src/Pure/Isar/proof.ML

tuned locale interface;

(*  Title:      Pure/Isar/proof.ML
    ID:         $Id$
    Author:     Markus Wenzel, TU Muenchen
    License:    GPL (GNU GENERAL PUBLIC LICENSE)

Proof states and methods.
*)

signature BASIC_PROOF =
sig
  val FINDGOAL: (int -> thm -> 'a Seq.seq) -> thm -> 'a Seq.seq
  val HEADGOAL: (int -> thm -> 'a Seq.seq) -> thm -> 'a Seq.seq
end;

signature PROOF =
sig
  include BASIC_PROOF
  type context
  type state
  exception STATE of string * state
  val check_result: string -> state -> 'a Seq.seq -> 'a Seq.seq
  val init_state: theory -> state
  val context_of: state -> context
  val theory_of: state -> theory
  val sign_of: state -> Sign.sg
  val warn_extra_tfrees: state -> state -> state
  val reset_thms: string -> state -> state
  val the_facts: state -> thm list
  val the_fact: state -> thm
  val get_goal: state -> context * (thm list * thm)
  val goal_facts: (state -> thm list) -> state -> state
  val use_facts: state -> state
  val reset_facts: state -> state
  val is_chain: state -> bool
  val assert_forward: state -> state
  val assert_forward_or_chain: state -> state
  val assert_backward: state -> state
  val assert_no_chain: state -> state
  val enter_forward: state -> state
  val verbose: bool ref
  val pretty_state: int -> state -> Pretty.T list
  val pretty_goals: bool -> state -> Pretty.T list
  val level: state -> int
  type method
  val method: (thm list -> tactic) -> method
  val method_cases: (thm list -> thm -> (thm * (string * RuleCases.T) list) Seq.seq) -> method
  val refine: (context -> method) -> state -> state Seq.seq
  val refine_end: (context -> method) -> state -> state Seq.seq
  val match_bind: (string list * string) list -> state -> state
  val match_bind_i: (term list * term) list -> state -> state
  val let_bind: (string list * string) list -> state -> state
  val let_bind_i: (term list * term) list -> state -> state
  val simple_have_thms: string -> thm list -> state -> state
  val have_thmss: ((string * context attribute list) *
    (thm list * context attribute list) list) list -> state -> state
  val with_thmss: ((string * context attribute list) *
    (thm list * context attribute list) list) list -> state -> state
  val fix: (string list * string option) list -> state -> state
  val fix_i: (string list * typ option) list -> state -> state
  val assm: ProofContext.exporter
    -> ((string * context attribute list) * (string * (string list * string list)) list) list
    -> state -> state
  val assm_i: ProofContext.exporter
    -> ((string * context attribute list) * (term * (term list * term list)) list) list
    -> state -> state
  val assume:
    ((string * context attribute list) * (string * (string list * string list)) list) list
    -> state -> state
  val assume_i: ((string * context attribute list) * (term * (term list * term list)) list) list
    -> state -> state
  val presume:
    ((string * context attribute list) * (string * (string list * string list)) list) list
    -> state -> state
  val presume_i: ((string * context attribute list) * (term * (term list * term list)) list) list
    -> state -> state
  val def: string -> context attribute list -> string *  (string * string list) -> state -> state
  val def_i: string -> context attribute list -> string * (term * term list) -> state -> state
  val invoke_case: string * string option list * context attribute list -> state -> state
  val multi_theorem: string -> bstring * theory attribute list
    -> (xstring * context attribute list) option -> context attribute Locale.element list
    -> ((bstring * theory attribute list) * (string * (string list * string list)) list) list
    -> theory -> state
  val multi_theorem_i: string -> bstring * theory attribute list
    -> (string * context attribute list) option -> context attribute Locale.element_i list
    -> ((bstring * theory attribute list) * (term * (term list * term list)) list) list
    -> theory -> state
  val theorem: string
    -> (xstring * context attribute list) option -> context attribute Locale.element list
    -> bstring -> theory attribute list -> string * (string list * string list) -> theory -> state
  val theorem_i: string
    -> (string * context attribute list) option -> context attribute Locale.element_i list
    -> bstring -> theory attribute list -> term * (term list * term list) -> theory -> state
  val chain: state -> state
  val from_facts: thm list -> state -> state
  val show: (bool -> state -> state) -> (state -> state Seq.seq)
    -> ((string * context attribute list) * (string * (string list * string list)) list) list
    -> bool -> state -> state
  val show_i: (bool -> state -> state) -> (state -> state Seq.seq)
    -> ((string * context attribute list) * (term * (term list * term list)) list) list
    -> bool -> state -> state
  val have: (state -> state Seq.seq)
    -> ((string * context attribute list) * (string * (string list * string list)) list) list
    -> state -> state
  val have_i: (state -> state Seq.seq)
    -> ((string * context attribute list) * (term * (term list * term list)) list) list
    -> state -> state
  val at_bottom: state -> bool
  val local_qed: (state -> state Seq.seq)
    -> (context -> string * (string * thm list) list -> unit) * (context -> thm -> unit)
    -> state -> state Seq.seq
  val global_qed: (state -> state Seq.seq) -> state
    -> (theory * ((string * string) * (string * thm list) list)) Seq.seq
  val begin_block: state -> state
  val end_block: state -> state Seq.seq
  val next_block: state -> state
end;

