/*
     This file is part of GNUnet.
     Copyright (C) 2009, 2010, 2012, 2014, 2016 GNUnet e.V.

     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 statistics/gnunet-service-statistics.c
 * @brief program that tracks statistics
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_bio_lib.h"
#include "gnunet_container_lib.h"
#include "gnunet_disk_lib.h"
#include "gnunet_getopt_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_service_lib.h"
#include "gnunet_statistics_service.h"
#include "gnunet_strings_lib.h"
#include "gnunet_time_lib.h"
#include "statistics.h"

/**
 * Watch entry.
 */
struct WatchEntry {
  /**
   * Watch entries are kept in a linked list.
   */
  struct WatchEntry *next;

  /**
   * Watch entries are kept in a linked list.
   */
  struct WatchEntry *prev;

  /**
   * For which client is this watch entry?
   */
  struct ClientEntry *ce;

  /**
   * Last value we communicated to the client for this watch entry.
   */
  uint64_t last_value;

  /**
   * Unique watch number for this client and this watched value.
   */
  uint32_t wid;

  /**
   * Is last_value valid
   * #GNUNET_NO : last_value is n/a, #GNUNET_YES: last_value is valid
   */
  int last_value_set;
};


/**
 * We keep the statistics organized by subsystem for faster
 * lookup during SET operations.
 */
struct SubsystemEntry;


/**
 * Entry in the statistics list.
 */
struct StatsEntry {
  /**
   * This is a linked list.
   */
  struct StatsEntry *next;

  /**
   * This is a linked list.
   */
  struct StatsEntry *prev;

  /**
   * Subsystem this entry belongs to.
   */
  struct SubsystemEntry *subsystem;

  /**
   * Name for the value stored by this entry, allocated at the end of
   * this struct.
   */
  const char *name;

  /**
   * Watch context for changes to this value, or NULL for none.
   */
  struct WatchEntry *we_head;

  /**
   * Watch context for changes to this value, or NULL for none.
   */
  struct WatchEntry *we_tail;

  /**
   * Our value.
   */
  uint64_t value;

  /**
   * Unique ID.
   */
  uint32_t uid;

  /**
   * Is this value persistent?
   */
  int persistent;

  /**
   * Is this value set?
   * #GNUNET_NO: value is n/a, #GNUNET_YES: value is valid
   */
  int set;
};


/**
 * We keep the statistics organized by subsystem for faster
 * lookup during SET operations.
 */
struct SubsystemEntry {
  /**
   * Subsystems are kept in a DLL.
   */
  struct SubsystemEntry *next;

  /**
   * Subsystems are kept in a DLL.
   */
  struct SubsystemEntry *prev;

  /**
   * Head of list of values kept for this subsystem.
   */
  struct StatsEntry *stat_head;

  /**
   * Tail of list of values kept for this subsystem.
   */
  struct StatsEntry *stat_tail;

  /**
   * Name of the subsystem this entry is for, allocated at
   * the end of this struct, do not free().
   */
  const char *service;
};


/**
 * Client entry.
 */
struct ClientEntry {
  /**
   * Corresponding server handle.
   */
  struct GNUNET_SERVICE_Client *client;

  /**
   * Corresponding message queue.
   */
  struct GNUNET_MQ_Handle *mq;

  /**
   * Which subsystem is this client writing to (SET/UPDATE)?
   */
  struct SubsystemEntry *subsystem;

  /**
   * Maximum watch ID used by this client so far.
   */
  uint32_t max_wid;
};


/**
 * Our configuration.
 */
static const struct GNUNET_CONFIGURATION_Handle *cfg;

/**
 * Head of linked list of subsystems with active statistics.
 */
static struct SubsystemEntry *sub_head;

/**
 * Tail of linked list of subsystems with active statistics.
 */
static struct SubsystemEntry *sub_tail;

/**
 * Number of connected clients.
 */
static unsigned int client_count;

/**
 * Our notification context.
 */
static struct GNUNET_NotificationContext *nc;

/**
 * Counter used to generate unique values.
 */
static uint32_t uidgen;

/**
 * Set to #GNUNET_YES if we are shutting down as soon as possible.
 */
static int in_shutdown;


