(* Title: ../contextC.sml

    Author: Walther Neuper, Mathias Lehnfeld

    (c) due to copyright terms

 *)

 (* Extension to Isabelle's naming conventions: "C" indicates Isac add-ons to an Isabelle module *)

 signature CONTEXT_C =

 sig

   val empty : Proof.context

   val is_empty : Proof.context -> bool

   val for_ERROR: 'a -> Proof.context

   val declare_constraints: term -> Proof.context -> Proof.context

   val add_constraints: term list -> Proof.context -> Proof.context

   val init_while_parsing: Formalise.model -> theory -> term list * Proof.context

   val init_for_prog: Proof.context -> term list -> Proof.context

   val get_assumptions : Proof.context -> term list

   val insert_assumptions : term list -> Proof.context -> Proof.context

   val avoid_contradict: term -> term list -> term * term list

   val subpbl_to_caller : Proof.context -> term -> Proof.context -> term * Proof.context

 \<^isac_test>\<open>

   val transfer_asms_from_to : Proof.context -> Proof.context -> Proof.context

   val contradict : term list -> term -> bool

   val insert_assumptions_cao : Proof.context -> term list -> Proof.context

 \<close>

 end

 structure ContextC(**) : CONTEXT_C(**) =

 struct

 val empty = Proof_Context.init_global @{theory "Pure"};

 (* ATTENTION: does _not_ recognise Variable.declare_constraints, etc...*)

 fun is_empty ctxt = Context.eq_thy (Proof_Context.theory_of ctxt, @{theory "Pure"});

 fun for_ERROR _ = "Isac_Knowledge" |> Know_Store.get_via_last_thy |> Proof_Context.init_global

 val declare_constraints = Variable.declare_constraints

 fun add_constraints ts ctxt =

   fold Variable.declare_constraints (TermC.vars' ts) ctxt

 fun build_while_parsing_ [] (ts, ctxt) = (ts, ctxt)

   | build_while_parsing_ (str :: strs) (ts, ctxt) = 

     let

       val t as (_ $ tm) = Syntax.read_term ctxt str

         handle ERROR msg => raise ERROR ("ContextC.init_while_parsing " ^ quote str ^ " " ^ msg)

       val vars = TermC.vars tm

       val ctxt' = add_constraints vars ctxt

     in build_while_parsing_ strs (ts @ [t], ctxt') end

 (* shouldn't that be done by fold ?

    fn: string * Proof.context -> term list * Proof.context -> term list * Proof.context *)

 fun init_while_parsing strs thy = build_while_parsing_ strs ([], Proof_Context.init_global thy)

 (* in Subproblem take respective actual arguments from program *)

 fun init_for_prog ctxt ts =

   let

     val frees = TermC.vars' ts

     val _ = TermC.raise_type_conflicts frees

   in

     fold Variable.declare_constraints frees ctxt

   end

 structure Context_Data = Proof_Data (type T = term list fun init _ = []);

 fun get_assumptions ctxt = Context_Data.get ctxt

 fun insert_assumptions asms = Context_Data.map (fn xs => distinct op = (asms @ xs))

 (* 

   transfer assumptions from one to another ctxt.

   does NOT respect scope: in a calculation identifiers are unique.

   but environments are scoped as usual in Luacs-interpretation.

 *)

 fun transfer_asms_from_to from_ctxt to_ctxt =

   let

     val to_vars = get_assumptions to_ctxt |> map TermC.vars |> flat

     fun transfer [] to_ctxt = to_ctxt

       | transfer (from_asm :: fas) to_ctxt =

           if inter op = (TermC.vars from_asm) to_vars = []

           then transfer fas to_ctxt

           else transfer fas (insert_assumptions [from_asm] to_ctxt)

   in

     transfer (get_assumptions from_ctxt) to_ctxt

   end

 (* there is still much TODO: factorise polynomials, etc *)

 fun contradict asm res = fold (curry or_) (map (fn p => TermC.negates res p) asm) false;

 (*

   Check a term for contradiction with a predicate list.

   This makes only sense for types bool and bool list. In these cases return

   the probably updated term together with 

   a respective list of non-contradicting predicates

 *)

 fun avoid_contradict t preds = 

   if TermC.is_bool_list t then

     let

       val no_contra = t |> TermC.dest_list' |> filter_out (contradict preds)

     in

       (no_contra |> TermC.list2isalist HOLogic.boolT, no_contra)

     end

   else if Term.type_of t = HOLogic.boolT then

     if contradict preds t then (@{term bool_undef}, []) else (t, [t])

   else (t (* type_of t \<noteq> bool *), [(* no predicate to add *)])

 (* for Canonical Argument Order used by |> below *)

 fun insert_assumptions_cao ctxt tms  = insert_assumptions tms ctxt

 fun subpbl_to_caller sub_ctxt expr_val caller_ctxt = caller_ctxt

   |> get_assumptions 

   |> avoid_contradict expr_val

   |> apsnd (insert_assumptions_cao caller_ctxt)

   |> apsnd (transfer_asms_from_to sub_ctxt)

 end