(*  Nominal Mutual Functions

    Author:  Christian Urban

    heavily based on the code of Alexander Krauss

    (code forked on 14 January 2011)

Main entry points to the nominal function package.

*)

signature NOMINAL_FUNCTION =

sig

  include FUNCTION_DATA

  val add_nominal_function: (binding * typ option * mixfix) list ->

    (Proof.context -> tactic) -> local_theory -> info * local_theory

  val add_nominal_function_cmd: (binding * string option * mixfix) list ->

    (Proof.context -> tactic) -> local_theory -> info * local_theory

  val nominal_function: (binding * typ option * mixfix) list ->

    local_theory -> Proof.state

  val nominal_function_cmd: (binding * string option * mixfix) list ->

    local_theory -> Proof.state

  val setup : theory -> theory

  val get_congs : Proof.context -> thm list

  val get_info : Proof.context -> term -> info

end

structure Nominal_Function : NOMINAL_FUNCTION =

struct

open Function_Lib

(* Check for all sorts of errors in the input - nominal needs a different checking function *)

fun nominal_check_defs ctxt fixes eqs =

  let

    val fnames = map (fst o fst) fixes

    fun check geq =

      let

        fun input_error msg = error (cat_lines [msg, Syntax.string_of_term ctxt geq])

        fun check_head fname =

          member (op =) fnames fname orelse

          input_error ("Illegal equation head. Expected " ^ commas_quote fnames)

        val (fname, qs, gs, args, rhs) = split_def ctxt check_head geq

        val _ = length args > 0 orelse input_error "Function has no arguments:"

        fun add_bvs t is = add_loose_bnos (t, 0, is)

        val rvs = (subtract (op =) (fold add_bvs args []) (add_bvs rhs []))

                    |> map (fst o nth (rev qs))

        val _ = forall (not o Term.exists_subterm

          (fn Free (n, _) => member (op =) fnames n | _ => false)) (gs @ args)

          orelse input_error "Defined function may not occur in premises or arguments"

        val freeargs = map (fn t => subst_bounds (rev (map Free qs), t)) args

        val funvars = filter (fn q => exists (exists_subterm (fn (Free q') $ _ => q = q' | _ => false)) freeargs) qs

        val _ = null funvars orelse (warning (cat_lines

          ["Bound variable" ^ plural " " "s " funvars ^

          commas_quote (map fst funvars) ^ " occur" ^ plural "s" "" funvars ^

          " in function position.", "Misspelled constructor???"]); true)

      in

        (fname, length args)

      end

    val grouped_args = AList.group (op =) (map check eqs)

    val _ = grouped_args

      |> map (fn (fname, ars) =>

        length (distinct (op =) ars) = 1

        orelse error ("Function " ^ quote fname ^

          " has different numbers of arguments in different equations"))

    val not_defined = subtract (op =) (map fst grouped_args) fnames

    val _ = null not_defined

      orelse error ("No defining equations for function" ^

        plural " " "s " not_defined ^ commas_quote not_defined)

    fun check_sorts ((fname, fT), _) =

      Sorts.of_sort (Sign.classes_of (ProofContext.theory_of ctxt)) (fT, HOLogic.typeS)

      orelse error (cat_lines

      ["Type of " ^ quote fname ^ " is not of sort " ^ quote "type" ^ ":",

       Syntax.string_of_typ (Config.put show_sorts true ctxt) fT])

    val _ = map check_sorts fixes

  in

    ()

  end

val simp_attribs = map (Attrib.internal o K)

  [Simplifier.simp_add,

   Code.add_default_eqn_attribute,

   Nitpick_Simps.add]

val psimp_attribs = map (Attrib.internal o K)

  [Nitpick_Psimps.add]

fun mk_defname fixes = fixes |> map (fst o fst) |> space_implode "_"

fun add_simps fnames post sort extra_qualify label mod_binding moreatts

  simps lthy =

  let

    val spec = post simps

      |> map (apfst (apsnd (fn ats => moreatts @ ats)))

      |> map (apfst (apfst extra_qualify))

    val (saved_spec_simps, lthy) =

      fold_map Local_Theory.note spec lthy

    val saved_simps = maps snd saved_spec_simps

    val simps_by_f = sort saved_simps

    fun add_for_f fname simps =

      Local_Theory.note

        ((mod_binding (Binding.qualify true fname (Binding.name label)), []), simps)

      #> snd

  in

    (saved_simps, fold2 add_for_f fnames simps_by_f lthy)

  end

(* nominal *)

fun prepare_nominal_function is_external prep default_constraint fixspec eqns config lthy =

  let

    val constrn_fxs = map (fn (b, T, mx) => (b, SOME (the_default default_constraint T), mx))

    val ((fixes0, spec0), ctxt') = prep (constrn_fxs fixspec) eqns lthy

    val fixes = map (apfst (apfst Binding.name_of)) fixes0;

    val spec = map (fn (bnd, prop) => (bnd, [prop])) spec0;

    val (eqs, post, sort_cont, cnames) =  

      empty_preproc nominal_check_defs config ctxt' fixes spec (* nominal *)

    val defname = mk_defname fixes

    val _ =

      if is_some default then Output.legacy_feature

        "'function (default)'. Use 'partial_function'."

