(* 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 del comando DIFF
 *)

exception NotCompatible;;

(* intersect_attributes is successful iff there is no attribute with *)
(* two different values in the two lists. The returned list is the   *)
(* union of the two lists.                                           *)
let rec intersect_attributes (attr1, attr2) =
 match attr1, attr2 with
    [],_ -> attr2
  | _,[] -> attr1
  | (key1,value1)::tl1, (key2,_)::_ when key1 < key2 ->
      (key1,value1)::(intersect_attributes (tl1,attr2))
  | (key1,_)::_, (key2,value2)::tl2 when key2 < key1 ->
      (key2,value2)::(intersect_attributes (attr1,tl2))
  | entry1::tl1, entry2::tl2 when entry1 = entry2 ->
     entry1::(intersect_attributes (tl1,tl2))
  | _, _ -> raise NotCompatible  (* same keys, different values *)
;;

(*
 * implementazione del comando DIFF
 *)
let rec diff_ex l1 l2 =
 let module S = Mathql_semantics in
  match (l1, l2) with
     [],_ -> []
   | l,[] -> l
   | {S.uri = uri1}::_, {S.uri = uri2}::tl2 when uri2 < uri1 ->
      (diff_ex l1 tl2)
   | {S.uri = uri1 ; S.attributes = attributes1}::tl1,
     {S.uri = uri2}::_ when uri1 < uri2 ->
      {S.uri = uri1 ; S.attributes = attributes1 ; S.extra = ""}::(diff_ex tl1 l2)
   | {S.uri = uri1 ; S.attributes = attributes1}::tl1,
     {S.uri = uri2 ; S.attributes = attributes2}::tl2 ->
       try
        let attributes' = intersect_attributes (attributes1, attributes2) in 
         diff_ex tl1 tl2
       with
        NotCompatible ->
         {S.uri = uri1 ; S.attributes = attributes1 ; S.extra = ""}::(diff_ex tl1 tl2)
;;

let diff_ex l1 l2 =
 let before = Unix.time () in
 let res = diff_ex l1 l2 in
 let after = Unix.time () in
  let ll1 = string_of_int (List.length l1) in
  let ll2 = string_of_int (List.length l2) in
  let diff = string_of_float (after -. before) in
  print_endline
   ("DIFF(" ^ ll1 ^ ", " ^ ll2 ^ ") = " ^ string_of_int (List.length res) ^
    ": " ^ diff ^ "s") ;
  flush stdout ;
  res
;;