(*  Nominal Mutual Functions

    Author:  Christian Urban

    heavily based on the code of Alexander Krauss

    (code forked on 14 January 2011)

Mutual recursive nominal function definitions.

*)

signature NOMINAL_FUNCTION_MUTUAL =

sig

  val prepare_nominal_function_mutual : Nominal_Function_Common.nominal_function_config

    -> string (* defname *)

    -> ((string * typ) * mixfix) list

    -> term list

    -> local_theory

    -> ((thm (* goalstate *)

        * (thm -> Function_Common.function_result) (* proof continuation *)

       ) * local_theory)

end

structure Nominal_Function_Mutual: NOMINAL_FUNCTION_MUTUAL =

struct

open Function_Lib

open Function_Common

open Nominal_Function_Common

type qgar = string * (string * typ) list * term list * term list * term

datatype mutual_part = MutualPart of

 {i : int,

  i' : int,

  fvar : string * typ,

  cargTs: typ list,

  f_def: term,

  f: term option,

  f_defthm : thm option}

datatype mutual_info = Mutual of

 {n : int,

  n' : int,

  fsum_var : string * typ,

  ST: typ,

  RST: typ,

  parts: mutual_part list,

  fqgars: qgar list,

  qglrs: ((string * typ) list * term list * term * term) list,

  fsum : term option}

fun mutual_induct_Pnames n =

  if n < 5 then fst (chop n ["P","Q","R","S"])

  else map (fn i => "P" ^ string_of_int i) (1 upto n)

fun get_part fname =

  the o find_first (fn (MutualPart {fvar=(n,_), ...}) => n = fname)

(* FIXME *)

fun mk_prod_abs e (t1, t2) =

  let

    val bTs = rev (map snd e)

    val T1 = fastype_of1 (bTs, t1)

    val T2 = fastype_of1 (bTs, t2)

  in

    HOLogic.pair_const T1 T2 $ t1 $ t2

  end

fun analyze_eqs ctxt defname fs eqs =

  let

    val num = length fs

    val fqgars = map (split_def ctxt (K true)) eqs

    val arity_of = map (fn (fname,_,_,args,_) => (fname, length args)) fqgars

      |> AList.lookup (op =) #> the

    fun curried_types (fname, fT) =

      let

        val (caTs, uaTs) = chop (arity_of fname) (binder_types fT)

      in

        (caTs, uaTs ---> body_type fT)

      end

    val (caTss, resultTs) = split_list (map curried_types fs)

    val argTs = map (foldr1 HOLogic.mk_prodT) caTss

    val dresultTs = distinct (op =) resultTs

    val n' = length dresultTs

    val RST = Balanced_Tree.make (uncurry SumTree.mk_sumT) dresultTs

    val ST = Balanced_Tree.make (uncurry SumTree.mk_sumT) argTs

    val fsum_type = ST --> RST

    val ([fsum_var_name], _) = Variable.add_fixes [ defname ^ "_sum" ] ctxt

    val fsum_var = (fsum_var_name, fsum_type)

    fun define (fvar as (n, _)) caTs resultT i =

      let

        val vars = map_index (fn (j,T) => Free ("x" ^ string_of_int j, T)) caTs (* FIXME: Bind xs properly *)

        val i' = find_index (fn Ta => Ta = resultT) dresultTs + 1

        val f_exp = SumTree.mk_proj RST n' i' (Free fsum_var $ SumTree.mk_inj ST num i (foldr1 HOLogic.mk_prod vars))

        val def = Term.abstract_over (Free fsum_var, fold_rev lambda vars f_exp)

        val rew = (n, fold_rev lambda vars f_exp)

      in

        (MutualPart {i=i, i'=i', fvar=fvar,cargTs=caTs,f_def=def,f=NONE,f_defthm=NONE}, rew)

      end

    val (parts, rews) = split_list (map4 define fs caTss resultTs (1 upto num))

