def sync():
    server = Server(API_BASE_URL, CONTROLLER_ID)
    local = File(STATE_FILE)
    server_state = server.get_state()

    if local.present():
        local.load()
    else:
        local.data = server_state
        local.save()

    local_state = local.data

    changer = Changer(local_state, remote_state)
    current_state = changer.process_change()

    server.post_state(current_state)