/*
 * Copyright 2014-2015 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.net.packet.impl;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
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.apache.felix.scr.annotations.Service;
import org.onosproject.core.ApplicationId;
import org.onosproject.core.CoreService;
import org.onosproject.net.Device;
import org.onosproject.net.device.DeviceEvent;
import org.onosproject.net.device.DeviceListener;
import org.onosproject.net.device.DeviceService;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.FlowRuleService;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flowobjective.DefaultForwardingObjective;
import org.onosproject.net.flowobjective.FlowObjectiveService;
import org.onosproject.net.flowobjective.ForwardingObjective;
import org.onosproject.net.flowobjective.Objective;
import org.onosproject.net.flowobjective.ObjectiveContext;
import org.onosproject.net.flowobjective.ObjectiveError;
import org.onosproject.net.packet.DefaultPacketRequest;
import org.onosproject.net.packet.OutboundPacket;
import org.onosproject.net.packet.PacketContext;
import org.onosproject.net.packet.PacketEvent;
import org.onosproject.net.packet.PacketPriority;
import org.onosproject.net.packet.PacketProcessor;
import org.onosproject.net.packet.PacketProcessorEntry;
import org.onosproject.net.packet.PacketProvider;
import org.onosproject.net.packet.PacketProviderRegistry;
import org.onosproject.net.packet.PacketProviderService;
import org.onosproject.net.packet.PacketRequest;
import org.onosproject.net.packet.PacketService;
import org.onosproject.net.packet.PacketStore;
import org.onosproject.net.packet.PacketStoreDelegate;
import org.onosproject.net.provider.AbstractProviderRegistry;
import org.onosproject.net.provider.AbstractProviderService;
import org.slf4j.Logger;

import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import static com.google.common.base.Preconditions.checkNotNull;
import static org.onlab.util.Tools.groupedThreads;
import static org.onosproject.security.AppGuard.checkPermission;
import static org.onosproject.security.AppPermission.Type.*;
import static org.slf4j.LoggerFactory.getLogger;

/**
 * Provides a basic implementation of the packet SB &amp; NB APIs.
 */
@Component(immediate = true)
@Service
public class PacketManager
        extends AbstractProviderRegistry<PacketProvider, PacketProviderService>
        implements PacketService, PacketProviderRegistry {

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

    private static final String TABLE_TYPE_MSG =
            "Table Type cannot be null. For requesting packets without " +
                    "table hints, use other methods in the packetService API";

    private final PacketStoreDelegate delegate = new InternalStoreDelegate();

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    private DeviceService deviceService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    private FlowRuleService flowService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    private PacketStore store;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    private FlowObjectiveService objectiveService;

    private ExecutorService eventHandlingExecutor;

    private final DeviceListener deviceListener = new InternalDeviceListener();

    private final List<ProcessorEntry> processors = Lists.newCopyOnWriteArrayList();

    private ApplicationId appId;

    @Activate
    public void activate() {
        eventHandlingExecutor = Executors.newSingleThreadExecutor(
                groupedThreads("onos/net/packet", "event-handler"));
        appId = coreService.getAppId(CoreService.CORE_APP_NAME);
        store.setDelegate(delegate);
        deviceService.addListener(deviceListener);
        store.existingRequests().forEach(this::pushToAllDevices);
        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        store.unsetDelegate(delegate);
        deviceService.removeListener(deviceListener);
        eventHandlingExecutor.shutdown();
        log.info("Stopped");
    }

    @Override
    public void addProcessor(PacketProcessor processor, int priority) {
        checkPermission(PACKET_EVENT);
        checkNotNull(processor, "Processor cannot be null");
        ProcessorEntry entry = new ProcessorEntry(processor, priority);

        // Insert the new processor according to its priority.
        int i = 0;
        for (; i < processors.size(); i++) {
            if (priority < processors.get(i).priority()) {
                break;
            }
        }
        processors.add(i, entry);
    }

    @Override
    public void removeProcessor(PacketProcessor processor) {
        checkPermission(PACKET_EVENT);
        checkNotNull(processor, "Processor cannot be null");

        // Remove the processor entry.
        for (int i = 0; i < processors.size(); i++) {
            if (processors.get(i).processor() == processor) {
                processors.remove(i);
                break;
            }
        }
    }

    @Override
    public List<PacketProcessorEntry> getProcessors() {
        return ImmutableList.copyOf(processors);
    }

    @Override
    public void requestPackets(TrafficSelector selector, PacketPriority priority,
                               ApplicationId appId) {
        checkPermission(PACKET_READ);
        checkNotNull(selector, "Selector cannot be null");
        checkNotNull(appId, "Application ID cannot be null");

        PacketRequest request = new DefaultPacketRequest(selector, priority, appId);
        store.requestPackets(request);
    }

    @Override
    public void cancelPackets(TrafficSelector selector, PacketPriority priority,
                              ApplicationId appId) {
        checkPermission(PACKET_READ);
        checkNotNull(selector, "Selector cannot be null");
        checkNotNull(appId, "Application ID cannot be null");

        PacketRequest request = new DefaultPacketRequest(selector, priority, appId);
        store.cancelPackets(request);
    }

    @Override
    public List<PacketRequest> getRequests() {
        return store.existingRequests();
    }

    /**
     * Pushes all rules to the specified device.
     *
     * @param device device on which to install packet request flows
     */
    private void pushRulesToDevice(Device device) {
        log.debug("Pushing packet requests to device {}", device.id());
        for (PacketRequest request : store.existingRequests()) {
            pushRule(device, request);
        }
    }

