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

     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 peerstore/gnunet-service-peerstore.c
 * @brief peerstore service implementation
 * @author Omar Tarabai
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "peerstore.h"
#include "gnunet_peerstore_plugin.h"
#include "peerstore_common.h"

/**
 * Connected client entry
 */
struct ClientEntry
{
  /**
   * DLL.
   */
  struct ClientEntry *next;

  /**
   * DLL.
   */
  struct ClientEntry *prev;

  /**
   * Corresponding server handle.
   */
  struct GNUNET_SERVER_Client *client;
};

/**
 * Interval for expired records cleanup (in seconds)
 */
#define EXPIRED_RECORDS_CLEANUP_INTERVAL 300    /* 5mins */

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

/**
 * Database plugin library name
 */
static char *db_lib_name;

/**
 * Database handle
 */
static struct GNUNET_PEERSTORE_PluginFunctions *db;

/**
 * Hashmap with all watch requests
 */
static struct GNUNET_CONTAINER_MultiHashMap *watchers;

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

/**
 * Head of linked list of connected clients
 */
static struct ClientEntry *client_head;

/**
 * Tail of linked list of connected clients
 */
static struct ClientEntry *client_tail;

/**
 * Are we in the process of shutting down the service? #GNUNET_YES / #GNUNET_NO
 */
static int in_shutdown;

/**
 * Perform the actual shutdown operations
 */
static void
do_shutdown ()
{
  if (NULL != db_lib_name)
  {
    GNUNET_break (NULL == GNUNET_PLUGIN_unload (db_lib_name, db));
    GNUNET_free (db_lib_name);
    db_lib_name = NULL;
  }
  if (NULL != nc)
  {
    GNUNET_SERVER_notification_context_destroy (nc);
    nc = NULL;
  }
  if (NULL != watchers)
  {
    GNUNET_CONTAINER_multihashmap_destroy (watchers);
    watchers = NULL;
  }
  GNUNET_SCHEDULER_shutdown ();
}


/**
 * Task run during shutdown.
 *
 * @param cls unused
 * @param tc unused
 */
static void
shutdown_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  in_shutdown = GNUNET_YES;
  if (NULL == client_head)      /* Only when no connected clients. */
    do_shutdown ();
}


/* Forward declaration */
static void
expire_records_continuation (void *cls, int success);


/**
 * Deletes any expired records from storage
 */
static void
cleanup_expired_records (void *cls,
                         const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  int ret;

  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
    return;
  GNUNET_assert (NULL != db);
  ret =
      db->expire_records (db->cls, GNUNET_TIME_absolute_get (),
                          expire_records_continuation, NULL);
  if (GNUNET_OK != ret)
  {
    GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply
                                  (GNUNET_TIME_UNIT_SECONDS,
                                   EXPIRED_RECORDS_CLEANUP_INTERVAL),
                                  &cleanup_expired_records, NULL);
  }
}


/**
 * Continuation to expire_records called by the peerstore plugin
 *
 * @param cls unused
 * @param success count of records deleted or #GNUNET_SYSERR
 */
static void
expire_records_continuation (void *cls, int success)
{
  if (success > 0)
    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "%d records expired.\n", success);
  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply
                                (GNUNET_TIME_UNIT_SECONDS,
                                 EXPIRED_RECORDS_CLEANUP_INTERVAL),
                                &cleanup_expired_records, NULL);
}


/**
 * Search for a disconnected client and remove it
 *
 * @param cls closuer, a 'struct GNUNET_PEERSTORE_Record *'
 * @param key hash of record key
 * @param value the watcher client, a 'struct GNUNET_SERVER_Client *'
 * @return #GNUNET_OK to continue iterating
 */
static int
client_disconnect_it (void *cls, const struct GNUNET_HashCode *key, void *value)
{
  if (cls == value)
    GNUNET_CONTAINER_multihashmap_remove (watchers, key, value);
  return GNUNET_OK;
}


