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/*
     This file is part of GNUnet.
     (C) 2001 - 2013 Christian Grothoff (and other contributing authors)

     GNUnet 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 3, or (at your
     option) any later version.

     GNUnet 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 GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file mesh/mesh_path.c
 * @brief Path handling functions
 * @author Bartlomiej Polot
 */

#include "mesh.h"
#include "mesh_path.h"
#include "gnunet-service-mesh_peer.h"

/**
 * @brief Destroy a path after some time has past.
 *
 * If the path is returned from DHT again after a while, try again.
 *
 * @param cls Closure (path to destroy).
 * @param tc Task context.
 */
static void
path_destroy_delayed (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct MeshPeerPath *path = cls;
  struct MeshPeer *peer;

  path->path_delete = GNUNET_SCHEDULER_NO_TASK;
  peer = GMP_get_short (path->peers[path->length - 1]);
  GMP_remove_path (peer, path);
}


/**
 * Create a new path
 *
 * @param length How many hops will the path have.
 *
 * @return A newly allocated path with a peer array of the specified length.
 */
struct MeshPeerPath *
path_new (unsigned int length)
{
  struct MeshPeerPath *p;

  p = GNUNET_new (struct MeshPeerPath);
  if (length > 0)
  {
    p->length = length;
    p->peers = GNUNET_malloc (length * sizeof (GNUNET_PEER_Id));
  }
  return p;
}


/**
 * Invert the path
 *
 * @param path the path to invert
 */
void
path_invert (struct MeshPeerPath *path)
{
  GNUNET_PEER_Id aux;
  unsigned int i;

  for (i = 0; i < path->length / 2; i++)
  {
    aux = path->peers[i];
    path->peers[i] = path->peers[path->length - i - 1];
    path->peers[path->length - i - 1] = aux;
  }
}


/**
 * Duplicate a path, incrementing short peer's rc.
 *
 * @param path The path to duplicate.
 */
struct MeshPeerPath *
path_duplicate (const struct MeshPeerPath *path)
{
  struct MeshPeerPath *aux;
  unsigned int i;

  aux = path_new (path->length);
  memcpy (aux->peers, path->peers, path->length * sizeof (GNUNET_PEER_Id));
  for (i = 0; i < aux->length; i++)
    GNUNET_PEER_change_rc (aux->peers[i], 1);
  return aux;
}


/**
 * Get the length of a path.
 *
 * @param path The path to measure, with the local peer at any point of it.
 *
 * @return Number of hops to reach destination.
 *         UINT_MAX in case the peer is not in the path.
 */
unsigned int
path_get_length (struct MeshPeerPath *path)
{
  if (NULL == path)
    return UINT_MAX;
  return path->length;
}



/**
 * Mark path as invalid: keep it aroud for a while to avoid trying it in a loop.
 *
 * DHT_get sometimes returns bad cached results, for instance, on a locally
 * cached result where the PUT followed a path that is no longer current.
 *
 * @param p Path to invalidate.
 */
void
path_invalidate (struct MeshPeerPath *p)
{
  if (GNUNET_SCHEDULER_NO_TASK != p->path_delete)
    return;

  p->path_delete = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_MINUTES,
                                                 &path_destroy_delayed, p);
}


/**
 * Test if a path is valid (or at least not known to be invalid).
 *
 * @param path Path to test.
 *
 * @return #GNUNET_YES If the path is valid or unknown,
 *         #GNUNET_NO If the path is known to be invalid.
 */
int
path_is_valid (const struct MeshPeerPath *path)
{
  return (GNUNET_SCHEDULER_NO_TASK == path->path_delete);
}


/**
 * Destroy the path and free any allocated resources linked to it
 *
 * @param p the path to destroy
 *
 * @return GNUNET_OK on success
 */
int
path_destroy (struct MeshPeerPath *p)
{
  if (NULL == p)
    return GNUNET_OK;

  GNUNET_PEER_decrement_rcs (p->peers, p->length);
  GNUNET_free_non_null (p->peers);
  if (GNUNET_SCHEDULER_NO_TASK != p->path_delete)
    GNUNET_SCHEDULER_cancel (p->path_delete);
  GNUNET_free (p);
  return GNUNET_OK;
}

void
path_debug (struct MeshPeerPath *p)
{
  unsigned int i;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "PATH:\n");
  for (i = 0; i < p->length; i++)
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "  %s\n",
                GNUNET_i2s (GNUNET_PEER_resolve2 (p->peers[i])));
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "END\n");
}