signature PRIVATE_PROOF =
sig
  include PROOF
  val put_data: Object.kind -> ('a -> Object.T) -> 'a -> state -> state
end;

structure Proof: PRIVATE_PROOF =
struct


(** proof state **)

type context = ProofContext.context;


(* type goal *)

datatype kind =
  Theorem of string *                           (*theorem kind*)
    (bstring * theory attribute list) *         (*common result binding*)
    (string * context attribute list) option *  (*target locale*)
    theory attribute list list |                (*attributes of individual result binding*)
  Show of context attribute list list |         (*intermediate result, solving subgoal*)
  Have of context attribute list list;          (*intermediate result*)

fun common_name "" = "" | common_name a = " " ^ a;

fun kind_name _ (Theorem (s, (a, _), None, _)) = s ^ common_name a
  | kind_name sg (Theorem (s, (a, _), Some (name, _), _)) =
      s ^ common_name a ^ " (in " ^ Locale.cond_extern sg name ^ ")"
  | kind_name _ (Show _) = "show"
  | kind_name _ (Have _) = "have";

type goal =
 (kind *             (*result kind*)
  string list *      (*result names*)
  term list list) *  (*result statements*)
 (thm list *         (*use facts*)
  thm);              (*goal: subgoals ==> statement*)


(* type mode *)

datatype mode = Forward | ForwardChain | Backward;
val mode_name = (fn Forward => "state" | ForwardChain => "chain" | Backward => "prove");


(* datatype state *)

datatype node =
  Node of
   {context: context,
    facts: thm list option,
    mode: mode,
    goal: (goal * (state -> state Seq.seq)) option}
and state =
  State of
    node *              (*current*)
    node list;          (*parents wrt. block structure*)

fun make_node (context, facts, mode, goal) =
  Node {context = context, facts = facts, mode = mode, goal = goal};


exception STATE of string * state;

fun err_malformed name state =
  raise STATE (name ^ ": internal error -- malformed proof state", state);

fun check_result msg state sq =
  (case Seq.pull sq of
    None => raise STATE (msg, state)
  | Some s_sq => Seq.cons s_sq);


fun map_current f (State (Node {context, facts, mode, goal}, nodes)) =
  State (make_node (f (context, facts, mode, goal)), nodes);

fun init_state thy =
  State (make_node (ProofContext.init thy, None, Forward, None), []);



(** basic proof state operations **)

(* context *)

fun context_of (State (Node {context, ...}, _)) = context;
val theory_of = ProofContext.theory_of o context_of;
val sign_of = ProofContext.sign_of o context_of;

fun map_context f = map_current (fn (ctxt, facts, mode, goal) => (f ctxt, facts, mode, goal));

fun map_context_result f (state as State (Node {context, facts, mode, goal}, nodes)) =
  let val (context', result) = f context
  in (State (make_node (context', facts, mode, goal), nodes), result) end;


fun put_data kind f = map_context o ProofContext.put_data kind f;
val warn_extra_tfrees = map_context o ProofContext.warn_extra_tfrees o context_of;
val add_binds_i = map_context o ProofContext.add_binds_i;
val auto_bind_goal = map_context o ProofContext.auto_bind_goal;
val auto_bind_facts = map_context o ProofContext.auto_bind_facts;
val put_thms = map_context o ProofContext.put_thms;
val put_thmss = map_context o ProofContext.put_thmss;
val reset_thms = map_context o ProofContext.reset_thms;
val get_case = ProofContext.get_case o context_of;


