/*
 * Copyright 2016-present Open Networking Foundation
 *
 * 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.segmentrouting;

import com.google.common.collect.Sets;

import org.onlab.packet.IpPrefix;
import org.onlab.packet.MacAddress;
import org.onlab.packet.VlanId;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.Host;
import org.onosproject.net.PortNumber;
import org.onosproject.net.host.HostEvent;
import org.onosproject.routeservice.ResolvedRoute;
import org.onosproject.routeservice.RouteEvent;
import org.onosproject.net.DeviceId;
import org.onosproject.routeservice.RouteInfo;
import org.onosproject.segmentrouting.config.DeviceConfigNotFoundException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.Collection;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;

/**
 * Handles RouteEvent and manages routing entries.
 */
public class RouteHandler {
    private static final Logger log = LoggerFactory.getLogger(RouteHandler.class);
    private final SegmentRoutingManager srManager;

    RouteHandler(SegmentRoutingManager srManager) {
        this.srManager = srManager;
    }

    protected void init(DeviceId deviceId) {
        srManager.routeService.getRouteTables().stream()
                .map(srManager.routeService::getRoutes)
                .flatMap(Collection::stream)
                .map(RouteInfo::allRoutes)
                .filter(allRoutes -> allRoutes.stream().anyMatch(resolvedRoute ->
                        srManager.nextHopLocations(resolvedRoute).stream()
                                .anyMatch(cp -> deviceId.equals(cp.deviceId()))))
                .forEach(rr -> processRouteAddedInternal(rr, true));
    }

    void processRouteAdded(RouteEvent event) {
        processRouteAddedInternal(event.alternatives(), false);
    }

    /**
     * Internal logic that handles route addition.
     *
     * @param routes collection of routes to be processed
     * @param populateRouteOnly true if we only want to populateRoute but not populateSubnet.
     *                          Set it to true when initializing a device coming up.
     *                          populateSubnet will be done when link comes up later so it is redundant.
     *                          populateRoute still needs to be done for statically configured next hop hosts.
     */
    private void processRouteAddedInternal(Collection<ResolvedRoute> routes, boolean populateRouteOnly) {
        if (!isReady()) {
            log.info("System is not ready. Skip adding route for {}", routes);
            return;
        }

        log.info("processRouteAddedInternal. routes={}", routes);

        if (routes.size() > 2) {
            log.info("Route {} has more than two next hops. Do not process route change", routes);
            return;
        }

        if (routes.isEmpty()) {
            log.warn("No resolved route found. Abort processRouteAddedInternal");
            return;
        }

        Set<ConnectPoint> allLocations = Sets.newHashSet();
        Set<IpPrefix> allPrefixes = Sets.newHashSet();
        routes.forEach(route -> {
            allLocations.addAll(srManager.nextHopLocations(route));
            allPrefixes.add(route.prefix());
        });
        log.debug("RouteAdded. populateSubnet {}, {}", allLocations, allPrefixes);
        srManager.defaultRoutingHandler.populateSubnet(allLocations, allPrefixes);

        routes.forEach(route -> {
            IpPrefix prefix = route.prefix();
            MacAddress nextHopMac = route.nextHopMac();
            VlanId nextHopVlan = route.nextHopVlan();
            Set<ConnectPoint> locations = srManager.nextHopLocations(route);

            locations.forEach(location -> {
                log.debug("RouteAdded. addSubnet {}, {}", location, prefix);
                srManager.deviceConfiguration.addSubnet(location, prefix);
                log.debug("RouteAdded populateRoute {}, {}, {}, {}", location, prefix, nextHopMac, nextHopVlan);
                srManager.defaultRoutingHandler.populateRoute(location.deviceId(), prefix,
                        nextHopMac, nextHopVlan, location.port(), false);

                processSingleLeafPairIfNeeded(locations, location, prefix, nextHopVlan);
            });
        });
    }

    void processRouteUpdated(RouteEvent event) {
        processRouteUpdatedInternal(Sets.newHashSet(event.alternatives()),
                Sets.newHashSet(event.prevAlternatives()));
    }

    void processAlternativeRoutesChanged(RouteEvent event) {
        processRouteUpdatedInternal(Sets.newHashSet(event.alternatives()),
                Sets.newHashSet(event.prevAlternatives()));
    }

    private void processRouteUpdatedInternal(Set<ResolvedRoute> routes, Set<ResolvedRoute> oldRoutes) {
        if (!isReady()) {
            log.info("System is not ready. Skip updating route for {} -> {}", oldRoutes, routes);
            return;
        }

        log.info("processRouteUpdatedInternal. routes={}, oldRoutes={}", routes, oldRoutes);

        if (routes.size() > 2) {
            log.info("Route {} has more than two next hops. Do not process route change", routes);
            return;
        }

