#include <QtBluetooth/QBluetoothServiceInfo>

#include "metawatchbttransport.h"

namespace
{

const quint8 bit_rev_table[16] = {
	0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15
};

const quint16 crc_table[256] = {
	0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
	0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
	0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
	0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
	0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
	0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
	0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
	0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
	0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
	0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
	0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
	0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
	0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
	0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
	0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
	0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
	0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
	0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
	0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
	0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
	0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
	0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
	0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
	0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
	0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
	0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
	0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
	0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
	0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
	0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
	0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
	0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
};

#if 0 /* This snippet was used to build the table seen above. */
	quint16 remainder;
	int dividend;
	quint8 bit;

	for (dividend = 0; dividend < 256; dividend++) {
		remainder = dividend << 8;
		for (bit = 8; bit > 0; bit--) {
			if (remainder & 0x8000) {
				remainder = (remainder << 1) ^ 0x1021;
			} else {
				remainder = (remainder << 1);
			}
		}
		if ((dividend % 8) == 0) {
			printf(",\n0x%04hx", remainder);
		} else {
			printf(", 0x%04hx", remainder);
		}
	}
#endif

quint16 compute_crc(const QByteArray &data)
{
	const int size = data.size();
	quint16 remainder = 0xFFFF;

	for (int i = 0; i < size; i++) {
		quint8 byte = data[i];
		byte = (bit_rev_table[byte & 0xF] << 4) | bit_rev_table[(byte & 0xF0) >> 4];
		remainder = crc_table[byte ^ (remainder >> 8)] ^ (remainder << 8);
	}

	return remainder;
}

}

MetaWatchBTTransport::MetaWatchBTTransport(const QBluetoothAddress &address, QObject *parent) :
	MetaWatchTransport(parent), _addr(address),	_socket(0)
{

}

MetaWatchBTTransport::~MetaWatchBTTransport()
{
	disconnectDevice();
}

bool MetaWatchBTTransport::isDeviceConnected() const
{
	return _socket && _socket->state() == QBluetoothSocket::ConnectedState;
}

void MetaWatchBTTransport::sendMessage(quint8 type, quint8 options, const QByteArray &payload)
{
	QByteArray packet = encode(type, options, payload);
	qDebug() << "Send:" << packet.toHex();
	qint64 written = _socket->write(packet);
	if (written < packet.size()) {
		qWarning() << "Packet not fully writen";
	}
}

void MetaWatchBTTransport::connectDevice()
{
	qDebug() << "Trying to connect to" << _addr.toString();

	if (_socket) {
		disconnectDevice();
	}

	// Sadly, seems that QBluetoothSocket doesn't really like been closed and reopened,
	// so we recreate it every time.
	_socket = new QBluetoothSocket(QBluetoothServiceInfo::RfcommProtocol, this);
	connect(_socket, &QBluetoothSocket::connected, this, &MetaWatchBTTransport::handleSocketConnected);
	connect(_socket, &QBluetoothSocket::disconnected, this, &MetaWatchBTTransport::handleSocketDisconnected);
	connect(_socket, &QBluetoothSocket::readyRead, this, &MetaWatchBTTransport::handleSocketData);

	// Let's hardcode MetaWatch's RFCOMM port (1) in order to avoid having
	// to look it up (which would need an SDP query).
	_socket->connectToService(_addr, 1);
}

void MetaWatchBTTransport::disconnectDevice()
{
	if (_socket) {
		_socket->close();
		_socket->deleteLater();
		disconnect(_socket, 0, this, 0);
		_socket = 0;
	}
}

QByteArray MetaWatchBTTransport::encode(quint8 type, quint8 options, const QByteArray &payload)
{
	QByteArray packet;

	quint8 message_size = 6 + payload.size();
	packet.reserve(message_size);

	packet.append(0x01);
	packet.append(message_size);
	packet.append(type);
	packet.append(options);

	packet.append(payload);

	packet.append("\0\0", 2);

	quint16 crc = compute_crc(packet); // Replace CRC with computed CRC
	packet[message_size - 2] = crc & 0xFF;
	packet[message_size - 1] = crc >> 8;

	return packet;
}

bool MetaWatchBTTransport::decode(const QByteArray &packet, quint8 *type, quint8 *options, QByteArray *payload)
{
	if (packet.size() < 6) {
		qWarning() << "Message too short";
	}

	if (packet.at(0) != 0x1) {
		qWarning() << "Invalid packet header";
		return false;
	}

	quint8 message_size = packet[1];
	if (message_size < 6 || message_size > 32 || message_size != packet.size()) {
		qWarning() << "Invalid message size:" << message_size;
	}

	*type = packet[2];
	*options = packet[3];

	*payload = packet.mid(4, message_size - 6);

	// Don't compare received CRC... what for? RFCOMM already guarantees reliability.

	return true;
}

void MetaWatchBTTransport::handleSocketConnected()
{
	qDebug() << "MW connected";
	emit connected();
}

void MetaWatchBTTransport::handleSocketDisconnected()
{
	qDebug() << "MW disconnected";
	emit disconnected();
}

void MetaWatchBTTransport::handleSocketData()
{
	const int min_message_size = 6;
	while (_socket->bytesAvailable() >= min_message_size) {
		char header[2];
		qint64 bytes_read = _socket->peek(header, sizeof(header));
		if (bytes_read < 2) {
			qWarning() << "Unable to peek received data";
			break;
		}

		if (header[0] != 0x01 || header[1] > 32) {
			qWarning() << "Received garbage data";
			_socket->readAll(); // let's discard all pending data.
			break;
		}
		if (_socket->bytesAvailable() < header[1]) {
			// Not enough data to complete the entire frame
			break;
		}

		QByteArray data = _socket->read(header[1]);
		if (data.size() != header[1]) {
			qWarning() << "Received incomplete packet";
			_socket->readAll(); // discard all other pending data.
			break;
		}

		qDebug() << "Recv:" << data.toHex();

		quint8 type, options;
		QByteArray payload;

		if (decode(data, &type, &options, &payload)) {
			emit messageReceived(type, options, payload);
		} else {
			qWarning() << "Failed to decode message from metawatch:" << data.toHex();
		}
	}
}