/*
Copyright (c) 2021 Roger Light <roger@atchoo.org>

All rights reserved. This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
and Eclipse Distribution License v1.0 which accompany this distribution.

The Eclipse Public License is available at
   https://www.eclipse.org/legal/epl-2.0/
and the Eclipse Distribution License is available at
  http://www.eclipse.org/org/documents/edl-v10.php.

SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause

Contributors:
   Roger Light - initial implementation and documentation.
*/

/*
 * This is an *example* plugin which forces all messages processed by the
 * broker to be treated as though they had the retained bit set.
 *
 * Compile with:
 *   gcc -I<path to mosquitto-repo/include> -fPIC -shared mosquitto_force_retain.c -o mosquitto_force_retain.so
 *
 * Use in config with:
 *
 *   plugin /path/to/mosquitto_force_retain.so
 *
 * Note that this only works on Mosquitto 2.0 or later.
 */
#include <stdio.h>
#include <string.h>

#include "mosquitto_broker.h"
#include "mosquitto_plugin.h"
#include "mosquitto.h"
#include "mqtt_protocol.h"

#define PLUGIN_NAME "force-retain"
#define PLUGIN_VERSION "1.0"

#define UNUSED(A) (void)(A)

MOSQUITTO_PLUGIN_DECLARE_VERSION(5);

static mosquitto_plugin_id_t *mosq_pid = NULL;

static int callback_message(int event, void *event_data, void *userdata)
{
	struct mosquitto_evt_message *ed = event_data;

	UNUSED(event);
	UNUSED(userdata);

	ed->retain = true;

	return MOSQ_ERR_SUCCESS;
}

int mosquitto_plugin_init(mosquitto_plugin_id_t *identifier, void **user_data, struct mosquitto_opt *opts, int opt_count)
{
	UNUSED(user_data);
	UNUSED(opts);
	UNUSED(opt_count);

	mosq_pid = identifier;
	mosquitto_plugin_set_info(identifier, PLUGIN_NAME, PLUGIN_VERSION);
	return mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE_WRITE, callback_message, NULL, NULL);
}

/* mosquitto_plugin_cleanup() is optional in 2.1 and later. Use it only if you have your own cleanup to do */
int mosquitto_plugin_cleanup(void *user_data, struct mosquitto_opt *opts, int opt_count)
{
	UNUSED(user_data);
	UNUSED(opts);
	UNUSED(opt_count);

	return MOSQ_ERR_SUCCESS;
}