/*
 * Copyright 2012 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.util.Calendar;
import java.util.TimeZone;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.traccar.GenericProtocolDecoder;
import org.traccar.helper.Crc;
import org.traccar.helper.Log;
import org.traccar.model.DataManager;
import org.traccar.model.Position;

/**
 * T55 tracker protocol decoder
 */
public class Gt06ProtocolDecoder extends GenericProtocolDecoder {
    
    private Long deviceId;

    /**
     * Initialize
     */
    public Gt06ProtocolDecoder(DataManager dataManager) {
        super(dataManager);
    }
    
    private String readImei(ChannelBuffer buf) {
        int b = buf.readUnsignedByte();
        StringBuilder imei = new StringBuilder();
        imei.append(b & 0x0F);
        for (int i = 0; i < 7; i++) {
            b = buf.readUnsignedByte();
            imei.append((b & 0xF0) >> 4);
            imei.append(b & 0x0F);
        }
        return imei.toString();
    }

    private static final int MSG_LOGIN = 0x01;
    private static final int MSG_DATA = 0x12;
    private static final int MSG_HEARTBEAT = 0x13;
    private static final int MSG_STRING = 0x15;
    private static final int MSG_ALARM = 0x16;
    
    private static void sendResponse(Channel channel, int type, int index) {
        if (channel == null) {
            ChannelBuffer response = ChannelBuffers.directBuffer(10);
            response.writeByte(0x78); response.writeByte(0x78); // header
            response.writeByte(0x05); // size
            response.writeByte(type);
            response.writeShort(index);
            response.writeShort(Crc.crc16Ccitt(response.toByteBuffer(2, 4)));
            response.writeByte(0x0D); response.writeByte(0x0A); // ending
            channel.write(response);
        }
    }
    
    /**
     * Decode message
     */
    @Override
    protected Object decode(
            ChannelHandlerContext ctx, Channel channel, Object msg)
            throws Exception {

        ChannelBuffer buf = (ChannelBuffer) msg;
        
        buf.skipBytes(2); // header
        buf.readByte(); // size
        
        int type = buf.readUnsignedByte();
        
        if (type == MSG_LOGIN) {
            String imei = readImei(buf);
            try {
                deviceId = getDataManager().getDeviceByImei(imei).getId();
                sendResponse(channel, type, buf.readUnsignedShort());
            } catch(Exception error) {
                Log.warning("Unknown device - " + imei);
            }
        }
        
        else if (type == MSG_HEARTBEAT) {
            buf.skipBytes(5);
            sendResponse(channel, type, buf.readUnsignedShort());
        }
        
        else if (type == MSG_DATA) {
            // Create new position
            Position position = new Position();
            position.setDeviceId(deviceId);
            StringBuilder extendedInfo = new StringBuilder("<protocol>gt06</protocol>");
            
            // Date and time
            Calendar time = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
            time.clear();
            time.set(Calendar.YEAR, 2000 + buf.readUnsignedByte());
            time.set(Calendar.MONTH, buf.readUnsignedByte() - 1);
            time.set(Calendar.DAY_OF_MONTH, buf.readUnsignedByte());
            time.set(Calendar.HOUR, buf.readUnsignedByte());
            time.set(Calendar.MINUTE, buf.readUnsignedByte());
            time.set(Calendar.SECOND, buf.readUnsignedByte());
            position.setTime(time.getTime());
            
            // Satellites count
            extendedInfo.append("<satellites>");
            extendedInfo.append(buf.readUnsignedByte());
            extendedInfo.append("</satellites>");
            
            // Latitude
            double latitude = buf.readUnsignedInt() / (60.0 * 30000.0);
            
            // Longitude
            double longitude = buf.readUnsignedInt() / (60.0 * 30000.0);
            
            // Speed
            position.setSpeed((double) buf.readUnsignedByte());

            // Course and flags
            int union = buf.readUnsignedShort();
            position.setCourse((double) (union & 0x03FF));
            position.setValid((union & 0x1000) != 0);
            if ((union & 0x0400) == 0) latitude = -latitude;
            if ((union & 0x0800) == 0) longitude = -longitude;
            
            position.setLatitude(latitude);
            position.setLongitude(longitude);
            position.setAltitude(0.0);
            
            // Cell information
            extendedInfo.append("<mcc>");
            extendedInfo.append(buf.readUnsignedShort());
            extendedInfo.append("</mcc>");
            extendedInfo.append("<mnc>");
            extendedInfo.append(buf.readUnsignedByte());
            extendedInfo.append("</mnc>");
            extendedInfo.append("<lac>");
            extendedInfo.append(buf.readUnsignedShort());
            extendedInfo.append("</lac>");
            extendedInfo.append("<cell>");
            extendedInfo.append(buf.readUnsignedShort() << 8 + buf.readUnsignedByte());
            extendedInfo.append("</cell>");
            
            // Index
            position.setId((long) buf.readUnsignedShort());

            position.setExtendedInfo(extendedInfo.toString());
            return position;
        }

        return null;
    }

}