    /**
     * Pushes a packet request flow rule to all devices.
     *
     * @param request the packet request
     */
    private void pushToAllDevices(PacketRequest request) {
        log.debug("Pushing packet request {} to all devices", request);
        for (Device device : deviceService.getDevices()) {
            pushRule(device, request);
        }
    }

    /**
     * Removes packet request flow rule from all devices.
     *
     * @param request the packet request
     */
    private void removeFromAllDevices(PacketRequest request) {
        deviceService.getAvailableDevices().forEach(d -> removeRule(d, request));
    }

    /**
     * Pushes packet intercept flow rules to the device.
     *
     * @param device  the device to push the rules to
     * @param request the packet request
     */
    private void pushRule(Device device, PacketRequest request) {
        if (!device.type().equals(Device.Type.SWITCH)) {
            return;
        }

        ForwardingObjective forwarding = createBuilder(request)
                .add(new ObjectiveContext() {
                    @Override
                    public void onError(Objective objective, ObjectiveError error) {
                        log.warn("Failed to install packet request {} to {}: {}",
                                 request, device.id(), error);
                    }
                });

        objectiveService.forward(device.id(), forwarding);
    }

    /**
     * Removes packet intercept flow rules from the device.
     *
     * @param device  the device to remove the rules deom
     * @param request the packet request
     */
    private void removeRule(Device device, PacketRequest request) {
        if (!device.type().equals(Device.Type.SWITCH)) {
            return;
        }
        ForwardingObjective forwarding = createBuilder(request)
                .remove(new ObjectiveContext() {
                    @Override
                    public void onError(Objective objective, ObjectiveError error) {
                        log.warn("Failed to withdraw packet request {} from {}: {}",
                                 request, device.id(), error);
                    }
                });
        objectiveService.forward(device.id(), forwarding);
    }

    private DefaultForwardingObjective.Builder createBuilder(PacketRequest request) {
        return DefaultForwardingObjective.builder()
                .withPriority(request.priority().priorityValue())
                .withSelector(request.selector())
                .fromApp(appId)
                .withFlag(ForwardingObjective.Flag.VERSATILE)
                .withTreatment(DefaultTrafficTreatment.builder().punt().build())
                .makePermanent();
    }

    @Override
    public void emit(OutboundPacket packet) {
        checkPermission(PACKET_WRITE);
        checkNotNull(packet, "Packet cannot be null");
        store.emit(packet);
    }

    private void localEmit(OutboundPacket packet) {
        Device device = deviceService.getDevice(packet.sendThrough());
        if (device == null) {
            return;
        }
        PacketProvider packetProvider = getProvider(device.providerId());
        if (packetProvider != null) {
            packetProvider.emit(packet);
        }
    }

    @Override
    protected PacketProviderService createProviderService(PacketProvider provider) {
        return new InternalPacketProviderService(provider);
    }

    /**
     * Personalized packet provider service issued to the supplied provider.
     */
    private class InternalPacketProviderService
            extends AbstractProviderService<PacketProvider>
            implements PacketProviderService {

        protected InternalPacketProviderService(PacketProvider provider) {
            super(provider);
        }

        @Override
        public void processPacket(PacketContext context) {
            // TODO filter packets sent to processors based on registrations
            for (ProcessorEntry entry : processors) {
                try {
                    long start = System.nanoTime();
                    entry.processor().process(context);
                    entry.addNanos(System.nanoTime() - start);
                } catch (Exception e) {
                    log.warn("Packet processor {} threw an exception", entry.processor(), e);
                }
            }
        }

    }

    /**
     * Internal callback from the packet store.
     */
    private class InternalStoreDelegate implements PacketStoreDelegate {
        @Override
        public void notify(PacketEvent event) {
            localEmit(event.subject());
        }

        @Override
        public void requestPackets(PacketRequest request) {
            pushToAllDevices(request);
        }

        @Override
        public void cancelPackets(PacketRequest request) {
            removeFromAllDevices(request);
        }
    }

    /**
     * Internal listener for device service events.
     */
    private class InternalDeviceListener implements DeviceListener {
        @Override
        public void event(DeviceEvent event) {
            eventHandlingExecutor.execute(() -> {
                try {
                    Device device = event.subject();
                    switch (event.type()) {
                        case DEVICE_ADDED:
                        case DEVICE_AVAILABILITY_CHANGED:
                            if (deviceService.isAvailable(event.subject().id())) {
                                pushRulesToDevice(device);
                            }
                            break;
                        default:
                            break;
                    }
                } catch (Exception e) {
                    log.warn("Failed to process {}", event, e);
                }
            });
        }
    }

    /**
     * Entity for tracking stats for a packet processor.
     */
    private class ProcessorEntry implements PacketProcessorEntry {
        private final PacketProcessor processor;
        private final int priority;
        private long invocations = 0;
        private long nanos = 0;

        public ProcessorEntry(PacketProcessor processor, int priority) {
            this.processor = processor;
            this.priority = priority;
        }

        @Override
        public PacketProcessor processor() {
            return processor;
        }

        @Override
        public int priority() {
            return priority;
        }

        @Override
        public long invocations() {
            return invocations;
        }

        @Override
        public long totalNanos() {
            return nanos;
        }

        @Override
        public long averageNanos() {
            return invocations > 0 ? nanos / invocations : 0;
        }

        void addNanos(long nanos) {
            this.nanos += nanos;
            this.invocations++;
        }
    }
}