(* facts *)

fun the_facts (State (Node {facts = Some facts, ...}, _)) = facts
  | the_facts state = raise STATE ("No current facts available", state);

fun the_fact state =
  (case the_facts state of
    [thm] => thm
  | _ => raise STATE ("Single fact expected", state));

fun assert_facts state = (the_facts state; state);
fun get_facts (State (Node {facts, ...}, _)) = facts;


val thisN = "this";

fun put_facts facts state =
  state
  |> map_current (fn (ctxt, _, mode, goal) => (ctxt, facts, mode, goal))
  |> (case facts of None => reset_thms thisN | Some ths => put_thms (thisN, ths));

val reset_facts = put_facts None;

fun these_factss (state, named_factss) =
  state
  |> put_thmss named_factss
  |> put_facts (Some (flat (map #2 named_factss)));


(* goal *)

local
  fun find i (state as State (Node {goal = Some goal, ...}, _)) = (context_of state, (i, goal))
    | find i (State (Node {goal = None, ...}, node :: nodes)) = find (i + 1) (State (node, nodes))
    | find _ (state as State (_, [])) = err_malformed "find_goal" state;
in val find_goal = find 0 end;

fun get_goal state =
  let val (ctxt, (_, ((_, x), _))) = find_goal state
  in (ctxt, x) end;

fun put_goal goal = map_current (fn (ctxt, facts, mode, _) => (ctxt, facts, mode, goal));

fun map_goal f g (State (Node {context, facts, mode, goal = Some goal}, nodes)) =
      State (make_node (f context, facts, mode, Some (g goal)), nodes)
  | map_goal f g (State (nd, node :: nodes)) =
      let val State (node', nodes') = map_goal f g (State (node, nodes))
      in map_context f (State (nd, node' :: nodes')) end
  | map_goal _ _ state = state;

fun goal_facts get state =
  state
  |> map_goal I (fn ((result, (_, thm)), f) => ((result, (get state, thm)), f));

fun use_facts state =
  state
  |> goal_facts the_facts
  |> reset_facts;


(* mode *)

fun get_mode (State (Node {mode, ...}, _)) = mode;
fun put_mode mode = map_current (fn (ctxt, facts, _, goal) => (ctxt, facts, mode, goal));

val enter_forward = put_mode Forward;
val enter_forward_chain = put_mode ForwardChain;
val enter_backward = put_mode Backward;

fun assert_mode pred state =
  let val mode = get_mode state in
    if pred mode then state
    else raise STATE ("Illegal application of proof command in "
      ^ quote (mode_name mode) ^ " mode", state)
  end;

fun is_chain state = get_mode state = ForwardChain;
val assert_forward = assert_mode (equal Forward);
val assert_forward_or_chain = assert_mode (equal Forward orf equal ForwardChain);
val assert_backward = assert_mode (equal Backward);
val assert_no_chain = assert_mode (not_equal ForwardChain);


(* blocks *)

fun level (State (_, nodes)) = length nodes;

fun open_block (State (node, nodes)) = State (node, node :: nodes);

fun new_block state =
  state
  |> open_block
  |> put_goal None;

fun close_block (state as State (_, node :: nodes)) = State (node, nodes)
  | close_block state = raise STATE ("Unbalanced block parentheses", state);



(** pretty_state **)

val verbose = ProofContext.verbose;

fun pretty_goals_local ctxt = Display.pretty_goals_aux
  (ProofContext.pretty_sort ctxt, ProofContext.pretty_typ ctxt, ProofContext.pretty_term ctxt);

fun pretty_facts _ _ None = []
  | pretty_facts s ctxt (Some ths) =
      [Pretty.big_list (s ^ "this:") (map (ProofContext.pretty_thm ctxt) ths), Pretty.str ""];

fun pretty_state nr (state as State (Node {context = ctxt, facts, mode, goal = _}, nodes)) =
  let
    val ref (_, _, begin_goal) = Display.current_goals_markers;

    fun levels_up 0 = ""
      | levels_up 1 = ", 1 level up"
      | levels_up i = ", " ^ string_of_int i ^ " levels up";

