/*
     This file is part of GNUnet.
     Copyright (C)

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file rps/rps-sampler_common.c
 * @brief Code common to client and service sampler
 * @author Julius Bünger
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_statistics_service.h"

#include "rps-sampler_common.h"
#include "gnunet-service-rps_sampler_elem.h"

#include <math.h>
#include <inttypes.h>

#include "rps-test_util.h"

#define LOG(kind, ...) GNUNET_log_from(kind, "rps-sampler_common", __VA_ARGS__)

/**
 * @brief Context for a callback. Contains callback and closure.
 *
 * Meant to be an entry in an DLL.
 */
struct SamplerNotifyUpdateCTX {
  /**
   * @brief The Callback to call on updates
   */
  SamplerNotifyUpdateCB notify_cb;

  /**
   * @brief The according closure.
   */
  void *cls;

  /**
   * @brief Next element in DLL.
   */
  struct SamplerNotifyUpdateCTX *next;

  /**
   * @brief Previous element in DLL.
   */
  struct SamplerNotifyUpdateCTX *prev;
};


/**
 * Closure to _get_n_rand_peers_ready_cb()
 */
struct RPS_SamplerRequestHandle {
  /**
   * DLL
   */
  struct RPS_SamplerRequestHandle *next;
  struct RPS_SamplerRequestHandle *prev;

  /**
   * Number of peers we are waiting for.
   */
  uint32_t num_peers;

  /**
   * Number of peers we currently have.
   */
  uint32_t cur_num_peers;

  /**
   * Pointer to the array holding the ids.
   */
  struct GNUNET_PeerIdentity *ids;

  /**
   * Head and tail for the DLL to store the tasks for single requests
   */
  struct GetPeerCls *gpc_head;
  struct GetPeerCls *gpc_tail;

  /**
   * Sampler.
   */
  struct RPS_Sampler *sampler;

  /**
   * Callback to be called when all ids are available.
   */
  RPS_sampler_n_rand_peers_ready_cb callback;

  /**
   * Closure given to the callback
   */
  void *cls;
};


/**
 * Closure to _get_rand_peer_info()
 */
struct RPS_SamplerRequestHandleSingleInfo {
  /**
   * DLL
   */
  struct RPS_SamplerRequestHandleSingleInfo *next;
  struct RPS_SamplerRequestHandleSingleInfo *prev;

  /**
   * Pointer to the id
   */
  struct GNUNET_PeerIdentity *id;

  /**
   * Head and tail for the DLL to store the tasks for single requests
   */
  struct GetPeerCls *gpc_head;
  struct GetPeerCls *gpc_tail;

  /**
   * Sampler.
   */
  struct RPS_Sampler *sampler;

  /**
   * Callback to be called when all ids are available.
   */
  RPS_sampler_sinlge_info_ready_cb callback;

  /**
   * Closure given to the callback
   */
  void *cls;
};


/**
 * @brief Update the current estimate of the network size stored at the sampler
 *
 * Used for computing the condition when to return elements to the client
 *
 * Only used/useful with the client sampler
 * (Maybe move to rps-sampler_client.{h|c} ?)
 *
 * @param sampler The sampler to update
 * @param num_peers The estimated value
 */
void
RPS_sampler_update_with_nw_size(struct RPS_Sampler *sampler,
                                uint32_t num_peers)
{
  sampler->num_peers_estim = num_peers;
}


/**
 * @brief Set the probability that is needed at least with what a sampler
 * element has to have observed all elements from the network.
 *
 * Only used/useful with the client sampler
 * (Maybe move to rps-sampler_client.{h|c} ?)
 *
 * @param sampler
 * @param desired_probability
 */
void
RPS_sampler_set_desired_probability(struct RPS_Sampler *sampler,
                                    double desired_probability)
{
  sampler->desired_probability = desired_probability;
}


/**
 * @brief Set the deficiency factor.
 *
 * Only used/useful with the client sampler
 * (Maybe move to rps-sampler_client.{h|c} ?)
 *
 * @param sampler
 * @param desired_probability
 */
void
RPS_sampler_set_deficiency_factor(struct RPS_Sampler *sampler,
                                  double deficiency_factor)
{
  sampler->deficiency_factor = deficiency_factor;
}


