/*
 * Copyright 2017 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 org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.traccar.BaseProtocolDecoder;
import org.traccar.DeviceSession;
import org.traccar.helper.UnitsConverter;
import org.traccar.model.Position;

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

public class DmtProtocolDecoder extends BaseProtocolDecoder {

    public DmtProtocolDecoder(DmtProtocol protocol) {
        super(protocol);
    }

    public static final int MSG_HELLO = 0x00;
    public static final int MSG_HELLO_RESPONSE = 0x01;
    public static final int MSG_DATA_RECORD = 0x04;
    public static final int MSG_COMMIT = 0x05;
    public static final int MSG_COMMIT_RESPONSE = 0x06;

    @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(); // length

        if (type == MSG_HELLO) {

            buf.readUnsignedInt(); // device serial number

            DeviceSession deviceSession = getDeviceSession(
                    channel, remoteAddress, buf.readBytes(15).toString(StandardCharsets.US_ASCII));

            if (channel != null) {
                ChannelBuffer response = ChannelBuffers.dynamicBuffer(ByteOrder.LITTLE_ENDIAN, 0);
                response.writeByte(0x02); response.writeByte(0x55); // header
                response.writeByte(MSG_HELLO_RESPONSE);
                response.writeShort(4 + 4);
                response.writeInt((int) (System.currentTimeMillis() / 1000));
                response.writeInt(deviceSession != null ? 0 : 1); // flags
                channel.write(response);
            }

        } else if (type == MSG_COMMIT) {

            if (channel != null) {
                ChannelBuffer response = ChannelBuffers.dynamicBuffer(ByteOrder.LITTLE_ENDIAN, 0);
                response.writeByte(0x02); response.writeByte(0x55); // header
                response.writeByte(MSG_COMMIT_RESPONSE);
                response.writeShort(1);
                response.writeByte(1); // flags (success)
                channel.write(response);
            }

        } else if (type == MSG_DATA_RECORD) {

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

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

            while (buf.readable()) {

                int recordEnd = buf.readerIndex() + buf.readUnsignedShort();

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

                position.set(Position.KEY_INDEX, buf.readUnsignedInt());

                position.setDeviceTime(new Date(1356998400000L + buf.readUnsignedInt() * 1000)); // since 1 Jan 2013

                position.set(Position.KEY_EVENT, buf.readUnsignedByte());

                while (buf.readerIndex() < recordEnd) {

                    int fieldId = buf.readUnsignedByte();
                    int fieldLength = buf.readUnsignedByte();
                    int fieldEnd = buf.readerIndex() + (fieldLength == 255 ? buf.readUnsignedShort() : fieldLength);

                    if (fieldId == 0) {

                        position.setFixTime(new Date(1356998400000L + buf.readUnsignedInt() * 1000));
                        position.setLatitude(buf.readInt() * 0.0000001);
                        position.setLongitude(buf.readInt() * 0.0000001);
                        position.setSpeed(UnitsConverter.knotsFromCps(buf.readUnsignedShort()));

                        buf.readUnsignedByte(); // speed accuracy

                        position.setCourse(buf.readUnsignedByte() * 2);

                        position.set(Position.KEY_PDOP, buf.readUnsignedByte() * 0.1);

                        position.setAccuracy(buf.readUnsignedByte());
                        position.setValid(buf.readUnsignedByte() != 0);

                    }

                    buf.readerIndex(fieldEnd);

                }

                if (position.getFixTime() == null) {
                    getLastLocation(position, position.getDeviceTime());
                }

                positions.add(position);

            }

            return positions;

        }

        return null;
    }

}