    fun subgoals 0 = ""
      | subgoals 1 = ", 1 subgoal"
      | subgoals n = ", " ^ string_of_int n ^ " subgoals";

    fun prt_names names =
      (case filter_out (equal "") names of [] => ""
      | nms => " " ^ enclose "(" ")" (space_implode " and " (take (7, nms) @
          (if length nms > 7 then ["..."] else []))));

    fun prt_goal (_, (i, (((kind, names, _), (goal_facts, thm)), _))) =
      pretty_facts "using " ctxt
        (if mode <> Backward orelse null goal_facts then None else Some goal_facts) @
      [Pretty.str ("goal (" ^ kind_name (sign_of state) kind ^ prt_names names ^
          levels_up (i div 2) ^ subgoals (Thm.nprems_of thm) ^ "):")] @
      pretty_goals_local ctxt begin_goal (true, true) (! Display.goals_limit) thm;

    val ctxt_prts =
      if ! verbose orelse mode = Forward then ProofContext.pretty_context ctxt
      else if mode = Backward then ProofContext.pretty_asms ctxt
      else [];

    val prts =
     [Pretty.str ("proof (" ^ mode_name mode ^ "): step " ^ string_of_int nr ^
        (if ! verbose then ", depth " ^ string_of_int (length nodes div 2 - 1)
        else "")), Pretty.str ""] @
     (if null ctxt_prts then [] else ctxt_prts @ [Pretty.str ""]) @
     (if ! verbose orelse mode = Forward then
       (pretty_facts "" ctxt facts @ prt_goal (find_goal state))
      else if mode = ForwardChain then pretty_facts "picking " ctxt facts
      else prt_goal (find_goal state))
  in prts end;

fun pretty_goals main state =
  let val (ctxt, (_, ((_, (_, thm)), _))) = find_goal state
  in pretty_goals_local ctxt "" (false, main) (! Display.goals_limit) thm end;



(** proof steps **)

(* datatype method *)

datatype method =
  Method of thm list -> thm -> (thm * (string * RuleCases.T) list) Seq.seq;

fun method tac = Method (fn facts => fn st => Seq.map (rpair []) (tac facts st));
val method_cases = Method;


(* refine goal *)

local

fun check_sign sg state =
  if Sign.subsig (sg, sign_of state) then state
  else raise STATE ("Bad signature of result: " ^ Sign.str_of_sg sg, state);

fun gen_refine current_context meth_fun state =
  let
    val (goal_ctxt, (_, ((result, (facts, thm)), f))) = find_goal state;
    val Method meth = meth_fun (if current_context then context_of state else goal_ctxt);

    fun refn (thm', cases) =
      state
      |> check_sign (Thm.sign_of_thm thm')
      |> map_goal (ProofContext.add_cases cases) (K ((result, (facts, thm')), f));
  in Seq.map refn (meth facts thm) end;

in

val refine = gen_refine true;
val refine_end = gen_refine false;

end;


(* goal addressing *)

fun FINDGOAL tac st =
  let fun find (i, n) = if i > n then Seq.fail else Seq.APPEND (tac i, find (i + 1, n))
  in find (1, Thm.nprems_of st) st end;

fun HEADGOAL tac = tac 1;


(* export results *)

fun refine_tac rule =
  Tactic.rtac rule THEN_ALL_NEW (SUBGOAL (fn (goal, i) =>
    if can Logic.dest_goal (Logic.strip_assums_concl goal) then
      Tactic.etac Drule.triv_goal i
    else all_tac));

fun export_goal inner print_rule raw_rule state =
  let
    val (outer, (_, ((result, (facts, thm)), f))) = find_goal state;
    val exp_tac = ProofContext.export true inner outer;
    fun exp_rule rule =
      let
        val _ = print_rule outer rule;
        val thmq = FINDGOAL (refine_tac rule) thm;
      in Seq.map (fn th => map_goal I (K ((result, (facts, th)), f)) state) thmq end;
  in raw_rule |> exp_tac |> (Seq.flat o Seq.map exp_rule) end;

fun export_goals inner print_rule raw_rules =
  Seq.EVERY (map (export_goal inner print_rule) raw_rules);

fun transfer_facts inner_state state =
  (case get_facts inner_state of
    None => Seq.single (reset_facts state)
  | Some thms =>
      let
        val exp_tac = ProofContext.export false (context_of inner_state) (context_of state);
        val thmqs = map exp_tac thms;
      in Seq.map (fn ths => put_facts (Some ths) state) (Seq.commute thmqs) end);


