/*
 * Copyright 2014 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.fwd;

import static org.slf4j.LoggerFactory.getLogger;

import java.util.Dictionary;
import java.util.Set;

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.Modified;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.onlab.packet.Ethernet;
import org.onosproject.core.ApplicationId;
import org.onosproject.core.CoreService;
import org.onosproject.net.Host;
import org.onosproject.net.HostId;
import org.onosproject.net.Path;
import org.onosproject.net.PortNumber;
import org.onosproject.net.flow.DefaultFlowRule;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.FlowRule;
import org.onosproject.net.flow.FlowRuleService;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.host.HostService;
import org.onosproject.net.packet.InboundPacket;
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.net.topology.TopologyService;
import org.osgi.service.component.ComponentContext;
import org.slf4j.Logger;

/**
 * Sample reactive forwarding application.
 */
@Component(immediate = true)
public class ReactiveForwarding {

    private static final int TIMEOUT = 10;
    private static final int PRIORITY = 10;

    private final Logger log = getLogger(getClass());

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected TopologyService topologyService;

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected HostService hostService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected FlowRuleService flowRuleService;

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

    private ReactivePacketProcessor processor = new ReactivePacketProcessor();

    private ApplicationId appId;

    @Property(name = "packetOutOnly", boolValue = false,
            label = "Enable packet-out only forwarding; default is false")
    private boolean packetOutOnly = false;

    @Property(name = "ipv6Forwarding", boolValue = false,
            label = "Enable IPv6 forwarding; default is false")
    private boolean ipv6Forwarding = false;

    @Activate
    public void activate(ComponentContext context) {
        appId = coreService.registerApplication("org.onosproject.fwd");

        packetService.addProcessor(processor, PacketProcessor.ADVISOR_MAX + 2);
        readComponentConfiguration(context);

        TrafficSelector.Builder selector = DefaultTrafficSelector.builder();
        selector.matchEthType(Ethernet.TYPE_IPV4);
        packetService.requestPackets(selector.build(), PacketPriority.REACTIVE, appId);

        log.info("Started with Application ID {}", appId.id());
    }

    @Deactivate
    public void deactivate() {
        flowRuleService.removeFlowRulesById(appId);
        packetService.removeProcessor(processor);
        processor = null;
        log.info("Stopped");
    }

    @Modified
    public void modified(ComponentContext context) {
        readComponentConfiguration(context);
    }

    /**
     * Extracts properties from the component configuration context.
     *
     * @param context the component context
     */
    private void readComponentConfiguration(ComponentContext context) {
        Dictionary<?, ?> properties = context.getProperties();
        boolean packetOutOnlyEnabled = isPropertyEnabled(properties, "packetOutOnly");
        if (packetOutOnly != packetOutOnlyEnabled) {
            packetOutOnly = packetOutOnlyEnabled;
            log.info("Configured. Packet-out only forwarding is {}",
                    packetOutOnly ? "enabled" : "disabled");
        }
        boolean ipv6ForwardingEnabled = isPropertyEnabled(properties, "ipv6Forwarding");
        if (ipv6Forwarding != ipv6ForwardingEnabled) {
            ipv6Forwarding = ipv6ForwardingEnabled;
            log.info("Configured. IPv6 forwarding is {}",
                    ipv6Forwarding ? "enabled" : "disabled");
        }
    }

    /**
     * Check property name is defined and set to true.
     *
     * @param properties properties to be looked up
     * @param propertyName the name of the property to look up
     * @return true when the propertyName is defined and set to true
     */
    private static boolean isPropertyEnabled(Dictionary<?, ?> properties, String propertyName) {
        boolean enabled = false;
        try {
            String flag = (String) properties.get(propertyName);
            if (flag != null) {
                enabled = flag.trim().equals("true");
            }
        } catch (ClassCastException e) {
            // No propertyName defined.
            enabled = false;
        }
        return enabled;
    }

    /**
     * Packet processor responsible for forwarding packets along their paths.
     */
    private class ReactivePacketProcessor implements PacketProcessor {

        @Override
        public void process(PacketContext context) {
            // Stop processing if the packet has been handled, since we
            // can't do any more to it.
            if (context.isHandled()) {
                return;
            }

