/*
     This file is part of GNUnet
     Copyright (C) 2012, 2013, 2018 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
 */

/**
 * @author Christian Grothoff
 *
 * @file
 * API that can be used to store naming information on a GNUnet node;
 *
 * @defgroup namestore  Name Store service
 * Store naming information on a GNUnet node.
 *
 * Naming information can either be records for which this peer/user is
 * authoritative, or blocks which are cached, encrypted naming data from other
 * peers.
 *
 * @see [Documentation](https://gnunet.org/namestore-subsystem)
 *
 * @{
 */
#ifndef GNUNET_NAMESTORE_SERVICE_H
#define GNUNET_NAMESTORE_SERVICE_H

#include "gnunet_util_lib.h"
#include "gnunet_block_lib.h"
#include "gnunet_gnsrecord_lib.h"

#ifdef __cplusplus
extern "C"
{
#if 0                           /* keep Emacsens' auto-indent happy */
}
#endif
#endif


/**
 * Entry in the queue.
 */
struct GNUNET_NAMESTORE_QueueEntry;

/**
 * Handle to the namestore service.
 */
struct GNUNET_NAMESTORE_Handle;

/**
 * Handle to the namestore zone iterator.
 */
struct GNUNET_NAMESTORE_ZoneIterator;


/**
 * Connect to the namestore service.
 *
 * @param cfg configuration to use
 * @return handle to use to access the service
 */
struct GNUNET_NAMESTORE_Handle *
GNUNET_NAMESTORE_connect (const struct GNUNET_CONFIGURATION_Handle *cfg);


/**
 * Disconnect from the namestore service (and free associated
 * resources).  Must not be called from within operation callbacks of
 * the API.
 *
 * @param h handle to the namestore
 */
void
GNUNET_NAMESTORE_disconnect (struct GNUNET_NAMESTORE_Handle *h);


/**
 * Continuation called to notify client about result of the
 * operation.
 *
 * @param cls closure
 * @param success #GNUNET_SYSERR on failure (including timeout/queue drop/failure to validate)
 *                #GNUNET_NO if content was already there or not found
 *                #GNUNET_YES (or other positive value) on success
 * @param emsg NULL on success, otherwise an error message
 */
typedef void
(*GNUNET_NAMESTORE_ContinuationWithStatus) (void *cls,
                                            int32_t success,
                                            const char *emsg);


/**
 * Store an item in the namestore.  If the item is already present,
 * it is replaced with the new record.  Use an empty array to
 * remove all records under the given name.
 *
 * The continuation is called after the value has been stored in the
 * database. Monitors may be notified asynchronously (basically with
 * a buffer). However, if any monitor is consistently too slow to
 * keep up with the changes, calling @a cont will be delayed until the
 * monitors do keep up.
 *
 * @param h handle to the namestore
 * @param pkey private key of the zone
 * @param label name that is being mapped
 * @param rd_count number of records in the 'rd' array
 * @param rd array of records with data to store
 * @param cont continuation to call when done
 * @param cont_cls closure for @a cont
 * @return handle to abort the request
 */
struct GNUNET_NAMESTORE_QueueEntry *
GNUNET_NAMESTORE_records_store (struct GNUNET_NAMESTORE_Handle *h,
                                const struct
                                GNUNET_CRYPTO_EcdsaPrivateKey *pkey,
                                const char *label,
                                unsigned int rd_count,
                                const struct GNUNET_GNSRECORD_Data *rd,
                                GNUNET_NAMESTORE_ContinuationWithStatus cont,
                                void *cont_cls);


/**
 * Process a record that was stored in the namestore.
 *
 * @param cls closure
 * @param zone private key of the zone
 * @param label label of the records
 * @param rd_count number of entries in @a rd array, 0 if label was deleted
 * @param rd array of records with data to store
 */
typedef void
(*GNUNET_NAMESTORE_RecordMonitor) (void *cls,
                                   const struct
                                   GNUNET_CRYPTO_EcdsaPrivateKey *zone,
                                   const char *label,
                                   unsigned int rd_count,
                                   const struct GNUNET_GNSRECORD_Data *rd);


