/*
 * Usurpataion --- client-server protocol interface.
 *
 * Copyright (C) 2019 Ramūnas Mažeikis
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; version 2.1
 * of the License.
 *
 * This program 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */

#ifndef PROTOCOL_H_INCLUDED
#define PROTOCOL_H_INCLUDED

#include <errno.h>

#define	E_TLV_OVERFLOW	(1 << 0)
#define E_UNKNOWN_TYPE	(1 << 1)

enum packet_type {
	REGURAL,
	HEARTBEAT,
	DISCOVERY
};

enum tlv_type {
	/** NULL-terminated string. */
	TEXT,

	/** Fixed point. 1 decimal digit of precision. */
	FPI1,

	/** Literally time_t*/
	TIMESTAMP,

	/** Represents a request for lost message. Data is unsigned integer
	 * that uniquely identifies the message.
	 */
	REQUEST,

	/** Response to request. Begins with unsigned integer that represents
	 * which message is being repeated and the actual null-terminated
	 * message after that.
	 */
	REPLY,

	/** UUID that represents a particular device.
	 */
	UUID
};

struct packet_data {
	enum packet_type type;
	size_t packet_size;
	char *data;	/* Bytes representing tlv's */
};

struct tlv {
	enum tlv_type type;
	size_t length;
	void *data;
};

/*
 * Reads last packets received, parses and stores them to be later retreived
 * via get_tlv.
 * */
void get_last_data(void);

/* Returns tlv's parsed by get_last_data. Returned tlv is only valid until
 * next call to get_tlv.
 * */
struct tlv * get_tlv(void);

/* Any modifications made to the pending outgoing packet are nullified.
 * */
void clear_data(void);

/* Appends data to the next packet to be sent. Type of data is determined by
 * enum tlv_type.
 * */
int push_data(const char *data, enum tlv_type);

/* Sends packet towards the other end.
 * */
void flush_data(void);

#endif /* PROTOCOL_H_INCLUDED */