/*******************************************************************************
 * 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.onlab.onos.provider.lldp.impl;


import static org.slf4j.LoggerFactory.getLogger;

import java.nio.ByteBuffer;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import org.jboss.netty.util.Timeout;
import org.jboss.netty.util.TimerTask;
import org.onlab.onos.net.ConnectPoint;
import org.onlab.onos.net.Device;
import org.onlab.onos.net.DeviceId;
import org.onlab.onos.net.Link.Type;
import org.onlab.onos.net.Port;
import org.onlab.onos.net.PortNumber;
import org.onlab.onos.net.flow.DefaultTrafficTreatment;
import org.onlab.onos.net.link.DefaultLinkDescription;
import org.onlab.onos.net.link.LinkDescription;
import org.onlab.onos.net.link.LinkProviderService;
import org.onlab.onos.net.packet.DefaultOutboundPacket;
import org.onlab.onos.net.packet.OutboundPacket;
import org.onlab.onos.net.packet.PacketContext;
import org.onlab.onos.net.packet.PacketService;
import org.onlab.packet.Ethernet;
import org.onlab.packet.ONOSLLDP;
import org.onlab.util.Timer;
import org.slf4j.Logger;


/**
 * Run discovery process from a physical switch. Ports are initially labeled as
 * slow ports. When an LLDP is successfully received, label the remote port as
 * fast. Every probeRate milliseconds, loop over all fast ports and send an
 * LLDP, send an LLDP for a single slow port. Based on FlowVisor topology
 * discovery implementation.
 *
 * TODO: add 'fast discovery' mode: drop LLDPs in destination switch but listen
 * for flow_removed messages
 */
public class LinkDiscovery implements TimerTask {

    private final Device device;
    // send 1 probe every probeRate milliseconds
    private final long probeRate;
    private final Set<Long> slowPorts;
    private final Set<Long> fastPorts;
    // number of unacknowledged probes per port
    private final Map<Long, AtomicInteger> portProbeCount;
    // number of probes to send before link is removed
    private static final short MAX_PROBE_COUNT = 3;
    private final Logger log = getLogger(getClass());
    private final ONOSLLDP lldpPacket;
    private final Ethernet ethPacket;
    private Ethernet bddpEth;
    private final boolean useBDDP;
    private final LinkProviderService linkProvider;
    private final PacketService pktService;
    private Timeout timeout;

    /**
     * Instantiates discovery manager for the given physical switch. Creates a
     * generic LLDP packet that will be customized for the port it is sent out on.
     * Starts the the timer for the discovery process.
     *
     * @param device the physical switch
     * @param useBDDP flag to also use BDDP for discovery
     */
    public LinkDiscovery(Device device, PacketService pktService,
             LinkProviderService providerService, Boolean... useBDDP) {
        this.device = device;
        this.probeRate = 3000;
        this.linkProvider = providerService;
        this.pktService = pktService;
        this.slowPorts = Collections.synchronizedSet(new HashSet<Long>());
        this.fastPorts = Collections.synchronizedSet(new HashSet<Long>());
        this.portProbeCount = new HashMap<>();
        this.lldpPacket = new ONOSLLDP();
        this.lldpPacket.setChassisId(device.chassisId());
        this.lldpPacket.setDevice(device.id().toString());


        this.ethPacket = new Ethernet();
        this.ethPacket.setEtherType(Ethernet.TYPE_LLDP);
        this.ethPacket.setDestinationMACAddress(ONOSLLDP.LLDP_NICIRA);
        this.ethPacket.setPayload(this.lldpPacket);
        this.ethPacket.setPad(true);
        this.useBDDP = useBDDP.length > 0 ? useBDDP[0] : false;
        if (this.useBDDP) {
            this.bddpEth = new Ethernet();
            this.bddpEth.setPayload(this.lldpPacket);
            this.bddpEth.setEtherType(Ethernet.TYPE_BSN);
            this.bddpEth.setDestinationMACAddress(ONOSLLDP.BDDP_MULTICAST);
            this.bddpEth.setPad(true);
            log.info("Using BDDP to discover network");
        }

        start();
        this.log.debug("Started discovery manager for switch {}",
                       device.id());

    }

    /**
     * Add physical port port to discovery process.
     * Send out initial LLDP and label it as slow port.
     *
     * @param port the port
     */
    public void addPort(final Port port) {
        this.log.debug("sending init probe to port {}",
                           port.number().toLong());

        sendProbes(port.number().toLong());

        synchronized (this) {
            this.slowPorts.add(port.number().toLong());
        }


    }

    /**
     * Removes physical port from discovery process.
     *
     * @param port the port
     */
    public void removePort(final Port port) {
        // Ignore ports that are not on this switch

        long portnum = port.number().toLong();
        synchronized (this) {
            if (this.slowPorts.contains(portnum)) {
                this.slowPorts.remove(portnum);

            } else if (this.fastPorts.contains(portnum)) {
                this.fastPorts.remove(portnum);
                this.portProbeCount.remove(portnum);
                // no iterator to update
            } else {
                this.log.warn(
                        "tried to dynamically remove non-existing port {}",
                        portnum);
            }
        }
    }

