/*
 * Copyright 2021 Anton Tananaev (anton@traccar.org)
 *
 * 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 io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import org.traccar.BaseProtocolDecoder;
import org.traccar.DeviceSession;
import org.traccar.NetworkMessage;
import org.traccar.Protocol;
import org.traccar.helper.BcdUtil;
import org.traccar.helper.BitUtil;
import org.traccar.helper.DateBuilder;
import org.traccar.model.Position;

import java.net.SocketAddress;
import java.nio.charset.StandardCharsets;
import java.util.LinkedList;
import java.util.List;

public class Gs100ProtocolDecoder extends BaseProtocolDecoder {

    public Gs100ProtocolDecoder(Protocol protocol) {
        super(protocol);
    }

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

        ByteBuf buf = (ByteBuf) msg;

        String header = buf.readCharSequence(2, StandardCharsets.US_ASCII).toString();

        if (header.equals("GL")) {

            buf.skipBytes(1);
            String imei = buf.readCharSequence(buf.readUnsignedByte(), StandardCharsets.US_ASCII).toString();
            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);

            if (channel != null && deviceSession != null) {
                ByteBuf response = Unpooled.copiedBuffer("GS100", StandardCharsets.US_ASCII);
                channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
            }

            return null;

        } else {

            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
            if (deviceSession == null) {
                return null;
            }

            List<Position> positions = new LinkedList<>();

            int count = buf.readUnsignedByte();
            for (int i = 0; i < count; i++) {

                int endIndex = buf.readUnsignedByte() + buf.readerIndex();

                Position position = new Position(getProtocolName());
                position.setDeviceId(deviceSession.getDeviceId());

                int status = buf.readUnsignedMedium();
                position.set(Position.KEY_STATUS, status);

                if (BitUtil.check(status, 8 + 8 + 7)) {

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

                    position.setValid(true);

                    String coordinates = ByteBufUtil.hexDump(buf.readSlice(9));
                    position.setLongitude(Integer.parseInt(coordinates.substring(0, 3))
                            + Integer.parseInt(coordinates.substring(3, 9)) * 0.0001 / 60);
                    position.setLatitude(Integer.parseInt(coordinates.substring(10, 12))
                            + Integer.parseInt(coordinates.substring(12, 18)) * 0.0001 / 60);
                    int flags = Integer.parseInt(coordinates.substring(9, 10), 16);
                    if (!BitUtil.check(flags, 3)) {
                        position.setLongitude(-position.getLongitude());
                    }
                    if (!BitUtil.check(flags, 2)) {
                        position.setLatitude(-position.getLatitude());
                    }

                    String other = ByteBufUtil.hexDump(buf.readSlice(4));
                    position.setSpeed(Integer.parseInt(other.substring(0, 5)) * 0.01);
                    position.setCourse(Integer.parseInt(other.substring(5, 8)));

                } else {

                    getLastLocation(position, null);

                }

                positions.add(position);

                buf.readerIndex(endIndex);

            }

            if (channel != null) {
                ByteBuf response = Unpooled.buffer();
                response.writeCharSequence("GS100", StandardCharsets.US_ASCII);
                response.writeByte(count);
                channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
            }

            return positions.isEmpty() ? null : positions;

        }
    }

}

@@ -1019,24 +1019,66 @@
 ateBuilder;%0A
+import org.traccar.helper.UnitsConverter;%0A
 import org.t
@@ -4414,16 +4414,44 @@
 etSpeed(
+UnitsConverter.knotsFromKph(
 Integer.
@@ -4489,16 +4489,17 @@
  * 0.01)
+)
 ;%0A      

Fix speed decoding