/**
 * Write persistent statistics to disk.
 */
static void
save()
{
  struct SubsystemEntry *se;
  struct StatsEntry *pos;
  char *fn;
  struct GNUNET_BIO_WriteHandle *wh;
  uint16_t size;
  unsigned long long total;
  size_t nlen;
  size_t slen;
  struct GNUNET_STATISTICS_SetMessage *msg;

  if (GNUNET_OK != GNUNET_CONFIGURATION_get_value_filename(cfg,
                                                           "STATISTICS",
                                                           "DATABASE",
                                                           &fn))
    {
      GNUNET_log_config_missing(GNUNET_ERROR_TYPE_ERROR,
                                "STATISTICS",
                                "DATABASE");
      return;
    }
  (void)GNUNET_DISK_directory_create_for_file(fn);
  wh = GNUNET_BIO_write_open(fn);
  total = 0;
  while (NULL != (se = sub_head))
    {
      GNUNET_CONTAINER_DLL_remove(sub_head, sub_tail, se);
      slen = strlen(se->service) + 1;
      while (NULL != (pos = se->stat_head))
        {
          GNUNET_CONTAINER_DLL_remove(se->stat_head, se->stat_tail, pos);
          if ((pos->persistent) && (NULL != wh))
            {
              nlen = strlen(pos->name) + 1;
              size = sizeof(struct GNUNET_STATISTICS_SetMessage) + nlen + slen;
              GNUNET_assert(size < UINT16_MAX);
              msg = GNUNET_malloc(size);

              msg->header.size = htons((uint16_t)size);
              msg->header.type = htons(GNUNET_MESSAGE_TYPE_STATISTICS_SET);
              GNUNET_assert(nlen + slen ==
                            GNUNET_STRINGS_buffer_fill((char *)&msg[1],
                                                       nlen + slen,
                                                       2,
                                                       se->service,
                                                       pos->name));
              msg->flags =
                htonl(pos->persistent ? GNUNET_STATISTICS_SETFLAG_PERSISTENT : 0);
              msg->value = GNUNET_htonll(pos->value);
              if (GNUNET_OK != GNUNET_BIO_write(wh, msg, size))
                {
                  GNUNET_log_strerror_file(GNUNET_ERROR_TYPE_WARNING, "write", fn);
                  if (GNUNET_OK != GNUNET_BIO_write_close(wh))
                    GNUNET_log_strerror_file(GNUNET_ERROR_TYPE_WARNING, "close", fn);
                  wh = NULL;
                }
              else
                {
                  total += size;
                }
              GNUNET_free(msg);
            }
          GNUNET_free(pos);
        }
      GNUNET_free(se);
    }
  if (NULL != wh)
    {
      if (GNUNET_OK != GNUNET_BIO_write_close(wh))
        GNUNET_log_strerror_file(GNUNET_ERROR_TYPE_WARNING, "close", fn);
      if (0 == total)
        GNUNET_break(0 == unlink(fn));
      else
        GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                   _("Wrote %llu bytes of statistics to `%s'\n"),
                   total,
                   fn);
    }
  GNUNET_free_non_null(fn);
}


/**
 * Transmit the given stats value.
 *
 * @param client receiver of the value
 * @param e value to transmit
 */
static void
transmit(struct ClientEntry *ce, const struct StatsEntry *e)
{
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_STATISTICS_ReplyMessage *m;
  size_t size;

  size = strlen(e->subsystem->service) + 1 + strlen(e->name) + 1;
  GNUNET_assert(size < GNUNET_MAX_MESSAGE_SIZE);
  env = GNUNET_MQ_msg_extra(m, size, GNUNET_MESSAGE_TYPE_STATISTICS_VALUE);
  m->uid = htonl(e->uid);
  if (e->persistent)
    m->uid |= htonl(GNUNET_STATISTICS_PERSIST_BIT);
  m->value = GNUNET_htonll(e->value);
  GNUNET_assert(size == GNUNET_STRINGS_buffer_fill((char *)&m[1],
                                                   size,
                                                   2,
                                                   e->subsystem->service,
                                                   e->name));
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Transmitting value for `%s:%s' (%d): %llu\n",
             e->subsystem->service,
             e->name,
             e->persistent,
             (unsigned long long)e->value);
  GNUNET_MQ_send(ce->mq, env);
}