/**
 * @brief Add a callback that will be called when the next peer is inserted
 * into the sampler
 *
 * @param sampler The sampler on which update it will be called
 * @param notify_cb The callback
 * @param cls Closure given to the callback
 *
 * @return The context containing callback and closure
 */
struct SamplerNotifyUpdateCTX *
sampler_notify_on_update(struct RPS_Sampler *sampler,
                         SamplerNotifyUpdateCB notify_cb,
                         void *cls)
{
  struct SamplerNotifyUpdateCTX *notify_ctx;

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Inserting new context for notification\n");
  notify_ctx = GNUNET_new(struct SamplerNotifyUpdateCTX);
  notify_ctx->notify_cb = notify_cb;
  notify_ctx->cls = cls;
  GNUNET_CONTAINER_DLL_insert(sampler->notify_ctx_head,
                              sampler->notify_ctx_tail,
                              notify_ctx);
  return notify_ctx;
}


/**
 * Get the size of the sampler.
 *
 * @param sampler the sampler to return the size of.
 * @return the size of the sampler
 */
unsigned int
RPS_sampler_get_size(struct RPS_Sampler *sampler)
{
  return sampler->sampler_size;
}


/**
 * @brief Notify about update of the sampler.
 *
 * Call the callbacks that are waiting for notification on updates to the
 * sampler.
 *
 * @param sampler The sampler the updates are waiting for
 */
static void
notify_update(struct RPS_Sampler *sampler)
{
  struct SamplerNotifyUpdateCTX *tmp_notify_head;
  struct SamplerNotifyUpdateCTX *tmp_notify_tail;

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Calling callbacks waiting for update notification.\n");
  tmp_notify_head = sampler->notify_ctx_head;
  tmp_notify_tail = sampler->notify_ctx_tail;
  sampler->notify_ctx_head = NULL;
  sampler->notify_ctx_tail = NULL;
  for (struct SamplerNotifyUpdateCTX *notify_iter = tmp_notify_head;
       NULL != tmp_notify_head;
       notify_iter = tmp_notify_head)
    {
      GNUNET_assert(NULL != notify_iter->notify_cb);
      GNUNET_CONTAINER_DLL_remove(tmp_notify_head,
                                  tmp_notify_tail,
                                  notify_iter);
      notify_iter->notify_cb(notify_iter->cls);
      GNUNET_free(notify_iter);
    }
}


/**
 * Update every sampler element of this sampler with given peer
 *
 * @param sampler the sampler to update.
 * @param id the PeerID that is put in the sampler
 */
void
RPS_sampler_update(struct RPS_Sampler *sampler,
                   const struct GNUNET_PeerIdentity *id)
{
  for (uint32_t i = 0; i < sampler->sampler_size; i++)
    {
      RPS_sampler_elem_next(sampler->sampler_elements[i],
                            id);
    }
  notify_update(sampler);
}


/**
 * Reinitialise all previously initialised sampler elements with the given value.
 *
 * Used to get rid of a PeerID.
 *
 * FIXME: This should also consider currently pending requests
 *        (Pending requests already collect peerids. As long as not all
 *        requested IDs have been collected, they are kept.
 *        Ideally, the @p id should be removed from all pending requests. This
 *        seems quite complicated.)
 *
 * @param sampler the sampler to reinitialise a sampler element in.
 * @param id the id of the sampler elements to update.
 */
void
RPS_sampler_reinitialise_by_value(struct RPS_Sampler *sampler,
                                  const struct GNUNET_PeerIdentity *id)
{
  uint32_t i;

  for (i = 0; i < sampler->sampler_size; i++)
    {
      if (0 == GNUNET_memcmp(id,
                             &(sampler->sampler_elements[i]->peer_id)))
        {
          LOG(GNUNET_ERROR_TYPE_DEBUG, "Reinitialising sampler\n");
          RPS_sampler_elem_reinit(sampler->sampler_elements[i]);
        }
    }
}


/**
 * Counts how many Samplers currently hold a given PeerID.
 *
 * @param sampler the sampler to count ids in.
 * @param id the PeerID to count.
 *
 * @return the number of occurrences of id.
 */
uint32_t
RPS_sampler_count_id(struct RPS_Sampler *sampler,
                     const struct GNUNET_PeerIdentity *id)
{
  uint32_t count;
  uint32_t i;

  count = 0;
  for (i = 0; i < sampler->sampler_size; i++)
    {
      if (0 == GNUNET_memcmp(&sampler->sampler_elements[i]->peer_id, id)
          && EMPTY != sampler->sampler_elements[i]->is_empty)
        count++;
    }
  return count;
}


