/*
 * Copyright 2014 Anton Tananaev (anton.tananaev@gmail.com)
 *
 * 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.
 */
package org.traccar.protocol;

import java.net.SocketAddress;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.traccar.BaseProtocolDecoder;
import org.traccar.helper.ChannelBufferTools;
import org.traccar.helper.Checksum;
import org.traccar.helper.DateBuilder;
import org.traccar.helper.UnitsConverter;
import org.traccar.model.Event;
import org.traccar.model.Position;

public class KhdProtocolDecoder extends BaseProtocolDecoder {

    public KhdProtocolDecoder(KhdProtocol protocol) {
        super(protocol);
    }

    private String readSerialNumber(ChannelBuffer buf) {
        int b1 = buf.readUnsignedByte();
        int b2 = buf.readUnsignedByte();
        if (b2 > 0x80) {
            b2 -= 0x80;
        }
        int b3 = buf.readUnsignedByte();
        if (b3 > 0x80) {
            b3 -= 0x80;
        }
        int b4 = buf.readUnsignedByte();
        String serialNumber = String.format("%02d%02d%02d%02d", b1, b2, b3, b4);
        return String.valueOf(Long.parseLong(serialNumber));
    }

    public static final int MSG_LOGIN = 0xB1;
    public static final int MSG_CONFIRMATION = 0x21;
    public static final int MSG_ON_DEMAND = 0x81;
    public static final int MSG_POSITION_UPLOAD = 0x80;
    public static final int MSG_POSITION_REUPLOAD = 0x8E;
    public static final int MSG_ALARM = 0x82;
    public static final int MSG_REPLY = 0x85;
    public static final int MSG_PERIPHERAL = 0xA3;

    @Override
    protected Object decode(
            Channel channel, SocketAddress remoteAddress, Object msg) throws Exception {

        ChannelBuffer buf = (ChannelBuffer) msg;

        buf.skipBytes(2); // header
        int type = buf.readUnsignedByte();
        buf.readUnsignedShort(); // size

        if (type == MSG_ON_DEMAND || type == MSG_POSITION_UPLOAD || type == MSG_POSITION_REUPLOAD
                || type == MSG_ALARM || type == MSG_REPLY || type == MSG_PERIPHERAL) {

            Position position = new Position();
            position.setProtocol(getProtocolName());

            if (!identify(readSerialNumber(buf), channel)) {
                return null;
            }
            position.setDeviceId(getDeviceId());

            DateBuilder dateBuilder = new DateBuilder()
                    .setYear(ChannelBufferTools.readHexInteger(buf, 2))
                    .setMonth(ChannelBufferTools.readHexInteger(buf, 2))
                    .setDay(ChannelBufferTools.readHexInteger(buf, 2))
                    .setHour(ChannelBufferTools.readHexInteger(buf, 2))
                    .setMinute(ChannelBufferTools.readHexInteger(buf, 2))
                    .setSecond(ChannelBufferTools.readHexInteger(buf, 2));
            position.setTime(dateBuilder.getDate());

            position.setLatitude(ChannelBufferTools.readCoordinate(buf));
            position.setLongitude(ChannelBufferTools.readCoordinate(buf));
            position.setSpeed(UnitsConverter.knotsFromKph(ChannelBufferTools.readHexInteger(buf, 4)));
            position.setCourse(ChannelBufferTools.readHexInteger(buf, 4));

            int flags = buf.readUnsignedByte();
            position.setValid((flags & 0x80) != 0);

            if (type == MSG_ALARM) {

                buf.skipBytes(2);

            } else {

                position.set(Event.KEY_ODOMETER, buf.readUnsignedMedium());

                buf.skipBytes(4); // status
                buf.skipBytes(8); // other

            }

            // parse extra data

            return position;

        } else if (type == MSG_LOGIN && channel != null) {

            buf.skipBytes(4); // serial number
            buf.readByte(); // reserved

            ChannelBuffer response = ChannelBuffers.dynamicBuffer();
            response.writeByte(0x29); response.writeByte(0x29); // header
            response.writeByte(MSG_CONFIRMATION);
            response.writeShort(5); // size
            response.writeByte(buf.readUnsignedByte());
            response.writeByte(type);
            response.writeByte(0); // reserved
            response.writeByte(Checksum.xor(response.toByteBuffer()));
            response.writeByte(0x0D); // ending
            channel.write(response);

        }

        return null;
    }

}