/**
 * Callback called when a client connects to the service.
 *
 * @param cls closure for the service
 * @param c the new client that connected to the service
 * @param mq the message queue used to send messages to the client
 * @return @a c
 */
static void *
client_connect_cb(void *cls,
                  struct GNUNET_SERVICE_Client *c,
                  struct GNUNET_MQ_Handle *mq)
{
  struct ClientEntry *ce;

  ce = GNUNET_new(struct ClientEntry);
  ce->client = c;
  ce->mq = mq;
  client_count++;
  GNUNET_notification_context_add(nc, mq);
  return ce;
}


/**
 * Check integrity of GET-message.
 *
 * @param cls identification of the client
 * @param message the actual message
 * @return #GNUNET_OK if @a message is well-formed
 */
static int
check_get(void *cls, const struct GNUNET_MessageHeader *message)
{
  const char *service;
  const char *name;
  size_t size;

  size = ntohs(message->size) - sizeof(struct GNUNET_MessageHeader);
  if (size != GNUNET_STRINGS_buffer_tokenize((const char *)&message[1],
                                             size,
                                             2,
                                             &service,
                                             &name))
    {
      GNUNET_break(0);
      return GNUNET_SYSERR;
    }
  return GNUNET_OK;
}


/**
 * Handle GET-message.
 *
 * @param cls identification of the client
 * @param message the actual message
 */
static void
handle_get(void *cls, const struct GNUNET_MessageHeader *message)
{
  struct ClientEntry *ce = cls;
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_MessageHeader *end;
  const char *service;
  const char *name;
  size_t slen;
  size_t nlen;
  struct SubsystemEntry *se;
  struct StatsEntry *pos;
  size_t size;

  size = ntohs(message->size) - sizeof(struct GNUNET_MessageHeader);
  GNUNET_assert(size ==
                GNUNET_STRINGS_buffer_tokenize((const char *)&message[1],
                                               size,
                                               2,
                                               &service,
                                               &name));
  slen = strlen(service);
  nlen = strlen(name);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Received request for statistics on `%s:%s'\n",
             slen ? service : "*",
             nlen ? name : "*");
  for (se = sub_head; NULL != se; se = se->next)
    {
      if (!((0 == slen) || (0 == strcmp(service, se->service))))
        continue;
      for (pos = se->stat_head; NULL != pos; pos = pos->next)
        {
          if (!((0 == nlen) || (0 == strcmp(name, pos->name))))
            continue;
          transmit(ce, pos);
        }
    }
  env = GNUNET_MQ_msg(end, GNUNET_MESSAGE_TYPE_STATISTICS_END);
  GNUNET_MQ_send(ce->mq, env);
  GNUNET_SERVICE_client_continue(ce->client);
}


/**
 * Notify all clients listening about a change to a value.
 *
 * @param se value that changed
 */
static void
notify_change(struct StatsEntry *se)
{
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_STATISTICS_WatchValueMessage *wvm;
  struct WatchEntry *pos;

  for (pos = se->we_head; NULL != pos; pos = pos->next)
    {
      if (GNUNET_YES == pos->last_value_set)
        {
          if (pos->last_value == se->value)
            continue;
        }
      else
        {
          pos->last_value_set = GNUNET_YES;
        }
      env = GNUNET_MQ_msg(wvm, GNUNET_MESSAGE_TYPE_STATISTICS_WATCH_VALUE);
      wvm->flags =
        htonl(se->persistent ? GNUNET_STATISTICS_SETFLAG_PERSISTENT : 0);
      wvm->wid = htonl(pos->wid);
      wvm->reserved = htonl(0);
      wvm->value = GNUNET_htonll(se->value);
      GNUNET_MQ_send(pos->ce->mq, env);
      pos->last_value = se->value;
    }
}