(* prepare result *)

fun prep_result state ts raw_th =
  let
    val ctxt = context_of state;
    fun err msg = raise STATE (msg, state);

    val ngoals = Thm.nprems_of raw_th;
    val _ =
      if ngoals = 0 then ()
      else (err (Pretty.string_of (Pretty.chunks (pretty_goals_local ctxt "" (true, true)
            (! Display.goals_limit) raw_th @
          [Pretty.str (string_of_int ngoals ^ " unsolved goal(s)!")]))));

    val {hyps, sign, ...} = Thm.rep_thm raw_th;
    val tsig = Sign.tsig_of sign;
    val casms = flat (map #1 (ProofContext.assumptions_of (context_of state)));
    val bad_hyps = Library.gen_rems Term.aconv (hyps, map Thm.term_of casms);

    val th = raw_th RS Drule.rev_triv_goal;
    val ths = Drule.conj_elim_precise (length ts) th
      handle THM _ => err "Main goal structure corrupted";
    val props = map (#prop o Thm.rep_thm) ths;
  in
    conditional (not (null bad_hyps)) (fn () => err ("Additional hypotheses:\n" ^
        cat_lines (map (ProofContext.string_of_term ctxt) bad_hyps)));
    conditional (exists (not o Pattern.matches tsig) (ts ~~ props)) (fn () =>
      err ("Proved a different theorem: " ^ Pretty.string_of (ProofContext.pretty_thm ctxt th)));
    ths
  end;



(*** structured proof commands ***)

(** context **)

(* bind *)

fun gen_bind f x state =
  state
  |> assert_forward
  |> map_context (f x)
  |> reset_facts;

val match_bind = gen_bind (ProofContext.match_bind false);
val match_bind_i = gen_bind (ProofContext.match_bind_i false);
val let_bind = gen_bind (ProofContext.match_bind true);
val let_bind_i = gen_bind (ProofContext.match_bind_i true);


(* have_thmss etc. *)

fun have_thmss args state =
  state
  |> assert_forward
  |> map_context_result (ProofContext.have_thmss args)
  |> these_factss;

fun simple_have_thms name thms = have_thmss [((name, []), [(thms, [])])];

fun with_thmss args state =
  let val state' = state |> have_thmss args
  in state' |> simple_have_thms "" (the_facts state' @ the_facts state) end;


(* fix *)

fun gen_fix f xs state =
  state
  |> assert_forward
  |> map_context (f xs)
  |> reset_facts;

val fix = gen_fix ProofContext.fix;
val fix_i = gen_fix ProofContext.fix_i;


(* assume and presume *)

fun gen_assume f exp args state =
  state
  |> assert_forward
  |> map_context_result (f exp args)
  |> these_factss;

val assm = gen_assume ProofContext.assume;
val assm_i = gen_assume ProofContext.assume_i;
val assume = assm ProofContext.export_assume;
val assume_i = assm_i ProofContext.export_assume;
val presume = assm ProofContext.export_presume;
val presume_i = assm_i ProofContext.export_presume;



(** local definitions **)

fun gen_def fix prep_term prep_pats raw_name atts (x, (raw_rhs, raw_pats)) state =
  let
    val _ = assert_forward state;
    val ctxt = context_of state;

    (*rhs*)
    val name = if raw_name = "" then Thm.def_name x else raw_name;
    val rhs = prep_term ctxt raw_rhs;
    val T = Term.fastype_of rhs;
    val pats = prep_pats T (ProofContext.declare_term rhs ctxt) raw_pats;

    (*lhs*)
    val lhs = ProofContext.bind_skolem ctxt [x] (Free (x, T));
  in
    state
    |> fix [([x], None)]
    |> match_bind_i [(pats, rhs)]
    |> assm_i ProofContext.export_def [((name, atts), [(Logic.mk_equals (lhs, rhs), ([], []))])]
  end;

val def = gen_def fix ProofContext.read_term ProofContext.read_term_pats;
val def_i = gen_def fix_i ProofContext.cert_term ProofContext.cert_term_pats;