    fun convert_eqs (f, qs, gs, args, rhs) =

      let

        val MutualPart {i, i', ...} = get_part f parts

        val rhs' = rhs

             |> map_aterms (fn t as Free (n, _) => the_default t (AList.lookup (op =) rews n) | t => t)

      in

        (qs, gs, SumTree.mk_inj ST num i (foldr1 (mk_prod_abs qs) args),

         Envir.beta_norm (SumTree.mk_inj RST n' i' rhs'))

      end

    val qglrs = map convert_eqs fqgars

  in

    Mutual {n=num, n'=n', fsum_var=fsum_var, ST=ST, RST=RST,

      parts=parts, fqgars=fqgars, qglrs=qglrs, fsum=NONE}

  end

fun define_projections fixes mutual fsum lthy =

  let

    fun def ((MutualPart {i=i, i'=i', fvar=(fname, fT), cargTs, f_def, ...}), (_, mixfix)) lthy =

      let

        val ((f, (_, f_defthm)), lthy') =

          Local_Theory.define

            ((Binding.name fname, mixfix),

              ((Binding.conceal (Binding.name (fname ^ "_def")), []),

              Term.subst_bound (fsum, f_def))) lthy

      in

        (MutualPart {i=i, i'=i', fvar=(fname, fT), cargTs=cargTs, f_def=f_def,

           f=SOME f, f_defthm=SOME f_defthm },

         lthy')

      end

    val Mutual { n, n', fsum_var, ST, RST, parts, fqgars, qglrs, ... } = mutual

    val (parts', lthy') = fold_map def (parts ~~ fixes) lthy

  in

    (Mutual { n=n, n'=n', fsum_var=fsum_var, ST=ST, RST=RST, parts=parts',

       fqgars=fqgars, qglrs=qglrs, fsum=SOME fsum },

     lthy')

  end

fun in_context ctxt (f, pre_qs, pre_gs, pre_args, pre_rhs) F =

  let

    val thy = ProofContext.theory_of ctxt

    val oqnames = map fst pre_qs

    val (qs, _) = Variable.variant_fixes oqnames ctxt

      |>> map2 (fn (_, T) => fn n => Free (n, T)) pre_qs

    fun inst t = subst_bounds (rev qs, t)

    val gs = map inst pre_gs

    val args = map inst pre_args

    val rhs = inst pre_rhs

    val cqs = map (cterm_of thy) qs

    val ags = map (Thm.assume o cterm_of thy) gs

    val import = fold Thm.forall_elim cqs

      #> fold Thm.elim_implies ags

    val export = fold_rev (Thm.implies_intr o cprop_of) ags

      #> fold_rev forall_intr_rename (oqnames ~~ cqs)

  in

    F ctxt (f, qs, gs, args, rhs) import export

  end

fun recover_mutual_psimp all_orig_fdefs parts ctxt (fname, _, _, args, rhs)

  import (export : thm -> thm) sum_psimp_eq =

  let

    val (MutualPart {f=SOME f, ...}) = get_part fname parts

    val psimp = import sum_psimp_eq

    val (simp, restore_cond) =

      case cprems_of psimp of

        [] => (psimp, I)

      | [cond] => (Thm.implies_elim psimp (Thm.assume cond), Thm.implies_intr cond)

      | _ => raise General.Fail "Too many conditions"

  in

    Goal.prove ctxt [] []

      (HOLogic.Trueprop $ HOLogic.mk_eq (list_comb (f, args), rhs))

      (fn _ => (Local_Defs.unfold_tac ctxt all_orig_fdefs)

