(* Copyright (C) 2000, 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/.
 *)

(*
 * implementazione dei comandi USE/USED BY
 *)

open Utility;;
open Dbconn;;

(*
 * implementazione dei comandi USE/USED BY
 *
 * parametri:
 * alist: string list list; lista su cui eseguire il comando USE/USED BY
 * asvar: string; nome della variabile del comando use
 * usek: string; nome della tabella in cui ricercare le occorrenze;
 *               la distinzione fra l'esecuzione del comando USE e USED BY
 *               sta nell'utilizzo della tabella 'backPointer' per USE
 *               e 'refObj' per USED BY
 *
 * output: string list list; lista su cui e' stato eseguito il 
 *                           comando USE/USED BY
 *)
let use_ex alist asvar usek =
 let c = pgc () in
  List.fold_left
   (fun parziale xres ->
    let r1 = helm_property_id usek
    and r2 = helm_property_id "position"
    and r3 = helm_property_id "occurrence"
    in
     let qq = "select distinct t" ^ r3 ^ ".att1, t" ^ r2 ^ ".att1 " ^
      "from t" ^ r3 ^ ", t" ^ r2 ^ ", t" ^ r1 ^ " " ^
      "where " ^ "t" ^ r1 ^ ".att0 = '" ^ (List.hd xres) ^ "' and t" ^ r1 ^
      ".att1 = t" ^ r2 ^ ".att0 and t" ^ r1 ^ ".att1 = t" ^ r3 ^
      ".att0 order by t" ^ r3 ^ ".att1 asc"
     in
     (*let _ = print_endline ("use: " ^ qq) in*)
     let res = c#exec qq in
      parziale
      @
      if not (List.mem asvar (List.tl (List.hd alist))) then
       List.map
        (fun l -> [List.hd l] @ List.tl xres @ List.tl l)
        res#get_list
      else
       List.map
        (fun l ->
         let t =
          match xres with
             hd::tl -> (List.hd l)::tl
          |  [] -> []
         in
	  List.map
           snd
	   (Utility.set_assoc
	    asvar
	    (List.hd (List.tl l))
	    (List.combine (List.hd alist) t)
	   )
        )
        (List.find_all
         (fun l ->
          let currv =
           List.hd (List.tl l)
          and xresv =
           try (
            List.assoc
             asvar
             (List.combine
              (List.tl (List.hd alist))
              (List.tl xres)
             )
           ) with
            Not_found -> ""
          in
           xresv = "" or xresv = currv
         )
         res#get_list
        )
   )
   [ (List.hd alist)
     @
     if not (List.mem asvar (List.tl (List.hd alist))) then
      [asvar]
     else
      []
   ]
   (List.tl alist)
;;