/**
 * Lookup an item in the namestore.
 *
 * @param h handle to the namestore
 * @param pkey private key of the zone
 * @param label name that is being mapped
 * @param error_cb function to call on error (i.e. disconnect)
 *        the handle is afterwards invalid
 * @param error_cb_cls closure for @a error_cb
 * @param rm function to call with the result (with 0 records if we don't have that label);
 *        the handle is afterwards invalid
 * @param rm_cls closure for @a rm
 * @return handle to abort the request
 */
struct GNUNET_NAMESTORE_QueueEntry *
GNUNET_NAMESTORE_records_lookup (struct GNUNET_NAMESTORE_Handle *h,
                                 const struct
                                 GNUNET_CRYPTO_EcdsaPrivateKey *pkey,
                                 const char *label,
                                 GNUNET_SCHEDULER_TaskCallback error_cb,
                                 void *error_cb_cls,
                                 GNUNET_NAMESTORE_RecordMonitor rm,
                                 void *rm_cls);


/**
 * Look for an existing PKEY delegation record for a given public key.
 * Returns at most one result to the processor.
 *
 * @param h handle to the namestore
 * @param zone private key of the zone to look up in, never NULL
 * @param value_zone public key of the target zone (value), never NULL
 * @param error_cb function to call on error (i.e. disconnect)
 *        the handle is afterwards invalid
 * @param error_cb_cls closure for @a error_cb
 * @param proc function to call on the matching records, or with
 *        NULL (rd_count == 0) if there are no matching records;
 *        the handle is afterwards invalid
 * @param proc_cls closure for @a proc
 * @return a handle that can be used to
 *         cancel
 */
struct GNUNET_NAMESTORE_QueueEntry *
GNUNET_NAMESTORE_zone_to_name (struct GNUNET_NAMESTORE_Handle *h,
                               const struct GNUNET_CRYPTO_EcdsaPrivateKey *zone,
                               const struct
                               GNUNET_CRYPTO_EcdsaPublicKey *value_zone,
                               GNUNET_SCHEDULER_TaskCallback error_cb,
                               void *error_cb_cls,
                               GNUNET_NAMESTORE_RecordMonitor proc,
                               void *proc_cls);


/**
 * Cancel a namestore operation.  The final callback from the
 * operation must not have been done yet.  Must be called on any
 * namestore operation that has not yet completed prior to calling
 * #GNUNET_NAMESTORE_disconnect.
 *
 * @param qe operation to cancel
 */
void
GNUNET_NAMESTORE_cancel (struct GNUNET_NAMESTORE_QueueEntry *qe);


/**
 * Starts a new zone iteration (used to periodically PUT all of our
 * records into our DHT). This MUST lock the `struct GNUNET_NAMESTORE_Handle`
 * for any other calls than #GNUNET_NAMESTORE_zone_iterator_next() and
 * #GNUNET_NAMESTORE_zone_iteration_stop. @a proc will be called once
 * immediately, and then again after
 * #GNUNET_NAMESTORE_zone_iterator_next() is invoked.
 *
 * On error (disconnect), @a error_cb will be invoked.
 * On normal completion, @a finish_cb proc will be
 * invoked.
 *
 * @param h handle to the namestore
 * @param zone zone to access, NULL for all zones
 * @param error_cb function to call on error (i.e. disconnect),
 *        the handle is afterwards invalid
 * @param error_cb_cls closure for @a error_cb
 * @param proc function to call on each name from the zone; it
 *        will be called repeatedly with a value (if available)
 * @param proc_cls closure for @a proc
 * @param finish_cb function to call on completion
 *        the handle is afterwards invalid
 * @param finish_cb_cls closure for @a finish_cb
 * @return an iterator handle to use for iteration
 */
struct GNUNET_NAMESTORE_ZoneIterator *
GNUNET_NAMESTORE_zone_iteration_start (struct GNUNET_NAMESTORE_Handle *h,
                                       const struct
                                       GNUNET_CRYPTO_EcdsaPrivateKey *zone,
                                       GNUNET_SCHEDULER_TaskCallback error_cb,
                                       void *error_cb_cls,
                                       GNUNET_NAMESTORE_RecordMonitor proc,
                                       void *proc_cls,
                                       GNUNET_SCHEDULER_TaskCallback finish_cb,
                                       void *finish_cb_cls);