        Set<ConnectPoint> allLocations = Sets.newHashSet();
        Set<IpPrefix> allPrefixes = Sets.newHashSet();
        routes.forEach(route -> {
            allLocations.addAll(srManager.nextHopLocations(route));
            allPrefixes.add(route.prefix());
        });

        // Just come back from an invalid next hop count
        // Revoke subnet from all locations and reset oldRoutes such that system will be reprogrammed from scratch
        if (oldRoutes.size() > 2) {
            log.info("Revoke subnet {} and reset oldRoutes");
            // FIXME remove routes more precisely by memorizing the old locations
            srManager.defaultRoutingHandler.revokeSubnet(allPrefixes, null);
            oldRoutes = Sets.newHashSet();
        }

        log.debug("RouteUpdated. populateSubnet {}, {}", allLocations, allPrefixes);
        srManager.defaultRoutingHandler.populateSubnet(allLocations, allPrefixes);

        Set<ResolvedRoute> toBeRemoved = Sets.difference(oldRoutes, routes).immutableCopy();
        Set<ResolvedRoute> toBeAdded = Sets.difference(routes, oldRoutes).immutableCopy();

        toBeRemoved.forEach(route -> {
            srManager.nextHopLocations(route).forEach(oldLocation -> {
                if (toBeAdded.stream().map(srManager::nextHopLocations)
                        .flatMap(Set::stream).map(ConnectPoint::deviceId)
                        .noneMatch(deviceId -> deviceId.equals(oldLocation.deviceId()))) {
                    IpPrefix prefix = route.prefix();
                    log.debug("RouteUpdated. removeSubnet {}, {}", oldLocation, prefix);
                    srManager.deviceConfiguration.removeSubnet(oldLocation, prefix);
                    // We don't remove the flow on the old location in occasion of two next hops becoming one
                    // since the populateSubnet will point the old location to the new location via spine.
                }
            });
        });

        toBeAdded.forEach(route -> {
            IpPrefix prefix = route.prefix();
            MacAddress nextHopMac = route.nextHopMac();
            VlanId nextHopVlan = route.nextHopVlan();
            Set<ConnectPoint> locations = srManager.nextHopLocations(route);

            locations.forEach(location -> {
                log.debug("RouteUpdated. addSubnet {}, {}", location, prefix);
                srManager.deviceConfiguration.addSubnet(location, prefix);
                log.debug("RouteUpdated. populateRoute {}, {}, {}, {}", location, prefix, nextHopMac, nextHopVlan);
                srManager.defaultRoutingHandler.populateRoute(location.deviceId(), prefix,
                        nextHopMac, nextHopVlan, location.port(), false);

                processSingleLeafPairIfNeeded(locations, location, prefix, nextHopVlan);
            });
        });
    }

    void processRouteRemoved(RouteEvent event) {
        processRouteRemovedInternal(event.alternatives());
    }

    private void processRouteRemovedInternal(Collection<ResolvedRoute> routes) {
        if (!isReady()) {
            log.info("System is not ready. Skip removing route for {}", routes);
            return;
        }

        log.info("processRouteRemovedInternal. routes={}", routes);

        Set<IpPrefix> allPrefixes = Sets.newHashSet();
        routes.forEach(route -> {
            allPrefixes.add(route.prefix());
        });
        log.debug("RouteRemoved. revokeSubnet {}", allPrefixes);
        // FIXME remove routes more precisely by memorizing the old locations
        srManager.defaultRoutingHandler.revokeSubnet(allPrefixes, null);

        routes.forEach(route -> {
            IpPrefix prefix = route.prefix();
            MacAddress nextHopMac = route.nextHopMac();
            VlanId nextHopVlan = route.nextHopVlan();
            Set<ConnectPoint> locations = srManager.nextHopLocations(route);

            locations.forEach(location -> {
                log.debug("RouteRemoved. removeSubnet {}, {}", location, prefix);
                srManager.deviceConfiguration.removeSubnet(location, prefix);
                // We don't need to call revokeRoute again since revokeSubnet will remove the prefix
                // from all devices, including the ones that next hop attaches to.
                // revokeSubnet will also remove flow on the pair device (if exist) pointing to current location.
            });
        });
    }

    void processHostMovedEvent(HostEvent event) {
        log.info("processHostMovedEvent {}", event);
        MacAddress hostMac = event.subject().mac();
        VlanId hostVlanId = event.subject().vlan();

