/*
 * Copyright 2013 - 2018 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.channel.Channel;
import org.traccar.BaseProtocolDecoder;
import org.traccar.DeviceSession;
import org.traccar.NetworkMessage;
import org.traccar.helper.Parser;
import org.traccar.helper.PatternBuilder;
import org.traccar.model.Position;

import java.net.SocketAddress;
import java.util.regex.Pattern;

public class YwtProtocolDecoder extends BaseProtocolDecoder {

    public YwtProtocolDecoder(YwtProtocol protocol) {
        super(protocol);
    }

    private static final Pattern PATTERN = new PatternBuilder()
            .expression("%(..),")                // type
            .number("(d+):")                     // unit identifier
            .number("d+,")                       // subtype
            .number("(dd)(dd)(dd)")              // date (yymmdd)
            .number("(dd)(dd)(dd),")             // time (hhmmss)
            .expression("([EW])")
            .number("(ddd.d{6}),")               // longitude
            .expression("([NS])")
            .number("(dd.d{6}),")                // latitude
            .number("(d+)?,")                    // altitude
            .number("(d+),")                     // speed
            .number("(d+),")                     // course
            .number("(d+),")                     // satellite
            .expression("([^,]+),")              // report identifier
            .expression("([-0-9a-fA-F]+)")       // status
            .any()
            .compile();

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

        String sentence = (String) msg;

        // Synchronization
        if (sentence.startsWith("%SN") && channel != null) {
            int start = sentence.indexOf(':');
            int end = start;
            for (int i = 0; i < 4; i++) {
                end = sentence.indexOf(',', end + 1);
            }
            if (end == -1) {
                end = sentence.length();
            }

            channel.writeAndFlush(new NetworkMessage("%AT+SN=" + sentence.substring(start, end), remoteAddress));
            return null;
        }

        Parser parser = new Parser(PATTERN, sentence);
        if (!parser.matches()) {
            return null;
        }

        Position position = new Position(getProtocolName());

        String type = parser.next();

        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
        if (deviceSession == null) {
            return null;
        }
        position.setDeviceId(deviceSession.getDeviceId());

        position.setTime(parser.nextDateTime());

        position.setLongitude(parser.nextCoordinate(Parser.CoordinateFormat.HEM_DEG));
        position.setLatitude(parser.nextCoordinate(Parser.CoordinateFormat.HEM_DEG));
        position.setAltitude(parser.nextDouble(0));
        position.setSpeed(parser.nextDouble(0));
        position.setCourse(parser.nextDouble(0));

        int satellites = parser.nextInt(0);
        position.setValid(satellites >= 3);
        position.set(Position.KEY_SATELLITES, satellites);

        String reportId = parser.next();

        position.set(Position.KEY_STATUS, parser.next());

        // Send response
        if ((type.equals("KP") || type.equals("EP")) && channel != null) {
            channel.writeAndFlush(new NetworkMessage("%AT+" + type + "=" + reportId + "\r\n", remoteAddress));
        }

        return position;
    }

}

@@ -863,24 +863,66 @@
 ernBuilder;%0A
+import org.traccar.helper.UnitsConverter;%0A
 import org.t
@@ -3578,16 +3578,44 @@
 etSpeed(
+UnitsConverter.knotsFromKph(
 parser.n
@@ -3616,33 +3616,33 @@
 rser.nextDouble(
-0
+)
 ));%0A        posi
@@ -3670,25 +3670,24 @@
 .nextDouble(
-0
 ));%0A%0A       
@@ -3719,17 +3719,16 @@
 nextInt(
-0
 );%0A     
@@ -3763,12 +3763,12 @@
 tes 
-%3E= 3
+!= 0
 );%0A 

Fix YWT speed decoding