state

         handle Runtime.UNDEF => apply_tr int tr state

           | FAILURE (alt_state, UNDEF) => apply_tr int tr alt_state

           | exn as FAILURE _ => raise exn

           | exn => raise FAILURE (state, exn);

 in

 fun apply_trans int trs state = (apply_union int trs state, NONE)

   handle FAILURE (alt_state, exn) => (alt_state, SOME exn) | exn => (state, SOME exn);

 end;

 (* datatype transition *)

 datatype transition = Transition of

  {name: string,              (*command name*)

   pos: Position.T,           (*source position*)

   int_only: bool,            (*interactive-only*)

   print: bool,               (*print result state*)

   no_timing: bool,           (*suppress timing*)

   trans: trans list};        (*primitive transitions (union)*)

 fun make_transition (name, pos, int_only, print, no_timing, trans) =

   Transition {name = name, pos = pos, int_only = int_only, print = print, no_timing = no_timing,

     trans = trans};

 fun map_transition f (Transition {name, pos, int_only, print, no_timing, trans}) =

   make_transition (f (name, pos, int_only, print, no_timing, trans));

 val empty = make_transition ("", Position.none, false, false, false, []);

 (* diagnostics *)

 fun init_of (Transition {trans = [Init (name, _, _)], ...}) = SOME name

   | init_of _ = NONE;

 fun name_of (Transition {name, ...}) = name;

 fun pos_of (Transition {pos, ...}) = pos;

 fun str_of tr = quote (name_of tr) ^ Position.str_of (pos_of tr);

 fun command_msg msg tr = msg ^ "command " ^ str_of tr;

 fun at_command tr = command_msg "At " tr ^ ".";

 fun type_error tr state =

   ERROR (command_msg "Illegal application of " tr ^ " " ^ str_of_state state);

 (* modify transitions *)

 fun name name = map_transition (fn (_, pos, int_only, print, no_timing, trans) =>

   (name, pos, int_only, print, no_timing, trans));

 fun position pos = map_transition (fn (name, _, int_only, print, no_timing, trans) =>

   (name, pos, int_only, print, no_timing, trans));

 fun interactive int_only = map_transition (fn (name, pos, _, print, no_timing, trans) =>

   (name, pos, int_only, print, no_timing, trans));

 val no_timing = map_transition (fn (name, pos, int_only, print, _, trans) =>

   (name, pos, int_only, print, true, trans));

 fun add_trans tr = map_transition (fn (name, pos, int_only, print, no_timing, trans) =>

   (name, pos, int_only, print, no_timing, tr :: trans));

 val reset_trans = map_transition (fn (name, pos, int_only, print, no_timing, _) =>

   (name, pos, int_only, print, no_timing, []));

 fun set_print print = map_transition (fn (name, pos, int_only, _, no_timing, trans) =>

   (name, pos, int_only, print, no_timing, trans));

 val print = set_print true;

 (* basic transitions *)

 fun init_theory name f exit = add_trans (Init (name, f, exit));

 val exit = add_trans Exit;

 val keep' = add_trans o Keep;

 fun present_transaction f g = add_trans (Transaction (f, g));

 fun transaction f = present_transaction f (K ());

 fun keep f = add_trans (Keep (fn _ => f));

 fun imperative f = keep (fn _ => f ());

 fun ignored pos = empty |> name "<ignored>" |> position pos |> imperative I;

 fun malformed pos msg =

   empty |> name "<malformed>" |> position pos |> imperative (fn () => error msg);

 val unknown_theory = imperative (fn () => warning "Unknown theory context");

 val unknown_proof = imperative (fn () => warning "Unknown proof context");

 val unknown_context = imperative (fn () => warning "Unknown context");

 (* theory transitions *)

 fun generic_theory f = transaction (fn _ =>

   (fn Theory (gthy, _) => Theory (f gthy, NONE)

     | _ => raise UNDEF));

 fun theory' f = transaction (fn int =>

   (fn Theory (Context.Theory thy, _) => Theory (Context.Theory (f int thy), NONE)

     | _ => raise UNDEF));

 fun theory f = theory' (K f);

 fun begin_local_theory begin f = transaction (fn _ =>

   (fn Theory (Context.Theory thy, _) =>

         let

           val lthy = f thy;

           val gthy = if begin then Context.Proof lthy else Context.Theory (loc_exit lthy);

         in Theory (gthy, SOME lthy) end

     | _ => raise UNDEF));

 val end_local_theory = transaction (fn _ =>

   (fn Theory (Context.Proof lthy, _) => Theory (Context.Theory (loc_exit lthy), SOME lthy)

     | _ => raise UNDEF));

 local

 fun local_theory_presentation loc f = present_transaction (fn int =>

   (fn Theory (gthy, _) =>

         let

           val finish = loc_finish loc gthy;

           val lthy' = f int (loc_begin loc gthy);

         in Theory (finish lthy', SOME lthy') end

     | _ => raise UNDEF));

 in

 fun local_theory' loc f = local_theory_presentation loc f (K ());

 fun local_theory loc f = local_theory' loc (K f);

 fun present_local_theory loc = local_theory_presentation loc (K I);

 end;