/**
 * Find the subsystem entry of the given name for the specified client.
 *
 * @param ce client looking for the subsystem, may contain a hint
 *           to find the entry faster, can be NULL
 * @param service name of the subsystem to look for
 * @return subsystem entry, never NULL (subsystem entry is created if necessary)
 */
static struct SubsystemEntry *
find_subsystem_entry(struct ClientEntry *ce, const char *service)
{
  size_t slen;
  struct SubsystemEntry *se;

  if (NULL != ce)
    se = ce->subsystem;
  else
    se = NULL;
  if ((NULL == se) || (0 != strcmp(service, se->service)))
    {
      for (se = sub_head; NULL != se; se = se->next)
        if (0 == strcmp(service, se->service))
          break;
      if (NULL != ce)
        ce->subsystem = se;
    }
  if (NULL != se)
    return se;
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Allocating new subsystem entry `%s'\n",
             service);
  slen = strlen(service) + 1;
  se = GNUNET_malloc(sizeof(struct SubsystemEntry) + slen);
  GNUNET_memcpy(&se[1], service, slen);
  se->service = (const char *)&se[1];
  GNUNET_CONTAINER_DLL_insert(sub_head, sub_tail, se);
  if (NULL != ce)
    ce->subsystem = se;
  return se;
}


/**
 * Find the statistics entry of the given subsystem.
 *
 * @param subsystem subsystem to look in
 * @param name name of the entry to look for
 * @return statistis entry, or NULL if not found
 */
static struct StatsEntry *
find_stat_entry(struct SubsystemEntry *se, const char *name)
{
  struct StatsEntry *pos;

  for (pos = se->stat_head; NULL != pos; pos = pos->next)
    if (0 == strcmp(name, pos->name))
      return pos;
  return NULL;
}


/**
 * Check format of SET-message.
 *
 * @param cls the `struct ClientEntry`
 * @param message the actual message
 * @return #GNUNET_OK if message is well-formed
 */
static int
check_set(void *cls, const struct GNUNET_STATISTICS_SetMessage *msg)
{
  const char *service;
  const char *name;
  size_t msize;

  msize = ntohs(msg->header.size) - sizeof(*msg);
  if (msize != GNUNET_STRINGS_buffer_tokenize((const char *)&msg[1],
                                              msize,
                                              2,
                                              &service,
                                              &name))
    {
      GNUNET_break(0);
      return GNUNET_SYSERR;
    }
  return GNUNET_OK;
}


/**
 * Handle SET-message.
 *
 * @param cls the `struct ClientEntry`
 * @param message the actual message
 */
static void
handle_set(void *cls, const struct GNUNET_STATISTICS_SetMessage *msg)
{
  struct ClientEntry *ce = cls;
  const char *service;
  const char *name;
  size_t nlen;
  uint16_t msize;
  uint16_t size;
  struct SubsystemEntry *se;
  struct StatsEntry *pos;
  uint32_t flags;
  uint64_t value;
  int64_t delta;
  int changed;
  int initial_set;

  msize = ntohs(msg->header.size);
  size = msize - sizeof(struct GNUNET_STATISTICS_SetMessage);
  GNUNET_assert(size == GNUNET_STRINGS_buffer_tokenize((const char *)&msg[1],
                                                       size,
                                                       2,
                                                       &service,
                                                       &name));
  se = find_subsystem_entry(ce, service);
  flags = ntohl(msg->flags);
  value = GNUNET_ntohll(msg->value);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Received request to update statistic on `%s:%s' (%u) to/by %llu\n",
             service,
             name,
             (unsigned int)flags,
             (unsigned long long)value);
  pos = find_stat_entry(se, name);
  if (NULL != pos)
    {
      initial_set = 0;
      if (0 == (flags & GNUNET_STATISTICS_SETFLAG_RELATIVE))
        {
          changed = (pos->value != value);
          pos->value = value;
        }
      else
        {
          delta = (int64_t)value;
          if ((delta < 0) && (pos->value < -delta))
            {
              changed = (0 != pos->value);
              pos->value = 0;
            }
          else
            {
              changed = (0 != delta);
              GNUNET_break((delta <= 0) || (pos->value + delta > pos->value));
              pos->value += delta;
            }
        }
      if (GNUNET_NO == pos->set)
        {
          pos->set = GNUNET_YES;
          initial_set = 1;
        }
      pos->persistent = (0 != (flags & GNUNET_STATISTICS_SETFLAG_PERSISTENT));
      if (pos != se->stat_head)
        {
          /* move to front for faster setting next time! */
          GNUNET_CONTAINER_DLL_remove(se->stat_head, se->stat_tail, pos);
          GNUNET_CONTAINER_DLL_insert(se->stat_head, se->stat_tail, pos);
        }
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "Statistic `%s:%s' updated to value %llu (%d).\n",
                 service,
                 name,
                 (unsigned long long)pos->value,
                 pos->persistent);
      if ((changed) || (1 == initial_set))
        notify_change(pos);
      GNUNET_SERVICE_client_continue(ce->client);
      return;
    }
  /* not found, create a new entry */
  nlen = strlen(name) + 1;
  pos = GNUNET_malloc(sizeof(struct StatsEntry) + nlen);
  GNUNET_memcpy(&pos[1], name, nlen);
  pos->name = (const char *)&pos[1];
  pos->subsystem = se;
  if ((0 == (flags & GNUNET_STATISTICS_SETFLAG_RELATIVE)) ||
      (0 < (int64_t)GNUNET_ntohll(msg->value)))
    {
      pos->value = GNUNET_ntohll(msg->value);
      pos->set = GNUNET_YES;
    }
  else
    {
      pos->set = GNUNET_NO;
    }
  pos->uid = uidgen++;
  pos->persistent = (0 != (flags & GNUNET_STATISTICS_SETFLAG_PERSISTENT));
  GNUNET_CONTAINER_DLL_insert(se->stat_head, se->stat_tail, pos);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "New statistic on `%s:%s' with value %llu created.\n",
             service,
             name,
             (unsigned long long)pos->value);
  if (NULL != ce)
    GNUNET_SERVICE_client_continue(ce->client);
}