         THEN EqSubst.eqsubst_tac ctxt [0] [simp] 1

         THEN (simp_tac (simpset_of ctxt)) 1) (* FIXME: global simpset?!! *)

    |> restore_cond

    |> export

  end

fun mk_applied_form ctxt caTs thm =

  let

    val thy = ProofContext.theory_of ctxt

    val xs = map_index (fn (i,T) => cterm_of thy (Free ("x" ^ string_of_int i, T))) caTs (* FIXME: Bind xs properly *)

  in

    fold (fn x => fn thm => Thm.combination thm (Thm.reflexive x)) xs thm

    |> Conv.fconv_rule (Thm.beta_conversion true)

    |> fold_rev Thm.forall_intr xs

    |> Thm.forall_elim_vars 0

  end

fun mutual_induct_rules lthy induct all_f_defs (Mutual {n, ST, parts, ...}) =

  let

    val cert = cterm_of (ProofContext.theory_of lthy)

    val newPs =

      map2 (fn Pname => fn MutualPart {cargTs, ...} =>

          Free (Pname, cargTs ---> HOLogic.boolT))

        (mutual_induct_Pnames (length parts)) parts

    fun mk_P (MutualPart {cargTs, ...}) P =

      let

        val avars = map_index (fn (i,T) => Var (("a", i), T)) cargTs

        val atup = foldr1 HOLogic.mk_prod avars

      in

        HOLogic.tupled_lambda atup (list_comb (P, avars))

      end

    val Ps = map2 mk_P parts newPs

    val case_exp = SumTree.mk_sumcases HOLogic.boolT Ps

    val induct_inst =

      Thm.forall_elim (cert case_exp) induct

      |> full_simplify SumTree.sumcase_split_ss

      |> full_simplify (HOL_basic_ss addsimps all_f_defs)

    fun project rule (MutualPart {cargTs, i, ...}) k =

      let

        val afs = map_index (fn (j,T) => Free ("a" ^ string_of_int (j + k), T)) cargTs (* FIXME! *)

        val inj = SumTree.mk_inj ST n i (foldr1 HOLogic.mk_prod afs)

      in

        (rule

         |> Thm.forall_elim (cert inj)

         |> full_simplify SumTree.sumcase_split_ss

         |> fold_rev (Thm.forall_intr o cert) (afs @ newPs),

         k + length cargTs)

      end

  in

    fst (fold_map (project induct_inst) parts 0)

  end

fun mk_partial_rules_mutual lthy inner_cont (m as Mutual {parts, fqgars, ...}) proof =

  let

    val result = inner_cont proof

    val FunctionResult {G, R, cases, psimps, simple_pinducts=[simple_pinduct],

      termination, domintros, ...} = result

    val (all_f_defs, fs) =

      map (fn MutualPart {f_defthm = SOME f_def, f = SOME f, cargTs, ...} =>

        (mk_applied_form lthy cargTs (Thm.symmetric f_def), f))

      parts

      |> split_list

    val all_orig_fdefs =

      map (fn MutualPart {f_defthm = SOME f_def, ...} => f_def) parts

    fun mk_mpsimp fqgar sum_psimp =

      in_context lthy fqgar (recover_mutual_psimp all_orig_fdefs parts) sum_psimp

    val rew_ss = HOL_basic_ss addsimps all_f_defs

    val mpsimps = map2 mk_mpsimp fqgars psimps

    val minducts = mutual_induct_rules lthy simple_pinduct all_f_defs m

    val mtermination = full_simplify rew_ss termination

    val mdomintros = Option.map (map (full_simplify rew_ss)) domintros

  in

    FunctionResult { fs=fs, G=G, R=R,

      psimps=mpsimps, simple_pinducts=minducts,

      cases=cases, termination=mtermination,

      domintros=mdomintros}

  end

(* nominal *)

fun prepare_nominal_function_mutual config defname fixes eqss lthy =

  let

    val mutual as Mutual {fsum_var=(n, T), qglrs, ...} =

      analyze_eqs lthy defname (map fst fixes) (map Envir.beta_eta_contract eqss)

    val ((fsum, goalstate, cont), lthy') =

      Nominal_Function_Core.prepare_nominal_function config defname [((n, T), NoSyn)] qglrs lthy

    val (mutual', lthy'') = define_projections fixes mutual fsum lthy'

    val mutual_cont = mk_partial_rules_mutual lthy'' cont mutual'

  in

    ((goalstate, mutual_cont), lthy'')

  end

end