/**
 * A client disconnected.  Remove all of its data structure entries.
 *
 * @param cls closure, NULL
 * @param client identification of the client
 */
static void
handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
{
  struct ClientEntry *ce;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "A client disconnected, cleaning up.\n");
  if (NULL != watchers)
    GNUNET_CONTAINER_multihashmap_iterate (watchers, &client_disconnect_it,
                                           client);
  ce = client_head;
  while (ce != NULL)
  {
    if (ce->client == client)
    {
      GNUNET_CONTAINER_DLL_remove (client_head, client_tail, ce);
      GNUNET_free (ce);
      break;
    }
    ce = ce->next;
  }
  if (NULL == client_head && in_shutdown)
    do_shutdown ();
}


/**
 * Function called by for each matching record.
 *
 * @param cls closure
 * @param record peerstore record found
 * @param emsg error message or NULL if no errors
 * @return #GNUNET_YES to continue iteration
 */
static int
record_iterator (void *cls, const struct GNUNET_PEERSTORE_Record *record,
                 const char *emsg)
{
  struct GNUNET_PEERSTORE_Record *cls_record = cls;
  struct StoreRecordMessage *srm;

  if (NULL == record)
  {
    /* No more records */
    struct GNUNET_MessageHeader endmsg;

    endmsg.size = htons (sizeof (struct GNUNET_MessageHeader));
    endmsg.type = htons (GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE_END);
    GNUNET_SERVER_notification_context_unicast (nc, cls_record->client, &endmsg,
                                                GNUNET_NO);
    GNUNET_SERVER_receive_done (cls_record->client,
                                NULL == emsg ? GNUNET_OK : GNUNET_SYSERR);
    PEERSTORE_destroy_record (cls_record);
    return GNUNET_NO;
  }

  srm =
      PEERSTORE_create_record_message (record->sub_system, record->peer,
                                       record->key, record->value,
                                       record->value_size, record->expiry,
                                       GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE_RECORD);
  GNUNET_SERVER_notification_context_unicast (nc, cls_record->client,
                                              (struct GNUNET_MessageHeader *)
                                              srm, GNUNET_NO);
  GNUNET_free (srm);
  return GNUNET_YES;
}


/**
 * Iterator over all watcher clients
 * to notify them of a new record
 *
 * @param cls closuer, a 'struct GNUNET_PEERSTORE_Record *'
 * @param key hash of record key
 * @param value the watcher client, a 'struct GNUNET_SERVER_Client *'
 * @return #GNUNET_YES to continue iterating
 */
static int
watch_notifier_it (void *cls, const struct GNUNET_HashCode *key, void *value)
{
  struct GNUNET_PEERSTORE_Record *record = cls;
  struct GNUNET_SERVER_Client *client = value;
  struct StoreRecordMessage *srm;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Found a watcher to update.\n");
  srm =
      PEERSTORE_create_record_message (record->sub_system, record->peer,
                                       record->key, record->value,
                                       record->value_size, record->expiry,
                                       GNUNET_MESSAGE_TYPE_PEERSTORE_WATCH_RECORD);
  GNUNET_SERVER_notification_context_unicast (nc, client,
                                              (const struct GNUNET_MessageHeader
                                               *) srm, GNUNET_NO);
  GNUNET_free (srm);
  return GNUNET_YES;
}


/**
 * Given a new record, notifies watchers
 *
 * @param record changed record to update watchers with
 */
static void
watch_notifier (struct GNUNET_PEERSTORE_Record *record)
{
  struct GNUNET_HashCode keyhash;

  PEERSTORE_hash_key (record->sub_system, record->peer, record->key, &keyhash);
  GNUNET_CONTAINER_multihashmap_get_multiple (watchers, &keyhash,
                                              &watch_notifier_it, record);
}