 (* proof transitions *)

 fun end_proof f = transaction (fn int =>

   (fn Proof (prf, (finish, _)) =>

         let val state = ProofNode.current prf in

           if can (Proof.assert_bottom true) state then

             let

               val ctxt' = f int state;

               val gthy' = finish ctxt';

             in Theory (gthy', SOME ctxt') end

           else raise UNDEF

         end

     | SkipProof (0, (gthy, _)) => Theory (gthy, NONE)

     | _ => raise UNDEF));

 local

 fun begin_proof init finish = transaction (fn int =>

   (fn Theory (gthy, _) =>

     let

       val prf = init int gthy;

       val skip = ! skip_proofs;

       val schematic = Proof.schematic_goal prf;

     in

       if skip andalso schematic then

         warning "Cannot skip proof of schematic goal statement"

       else ();

       if skip andalso not schematic then

         SkipProof (0, (finish gthy (Proof.global_skip_proof int prf), gthy))

       else Proof (ProofNode.init prf, (finish gthy, gthy))

     end

   | _ => raise UNDEF));

 in

 fun local_theory_to_proof' loc f = begin_proof

   (fn int => fn gthy => f int (loc_begin loc gthy))

   (loc_finish loc);

 fun local_theory_to_proof loc f = local_theory_to_proof' loc (K f);

 fun theory_to_proof f = begin_proof

   (K (fn Context.Theory thy => f thy | _ => raise UNDEF))

   (K (Context.Theory o ProofContext.theory_of));

 end;

 val forget_proof = transaction (fn _ =>

   (fn Proof (_, (_, orig_gthy)) => Theory (orig_gthy, NONE)

     | SkipProof (_, (_, orig_gthy)) => Theory (orig_gthy, NONE)

     | _ => raise UNDEF));

 val present_proof = present_transaction (fn _ =>

   (fn Proof (prf, x) => Proof (ProofNode.apply I prf, x)

     | skip as SkipProof _ => skip

     | _ => raise UNDEF));

 fun proofs' f = transaction (fn int =>

   (fn Proof (prf, x) => Proof (ProofNode.applys (f int) prf, x)

     | skip as SkipProof _ => skip

     | _ => raise UNDEF));

 fun proof' f = proofs' (Seq.single oo f);

 val proofs = proofs' o K;

 val proof = proof' o K;

 fun actual_proof f = transaction (fn _ =>

   (fn Proof (prf, x) => Proof (f prf, x)

     | _ => raise UNDEF));

 fun skip_proof f = transaction (fn _ =>

   (fn SkipProof (h, x) => SkipProof (f h, x)

     | _ => raise UNDEF));

 fun skip_proof_to_theory pred = transaction (fn _ =>

   (fn SkipProof (d, (gthy, _)) => if pred d then Theory (gthy, NONE) else raise UNDEF

   | _ => raise UNDEF));

 (** toplevel transactions **)

 (* identification *)

 fun get_id (Transition {pos, ...}) = Position.get_id pos;

 fun put_id id (tr as Transition {pos, ...}) = position (Position.put_id id pos) tr;

 (* thread position *)

 fun setmp_thread_position (Transition {pos, ...}) f x =

   Position.setmp_thread_data pos f x;

 fun status tr m =

   setmp_thread_position tr (fn () => Output.status (Markup.markup m "")) ();

 fun error_msg tr exn_info =

   setmp_thread_position tr (fn () =>

     Output.error_msg (ML_Compiler.exn_message (EXCURSION_FAIL exn_info))) ();

 (* post-transition hooks *)

 local val hooks = Unsynchronized.ref ([]: (transition -> state -> state -> unit) list) in

 fun add_hook f = CRITICAL (fn () => Unsynchronized.change hooks (cons f));

 fun get_hooks () = CRITICAL (fn () => ! hooks);

 end;