    /**
     * Method called by remote port to acknowledge receipt of LLDP sent by
     * this port. If slow port, updates label to fast. If fast port, decrements
     * number of unacknowledged probes.
     *
     * @param portNumber the port
     */
    public void ackProbe(final Long portNumber) {

        synchronized (this) {
            if (this.slowPorts.contains(portNumber)) {
                this.log.debug("Setting slow port to fast: {}:{}",
                        this.device.id(), portNumber);
                this.slowPorts.remove(portNumber);
                this.fastPorts.add(portNumber);
                this.portProbeCount.put(portNumber, new AtomicInteger(0));
            } else {
                if (this.fastPorts.contains(portNumber)) {
                    this.portProbeCount.get(portNumber).set(0);
                } else {
                    this.log.debug(
                            "Got ackProbe for non-existing port: {}",
                            portNumber);
                }
            }
        }
    }


    /**
     * Handles an incoming LLDP packet. Creates link in topology and sends ACK
     * to port where LLDP originated.
     */
    public boolean handleLLDP(PacketContext context) {
        Ethernet eth = context.inPacket().parsed();
        ONOSLLDP onoslldp = ONOSLLDP.parseONOSLLDP(eth);
        if (onoslldp != null) {
            final PortNumber dstPort =
                    context.inPacket().receivedFrom().port();
            final PortNumber srcPort = PortNumber.portNumber(onoslldp.getPort());
            final DeviceId srcDeviceId = DeviceId.deviceId(onoslldp.getDeviceString());
            final DeviceId dstDeviceId = context.inPacket().receivedFrom().deviceId();
            this.ackProbe(srcPort.toLong());
            ConnectPoint src = new ConnectPoint(srcDeviceId, srcPort);
            ConnectPoint dst = new ConnectPoint(dstDeviceId, dstPort);

            LinkDescription ld;
            if (eth.getEtherType() == Ethernet.TYPE_BSN) {
                ld = new DefaultLinkDescription(src, dst, Type.INDIRECT);
            } else {
                ld = new DefaultLinkDescription(src, dst, Type.DIRECT);
            }
            linkProvider.linkDetected(ld);
            return true;
        }
        return false;
    }


    /**
     * Execute this method every t milliseconds. Loops over all ports
     * labeled as fast and sends out an LLDP. Send out an LLDP on a single slow
     * port.
     *
     * @param t timeout
     * @throws Exception
     */
    @Override
    public void run(final Timeout t) {
        this.log.debug("sending probes");
        synchronized (this) {
            final Iterator<Long> fastIterator = this.fastPorts.iterator();
            Long portNumber;
            Integer probeCount;
            while (fastIterator.hasNext()) {
                portNumber = fastIterator.next();
                probeCount = this.portProbeCount.get(portNumber)
                        .getAndIncrement();

                if (probeCount < LinkDiscovery.MAX_PROBE_COUNT) {
                    this.log.debug("sending fast probe to port");
                    sendProbes(portNumber);
                } else {
                    // Update fast and slow ports
                    //fastIterator.remove();
                    //this.slowPorts.add(portNumber);
                    //this.portProbeCount.remove(portNumber);


                    ConnectPoint cp = new ConnectPoint(
                            device.id(),
                            PortNumber.portNumber(portNumber));
                    log.debug("Link down -> {}", cp);
                    linkProvider.linksVanished(cp);
                }
            }

            // send a probe for the next slow port
            if (!this.slowPorts.isEmpty()) {
                Iterator<Long> slowIterator = this.slowPorts.iterator();
                while (slowIterator.hasNext()) {
                    portNumber = slowIterator.next();
                    this.log.debug("sending slow probe to port {}", portNumber);

                    sendProbes(portNumber);

                }
            }
        }

        // reschedule timer
        timeout = Timer.getTimer().newTimeout(this, this.probeRate,
                TimeUnit.MILLISECONDS);
    }

    public void stop() {
        timeout.cancel();
    }

    public void start() {
        timeout = Timer.getTimer().newTimeout(this, 0,
                                              TimeUnit.MILLISECONDS);
    }

    /**
     * Creates packet_out LLDP for specified output port.
     *
     * @param port the port
     * @return Packet_out message with LLDP data
     */
    private OutboundPacket createOutBoundLLDP(final Long port) {
        if (port == null) {
            return null;
        }
        this.lldpPacket.setPortId(port.intValue());
        this.ethPacket.setSourceMACAddress("DE:AD:BE:EF:BA:11");

        final byte[] lldp = this.ethPacket.serialize();
        OutboundPacket outboundPacket = new DefaultOutboundPacket(
                this.device.id(),
                DefaultTrafficTreatment.builder().setOutput(
                        PortNumber.portNumber(port)).build(),
                ByteBuffer.wrap(lldp));
        return outboundPacket;
    }

    /**
     * Creates packet_out BDDP for specified output port.
     *
     * @param port the port
     * @return Packet_out message with LLDP data
     */
    private OutboundPacket createOutBoundBDDP(final Long port) {
        if (port == null) {
            return null;
        }
        this.lldpPacket.setPortId(port.intValue());
        this.bddpEth.setSourceMACAddress("DE:AD:BE:EF:BA:11");

        final byte[] bddp = this.bddpEth.serialize();
        OutboundPacket outboundPacket = new DefaultOutboundPacket(
                this.device.id(),
                DefaultTrafficTreatment.builder()
                        .setOutput(PortNumber.portNumber(port)).build(),
                ByteBuffer.wrap(bddp));
        return outboundPacket;
    }

    private void sendProbes(Long portNumber) {
        OutboundPacket pkt = this.createOutBoundLLDP(portNumber);
        pktService.emit(pkt);
        if (useBDDP) {
            OutboundPacket bpkt = this.createOutBoundBDDP(portNumber);
            pktService.emit(bpkt);
        }
    }

}