/**
 * Grow or shrink the size of the sampler.
 *
 * @param sampler the sampler to resize.
 * @param new_size the new size of the sampler
 */
static void
sampler_resize(struct RPS_Sampler *sampler, unsigned int new_size)
{
  unsigned int old_size;
  uint32_t i;

  // TODO check min and max size

  old_size = sampler->sampler_size;

  if (old_size > new_size)
    { /* Shrinking */
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "Shrinking sampler %d -> %d\n",
          old_size,
          new_size);

      for (i = new_size; i < old_size; i++)
        {
          RPS_sampler_elem_destroy(sampler->sampler_elements[i]);
        }

      GNUNET_array_grow(sampler->sampler_elements,
                        sampler->sampler_size,
                        new_size);
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "sampler->sampler_elements now points to %p\n",
          sampler->sampler_elements);
    }
  else if (old_size < new_size)
    { /* Growing */
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "Growing sampler %d -> %d\n",
          old_size,
          new_size);

      GNUNET_array_grow(sampler->sampler_elements,
                        sampler->sampler_size,
                        new_size);

      for (i = old_size; i < new_size; i++)
        { /* Add new sampler elements */
          sampler->sampler_elements[i] = RPS_sampler_elem_create();
        }
    }
  else
    {
      LOG(GNUNET_ERROR_TYPE_DEBUG, "Size remains the same -- nothing to do\n");
      return;
    }

  GNUNET_assert(sampler->sampler_size == new_size);
}


/**
 * Grow or shrink the size of the sampler.
 *
 * @param sampler the sampler to resize.
 * @param new_size the new size of the sampler
 */
void
RPS_sampler_resize(struct RPS_Sampler *sampler, unsigned int new_size)
{
  GNUNET_assert(0 < new_size);
  sampler_resize(sampler, new_size);
}


/**
 * Empty the sampler.
 *
 * @param sampler the sampler to empty.
 * @param new_size the new size of the sampler
 */
static void
sampler_empty(struct RPS_Sampler *sampler)
{
  sampler_resize(sampler, 0);
}


/**
 * Callback to _get_rand_peer() used by _get_n_rand_peers().
 *
 * Implements #RPS_sampler_rand_peer_ready_cont
 *
 * Checks whether all n peers are available. If they are,
 * give those back.
 * @param cls Closure
 * @param id Peer ID
 * @param probability The probability with which this sampler has seen all ids
 * @param num_observed How many ids this sampler has observed
 */
static void
check_n_peers_ready(void *cls,
                    const struct GNUNET_PeerIdentity *id,
                    double probability,
                    uint32_t num_observed)
{
  struct RPS_SamplerRequestHandle *req_handle = cls;

  (void)id;
  RPS_sampler_n_rand_peers_ready_cb tmp_cb;
  struct GNUNET_PeerIdentity *peers;
  uint32_t num_peers;
  void *cb_cls;
  (void)probability;
  (void)num_observed;

  req_handle->cur_num_peers++;
  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Got %" PRIX32 ". of %" PRIX32 " peers\n",
      req_handle->cur_num_peers, req_handle->num_peers);

  if (req_handle->num_peers == req_handle->cur_num_peers)
    { /* All peers are ready -- return those to the client */
      GNUNET_assert(NULL != req_handle->callback);

      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "returning %" PRIX32 " peers to the client\n",
          req_handle->num_peers);

      /* Copy pointers and peers temporarily as they
      * might be deleted from within the callback */
      tmp_cb = req_handle->callback;
      num_peers = req_handle->num_peers;
      peers = GNUNET_new_array(num_peers, struct GNUNET_PeerIdentity);
      GNUNET_memcpy(peers,
                    req_handle->ids,
                    num_peers * sizeof(struct GNUNET_PeerIdentity));
      cb_cls = req_handle->cls;
      RPS_sampler_request_cancel(req_handle);
      req_handle = NULL;
      tmp_cb(peers, num_peers, cb_cls);
      GNUNET_free(peers);
    }
}


