(* Copyright (C) 2002, HELM Team.
 *
 * This file is part of HELM, an Hypertextual, Electronic
 * Library of Mathematics, developed at the Computer Science
 * Department, University of Bologna, Italy.
 *
 * HELM is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * HELM is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HELM; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA  02111-1307, USA.
 *
 * For details, see the HELM World-Wide-Web page,
 * http://cs.unibo.it/helm/.
 *)

module C = Cic
module P = PrimitiveTactics
module T = Tacticals
module S = ProofEngineStructuralRules
module F = FreshNamesGenerator
module E = ProofEngineTypes
module H = ProofEngineHelpers
module Q = MetadataQuery

(*
let induction_tac ~term status =
  let (proof, goal) = status in
  let module C = Cic in
  let module R = CicReduction in
  let module P = PrimitiveTactics in
  let module T = Tacticals in
  let module S = ProofEngineStructuralRules in
  let module U = UriManager in 
   let (_,metasenv,_,_) = proof in
    let _,context,ty = CicUtil.lookup_meta goal metasenv in
     let termty = CicTypeChecker.type_of_aux' metasenv context term in	(* per ora non serve *)

     T.then_ ~start:(T.repeat_tactic 
                       ~tactic:(T.then_ ~start:(VariousTactics.generalize_tac ~term) (* chissa' se cosi' funziona? *)
                       ~continuation:(P.intros))
             ~continuation:(P.elim_intros_simpl ~term)
             status
;;
*)

(* unexported tactics *******************************************************)

let get_name context index =
   try match List.nth context (pred index) with
      | Some (Cic.Name name, _)     -> Some name
      | _                           -> None
   with Invalid_argument "List.nth" -> None

let rec scan_tac ~old_context_length ~index ~tactic =
   let scan_tac status =
      let (proof, goal) = status in
      let _, metasenv, _, _ = proof in
      let _, context, _ = CicUtil.lookup_meta goal metasenv in
      let context_length = List.length context in
      let rec aux index =
         match get_name context index with 
	    | _ when index <= 0 -> (proof, [goal])
	    | None              -> aux (pred index)
	    | Some what         -> 
	       let tac = T.then_ ~start:(tactic ~what)
	                         ~continuation:(scan_tac ~old_context_length:context_length ~index ~tactic)
               in
	       try E.apply_tactic tac status 
	       with E.Fail _ -> aux (pred index)
      in aux (index + context_length - old_context_length - 1)
   in
   E.mk_tactic scan_tac

let rec check_inductive_types types = function 
   | C.MutInd (uri, typeno, _) -> List.mem (uri, typeno) types
   | C.Appl (hd :: tl)         -> check_inductive_types types hd
   | _                         -> false

let elim_clear_tac ~mk_fresh_name_callback ~types ~what =
   let elim_clear_tac status =
      let (proof, goal) = status in
      let _, metasenv, _, _ = proof in
      let _, context, _ = CicUtil.lookup_meta goal metasenv in
      let index, ty = H.lookup_type metasenv context what in
      if check_inductive_types types ty then 
         let tac = T.then_ ~start:(P.elim_intros_tac ~mk_fresh_name_callback (C.Rel index))
	                   ~continuation:(S.clear what)
	 in
	 E.apply_tactic tac status
      else raise (E.Fail (lazy "unexported elim_clear: not an eliminable type"))
   in
   E.mk_tactic elim_clear_tac

(* elim type ****************************************************************)

let elim_type_tac ?(mk_fresh_name_callback = F.mk_fresh_name ~subst:[]) ?depth
  ?using what
=
  let elim what =
    P.elim_intros_simpl_tac ?using ?depth ~mk_fresh_name_callback what
  in
  let elim_type_tac status =
    let tac =
      T.thens ~start: (P.cut_tac what) ~continuations:[elim (C.Rel 1); T.id_tac]
    in
    E.apply_tactic tac status
  in
  E.mk_tactic elim_type_tac

(* decompose ****************************************************************)

(* robaglia --------------------------------------------------------------- *)

  (** perform debugging output? *)
let debug = false
let debug_print = fun _ -> ()

  (** debugging print *)
let warn s = debug_print (lazy ("DECOMPOSE: " ^ (Lazy.force s)))

(* search in term the Inductive Types and return a list of uris as triples like this: (uri,typeno,exp_named_subst) *)
let search_inductive_types ty =
   let rec aux types = function 
      | C.MutInd (uri, typeno, _) when (not (List.mem (uri, typeno) types)) -> 
         (uri, typeno) :: types
      | C.Appl applist -> List.fold_left aux types applist
      | _              -> types
   in
   aux [] ty
(* N.B: in un caso tipo (and A forall C:Prop.(or B C)) l'or *non* viene selezionato! *)