        Set<ConnectPoint> prevLocations = event.prevSubject().locations()
                .stream().map(h -> (ConnectPoint) h)
                .collect(Collectors.toSet());
        Set<ConnectPoint> newLocations = event.subject().locations()
                .stream().map(h -> (ConnectPoint) h)
                .collect(Collectors.toSet());
        List<Set<IpPrefix>> batchedSubnets =
                srManager.deviceConfiguration.getBatchedSubnets(event.subject().id());
        Set<DeviceId> newDeviceIds = newLocations.stream().map(ConnectPoint::deviceId)
                .collect(Collectors.toSet());

        // Set of deviceIDs of the previous locations where the host was connected
        // Used to determine if host moved to different connect points
        // on same device or moved to a different device altogether
        Set<DeviceId> oldDeviceIds = prevLocations.stream().map(ConnectPoint::deviceId)
                .collect(Collectors.toSet());

        // L3 Ucast bucket needs to be updated only once per host
        // and only when the no. of routes with the host as next-hop is not zero
        if (!batchedSubnets.isEmpty()) {
           // For each new location, if NextObj exists for the host, update with new location ..
           Sets.difference(newLocations, prevLocations).forEach(newLocation -> {
                    // NOTE: that we use the nexthop vlanId to retrieve the nextId
                    //       while the vlanId used to program the L3 unicast chain
                    //       is derived from the port configuration. In case of
                    //       a tagged interface we use host vlanId. Host vlan should
                    //       be part of the tags configured for that port. See the
                    //       code in DefaultGroupHandler.updateL3UcastGroupBucket
                    int nextId = srManager.getMacVlanNextObjectiveId(newLocation.deviceId(),
                            hostMac, hostVlanId, null, false);
                    if (nextId != -1) {
                        //Update the nextId group bucket
                        log.debug("HostMoved. NextId exists, update L3 Ucast Group Bucket {}, {}, {} --> {}",
                                newLocation, hostMac, hostVlanId, nextId);
                        srManager.updateMacVlanTreatment(newLocation.deviceId(), hostMac, hostVlanId,
                                newLocation.port(), nextId);
                    } else {
                        log.debug("HostMoved. NextId does not exist for this location {}, host {}/{}",
                                newLocation, hostMac, hostVlanId);
                    }
           });
        }

        batchedSubnets.forEach(subnets -> {
            log.debug("HostMoved. populateSubnet {}, {}", newLocations, subnets);
            srManager.defaultRoutingHandler.populateSubnet(newLocations, subnets);

            subnets.forEach(prefix -> {
                // For each old location
                Sets.difference(prevLocations, newLocations).forEach(prevLocation -> {

                    // Remove flows for unchanged IPs only when the host moves from a switch to another.
                    // Otherwise, do not remove and let the adding part update the old flow
                    if (newDeviceIds.contains(prevLocation.deviceId())) {
                        return;
                    }

                    log.debug("HostMoved. removeSubnet {}, {}", prevLocation, prefix);
                    srManager.deviceConfiguration.removeSubnet(prevLocation, prefix);

                    // Do not remove flow from a device if the route is still reachable via its pair device.
                    // If spine exists,
                    //     populateSubnet above will update the flow to point to its pair device via spine.
                    // If spine does not exist,
                    //     processSingleLeafPair below will update the flow to point to its pair device via pair port.
                    DeviceId pairDeviceId = srManager.getPairDeviceId(prevLocation.deviceId()).orElse(null);
                    if (newLocations.stream().anyMatch(n -> n.deviceId().equals(pairDeviceId))) {
                        return;
                    }

                    log.debug("HostMoved. revokeRoute {}, {}, {}, {}", prevLocation, prefix, hostMac, hostVlanId);
                    srManager.defaultRoutingHandler.revokeRoute(prevLocation.deviceId(), prefix,
                            hostMac, hostVlanId, prevLocation.port(), false);
                });

                // For each new location, add all new IPs.
                Sets.difference(newLocations, prevLocations).forEach(newLocation -> {
                    log.debug("HostMoved. addSubnet {}, {}", newLocation, prefix);
                    srManager.deviceConfiguration.addSubnet(newLocation, prefix);