/**
 * Callback to _get_rand_peer() used by _get_rand_peer_info().
 *
 * Implements #RPS_sampler_rand_peer_ready_cont
 *
 * @param cls Closure
 * @param id Peer ID
 * @param probability The probability with which this sampler has seen all ids
 * @param num_observed How many ids this sampler has observed
 */
static void
check_peer_info_ready(void *cls,
                      const struct GNUNET_PeerIdentity *id,
                      double probability,
                      uint32_t num_observed)
{
  struct RPS_SamplerRequestHandleSingleInfo *req_handle = cls;

  (void)id;
  RPS_sampler_sinlge_info_ready_cb tmp_cb;
  struct GNUNET_PeerIdentity *peer;
  void *cb_cls;
  (void)probability;
  (void)num_observed;

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Got single peer with additional info\n");

  GNUNET_assert(NULL != req_handle->callback);

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "returning single peer with info to the client\n");

  /* Copy pointers and peers temporarily as they
  * might be deleted from within the callback */
  tmp_cb = req_handle->callback;
  peer = GNUNET_new(struct GNUNET_PeerIdentity);
  GNUNET_memcpy(peer,
                req_handle->id,
                sizeof(struct GNUNET_PeerIdentity));
  cb_cls = req_handle->cls;
  RPS_sampler_request_single_info_cancel(req_handle);
  req_handle = NULL;
  tmp_cb(peer, cb_cls, probability, num_observed);
  GNUNET_free(peer);
}


/**
 * Get n random peers out of the sampled peers.
 *
 * We might want to reinitialise this sampler after giving the
 * corrsponding peer to the client.
 * Random with or without consumption?
 *
 * @param sampler the sampler to get peers from.
 * @param cb callback that will be called once the ids are ready.
 * @param cls closure given to @a cb
 * @param num_peers the number of peers requested
 */
struct RPS_SamplerRequestHandle *
RPS_sampler_get_n_rand_peers(struct RPS_Sampler *sampler,
                             uint32_t num_peers,
                             RPS_sampler_n_rand_peers_ready_cb cb,
                             void *cls)
{
  uint32_t i;
  struct RPS_SamplerRequestHandle *req_handle;
  struct GetPeerCls *gpc;

  GNUNET_assert(0 != sampler->sampler_size);
  if (0 == num_peers)
    return NULL;

  // TODO check if we have too much (distinct) sampled peers
  req_handle = GNUNET_new(struct RPS_SamplerRequestHandle);
  req_handle->num_peers = num_peers;
  req_handle->cur_num_peers = 0;
  req_handle->ids = GNUNET_new_array(num_peers, struct GNUNET_PeerIdentity);
  req_handle->sampler = sampler;
  req_handle->callback = cb;
  req_handle->cls = cls;
  GNUNET_CONTAINER_DLL_insert(sampler->req_handle_head,
                              sampler->req_handle_tail,
                              req_handle);

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Scheduling requests for %" PRIu32 " peers\n", num_peers);

  for (i = 0; i < num_peers; i++)
    {
      gpc = GNUNET_new(struct GetPeerCls);
      gpc->req_handle = req_handle;
      gpc->req_single_info_handle = NULL;
      gpc->cont = check_n_peers_ready;
      gpc->cont_cls = req_handle;
      gpc->id = &req_handle->ids[i];

      GNUNET_CONTAINER_DLL_insert(req_handle->gpc_head,
                                  req_handle->gpc_tail,
                                  gpc);
      // maybe add a little delay
      gpc->get_peer_task = GNUNET_SCHEDULER_add_now(sampler->get_peers,
                                                    gpc);
    }
  return req_handle;
}


/**
 * Get one random peer with additional information.
 *
 * @param sampler the sampler to get peers from.
 * @param cb callback that will be called once the ids are ready.
 * @param cls closure given to @a cb
 */
struct RPS_SamplerRequestHandleSingleInfo *
RPS_sampler_get_rand_peer_info(struct RPS_Sampler *sampler,
                               RPS_sampler_sinlge_info_ready_cb cb,
                               void *cls)
{
  struct RPS_SamplerRequestHandleSingleInfo *req_handle;
  struct GetPeerCls *gpc;

  GNUNET_assert(0 != sampler->sampler_size);