(* invoke_case *)

fun invoke_case (name, xs, atts) state =
  let
    val (state', (lets, asms)) =
      map_context_result (ProofContext.apply_case (get_case state name xs)) state;
  in
    state'
    |> add_binds_i lets
    |> assume_i [((name, atts), map (rpair ([], [])) asms)]
  end;



(** goals **)

(* forward chaining *)

fun chain state =
  state
  |> assert_forward
  |> assert_facts
  |> enter_forward_chain;

fun from_facts facts state =
  state
  |> put_facts (Some facts)
  |> chain;


(* setup goals *)

val rule_contextN = "rule_context";

fun setup_goal opt_block prepp autofix kind after_qed names raw_propss state =
  let
    val (state', (propss, gen_binds)) =
      state
      |> assert_forward_or_chain
      |> enter_forward
      |> opt_block
      |> map_context_result (fn ctxt => prepp (ctxt, raw_propss));

    val props = flat propss;
    val cprop = Thm.cterm_of (sign_of state') (foldr1 Logic.mk_conjunction props);
    val goal = Drule.mk_triv_goal cprop;

    val tvars = foldr Term.add_term_tvars (props, []);
    val vars = foldr Term.add_term_vars (props, []);
  in
    if null tvars then ()
    else raise STATE ("Goal statement contains illegal schematic type variable(s): " ^
      commas (map (Syntax.string_of_vname o #1) tvars), state);
    if null vars then ()
    else warning ("Goal statement contains unbound schematic variable(s): " ^
      commas (map (ProofContext.string_of_term (context_of state')) vars));
    state'
    |> map_context (autofix props)
    |> put_goal (Some (((kind, names, propss), ([], goal)), after_qed o map_context gen_binds))
    |> map_context (ProofContext.add_cases
     (if length props = 1 then RuleCases.make true goal [rule_contextN]
      else [(rule_contextN, RuleCases.empty)]))
    |> auto_bind_goal props
    |> (if is_chain state then use_facts else reset_facts)
    |> new_block
    |> enter_backward
  end;

(*global goals*)
fun global_goal prepp prep_locale activate kind a raw_locale elems args thy =
  let
    val st = thy |> init_state |> open_block;
    val (locale_ctxt, elems_ctxt) = context_of st |> activate
      ((case raw_locale of None => Locale.empty | Some (name, _) => Locale.Locale name), elems);
    val locale = apsome (apfst (prep_locale (Theory.sign_of thy))) raw_locale;
  in
    st
    |> map_context (K locale_ctxt)
    |> open_block
    |> map_context (K elems_ctxt)
    |> setup_goal I prepp ProofContext.fix_frees (Theorem (kind, a, locale, map (snd o fst) args))
      Seq.single (map (fst o fst) args) (map snd args)
  end;

val multi_theorem =
  global_goal ProofContext.bind_propp_schematic Locale.intern Locale.activate_context;
val multi_theorem_i =
  global_goal ProofContext.bind_propp_schematic_i (K I) Locale.activate_context_i;

fun theorem k locale elems name atts p =
  multi_theorem k (name, atts) locale elems [(("", []), [p])];
fun theorem_i k locale elems name atts p =
  multi_theorem_i k (name, atts) locale elems [(("", []), [p])];


(*local goals*)
fun local_goal' prepp kind (check: bool -> state -> state) f args int state =
  state
  |> setup_goal open_block prepp (K I) (kind (map (snd o fst) args))
    f (map (fst o fst) args) (map snd args)
  |> warn_extra_tfrees state
  |> check int;

fun local_goal prepp kind f args = local_goal' prepp kind (K I) f args false;

val show = local_goal' ProofContext.bind_propp Show;
val show_i = local_goal' ProofContext.bind_propp_i Show;
val have = local_goal ProofContext.bind_propp Have;
val have_i = local_goal ProofContext.bind_propp_i Have;



(** conclusions **)

