module MapBoundary
   def check_boundaries(min_lon, min_lat, max_lon, max_lat)
      # check the bbox is sane
      unless min_lon <= max_lon
        raise("The minimum longitude must be less than the maximum longitude, but it wasn't")
      end
      unless min_lat <= max_lat
        raise("The minimum latitude must be less than the maximum latitude, but it wasn't")
      end
      unless min_lon >= -180 && min_lat >= -90 && max_lon <= 180 && max_lat <= 90
        raise("The latitudes must be between -90 and 90, and longitudes between -180 and 180")
      end

      # check the bbox isn't too large
      requested_area = (max_lat-min_lat)*(max_lon-min_lon)
      if requested_area > APP_CONFIG['max_request_area']
        raise("The maximum bbox size is " + APP_CONFIG['max_request_area'].to_s + 
          ", and your request was too large. Either request a smaller area, or use planet.osm")
      end
    end
end