            InboundPacket pkt = context.inPacket();
            Ethernet ethPkt = pkt.parsed();

            if (ethPkt == null) {
                return;
            }

            // Bail if this is deemed to be a control packet.
            if (isControlPacket(ethPkt)) {
                return;
            }

            // Skip IPv6 multicast packet when IPv6 forward is disabled.
            if (!ipv6Forwarding && isIpv6Multicast(ethPkt)) {
                return;
            }

            HostId id = HostId.hostId(ethPkt.getDestinationMAC());

            // Do not process link-local addresses in any way.
            if (id.mac().isLinkLocal()) {
                return;
            }

            // Do we know who this is for? If not, flood and bail.
            Host dst = hostService.getHost(id);
            if (dst == null) {
                flood(context);
                return;
            }

            // Are we on an edge switch that our destination is on? If so,
            // simply forward out to the destination and bail.
            if (pkt.receivedFrom().deviceId().equals(dst.location().deviceId())) {
                if (!context.inPacket().receivedFrom().port().equals(dst.location().port())) {
                    installRule(context, dst.location().port());
                }
                return;
            }

            // Otherwise, get a set of paths that lead from here to the
            // destination edge switch.
            Set<Path> paths = topologyService.getPaths(topologyService.currentTopology(),
                                                       pkt.receivedFrom().deviceId(),
                                                       dst.location().deviceId());
            if (paths.isEmpty()) {
                // If there are no paths, flood and bail.
                flood(context);
                return;
            }

            // Otherwise, pick a path that does not lead back to where we
            // came from; if no such path, flood and bail.
            Path path = pickForwardPath(paths, pkt.receivedFrom().port());
            if (path == null) {
                log.warn("Doh... don't know where to go... {} -> {} received on {}",
                         ethPkt.getSourceMAC(), ethPkt.getDestinationMAC(),
                         pkt.receivedFrom());
                flood(context);
                return;
            }

            // Otherwise forward and be done with it.
            installRule(context, path.src().port());
        }

    }

    // Indicates whether this is a control packet, e.g. LLDP, BDDP
    private boolean isControlPacket(Ethernet eth) {
        short type = eth.getEtherType();
        return type == Ethernet.TYPE_LLDP || type == Ethernet.TYPE_BSN;
    }

    // Indicated whether this is an IPv6 multicast packet.
    private boolean isIpv6Multicast(Ethernet eth) {
        return eth.getEtherType() == Ethernet.TYPE_IPV6 && eth.isMulticast();
    }

    // Selects a path from the given set that does not lead back to the
    // specified port.
    private Path pickForwardPath(Set<Path> paths, PortNumber notToPort) {
        for (Path path : paths) {
            if (!path.src().port().equals(notToPort)) {
                return path;
            }
        }
        return null;
    }

    // Floods the specified packet if permissible.
    private void flood(PacketContext context) {
        if (topologyService.isBroadcastPoint(topologyService.currentTopology(),
                                             context.inPacket().receivedFrom())) {
            packetOut(context, PortNumber.FLOOD);
        } else {
            context.block();
        }
    }

    // Sends a packet out the specified port.
    private void packetOut(PacketContext context, PortNumber portNumber) {
        context.treatmentBuilder().setOutput(portNumber);
        context.send();
    }

    // Install a rule forwarding the packet to the specified port.
    private void installRule(PacketContext context, PortNumber portNumber) {
        // We don't yet support bufferids in the flowservice so packet out first.
        packetOut(context, portNumber);
        if (!packetOutOnly) {
            // Install the flow rule to handle this type of message from now on.
            Ethernet inPkt = context.inPacket().parsed();
            TrafficSelector.Builder builder = DefaultTrafficSelector.builder();
            builder.matchEthType(inPkt.getEtherType())
                    .matchEthSrc(inPkt.getSourceMAC())
                    .matchEthDst(inPkt.getDestinationMAC())
                    .matchInport(context.inPacket().receivedFrom().port());

            TrafficTreatment.Builder treat = DefaultTrafficTreatment.builder();
            treat.setOutput(portNumber);

            FlowRule f = new DefaultFlowRule(context.inPacket().receivedFrom().deviceId(),
                                             builder.build(), treat.build(), PRIORITY, appId, TIMEOUT, false);

            flowRuleService.applyFlowRules(f);
        }
    }

}