/*
 * Copyright 2023 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;

import io.netty.channel.Channel;
import io.netty.handler.codec.mqtt.MqttConnectMessage;
import io.netty.handler.codec.mqtt.MqttConnectReturnCode;
import io.netty.handler.codec.mqtt.MqttMessage;
import io.netty.handler.codec.mqtt.MqttMessageBuilders;
import io.netty.handler.codec.mqtt.MqttPublishMessage;
import io.netty.handler.codec.mqtt.MqttSubscribeMessage;
import org.traccar.session.DeviceSession;

import java.net.SocketAddress;

public abstract class BaseMqttProtocolDecoder extends BaseProtocolDecoder {

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

    protected abstract Object decode(DeviceSession deviceSession, MqttPublishMessage message) throws Exception;

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

        if (msg instanceof MqttConnectMessage) {

            MqttConnectMessage message = (MqttConnectMessage) msg;

            DeviceSession deviceSession = getDeviceSession(
                    channel, remoteAddress, message.payload().clientIdentifier());

            MqttConnectReturnCode returnCode = deviceSession != null
                    ? MqttConnectReturnCode.CONNECTION_ACCEPTED
                    : MqttConnectReturnCode.CONNECTION_REFUSED_IDENTIFIER_REJECTED;

            MqttMessage response = MqttMessageBuilders.connAck().returnCode(returnCode).build();

            if (channel != null) {
                channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
            }

        } else if (msg instanceof MqttSubscribeMessage) {

            MqttSubscribeMessage message = (MqttSubscribeMessage) msg;

            MqttMessage response = MqttMessageBuilders.subAck()
                    .packetId(message.variableHeader().messageId())
                    .build();

            if (channel != null) {
                channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
            }

        } else if (msg instanceof MqttPublishMessage) {

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

            MqttPublishMessage message = (MqttPublishMessage) msg;

            Object result = decode(deviceSession, message);

            MqttMessage response = MqttMessageBuilders.pubAck()
                    .packetId(message.variableHeader().packetId())
                    .build();

            if (channel != null) {
                channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
            }

            return result;

        }

        return null;
    }

}