/*
 * Usurpataion --- clinet-server protocol implementation.
 *
 * 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
 */

/**
 * Common parts of protocol implementation. Handling of anything that actually
 * deals with connection descriptor has to be implemented by device and daemon
 * separately.
 */

#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "protocol.h"
#include "protocol_private.h"
#include "net.h"

#define READ_AS(from, type)	(*(type*)(from))

int push_data(cd_t connection, const char *data, enum tlv_type type)
{
	int ret = E_UNKNOWN_TYPE;
	switch (type) {
	case TEXT:
		ret = push_string(connection, data);
		break;
	case FPI1:
		ret = push_fpi1(connection, data);
		break;
	case TIMESTAMP:
		ret = push_timestamp(connection, data);
		break;
	case REQUEST:
		ret = push_request(connection, data);
		break;
	case REPLY:
		ret = push_reply(connection, data);
		break;
	case UUID:
		ret = push_uuid(connection, data);
		break;
	}
	return ret;
}

static int push_string(cd_t connection, char *str)
{
	int ret = 0;
	size_t size = strlen(str);

	ret |= push_tlv_header(connection, TEXT, size);
	ret |= push_bytes(connection, str, size);
	return ret;
}

static int push_fpi1(cd_t connection, char *num)
{
	return		push_tlv_header(connection, FPI1, sizeof(fpi1_t))
		|	push_bytes(connection, num, sizeof(fpi1_t));
}

static int push_timestamp(cd_t connection, char *data)
{
	return		push_tlv_header(connection, TIMESTAMP, sizeof(time_t))
		|	push_bytes(connection, data, sizeof(time_t));
}

static int push_request(cd_t connection, char *data)
{
	return          push_tlv_header(connection, REQUEST, sizeof(msg_idx_t))
		|       push_bytes(connection, data, sizeof(msg_idx_t));
}

static int push_reply(cd_t connection, char *data)
{
	int ret = 0;
	size_t msglen = strlen(data + sizeof(msg_idx_t));
	ret |= push_tlv_header(connection, REPLY, msglen + sizeof(msg_idx_t));
	ret |= push_bytes(connection, data, msglen);
	return ret;
}

static int push_uuid(cd_t connection, char *data)
{
	return		push_tlv_header(connection, UUID, sizeof(uuid_t))
		|	push_bytes(connection, data, sizeof(uuid_t));
}

size_t tlv_count(const struct packet_data * const packet)
{
	size_t cursor = 0;
	size_t length = 0;
	size_t ret = 0;

	while (cursor < packet->packet_size) {
		cursor += sizeof(enum tlv_type);
		length = READ_AS(packet->data + cursor, enum tlv_type);
		cursor += sizeof(size_t) + length;
		ret++;
	}
	if (cursor != packet->packet_size) {
		errno = E_TLV_OVERFLOW;
	}
	return ret;
}

size_t get_tlvs(        const struct packet_data * const data,
			const struct tlv *buf,
			size_t buf_size)
{
	size_t tlvs_read = 0;
	size_t cursor = 0;

	while (cursor < data->packet_size && tlvs_read <= buf_size) {
		cursor += parse_tlv(data->data, cursor, buf + tlvs_read);
		tlvs_read++;
	}

	if (cursor > data->packet_size) {
		errno = E_TLV_OVERFLOW;
	}

	return tlvs_read;
}

size_t parse_tlv(char *data, size_t cursor, struct tlv *t)
{
	char *begin = data + cursor;

	t->type = READ_TLV_TYPE(data + cursor);
	cursor += sizeof(enum tlv_type);
	t->length += READ_SIZE_T(data + cursor);
	data += sizeof(size_t);
	t->data = data + cursor;

	return data + cursor - begin + 1UL;
}