(*  Title:      Pure/Isar/context_rules.ML

     ID:         $Id$

     Author:     Stefan Berghofer and Markus Wenzel, TU Muenchen

 Declarations of intro/elim/dest rules in Pure (see also

 Provers/classical.ML for a more specialized version of the same idea).

 *)

 signature CONTEXT_RULES =

 sig

   type netpair

   type T

   val netpair_bang: Proof.context -> netpair

   val netpair: Proof.context -> netpair

   val orderlist: ((int * int) * 'a) list -> 'a list

   val find_rules_netpair: bool -> thm list -> term -> netpair -> thm list

   val find_rules: bool -> thm list -> term -> Proof.context -> thm list list

   val print_rules: Proof.context -> unit

   val addSWrapper: ((int -> tactic) -> int -> tactic) -> theory -> theory

   val addWrapper: ((int -> tactic) -> int -> tactic) -> theory -> theory

   val Swrap: Proof.context -> (int -> tactic) -> int -> tactic

   val wrap: Proof.context -> (int -> tactic) -> int -> tactic

   val intro_bang: int option -> attribute

   val elim_bang: int option -> attribute

   val dest_bang: int option -> attribute

   val intro: int option -> attribute

   val elim: int option -> attribute

   val dest: int option -> attribute

   val intro_query: int option -> attribute

   val elim_query: int option -> attribute

   val dest_query: int option -> attribute

   val rule_del: attribute

   val add_args:

     (int option -> attribute) -> (int option -> attribute) -> (int option -> attribute) ->

     Attrib.src -> attribute

 end;

 structure ContextRules: CONTEXT_RULES =

 struct

 (** rule declaration contexts **)

 (* rule kinds *)

 val intro_bangK = (0, false);

 val elim_bangK = (0, true);

 val introK = (1, false);

 val elimK = (1, true);

 val intro_queryK = (2, false);

 val elim_queryK = (2, true);

 val kind_names =

  [(intro_bangK, "safe introduction rules (intro!)"),

   (elim_bangK, "safe elimination rules (elim!)"),

   (introK, "introduction rules (intro)"),

   (elimK, "elimination rules (elim)"),

   (intro_queryK, "extra introduction rules (intro?)"),

   (elim_queryK, "extra elimination rules (elim?)")];

 val rule_kinds = map #1 kind_names;

 val rule_indexes = distinct (op =) (map #1 rule_kinds);

 (* context data *)

 type netpair = ((int * int) * (bool * thm)) Net.net * ((int * int) * (bool * thm)) Net.net;

 val empty_netpairs: netpair list = replicate (length rule_indexes) (Net.empty, Net.empty);

 datatype T = Rules of

  {next: int,

   rules: (int * ((int * bool) * thm)) list,

   netpairs: netpair list,

   wrappers: (((int -> tactic) -> int -> tactic) * stamp) list *

     (((int -> tactic) -> int -> tactic) * stamp) list};

 fun make_rules next rules netpairs wrappers =

   Rules {next = next, rules = rules, netpairs = netpairs, wrappers = wrappers};

 fun add_rule (i, b) opt_w th (Rules {next, rules, netpairs, wrappers}) =

   let val w = (case opt_w of SOME w => w | NONE => Tactic.subgoals_of_brl (b, th)) in

     make_rules (next - 1) ((w, ((i, b), th)) :: rules)

       (nth_map i (Tactic.insert_tagged_brl ((w, next), (b, th))) netpairs) wrappers

   end;

 fun del_rule th (rs as Rules {next, rules, netpairs, wrappers}) =

   let

     fun eq_th (_, (_, th')) = Thm.eq_thm_prop (th, th');

     fun del b netpair = Tactic.delete_tagged_brl (b, th) netpair handle Net.DELETE => netpair;

   in

     if not (exists eq_th rules) then rs

     else make_rules next (filter_out eq_th rules) (map (del false o del true) netpairs) wrappers

   end;

 structure Rules = GenericDataFun

 (

   type T = T;

   val empty = make_rules ~1 [] empty_netpairs ([], []);

   val extend = I;

   fun merge _ (Rules {rules = rules1, wrappers = (ws1, ws1'), ...},

       Rules {rules = rules2, wrappers = (ws2, ws2'), ...}) =

     let

       val wrappers =

         (Library.merge (eq_snd (op =)) (ws1, ws2), Library.merge (eq_snd (op =)) (ws1', ws2'));

       val rules = Library.merge (fn ((_, (k1, th1)), (_, (k2, th2))) =>

           k1 = k2 andalso Thm.eq_thm_prop (th1, th2)) (rules1, rules2);

       val next = ~ (length rules);

       val netpairs = fold (fn (n, (w, ((i, b), th))) =>

           nth_map i (Tactic.insert_tagged_brl ((w, n), (b, th))))