  // TODO check if we have too much (distinct) sampled peers
  req_handle = GNUNET_new(struct RPS_SamplerRequestHandleSingleInfo);
  req_handle->id = GNUNET_malloc(sizeof(struct GNUNET_PeerIdentity));
  req_handle->sampler = sampler;
  req_handle->callback = cb;
  req_handle->cls = cls;
  GNUNET_CONTAINER_DLL_insert(sampler->req_handle_single_head,
                              sampler->req_handle_single_tail,
                              req_handle);

  gpc = GNUNET_new(struct GetPeerCls);
  gpc->req_handle = NULL;
  gpc->req_single_info_handle = req_handle;
  gpc->cont = check_peer_info_ready;
  gpc->cont_cls = req_handle;
  gpc->id = req_handle->id;

  GNUNET_CONTAINER_DLL_insert(req_handle->gpc_head,
                              req_handle->gpc_tail,
                              gpc);
  // maybe add a little delay
  gpc->get_peer_task = GNUNET_SCHEDULER_add_now(sampler->get_peers,
                                                gpc);
  return req_handle;
}


/**
 * Cancle a request issued through #RPS_sampler_n_rand_peers_ready_cb.
 *
 * @param req_handle the handle to the request
 */
void
RPS_sampler_request_cancel(struct RPS_SamplerRequestHandle *req_handle)
{
  struct GetPeerCls *i;

  while (NULL != (i = req_handle->gpc_head))
    {
      GNUNET_CONTAINER_DLL_remove(req_handle->gpc_head,
                                  req_handle->gpc_tail,
                                  i);
      if (NULL != i->get_peer_task)
        {
          GNUNET_SCHEDULER_cancel(i->get_peer_task);
        }
      if (NULL != i->notify_ctx)
        {
          GNUNET_CONTAINER_DLL_remove(req_handle->sampler->notify_ctx_head,
                                      req_handle->sampler->notify_ctx_tail,
                                      i->notify_ctx);
          GNUNET_free(i->notify_ctx);
          i->notify_ctx = NULL;
        }
      GNUNET_free(i);
    }
  GNUNET_free(req_handle->ids);
  req_handle->ids = NULL;
  GNUNET_CONTAINER_DLL_remove(req_handle->sampler->req_handle_head,
                              req_handle->sampler->req_handle_tail,
                              req_handle);
  GNUNET_free(req_handle);
}


/**
 * Cancle a request issued through #RPS_sampler_sinlge_info_ready_cb.
 *
 * @param req_handle the handle to the request
 */
void
RPS_sampler_request_single_info_cancel(
  struct RPS_SamplerRequestHandleSingleInfo *req_single_info_handle)
{
  struct GetPeerCls *i;

  while (NULL != (i = req_single_info_handle->gpc_head))
    {
      GNUNET_CONTAINER_DLL_remove(req_single_info_handle->gpc_head,
                                  req_single_info_handle->gpc_tail,
                                  i);
      if (NULL != i->get_peer_task)
        {
          GNUNET_SCHEDULER_cancel(i->get_peer_task);
        }
      if (NULL != i->notify_ctx)
        {
          GNUNET_CONTAINER_DLL_remove(req_single_info_handle->sampler->notify_ctx_head,
                                      req_single_info_handle->sampler->notify_ctx_tail,
                                      i->notify_ctx);
          GNUNET_free(i->notify_ctx);
          i->notify_ctx = NULL;
        }
      GNUNET_free(i);
    }
  GNUNET_free(req_single_info_handle->id);
  req_single_info_handle->id = NULL;
  GNUNET_CONTAINER_DLL_remove(req_single_info_handle->sampler->req_handle_single_head,
                              req_single_info_handle->sampler->req_handle_single_tail,
                              req_single_info_handle);
  GNUNET_free(req_single_info_handle);
}


/**
 * Cleans the sampler.
 */
void
RPS_sampler_destroy(struct RPS_Sampler *sampler)
{
  if (NULL != sampler->req_handle_head)
    {
      LOG(GNUNET_ERROR_TYPE_WARNING,
          "There are still pending requests. Going to remove them.\n");
      while (NULL != sampler->req_handle_head)
        {
          RPS_sampler_request_cancel(sampler->req_handle_head);
        }
    }
  sampler_empty(sampler);
  GNUNET_free(sampler);
}


/* end of rps-sampler_common.c */