(* 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/.
 *)


open Dbconn;;
open Utility;;
(*
 * implementazione del comando Relation 
 *)


let get_prop_id propl =
 let prop = List.hd propl in
  if prop="refObj" then "F"
  else if prop="backPointer" then "B"
       else assert false
;;



let relation_ex rop path rset attl =
 if path = [] then []
 else
 let usek = get_prop_id path in

let vvar = if attl = [] then "position"
           else List.hd attl
in	   
(*let (uril,atts) = List.split rset in*)
let _ = print_string ("RELATION "^usek)
and t = Unix.time () in
let result =
 let c = pgc () in
 List.sort
compare      
(List.fold_left (fun acc (uri,l) ->
                         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] -> (uri,[[(vvar,[context])]])
                                       | _ -> assert false ) 
	                      res#get_list) @ acc
	    )		      
            [] rset			      
)
(*Come faccio a togliere i duplicati????*)       


in
print_string (" = " ^ string_of_int (List.length result) ^ ": ") ; 
print_endline (string_of_float (Unix.time () -. t) ^ "s") ;
flush stdout ;
   result
;;