(* 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 MI = CicMkImplicit
module TC = CicTypeChecker 
module PET = ProofEngineTypes 
module PEH = ProofEngineHelpers 
module U  = CicUniv
module S = CicSubstitution
module PT = PrimitiveTactics
module T = Tacticals

let fail_msg1 = "no applicable simplification"

let error msg = raise (PET.Fail msg)

(* lapply *******************************************************************)

let lapply_tac ?(mk_fresh_name_callback = FreshNamesGenerator.mk_fresh_name ~subst:[]) 
               (* ?(substs = []) *) ?to_what what =
   let cut_tac term = PT.cut_tac ~mk_fresh_name_callback term in
   let apply_tac term = PT.apply_tac term in
   let strip_dependent_prods metasenv context t =
      let irl = MI.identity_relocation_list_for_metavariable context in
      let rec aux metasenv p xcontext = function
         | Cic.Prod (name, t1, t2) when not (TC.does_not_occur xcontext 0 1 t2) ->  
            let index = MI.new_meta metasenv [] in
            let metasenv = [index, context, t1] @ metasenv in
            let e, s = Some (name, Cic.Decl t1), Cic.Meta (index, irl) in    
	    aux metasenv (succ p) (e :: xcontext) (S.subst s t2)
         | Cic.Prod (name, t1, t2) -> metasenv, p, Some t1, t2
         | t                       -> metasenv, p, None, t 
      in
      aux metasenv 0 context t
   in
   let rec mk_continuations p l =
      if p <= 0 then l else mk_continuations (pred p) (T.id_tac :: l)
   in
   let lapply_tac (proof, goal) =
      let xuri, metasenv, u, t = proof in
      let _, context, _ = CicUtil.lookup_meta goal metasenv in
      let lemma, _ = TC.type_of_aux' metasenv context what U.empty_ugraph in
      match strip_dependent_prods metasenv context lemma with
         | metasenv, p, Some premise, conclusion ->
	    let premise_tac = 
	       match to_what with
	          | None      -> T.id_tac 
		  | Some term -> PT.apply_tac term 
	    in
	    let status = (xuri, metasenv, u, t), goal in
            let tac = T.thens ~start:(cut_tac premise)
	                      ~continuations:[  
		      T.thens ~start:(cut_tac conclusion)
			      ~continuations:[ T.id_tac; 
		      T.thens ~start:(PT.apply_tac what)
		              ~continuations:(mk_continuations p [PT.apply_tac ~term:(Cic.Rel 1)])
		                             ]; premise_tac ]
	    in
	    PET.apply_tactic tac status
         | metasenv, p, None, conclusion         ->
	    failwith "lapply_tac: not implemented"
   in
   PET.mk_tactic lapply_tac
   
(* fwd **********************************************************************)

let fwd_simpl_tac ~what ~dbd =
   let fwd_simpl_tac status =
      let (proof, goal) = status in
      let _, metasenv, _, _ = proof in
      let _, context, ty = CicUtil.lookup_meta goal metasenv in
      let major, _ = TC.type_of_aux' metasenv context what U.empty_ugraph in 
      match MetadataQuery.fwd_simpl ~dbd major with
         | []       -> error fail_msg1
         | uri :: _ -> prerr_endline (UriManager.string_of_uri uri); (proof, [])  
   in
   PET.mk_tactic fwd_simpl_tac