#include "packet.h"


/* PUBLIC
----------------------------------------*/
// builds a packet from raw data and returns the error code
uint8_t Packet::read(uint8_t buf[], uint8_t size){
	// 1. fail on invalid size
	if( size < 1          ) return PKTREAD_EMPTY;
	if( size > PROTO_SIZE ) return PKTREAD_OVERFLOW;

	// 2. extract packet type
	type = buf[0] == 0;

	// 3. extract depending on type
	return type ? read_discover(buf, size) : read_message(buf, size);

};

// writes the binary representation of the packet
uint8_t Packet::write(uint8_t buf[], uint8_t size){
	/* TODO */
	return 0;
};


/* PRIVATE
----------------------------------------*/
uint8_t Packet::read_discover(uint8_t buf[], uint8_t size){
	// 1. fail on invalid size
	if( size != DISCOVER_SIZE )
		return PKTREAD_INVALID_DISCOVER_FORMAT;

	// 2. extract fixed
	dsc.opcode = buf[0];
	dsc.wave   = buf[1];
	dsc.dist   = buf[2];

	return PKTREAD_OK;
};

uint8_t Packet::read_message(uint8_t buf[], uint8_t size){
	// 1. fail on invalid size
	if( size < MESSAGE_MIN_SIZE || size > MESSAGE_MAX_SIZE )
		return PKTREAD_INVALID_MESSAGE_FORMAT;

	// 2. extract fixed
	msg.opcode = buf[0];
	msg.dist   = buf[1];
	msg.ttl    = buf[2];
	msg.size   = buf[3];

	// 3. check message size
	if( size - 4 - 1 != msg.size )
		return PKTREAD_INVALID_MESSAGE_FORMAT;

	// 4. extract message
	strncpy(
		(char*) msg.data,
		(char*)buf+4,
		msg.size
	);

	return PKTREAD_OK;
};