      else ()

    val ((goal_state, cont), lthy') =

      Nominal_Function_Mutual.prepare_nominal_function_mutual config defname fixes eqs lthy

    fun afterqed [[proof]] lthy =

      let

        val FunctionResult {fs, R, psimps, simple_pinducts,

          termination, domintros, cases, ...} =

          cont (Thm.close_derivation proof)

        val fnames = map (fst o fst) fixes

        fun qualify n = Binding.name n

          |> Binding.qualify true defname

        val conceal_partial = if partials then I else Binding.conceal

        val addsmps = add_simps fnames post sort_cont

        val (((psimps', pinducts'), (_, [termination'])), lthy) =

          lthy

          |> addsmps (conceal_partial o Binding.qualify false "partial")

               "psimps" conceal_partial psimp_attribs psimps

          ||>> Local_Theory.note ((conceal_partial (qualify "pinduct"),

                 [Attrib.internal (K (Rule_Cases.case_names cnames)),

                  Attrib.internal (K (Rule_Cases.consumes 1)),

                  Attrib.internal (K (Induct.induct_pred ""))]), simple_pinducts)

          ||>> Local_Theory.note ((Binding.conceal (qualify "termination"), []), [termination])

          ||> (snd o Local_Theory.note ((qualify "cases",

                 [Attrib.internal (K (Rule_Cases.case_names cnames))]), [cases]))

          ||> (case domintros of NONE => I | SOME thms => 

                   Local_Theory.note ((qualify "domintros", []), thms) #> snd)

        val info = { add_simps=addsmps, case_names=cnames, psimps=psimps',

          pinducts=snd pinducts', simps=NONE, inducts=NONE, termination=termination',

          fs=fs, R=R, defname=defname, is_partial=true }

        val _ =

          if not is_external then ()

          else Specification.print_consts lthy (K false) (map fst fixes)

      in

        (info, 

         lthy |> Local_Theory.declaration false (add_function_data o morph_function_data info))

      end

  in

    ((goal_state, afterqed), lthy')

  end

fun gen_add_nominal_function is_external prep default_constraint fixspec eqns config tac lthy =

  let

    val ((goal_state, afterqed), lthy') =

      prepare_nominal_function is_external prep default_constraint fixspec eqns config lthy

    val pattern_thm =

      case SINGLE (tac lthy') goal_state of

        NONE => error "pattern completeness and compatibility proof failed"

      | SOME st => Goal.finish lthy' st

  in

    lthy'

    |> afterqed [[pattern_thm]]

  end

val add_nominal_function =

  gen_add_nominal_function false Specification.check_spec (Type_Infer.anyT HOLogic.typeS)

val add_nominal_function_cmd = gen_add_nominal_function true Specification.read_spec "_::type"

fun gen_nominal_function is_external prep default_constraint fixspec eqns config lthy =

  let

    val ((goal_state, afterqed), lthy') =

      prepare_nominal_function is_external prep default_constraint fixspec eqns config lthy

  in

    lthy'

    |> Proof.theorem NONE (snd oo afterqed) [[(Logic.unprotect (concl_of goal_state), [])]]

    |> Proof.refine (Method.primitive_text (K goal_state)) |> Seq.hd

  end

val nominal_function =

  gen_nominal_function false Specification.check_spec (Type_Infer.anyT HOLogic.typeS)

val nominal_function_cmd = gen_nominal_function true Specification.read_spec "_::type"

fun add_case_cong n thy =

  let

    val cong = #case_cong (Datatype.the_info thy n)

      |> safe_mk_meta_eq

  in

    Context.theory_map

      (Function_Ctx_Tree.map_function_congs (Thm.add_thm cong)) thy

  end

val setup_case_cong = Datatype.interpretation (K (fold add_case_cong))

(* setup *)

val setup =

  Attrib.setup @{binding fundef_cong}

    (Attrib.add_del Function_Ctx_Tree.cong_add Function_Ctx_Tree.cong_del)

    "declaration of congruence rule for function definitions"

  #> setup_case_cong

  #> Function_Relation.setup

  #> Function_Common.Termination_Simps.setup

val get_congs = Function_Ctx_Tree.get_function_congs

fun get_info ctxt t = Item_Net.retrieve (get_function ctxt) t

  |> the_single |> snd

(* outer syntax *)

(* nominal *)

val _ =

  Outer_Syntax.local_theory_to_proof "nominal_primrec" "define general recursive nominal functions"

  Keyword.thy_goal

     >> (fn ((config, fixes), statements) => nominal_function_cmd fixes statements config))

end