/**
 * Calls the record processor specified in #GNUNET_NAMESTORE_zone_iteration_start
 * for the next record.
 *
 * @param it the iterator
 * @param limit number of records to return to the iterator in one shot
 *         (before #GNUNET_NAMESTORE_zone_iterator_next is to be called again)
 */
void
GNUNET_NAMESTORE_zone_iterator_next (struct GNUNET_NAMESTORE_ZoneIterator *it,
                                     uint64_t limit);


/**
 * Stops iteration and releases the namestore handle for further calls.  Must
 * be called on any iteration that has not yet completed prior to calling
 * #GNUNET_NAMESTORE_disconnect.
 *
 * @param it the iterator
 */
void
GNUNET_NAMESTORE_zone_iteration_stop (struct GNUNET_NAMESTORE_ZoneIterator *it);


/**
 * Handle for a monitoring activity.
 */
struct GNUNET_NAMESTORE_ZoneMonitor;


/**
 * Begin monitoring a zone for changes.  Will first call the @a
 * monitor function on all existing records in the selected zone(s) if
 * @a iterate_first is #GNUNET_YES.  In any case, we will then call @a
 * sync_cb, and then afterwards call the @a monitor whenever a record
 * changes.  If the namestore disconnects, the @a error_cb function is
 * called with a disconnect event. Once the connection is
 * re-established, the process begins from the start (depending on @a
 * iterate_first, we will again first do all existing records, then @a
 * sync, then updates).
 *
 * @param cfg configuration to use to connect to namestore
 * @param zone zone to monitor, NULL for all zones
 * @param iterate_first #GNUNET_YES to first iterate over all existing records,
 *                      #GNUNET_NO to only return changes that happen from now on
 * @param error_cb function to call on error (i.e. disconnect); note that
 *         unlike the other error callbacks in this API, a call to this
 *         function does NOT destroy the monitor handle, it merely signals
 *         that monitoring is down. You need to still explicitly call
 *         #GNUNET_NAMESTORE_zone_monitor_stop().
 * @param error_cb_cls closure for @a error_cb
 * @param monitor function to call on zone changes, with an initial limit of 1
 * @param monitor_cls closure for @a monitor
 * @param sync_cb function called when we're in sync with the namestore
 * @param sync_cb_cls closure for @a sync_cb
 * @return handle to stop monitoring
 */
struct GNUNET_NAMESTORE_ZoneMonitor *
GNUNET_NAMESTORE_zone_monitor_start (const struct
                                     GNUNET_CONFIGURATION_Handle *cfg,
                                     const struct
                                     GNUNET_CRYPTO_EcdsaPrivateKey *zone,
                                     int iterate_first,
                                     GNUNET_SCHEDULER_TaskCallback error_cb,
                                     void *error_cb_cls,
                                     GNUNET_NAMESTORE_RecordMonitor monitor,
                                     void *monitor_cls,
                                     GNUNET_SCHEDULER_TaskCallback sync_cb,
                                     void *sync_cb_cls);


/**
 * Calls the monitor processor specified in #GNUNET_NAMESTORE_zone_monitor_start
 * for the next record(s).  This function is used to allow clients that merely
 * monitor the NAMESTORE to still throttle namestore operations, so we can be
 * sure that the monitors can keep up.
 *
 * Note that #GNUNET_NAMESTORE_records_store() only waits for this
 * call if the previous limit set by the client was already reached.
 * Thus, by using a @a limit greater than 1, monitors basically enable
 * a queue of notifications to be processed asynchronously with some
 * delay.  Note that even with a limit of 1 the
 * #GNUNET_NAMESTORE_records_store() function will run asynchronously
 * and the continuation may be invoked before the monitors completed
 * (or even started) processing the notification.  Thus, monitors will
 * only closely track the current state of the namestore, but not
 * be involved in the transactions.
 *
 * @param zm the monitor
 * @param limit number of records to return to the iterator in one shot
 *        (before #GNUNET_NAMESTORE_zone_monitor_next is to be called again)
 */
void
GNUNET_NAMESTORE_zone_monitor_next (struct GNUNET_NAMESTORE_ZoneMonitor *zm,
                                    uint64_t limit);


/**
 * Stop monitoring a zone for changes.
 *
 * @param zm handle to the monitor activity to stop
 */
void
GNUNET_NAMESTORE_zone_monitor_stop (struct GNUNET_NAMESTORE_ZoneMonitor *zm);


#if 0                           /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif

#endif

/** @} */  /* end of group */
