/**
 * @brief MAVConn message buffer class (internal)
 * @file msgbuffer.h
 * @author Vladimir Ermakov <vooon341@gmail.com>
 * @author Amy Wagoner <arwagoner@gmail.com> (adaptation to Gazebo)
 */
/**
 * Copyright 2017 MAVROS dev team. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <cassert>
#include "mavlink/v2.0/common/mavlink.h"

namespace gazebo {
/**
 * @brief Message buffer for internal use in libmavconn
 */
struct MsgBuffer {
	//! Maximum buffer size with padding for CRC bytes (280 + padding)
	static constexpr ssize_t MAX_SIZE = MAVLINK_MAX_PACKET_LEN + 16;
	uint8_t data[MAX_SIZE];
	ssize_t len;
	ssize_t pos;

	MsgBuffer() :
		pos(0),
		len(0)
	{ }

	/**
	 * @brief Buffer constructor from mavlink_message_t
	 */
	explicit MsgBuffer(const mavlink_message_t *msg) :
		pos(0)
	{
		len = mavlink_msg_to_send_buffer(data, msg);
		// paranoic check, it must be less than MAVLINK_MAX_PACKET_LEN
		assert(len < MAX_SIZE);
	}

	/**
	 * @brief Buffer constructor for send_bytes()
	 * @param[in] nbytes should be less than MAX_SIZE
	 */
	MsgBuffer(const uint8_t *bytes, ssize_t nbytes) :
		pos(0),
		len(nbytes)
	{
		assert(0 < nbytes && nbytes < MAX_SIZE);
		memcpy(data, bytes, nbytes);
	}

	virtual ~MsgBuffer() {
		pos = 0;
		len = 0;
	}

	uint8_t *dpos() {
		return data + pos;
	}

	ssize_t nbytes() {
		return len - pos;
	}
};
}	// namespace gazebo