 (* apply transitions *)

 local

 fun app int (tr as Transition {trans, print, no_timing, ...}) =

   setmp_thread_position tr (fn state =>

     let

       fun do_timing f x = (warning (command_msg "" tr); timeap f x);

       fun do_profiling f x = profile (! profiling) f x;

       val (result, status) =

          state |> (apply_trans int trans

           |> (if ! profiling > 0 andalso not no_timing then do_profiling else I)

           |> (if ! profiling > 0 orelse ! timing andalso not no_timing then do_timing else I));

       val _ = if int andalso not (! quiet) andalso print then print_state false result else ();

     in (result, Option.map (fn UNDEF => type_error tr state | exn => exn) status) end);

 in

 fun transition int tr st =

   let

     val hooks = get_hooks ();

     fun apply_hooks st' = hooks |> List.app (fn f => (try (fn () => f tr st st') (); ()));

     val ctxt = try context_of st;

     val res =

       (case app int tr st of

         (_, SOME TERMINATE) => NONE

       | (st', SOME (EXCURSION_FAIL exn_info)) => SOME (st', SOME exn_info)

       | (st', SOME exn) => SOME (st', SOME (Runtime.exn_context ctxt exn, at_command tr))

       | (st', NONE) => SOME (st', NONE));

     val _ = (case res of SOME (st', NONE) => apply_hooks st' | _ => ());

   in res end;

 end;

 (* commit final exit *)

 fun commit_exit pos =

   name "end" empty

   |> position pos

   |> add_trans CommitExit

   |> imperative (fn () => warning "Expected to find finished theory");

 (* nested commands *)

 fun command tr st =

   (case transition (! interact) tr st of

     SOME (st', NONE) => st'

   | SOME (_, SOME exn_info) => raise EXCURSION_FAIL exn_info

   | NONE => raise EXCURSION_FAIL (TERMINATE, at_command tr));

 fun command_result tr st =

   let val st' = command tr st

   in (st', st') end;

 fun run_command thy_name tr st =

   (case

       (case init_of tr of

         SOME name => Exn.capture (fn () => ThyLoad.check_name thy_name name) ()

       | NONE => Exn.Result ()) of

     Exn.Result () =>

       (case transition true tr st of

         SOME (st', NONE) => (status tr Markup.finished; SOME st')

       | SOME (_, SOME exn_info) => (error_msg tr exn_info; status tr Markup.failed; NONE)

       | NONE => (error_msg tr (TERMINATE, at_command tr); status tr Markup.failed; NONE))

   | Exn.Exn exn => (error_msg tr (exn, at_command tr); status tr Markup.failed; NONE));

 (* excursion of units, consisting of commands with proof *)

 structure States = ProofDataFun

 (

   type T = state list future option;

   fun init _ = NONE;

 );

 fun proof_result immediate (tr, proof_trs) st =

   let val st' = command tr st in

     if immediate orelse null proof_trs orelse

       not (can proof_of st') orelse Proof.is_relevant (proof_of st')

     then

       let val (states, st'') = fold_map command_result proof_trs st'

       in (Lazy.value ((tr, st') :: (proof_trs ~~ states)), st'') end

     else

       let

         val (body_trs, end_tr) = split_last proof_trs;

         val finish = Context.Theory o ProofContext.theory_of;

         val future_proof = Proof.global_future_proof

           (fn prf =>

             Future.fork_pri ~1 (fn () =>

               let val (states, result_state) =

                 (case st' of State (SOME (Proof (_, (_, orig_gthy)), exit), prev)

                   => State (SOME (Proof (ProofNode.init prf, (finish, orig_gthy)), exit), prev))

                 |> fold_map command_result body_trs

                 ||> command (end_tr |> set_print false);

               in (states, presentation_context_of result_state) end))

           #> (fn (states, ctxt) => States.put (SOME states) ctxt);

         val st'' = st' |> command (end_tr |> reset_trans |> end_proof (K future_proof));

         val states =

           (case States.get (presentation_context_of st'') of

             NONE => sys_error ("No future states for " ^ name_of tr ^ Position.str_of (pos_of tr))

           | SOME states => states);

         val result = Lazy.lazy

           (fn () => (tr, st') :: (body_trs ~~ Future.join states) @ [(end_tr, st'')]);

       in (result, st'') end

   end;

 fun excursion input =

   let

     val end_pos = if null input then error "No input" else pos_of (fst (List.last input));

     val immediate = not (Goal.future_enabled ());

     val (results, end_state) = fold_map (proof_result immediate) input toplevel;

     val _ =

       (case end_state of

         State (NONE, SOME (Theory (Context.Theory _, _), _)) =>

           command (commit_exit end_pos) end_state

       | _ => error "Unfinished development at end of input");

   in Lazy.lazy (fn () => maps Lazy.force results) end;

 end;