(* current goal *)

fun current_goal (State (Node {context, goal = Some goal, ...}, _)) = (context, goal)
  | current_goal state = raise STATE ("No current goal!", state);

fun assert_current_goal true (state as State (Node {goal = None, ...}, _)) =
      raise STATE ("No goal in this block!", state)
  | assert_current_goal false (state as State (Node {goal = Some _, ...}, _)) =
      raise STATE ("Goal present in this block!", state)
  | assert_current_goal _ state = state;

fun assert_bottom b (state as State (_, nodes)) =
  let val bot = (length nodes <= 2) in
    if b andalso not bot then raise STATE ("Not at bottom of proof!", state)
    else if not b andalso bot then raise STATE ("Already at bottom of proof!", state)
    else state
  end;

val at_bottom = can (assert_bottom true o close_block);

fun end_proof bot state =
  state
  |> assert_forward
  |> close_block
  |> assert_bottom bot
  |> assert_current_goal true
  |> goal_facts (K []);


(* local_qed *)

fun finish_local (print_result, print_rule) state =
  let
    val (goal_ctxt, (((kind, names, tss), (_, raw_thm)), after_qed)) = current_goal state;
    val outer_state = state |> close_block;
    val outer_ctxt = context_of outer_state;

    val ts = flat tss;
    val results = prep_result state ts raw_thm;
    val resultq =
      results |> map (ProofContext.export false goal_ctxt outer_ctxt)
      |> Seq.commute |> Seq.map (Library.unflat tss);

    val (attss, opt_solve) =
      (case kind of
        Show attss => (attss, export_goals goal_ctxt print_rule results)
      | Have attss => (attss, Seq.single)
      | _ => err_malformed "finish_local" state);
  in
    print_result goal_ctxt (kind_name (sign_of state) kind, names ~~ Library.unflat tss results);
    outer_state
    |> auto_bind_facts (map (ProofContext.generalize goal_ctxt outer_ctxt) ts)
    |> (fn st => Seq.map (fn res =>
      have_thmss ((names ~~ attss) ~~ map (single o Thm.no_attributes) res) st) resultq)
    |> (Seq.flat o Seq.map opt_solve)
    |> (Seq.flat o Seq.map after_qed)
  end;

fun local_qed finalize print state =
  state
  |> end_proof false
  |> finalize
  |> (Seq.flat o Seq.map (finish_local print));


(* global_qed *)

fun locale_prefix None f thy = f thy
  | locale_prefix (Some (loc, _)) f thy =
      thy |> Theory.add_path (Sign.base_name loc) |> f |>> Theory.parent_path;

fun locale_add_thmss None _ = I
  | locale_add_thmss (Some (loc, atts)) ths = Locale.add_thmss loc (map (rpair atts) ths);

fun finish_global state =
  let
    fun export inner outer th =
      (case Seq.pull (ProofContext.export false inner outer th) of
        Some (th', _) => th' |> Drule.local_standard
      | None => raise STATE ("Internal failure of theorem export", state));

    val (goal_ctxt, (((kind, names, tss), (_, raw_thm)), _)) = current_goal state;
    val locale_ctxt = context_of (state |> close_block);
    val theory_ctxt = context_of (state |> close_block |> close_block);

    val ts = flat tss;
    val locale_results =
      prep_result state ts raw_thm |> map (export goal_ctxt locale_ctxt);
    val results = locale_results
      |> map (Drule.strip_shyps_warning o export locale_ctxt theory_ctxt);

    val (k, (cname, catts), locale, attss) =
      (case kind of Theorem x => x | _ => err_malformed "finish_global" state);
    val (thy1, res') =
      theory_of state
      |> locale_prefix locale (PureThy.have_thmss [Drule.kind k]
          ((names ~~ attss) ~~ map (single o Thm.no_attributes) (Library.unflat tss results)))
      |>> locale_add_thmss locale (names ~~ Library.unflat tss locale_results);
    val thy2 = thy1 |> PureThy.add_thmss [((cname, flat (map #2 res')), catts)] |> #1;
  in (thy2, ((k, cname), res')) end;

(*note: clients should inspect first result only, as backtracking may destroy theory*)
fun global_qed finalize state =
  state
  |> end_proof true
  |> finalize
  |> Seq.map finish_global;



(** blocks **)

(* begin_block *)

fun begin_block state =
  state
  |> assert_forward
  |> new_block
  |> open_block;


(* end_block *)

fun end_block state =
  state
  |> assert_forward
  |> close_block
  |> assert_current_goal false
  |> close_block
  |> transfer_facts state;


(* next_block *)

fun next_block state =
  state
  |> assert_forward
  |> close_block
  |> new_block
  |> reset_facts;


end;

structure BasicProof: BASIC_PROOF = Proof;
open BasicProof;