(* 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://www.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 get_prop_id prop =
 if prop="refObj" then "F"
  else if prop="backPointer" then "B"
   else assert false
   ;;
   
 
let relation_ex rop path rset attl =
 let usek = get_prop_id (List.hd path) in 

let _ = print_string ("RELATION "^usek)
and t = Sys.time () in
let result =
 let c = pgc () in
  Sort.list
   (fun (uri1-> uri1 < uri2)
   (List.fold_left
    (fun parziale (uri,aset)->
     print_string uri ;
      let tv =
       pgresult_to_string
        (c#exec ("select id from registry where uri='" ^ uri ^ "'"))
      in
      let qq =
       "select uri, context from t" ^ tv ^ " where prop_id='" ^ usek ^
        "' order by uri asc"
      in
      let res = c#exec qq in
       (List.map
        (function
            [uri;context] -> {S.uri = uri ; S.attributes = [asvar, context] ; S.extra = ""}
          | _ -> assert false
        ) res#get_list
       ) @
       parziale
    ) [] rset
   )
in
print_string (" = " ^ string_of_int (List.length result) ^ ": ") ; 
print_endline (string_of_float (Sys.time () -. t) ^ "s") ;
flush stdout ;
   result
;;