                    //its a new connect point, not a move from an existing device, populateRoute
                    if (!oldDeviceIds.contains(newLocation.deviceId())) {
                       log.debug("HostMoved. populateRoute {}, {}, {}, {}", newLocation, prefix, hostMac, hostVlanId);
                       srManager.defaultRoutingHandler.populateRoute(newLocation.deviceId(), prefix,
                              hostMac, hostVlanId, newLocation.port(), false);
                    }
                });

                newLocations.forEach(location -> {
                    processSingleLeafPairIfNeeded(newLocations, location, prefix, hostVlanId);
                });
            });
        });

    }

    public void processIntfVlanUpdatedEvent(DeviceId deviceId, PortNumber portNum) {
        log.info("processIntfVlanUpdatedEvent {}/{}", deviceId, portNum);

        // Verify there are hosts attached to the port
        ConnectPoint connectPoint = new ConnectPoint(deviceId, portNum);
        Set<Host> hosts = srManager.hostService.getConnectedHosts(connectPoint);
        if (hosts == null || hosts.size() == 0) {
            log.debug("processIntfVlanUpdatedEvent: No hosts connected to {}", connectPoint);
            return;
        }

        // Iterate over the hosts and update if needed the vlan of the nextobjective
        hosts.forEach(host -> {
            // Verify if there is a nexthop and only then update the l3 indirect unicast chain
            int nextId = srManager.getMacVlanNextObjectiveId(deviceId, host.mac(), host.vlan(),
                    null, false);
            if (nextId != -1) {
                //Update the nextId group bucket
                log.debug("intfVlanUpdated. NextId exists, update L3 Ucast Group Bucket {}, {}, {} --> {}",
                        connectPoint, host.mac(), host.vlan(), nextId);
                // NOTE: that we use the nexthop vlanId to retrieve the nextId
                //       while the vlanId used to program the L3 unicast chain
                //       is derived from the port configuration. In case of
                //       a tagged interface we use host vlanId. Host vlan should
                //       be part of the tags configured for that port. See the
                //       code in DefaultGroupHandler.updateL3UcastGroupBucket
                srManager.updateMacVlanTreatment(deviceId, host.mac(), host.vlan(), portNum, nextId);
            } else {
                log.debug("intfVlanUpdated. NextId does not exist for this location {}, host {}/{}",
                        connectPoint, host.mac(), host.vlan());
            }
        });
    }

    private boolean isReady() {
        return Objects.nonNull(srManager.deviceConfiguration) &&
                Objects.nonNull(srManager.defaultRoutingHandler);
    }

    protected boolean processSingleLeafPairIfNeeded(Set<ConnectPoint> locations, ConnectPoint location, IpPrefix prefix,
                                                    VlanId nextHopVlan) {
        // Special handling for single leaf pair
        if (!srManager.getInfraDeviceIds().isEmpty()) {
            log.debug("Spine found. Skip single leaf pair handling");
            return false;
        }
        Optional<DeviceId> pairDeviceId = srManager.getPairDeviceId(location.deviceId());
        if (pairDeviceId.isEmpty()) {
            log.debug("Pair device of {} not found", location.deviceId());
            return false;
        }
        if (locations.stream().anyMatch(l -> l.deviceId().equals(pairDeviceId.get()))) {
            log.debug("Pair device has a next hop available. Leave it as is.");
            return false;
        }
        Optional<PortNumber> pairRemotePort = srManager.getPairLocalPort(pairDeviceId.get());
        if (pairRemotePort.isEmpty()) {
            log.debug("Pair remote port of {} not found", pairDeviceId.get());
            return false;
        }
        // Use routerMac of the pair device as the next hop
        MacAddress effectiveMac;
        try {
            effectiveMac = srManager.getDeviceMacAddress(location.deviceId());
        } catch (DeviceConfigNotFoundException e) {
            log.warn("Abort populateRoute on pair device {}. routerMac not found", pairDeviceId);
            return false;
        }
        // Since the pairLocalPort is trunk port, use assigned vlan of original port
        // when the host is untagged
        VlanId effectiveVlan = Optional.ofNullable(srManager.getInternalVlanId(location)).orElse(nextHopVlan);

        log.debug("Single leaf pair. populateRoute {}/{}, {}, {}, {}", pairDeviceId, pairRemotePort, prefix,
                effectiveMac, effectiveVlan);
        srManager.defaultRoutingHandler.populateRoute(pairDeviceId.get(), prefix,
                effectiveMac, effectiveVlan, pairRemotePort.get(), false);

        return true;
    }
}