(* roba seria ------------------------------------------------------------- *)

let decompose_tac ?(mk_fresh_name_callback = F.mk_fresh_name ~subst:[])
                  ?(user_types=[]) ~dbd what =
   let decompose_tac status =
      let (proof, goal) = status in
      let _, metasenv,_,_ = proof in
      let _, context, _ = CicUtil.lookup_meta goal metasenv in
      let types = List.rev_append user_types (Q.decomposables dbd) in
      let tactic = elim_clear_tac ~mk_fresh_name_callback ~types in
      let old_context_length = List.length context in
      let tac = T.then_ ~start:(tactic ~what)
                        ~continuation:(scan_tac ~old_context_length ~index:1 ~tactic)
      in
      E.apply_tactic tac status
   in
   E.mk_tactic decompose_tac
      
(*
module R = CicReduction

	let rec elim_clear_tac ~term' ~nr_of_hyp_still_to_elim status =
         let (proof, goal) = status in
         warn (lazy ("nr_of_hyp_still_to_elim=" ^ (string_of_int nr_of_hyp_still_to_elim)));
         if nr_of_hyp_still_to_elim <> 0 then
          let _,metasenv,_,_ = proof in
           let _,context,_ = CicUtil.lookup_meta goal metasenv in
            let old_context_len = List.length context in
            let termty,_ = 
	      CicTypeChecker.type_of_aux' metasenv context term' 
		CicUniv.empty_ugraph in
             warn (lazy ("elim_clear termty= " ^ CicPp.ppterm termty));
             match termty with
                C.MutInd (uri,typeno,exp_named_subst)
              | C.Appl((C.MutInd (uri,typeno,exp_named_subst))::_) 
                 when (List.mem (uri,typeno,exp_named_subst) urilist) ->
                   warn (lazy ("elim " ^ CicPp.ppterm termty));
		   ProofEngineTypes.apply_tactic 
                   (T.then_ 
                      ~start:(P.elim_intros_simpl_tac term')
                      ~continuation:(
                        (* clear the hyp that has just been eliminated *)
                        ProofEngineTypes.mk_tactic (fun status -> 
                          let (proof, goal) = status in
                          let _,metasenv,_,_ = proof in
                           let _,context,_ = CicUtil.lookup_meta goal metasenv in
                            let new_context_len = List.length context in   
                             warn (lazy ("newcon=" ^ (string_of_int new_context_len) ^ " & oldcon=" ^ (string_of_int old_context_len) ^ " & old_nr_of_hyp=" ^ (string_of_int nr_of_hyp_still_to_elim)));
                             let new_nr_of_hyp_still_to_elim = nr_of_hyp_still_to_elim + (new_context_len - old_context_len) - 1 in
                             let hyp_name =
                              match List.nth context new_nr_of_hyp_still_to_elim with
                                 None
                               | Some (Cic.Anonymous,_) -> assert false
                               | Some (Cic.Name name,_) -> name
                             in
			     ProofEngineTypes.apply_tactic
                             (T.then_ 
                                ~start:(
                                  if (term'==term) (* if it's the first application of elim, there's no need to clear the hyp *) 
                                   then begin debug_print (lazy ("%%%%%%% no clear")); T.id_tac end
                                   else begin debug_print (lazy ("%%%%%%% clear " ^ (string_of_int (new_nr_of_hyp_still_to_elim)))); (S.clear ~hyp:hyp_name) end)
                                ~continuation:(ProofEngineTypes.mk_tactic (elim_clear_tac ~term':(C.Rel new_nr_of_hyp_still_to_elim) ~nr_of_hyp_still_to_elim:new_nr_of_hyp_still_to_elim)))
                                status
                        )))
                      status
              | _ ->
                   let new_nr_of_hyp_still_to_elim = nr_of_hyp_still_to_elim - 1 in 
                    warn (lazy ("fail; hyp=" ^ (string_of_int new_nr_of_hyp_still_to_elim)));
                    elim_clear_tac ~term':(C.Rel new_nr_of_hyp_still_to_elim) ~nr_of_hyp_still_to_elim:new_nr_of_hyp_still_to_elim status
         else (* no hyp to elim left in this goal *)
          ProofEngineTypes.apply_tactic T.id_tac status

        in
         elim_clear_tac ~term':term ~nr_of_hyp_still_to_elim:1 status
*)