         (next upto ~1 ~~ rules) empty_netpairs;

     in make_rules (next - 1) rules netpairs wrappers end;

 );

 fun print_rules ctxt =

   let

     val Rules {rules, ...} = Rules.get (Context.Proof ctxt);

     fun prt_kind (i, b) =

       Pretty.big_list ((the o AList.lookup (op =) kind_names) (i, b) ^ ":")

         (map_filter (fn (_, (k, th)) =>

             if k = (i, b) then SOME (ProofContext.pretty_thm ctxt th) else NONE)

           (sort (int_ord o pairself fst) rules));

   in Pretty.writeln (Pretty.chunks (map prt_kind rule_kinds)) end;

 (* access data *)

 fun netpairs ctxt = let val Rules {netpairs, ...} = Rules.get (Context.Proof ctxt) in netpairs end;

 val netpair_bang = hd o netpairs;

 val netpair = hd o tl o netpairs;

 (* retrieving rules *)

 fun untaglist [] = []

   | untaglist [(k : int * int, x)] = [x]

   | untaglist ((k, x) :: (rest as (k', x') :: _)) =

       if k = k' then untaglist rest

       else x :: untaglist rest;

 fun orderlist brls =

   untaglist (sort (prod_ord int_ord int_ord o pairself fst) brls);

 fun orderlist_no_weight brls =

   untaglist (sort (int_ord o pairself (snd o fst)) brls);

 fun may_unify weighted t net =

   map snd ((if weighted then orderlist else orderlist_no_weight) (Net.unify_term net t));

 fun find_erules _ [] = K []

   | find_erules w (fact :: _) = may_unify w (Logic.strip_assums_concl (Thm.prop_of fact));

 fun find_irules w goal = may_unify w (Logic.strip_assums_concl goal);

 fun find_rules_netpair weighted facts goal (inet, enet) =

   find_erules weighted facts enet @ find_irules weighted goal inet;

 fun find_rules weighted facts goals =

   map (find_rules_netpair weighted facts goals) o netpairs;

 (* wrappers *)

 fun gen_add_wrapper upd w =

   Context.theory_map (Rules.map (fn (rs as Rules {next, rules, netpairs, wrappers}) =>

     make_rules next rules netpairs (upd (fn ws => (w, stamp ()) :: ws) wrappers)));

 val addSWrapper = gen_add_wrapper Library.apfst;

 val addWrapper = gen_add_wrapper Library.apsnd;

 fun gen_wrap which ctxt =

   let val Rules {wrappers, ...} = Rules.get (Context.Proof ctxt)

   in fold_rev fst (which wrappers) end;

 val Swrap = gen_wrap #1;

 val wrap = gen_wrap #2;

 (** attributes **)

 (* add and del rules *)

 fun rule_del (x, th) =

   (Rules.map (del_rule th o del_rule (Tactic.make_elim th)) x, th);

 fun rule_add k view opt_w =

   (fn (x, th) => (Rules.map (add_rule k opt_w (view th)) x, th)) o rule_del;

 val intro_bang  = rule_add intro_bangK I;

 val elim_bang   = rule_add elim_bangK I;

 val dest_bang   = rule_add elim_bangK Tactic.make_elim;

 val intro       = rule_add introK I;

 val elim        = rule_add elimK I;

 val dest        = rule_add elimK Tactic.make_elim;

 val intro_query = rule_add intro_queryK I;

 val elim_query  = rule_add elim_queryK I;

 val dest_query  = rule_add elim_queryK Tactic.make_elim;

 val _ = Context.>> (Context.map_theory

   (snd o PureThy.add_thms [(("", Drule.equal_intr_rule), [intro_query NONE])]));

 (* concrete syntax *)

 fun add_args a b c = Attrib.syntax

   (Scan.lift ((Args.bang >> K a || Args.query >> K c || Scan.succeed b) --

     Scan.option OuterParse.nat) >> (fn (f, n) => f n));

 val rule_atts =

  [("intro", add_args intro_bang intro intro_query, "declaration of introduction rule"),

   ("elim", add_args elim_bang elim elim_query, "declaration of elimination rule"),

   ("dest", add_args dest_bang dest dest_query, "declaration of destruction rule"),

   ("rule", Attrib.syntax (Scan.lift Args.del >> K rule_del),

     "remove declaration of intro/elim/dest rule")];

 val _ = Context.>> (Context.map_theory (Attrib.add_attributes rule_atts));

 end;