/**
 * Check integrity of WATCH-message.
 *
 * @param cls the `struct ClientEntry *`
 * @param message the actual message
 * @return #GNUNET_OK if message is well-formed
 */
static int
check_watch(void *cls, const struct GNUNET_MessageHeader *message)
{
  size_t size;
  const char *service;
  const char *name;

  size = ntohs(message->size) - sizeof(struct GNUNET_MessageHeader);
  if (size != GNUNET_STRINGS_buffer_tokenize((const char *)&message[1],
                                             size,
                                             2,
                                             &service,
                                             &name))
    {
      GNUNET_break(0);
      return GNUNET_SYSERR;
    }
  return GNUNET_OK;
}


/**
 * Handle WATCH-message.
 *
 * @param cls the `struct ClientEntry *`
 * @param message the actual message
 */
static void
handle_watch(void *cls, const struct GNUNET_MessageHeader *message)
{
  struct ClientEntry *ce = cls;
  const char *service;
  const char *name;
  uint16_t msize;
  uint16_t size;
  struct SubsystemEntry *se;
  struct StatsEntry *pos;
  struct WatchEntry *we;
  size_t nlen;

  if (NULL == nc)
    {
      GNUNET_SERVICE_client_drop(ce->client);
      return;
    }
  GNUNET_SERVICE_client_mark_monitor(ce->client);
  msize = ntohs(message->size);
  size = msize - sizeof(struct GNUNET_MessageHeader);
  GNUNET_assert(size ==
                GNUNET_STRINGS_buffer_tokenize((const char *)&message[1],
                                               size,
                                               2,
                                               &service,
                                               &name));
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
             "Received request to watch statistic on `%s:%s'\n",
             service,
             name);
  se = find_subsystem_entry(ce, service);
  pos = find_stat_entry(se, name);
  if (NULL == pos)
    {
      nlen = strlen(name) + 1;
      pos = GNUNET_malloc(sizeof(struct StatsEntry) + nlen);
      GNUNET_memcpy(&pos[1], name, nlen);
      pos->name = (const char *)&pos[1];
      pos->subsystem = se;
      GNUNET_CONTAINER_DLL_insert(se->stat_head, se->stat_tail, pos);
      pos->uid = uidgen++;
      pos->set = GNUNET_NO;
      GNUNET_log(GNUNET_ERROR_TYPE_DEBUG,
                 "New statistic on `%s:%s' with value %llu created.\n",
                 service,
                 name,
                 (unsigned long long)pos->value);
    }
  we = GNUNET_new(struct WatchEntry);
  we->ce = ce;
  we->last_value_set = GNUNET_NO;
  we->wid = ce->max_wid++;
  GNUNET_CONTAINER_DLL_insert(pos->we_head, pos->we_tail, we);
  if (0 != pos->value)
    notify_change(pos);
  GNUNET_SERVICE_client_continue(ce->client);
}


