--          This file is part of SmallEiffel The GNU Eiffel Compiler.
--          Copyright (C) 1994-98 LORIA - UHP - CRIN - INRIA - FRANCE
--            Dominique COLNET and Suzanne COLLIN - colnet@loria.fr 
--                       http://www.loria.fr/SmallEiffel
-- SmallEiffel 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, or (at your option)  any  later 
-- version. SmallEiffel 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  SmallEiffel;  see the file COPYING.  If not,
-- write to the  Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-- Boston, MA 02111-1307, USA.
--
class LEVEL
   
creation {ANY}
   make
   
feature {ANY}
   
   count: INTEGER;
	 -- Total count of occupied places.
   
   free_count: INTEGER is
      do
	 Result := park.count - count;
      end;
   
   capacity : INTEGER is
      do
	 Result := count + free_count;
      end;
   
   full: BOOLEAN is
      do
	 Result := count = capacity;
      end; 

feature {ANY} -- Modifications :
   
   make(max_cars: INTEGER) is
      require
	 max_cars > 0;
      do
	 !!park.make(1,max_cars);
	 !!tickets.make(park.lower,park.upper);
	 count := 0;
      ensure
	 count = 0;
      end;
   
   arrival(car: INTEGER; arrival_time: DATE) is
      require
	 not full;
	 car > 0;
      local
	 i: INTEGER;
	 stop: BOOLEAN;
	 ticket: TICKET;
      do
	 from  
	    i := park.lower;
	    stop := false;
	 until
	    stop
	 loop
	    if park @ i <= 0 then
	       stop := true;
	       park.put(car,i);
	       !!ticket.make(arrival_time);
	       tickets.put(ticket,i);
	       count := count + 1;
	    end;
	    i := i + 1;
	 end;
      ensure
	 count >= old count + 1;
      end;
   
   departure(car: INTEGER; departure_time: DATE; hour_price: REAL): REAL is
	 -- Gives price to pay or -1 when car is not at this level. 
      require
	 car > 0;
      local
	 i: INTEGER;
      do
	 i := park.index_of(car);   
	 if (i > park.upper) then
	    Result := -1;
	 else	 
	    Result := (tickets @ i).price(departure_time,hour_price);
	    tickets.put(Void,i);
	    park.put(0,i);
	    count := count - 1;
	 end;
      end;
   
feature {NONE}
   
   park: ARRAY[INTEGER];
   
   tickets: ARRAY[TICKET];

invariant
   
   count >= 0;
   
   free_count >= 0;
   
   capacity = count + free_count;
   
   capacity >= 1;

   tickets.count = park.count;

end -- LEVEL