/**
 * Handle a watch cancel request from client
 *
 * @param cls unused
 * @param client identification of the client
 * @param message the actual message
 */
static void
handle_watch_cancel (void *cls, struct GNUNET_SERVER_Client *client,
                     const struct GNUNET_MessageHeader *message)
{
  struct StoreKeyHashMessage *hm;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Received a watch cancel request.\n");
  hm = (struct StoreKeyHashMessage *) message;
  GNUNET_CONTAINER_multihashmap_remove (watchers, &hm->keyhash, client);
  GNUNET_SERVER_receive_done (client, GNUNET_OK);
}


/**
 * Handle a watch request from client
 *
 * @param cls unused
 * @param client identification of the client
 * @param message the actual message
 */
static void
handle_watch (void *cls, struct GNUNET_SERVER_Client *client,
              const struct GNUNET_MessageHeader *message)
{
  struct StoreKeyHashMessage *hm;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Received a watch request.\n");
  hm = (struct StoreKeyHashMessage *) message;
  GNUNET_SERVER_client_mark_monitor (client);
  GNUNET_SERVER_notification_context_add (nc, client);
  GNUNET_CONTAINER_multihashmap_put (watchers, &hm->keyhash, client,
                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
  GNUNET_SERVER_receive_done (client, GNUNET_OK);
}


/**
 * Handle an iterate request from client
 *
 * @param cls unused
 * @param client identification of the client
 * @param message the actual message
 */
static void
handle_iterate (void *cls, struct GNUNET_SERVER_Client *client,
                const struct GNUNET_MessageHeader *message)
{
  struct GNUNET_PEERSTORE_Record *record;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Received an iterate request.\n");
  record = PEERSTORE_parse_record_message (message);
  if (NULL == record)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, _("Malformed iterate request.\n"));
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    return;
  }
  if (NULL == record->sub_system)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _("Sub system not supplied in client iterate request.\n"));
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    PEERSTORE_destroy_record (record);
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Iterate request: ss `%s', peer `%s', key `%s'\n",
              record->sub_system,
              (NULL == record->peer) ? "NULL" : GNUNET_i2s (record->peer),
              (NULL == record->key) ? "NULL" : record->key);
  GNUNET_SERVER_notification_context_add (nc, client);
  record->client = client;
  if (GNUNET_OK !=
      db->iterate_records (db->cls, record->sub_system, record->peer,
                           record->key, &record_iterator, record))
  {
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    PEERSTORE_destroy_record (record);
  }
}


/**
 * Continuation of store_record called by the peerstore plugin
 *
 * @param cls closure
 * @param success result
 */
static void
store_record_continuation (void *cls, int success)
{
  struct GNUNET_PEERSTORE_Record *record = cls;

  GNUNET_SERVER_receive_done (record->client, success);
  if (GNUNET_OK == success)
  {
    watch_notifier (record);
  }
  PEERSTORE_destroy_record (record);
}


/**
 * Handle a store request from client
 *
 * @param cls unused
 * @param client identification of the client
 * @param message the actual message
 */
static void
handle_store (void *cls, struct GNUNET_SERVER_Client *client,
              const struct GNUNET_MessageHeader *message)
{
  struct GNUNET_PEERSTORE_Record *record;
  struct StoreRecordMessage *srm;

  record = PEERSTORE_parse_record_message (message);
  if (NULL == record)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _("Malformed store request from client\n"));
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    return;
  }
  srm = (struct StoreRecordMessage *) message;
  if (NULL == record->sub_system || NULL == record->peer || NULL == record->key)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _("Full key not supplied in client store request\n"));
    PEERSTORE_destroy_record (record);
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Received a store request (size: %lu).\n" " Sub system `%s'\n"
              " Peer `%s'\n" " Key `%s'\n" " Value size %lu\n"
              " Options: %d.\n", record->value_size, record->sub_system,
              GNUNET_i2s (record->peer), record->key, record->value_size,
              ntohl (srm->options));
  record->client = client;
  if (GNUNET_OK !=
      db->store_record (db->cls, record->sub_system, record->peer, record->key,
                        record->value, record->value_size, *record->expiry,
                        ntohl (srm->options), store_record_continuation,
                        record))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _("Failed to store requested value, database error."));
    PEERSTORE_destroy_record (record);
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    return;
  }
}