/**
 * Handle DISCONNECT-message.  Sync to disk and send
 * back a #GNUNET_MESSAGE_TYPE_STATISTICS_DISCONNECT_CONFIRM
 * message.
 *
 * @param cls the `struct ClientEntry *`
 * @param message the actual message
 */
static void
handle_disconnect(void *cls, const struct GNUNET_MessageHeader *message)
{
  struct ClientEntry *ce = cls;
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_MessageHeader *msg;

  env = GNUNET_MQ_msg(msg, GNUNET_MESSAGE_TYPE_STATISTICS_DISCONNECT_CONFIRM);
  GNUNET_MQ_send(ce->mq, env);
  GNUNET_SERVICE_client_continue(ce->client);
}


/**
 * Actually perform the shutdown.
 */
static void
do_shutdown()
{
  struct WatchEntry *we;
  struct StatsEntry *pos;
  struct SubsystemEntry *se;

  if (NULL == nc)
    return;
  save();
  GNUNET_notification_context_destroy(nc);
  nc = NULL;
  GNUNET_assert(0 == client_count);
  while (NULL != (se = sub_head))
    {
      GNUNET_CONTAINER_DLL_remove(sub_head, sub_tail, se);
      while (NULL != (pos = se->stat_head))
        {
          GNUNET_CONTAINER_DLL_remove(se->stat_head, se->stat_tail, pos);
          while (NULL != (we = pos->we_head))
            {
              GNUNET_break(0);
              GNUNET_CONTAINER_DLL_remove(pos->we_head, pos->we_tail, we);
              GNUNET_free(we);
            }
          GNUNET_free(pos);
        }
      GNUNET_free(se);
    }
}


/**
 * Task run during shutdown.
 *
 * @param cls unused
 */
static void
shutdown_task(void *cls)
{
  in_shutdown = GNUNET_YES;
  if (0 != client_count)
    return;
  do_shutdown();
}


/**
 * A client disconnected.  Remove all of its data structure entries.
 *
 * @param cls closure, NULL
 * @param client identification of the client
 * @param app_cls the `struct ClientEntry *`
 */
static void
client_disconnect_cb(void *cls,
                     struct GNUNET_SERVICE_Client *client,
                     void *app_cls)
{
  struct ClientEntry *ce = app_cls;
  struct WatchEntry *we;
  struct WatchEntry *wen;
  struct StatsEntry *pos;
  struct SubsystemEntry *se;

  client_count--;
  for (se = sub_head; NULL != se; se = se->next)
    {
      for (pos = se->stat_head; NULL != pos; pos = pos->next)
        {
          wen = pos->we_head;
          while (NULL != (we = wen))
            {
              wen = we->next;
              if (we->ce != ce)
                continue;
              GNUNET_CONTAINER_DLL_remove(pos->we_head, pos->we_tail, we);
              GNUNET_free(we);
            }
        }
    }
  GNUNET_free(ce);
  if ((0 == client_count) && (GNUNET_YES == in_shutdown))
    do_shutdown();
}


/**
 * We've read a `struct GNUNET_STATISTICS_SetMessage *` from
 * disk. Check that it is well-formed, and if so pass it to
 * the handler for set messages.
 *
 * @param cls NULL
 * @param message the message found on disk
 * @return #GNUNET_OK on success,
 *    #GNUNET_NO to stop further processing (no error)
 *    #GNUNET_SYSERR to stop further processing with error
 */
static int
inject_message(void *cls, const struct GNUNET_MessageHeader *message)
{
  uint16_t msize = ntohs(message->size);
  const struct GNUNET_STATISTICS_SetMessage *sm;

  sm = (const struct GNUNET_STATISTICS_SetMessage *)message;
  if ((sizeof(struct GNUNET_STATISTICS_SetMessage) > msize) ||
      (GNUNET_OK != check_set(NULL, sm)))
    {
      GNUNET_break(0);
      return GNUNET_SYSERR;
    }
  handle_set(NULL, sm);
  return GNUNET_OK;
}


