/****************************************************************************
 *
 *   Copyright (c) 2012-2019 PX4 Development Team. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name PX4 nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
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 ****************************************************************************/

/**
 * @file Subscription.cpp
 *
 */

#include "Subscription.hpp"
#include <px4_platform_common/defines.h>

namespace uORB
{

bool Subscription::subscribe()
{
	// check if already subscribed
	if (_node != nullptr) {
		return true;
	}

	if (_orb_id != ORB_ID::INVALID) {

		DeviceMaster *device_master = uORB::Manager::get_instance()->get_device_master();

		if (device_master != nullptr) {

			if (!device_master->deviceNodeExists(_orb_id, _instance)) {
				return false;
			}

			uORB::DeviceNode *node = device_master->getDeviceNode(get_topic(), _instance);

			if (node != nullptr) {
				_node = node;
				_node->add_internal_subscriber();

				const unsigned curr_gen = _node->published_message_count();

				// If there were any previous publications allow the subscriber to read them
				_last_generation = curr_gen - math::min((unsigned)_node->get_queue_size(), curr_gen);

				return true;
			}
		}
	}

	return false;
}

void Subscription::unsubscribe()
{
	if (_node != nullptr) {
		_node->remove_internal_subscriber();
	}

	_node = nullptr;
	_last_generation = 0;
}

bool Subscription::ChangeInstance(uint8_t instance)
{
	if (instance != _instance) {
		DeviceMaster *device_master = uORB::Manager::get_instance()->get_device_master();

		if (device_master != nullptr) {
			if (!device_master->deviceNodeExists(_orb_id, _instance)) {
				return false;
			}

			// if desired new instance exists, unsubscribe from current
			unsubscribe();
			_instance = instance;
			subscribe();
			return true;
		}

	} else {
		// already on desired index
		return true;
	}

	return false;
}

} // namespace uORB