/**
 * Creates an entry for a new client or returns it if it already exists.
 *
 * @param client Client handle
 * @return Client entry struct
 */
static struct ClientEntry *
make_client_entry (struct GNUNET_SERVER_Client *client)
{
  struct ClientEntry *ce;

  ce = client_head;
  while (NULL != ce)
  {
    if (ce->client == client)
      return ce;
    ce = ce->next;
  }
  if (GNUNET_YES == in_shutdown)
  {
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    return NULL;
  }
  ce = GNUNET_new (struct ClientEntry);
  ce->client = client;
  GNUNET_CONTAINER_DLL_insert (client_head, client_tail, ce);
  return ce;
}


/**
 * Callback on a new client connection
 *
 * @param cls closure (unused)
 * @param client identification of the client
 */
static void
handle_client_connect (void *cls, struct GNUNET_SERVER_Client *client)
{
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "New client connection created.\n");
  make_client_entry (client);
}


/**
 * Peerstore service runner.
 *
 * @param cls closure
 * @param server the initialized server
 * @param c configuration to use
 */
static void
run (void *cls, struct GNUNET_SERVER_Handle *server,
     const struct GNUNET_CONFIGURATION_Handle *c)
{
  static const struct GNUNET_SERVER_MessageHandler handlers[] = {
    {&handle_store, NULL, GNUNET_MESSAGE_TYPE_PEERSTORE_STORE, 0},
    {&handle_iterate, NULL, GNUNET_MESSAGE_TYPE_PEERSTORE_ITERATE, 0},
    {&handle_watch, NULL, GNUNET_MESSAGE_TYPE_PEERSTORE_WATCH,
     sizeof (struct StoreKeyHashMessage)},
    {&handle_watch_cancel, NULL, GNUNET_MESSAGE_TYPE_PEERSTORE_WATCH_CANCEL,
     sizeof (struct StoreKeyHashMessage)},
    {NULL, NULL, 0, 0}
  };
  char *database;

  in_shutdown = GNUNET_NO;
  cfg = c;
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_string (cfg, "peerstore", "DATABASE",
                                             &database))
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, _("No database backend configured\n"));

  else
  {
    GNUNET_asprintf (&db_lib_name, "libgnunet_plugin_peerstore_%s", database);
    db = GNUNET_PLUGIN_load (db_lib_name, (void *) cfg);
    GNUNET_free (database);
  }
  if (NULL == db)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _("Could not load database backend `%s'\n"), db_lib_name);
    GNUNET_SCHEDULER_add_now (&shutdown_task, NULL);
    return;
  }
  nc = GNUNET_SERVER_notification_context_create (server, 16);
  watchers = GNUNET_CONTAINER_multihashmap_create (10, GNUNET_NO);
  GNUNET_SCHEDULER_add_now (&cleanup_expired_records, NULL);
  GNUNET_SERVER_add_handlers (server, handlers);
  GNUNET_SERVER_connect_notify (server, &handle_client_connect, NULL);
  GNUNET_SERVER_disconnect_notify (server, &handle_client_disconnect, NULL);
  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &shutdown_task,
                                NULL);
}


/**
 * The main function for the peerstore service.
 *
 * @param argc number of arguments from the command line
 * @param argv command line arguments
 * @return 0 ok, 1 on error
 */
int
main (int argc, char *const *argv)
{
  return (GNUNET_OK ==
          GNUNET_SERVICE_run (argc, argv, "peerstore",
                              GNUNET_SERVICE_OPTION_SOFT_SHUTDOWN, &run,
                              NULL)) ? 0 : 1;
}

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