/**
 * Load persistent values from disk.  Disk format is exactly the same
 * format that we also use for setting the values over the network.
 */
static void
load()
{
  char *fn;
  struct GNUNET_BIO_ReadHandle *rh;
  uint64_t fsize;
  char *buf;
  struct GNUNET_MessageStreamTokenizer *mst;

  if (GNUNET_OK != GNUNET_CONFIGURATION_get_value_filename(cfg,
                                                           "STATISTICS",
                                                           "DATABASE",
                                                           &fn))
    {
      GNUNET_log_config_missing(GNUNET_ERROR_TYPE_ERROR,
                                "STATISTICS",
                                "DATABASE");
      return;
    }
  if ((GNUNET_OK !=
       GNUNET_DISK_file_size(fn, &fsize, GNUNET_NO, GNUNET_YES)) ||
      (0 == fsize))
    {
      GNUNET_free(fn);
      return;
    }
  buf = GNUNET_malloc(fsize);
  rh = GNUNET_BIO_read_open(fn);
  if (!rh)
    {
      GNUNET_free(buf);
      GNUNET_free(fn);
      return;
    }
  if (GNUNET_OK != GNUNET_BIO_read(rh, fn, buf, fsize))
    {
      GNUNET_log_strerror_file(GNUNET_ERROR_TYPE_WARNING, "read", fn);
      GNUNET_break(GNUNET_OK == GNUNET_BIO_read_close(rh, NULL));
      GNUNET_free(buf);
      GNUNET_free(fn);
      return;
    }
  GNUNET_log(GNUNET_ERROR_TYPE_INFO,
             _("Loading %llu bytes of statistics from `%s'\n"),
             (unsigned long long)fsize,
             fn);
  mst = GNUNET_MST_create(&inject_message, NULL);
  GNUNET_break(
    GNUNET_OK ==
    GNUNET_MST_from_buffer(mst, buf, (size_t)fsize, GNUNET_YES, GNUNET_NO));
  GNUNET_MST_destroy(mst);
  GNUNET_free(buf);
  GNUNET_break(GNUNET_OK == GNUNET_BIO_read_close(rh, NULL));
  GNUNET_free(fn);
}


/**
 * Process statistics requests.
 *
 * @param cls closure
 * @param c configuration to use
 * @param service the initialized service
 */
static void
run(void *cls,
    const struct GNUNET_CONFIGURATION_Handle *c,
    struct GNUNET_SERVICE_Handle *service)
{
  cfg = c;
  nc = GNUNET_notification_context_create(16);
  load();
  GNUNET_SCHEDULER_add_shutdown(&shutdown_task, NULL);
}


/**
 * Define "main" method using service macro.
 */
GNUNET_SERVICE_MAIN(
  "statistics",
  GNUNET_SERVICE_OPTION_SOFT_SHUTDOWN,
  &run,
  &client_connect_cb,
  &client_disconnect_cb,
  NULL,
  GNUNET_MQ_hd_var_size(set,
                        GNUNET_MESSAGE_TYPE_STATISTICS_SET,
                        struct GNUNET_STATISTICS_SetMessage,
                        NULL),
  GNUNET_MQ_hd_var_size(get,
                        GNUNET_MESSAGE_TYPE_STATISTICS_GET,
                        struct GNUNET_MessageHeader,
                        NULL),
  GNUNET_MQ_hd_var_size(watch,
                        GNUNET_MESSAGE_TYPE_STATISTICS_WATCH,
                        struct GNUNET_MessageHeader,
                        NULL),
  GNUNET_MQ_hd_fixed_size(disconnect,
                          GNUNET_MESSAGE_TYPE_STATISTICS_DISCONNECT,
                          struct GNUNET_MessageHeader,
                          NULL),
  GNUNET_MQ_handler_end());


#if defined(LINUX) && defined(__GLIBC__)
#include <malloc.h>

/**
 * MINIMIZE heap size (way below 128k) since this process doesn't need much.
 */
void __attribute__ ((constructor)) GNUNET_STATISTICS_memory_init()
{
  mallopt(M_TRIM_THRESHOLD, 4 * 1024);
  mallopt(M_TOP_PAD, 1 * 1024);
  malloc_trim(0);
}
#endif


/* end of gnunet-service-statistics.c */