/*
 * Copyright 2015 Open Networking Laboratory
 *
 * 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.onosproject.reactive.routing;
import static org.slf4j.LoggerFactory.getLogger;

import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Deactivate;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.onlab.packet.Ethernet;
import org.onlab.packet.IPv4;
import org.onlab.packet.IpAddress;
import org.onlab.packet.MacAddress;
import org.onosproject.core.ApplicationId;
import org.onosproject.core.CoreService;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.packet.DefaultOutboundPacket;
import org.onosproject.net.packet.InboundPacket;
import org.onosproject.net.packet.OutboundPacket;
import org.onosproject.net.packet.PacketContext;
import org.onosproject.net.packet.PacketPriority;
import org.onosproject.net.packet.PacketProcessor;
import org.onosproject.net.packet.PacketService;
import org.onosproject.routing.RoutingService;
import org.slf4j.Logger;

/**
 * This is reactive routing to handle 3 cases:
 * (1) one host wants to talk to another host, both two hosts are in
 * SDN network.
 * (2) one host in SDN network wants to talk to another host in Internet.
 * (3) one host from Internet wants to talk to another host in SDN network.
 */
@Component(immediate = true)
public class SdnIpReactiveRouting {

    private static final String APP_NAME = "org.onosproject.reactive.routing";
    private final Logger log = getLogger(getClass());

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected CoreService coreService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected PacketService packetService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected RoutingService routingService;

    private ApplicationId appId;

    private ReactiveRoutingProcessor processor =
            new ReactiveRoutingProcessor();

    @Activate
    public void activate() {
        appId = coreService.registerApplication(APP_NAME);
        packetService.addProcessor(processor,
                                   PacketProcessor.ADVISOR_MAX + 2);

        TrafficSelector.Builder selector = DefaultTrafficSelector.builder();
        // TODO: to support IPv6 later
        selector.matchEthType(Ethernet.TYPE_IPV4);
        packetService.requestPackets(selector.build(),
                                     PacketPriority.REACTIVE, appId);

        log.info("SDN-IP Reactive Routing Started");
    }

    @Deactivate
    public void deactivate() {
        packetService.removeProcessor(processor);
        processor = null;
        log.info("SDN-IP Reactive Routing Stopped");
    }

    private class ReactiveRoutingProcessor implements PacketProcessor {
        @Override
        public void process(PacketContext context) {

            InboundPacket pkt = context.inPacket();
            Ethernet ethPkt = pkt.parsed();
            if (ethPkt == null) {
                return;
            }

            // In theory, we do not need to check whether it is Ethernet
            // TYPE_IPV4. However, due to the current implementation of the
            // packetService, we will receive all packets from all subscribers.
            // Hence, we have to check the Ethernet type again here.
            if (ethPkt.getEtherType() != Ethernet.TYPE_IPV4) {
                return;
            }

            // Parse packet
            IPv4 ipv4Packet = (IPv4) ethPkt.getPayload();
            IpAddress dstIp =
                    IpAddress.valueOf(ipv4Packet.getDestinationAddress());
            IpAddress srcIp =
                    IpAddress.valueOf(ipv4Packet.getSourceAddress());
            ConnectPoint srcConnectPoint = pkt.receivedFrom();
            MacAddress srcMac = ethPkt.getSourceMAC();
            routingService.packetReactiveProcessor(dstIp, srcIp,
                                                   srcConnectPoint, srcMac);

            // TODO emit packet first or packetReactiveProcessor first
            ConnectPoint egressConnectPoint = null;
            egressConnectPoint = routingService.getEgressConnectPoint(dstIp);
            if (egressConnectPoint != null) {
                forwardPacketToDst(context, egressConnectPoint);
            }
        }
    }

    /**
     * Emits the specified packet onto the network.
     *
     * @param context the packet context
     * @param connectPoint the connect point where the packet should be
     *        sent out
     */
    private void forwardPacketToDst(PacketContext context,
                                    ConnectPoint connectPoint) {
        TrafficTreatment treatment = DefaultTrafficTreatment.builder()
                .setOutput(connectPoint.port()).build();
        OutboundPacket packet =
                new DefaultOutboundPacket(connectPoint.deviceId(), treatment,
                                          context.inPacket().unparsed());
        packetService.emit(packet);
        log.trace("sending packet: {}", packet);
    }

}