/**
 * \addtogroup uip6
 * @{
 */
/*
 * Copyright (c) 2010, Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This file is part of the Contiki operating system.
 *
 * $Id: rpl-of0.c,v 1.6 2011/01/04 20:43:28 nvt-se Exp $
 */
/**
 * \file
 *         An implementation of RPL's objective function 0.
 *
 * \author Joakim Eriksson <joakime@sics.se>, Nicolas Tsiftes <nvt@sics.se>
 */

#include "net/rpl/rpl.h"

#define DEBUG DEBUG_ANNOTATE
#include "net/uip-debug.h"

#include "net/neighbor-info.h"

static void reset(void *);
static rpl_parent_t *best_parent(rpl_parent_t *, rpl_parent_t *);
static rpl_rank_t calculate_rank(rpl_parent_t *, rpl_rank_t);

rpl_of_t rpl_of0 = {
  reset,
  NULL,
  best_parent,
  calculate_rank,
  0
};

#define DEFAULT_RANK_INCREMENT  DEFAULT_MIN_HOPRANKINC

static void
reset(void *dag)
{
  PRINTF("RPL: Resetting OF0\n");
}

static rpl_rank_t
calculate_rank(rpl_parent_t *p, rpl_rank_t base_rank)
{
  if(base_rank == 0) {
    if(p == NULL) {
      return INFINITE_RANK;
    }
    base_rank = p->rank;
  }

  if((rpl_rank_t)(base_rank + DEFAULT_RANK_INCREMENT) < base_rank) {
    PRINTF("RPL: OF0 rank %d incremented to infinite rank due to wrapping\n",
        base_rank);
    return INFINITE_RANK;
  }
  return base_rank + DEFAULT_RANK_INCREMENT;

}

static rpl_parent_t *
best_parent(rpl_parent_t *p1, rpl_parent_t *p2)
{
  PRINTF("RPL: Comparing parent ");
  PRINT6ADDR(&p1->addr);
  PRINTF(" (confidence %d, rank %d) with parent ",
        p1->etx, p1->rank);
  PRINT6ADDR(&p2->addr);
  PRINTF(" (confidence %d, rank %d)\n",
        p2->etx, p2->rank);


  /* Compare two parents by looking both and their rank and at the ETX
     for that parent. We choose the parent that has the most
     favourable combination. */
  if(DAG_RANK(p1->rank, (rpl_dag_t *)p1->dag) * ETX_DIVISOR + p1->etx <
     DAG_RANK(p2->rank, (rpl_dag_t *)p1->dag) * ETX_DIVISOR + p2->etx) {
    return p1;
  } else {
    return p2;
  }

  /* This is the old code, which isn't used now, but left here in case
     we would like to use it later (if the above code turns out to not
     work as well as we expect it to. The old code first favoured the
     parent with a lower rank, then used the ETX to compare two
     parents with the same rank. This is not ideal since you may have
     a parent with a low rank on the edge of your range that will have
     a very bad ETX. But the code below would nevertheless pick that
     one. */
  if(p1->rank < p2->rank) {
    return p1;
  } else if(p2->rank < p1->rank) {
    return p2;
  }

  if(p1->etx < p2->etx) {
    return p1;
  } else {
    return p2;
  }
}