/*
 * 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.intent.impl.compiler;

import java.util.Collections;
import java.util.List;
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.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.onlab.util.Frequency;
import org.onosproject.net.ChannelSpacing;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.GridType;
import org.onosproject.net.Link;
import org.onosproject.net.OchPort;
import org.onosproject.net.OchSignal;
import org.onosproject.net.OmsPort;
import org.onosproject.net.Path;
import org.onosproject.net.Port;
import org.onosproject.net.device.DeviceService;
import org.onosproject.net.intent.Intent;
import org.onosproject.net.intent.IntentCompiler;
import org.onosproject.net.intent.IntentExtensionService;
import org.onosproject.net.intent.OpticalConnectivityIntent;
import org.onosproject.net.intent.OpticalPathIntent;
import org.onosproject.net.resource.link.DefaultLinkResourceRequest;
import org.onosproject.net.resource.device.DeviceResourceService;
import org.onosproject.net.resource.link.LambdaResource;
import org.onosproject.net.resource.link.LambdaResourceAllocation;
import org.onosproject.net.resource.link.LinkResourceAllocations;
import org.onosproject.net.resource.link.LinkResourceRequest;
import org.onosproject.net.resource.link.LinkResourceService;
import org.onosproject.net.resource.ResourceAllocation;
import org.onosproject.net.resource.ResourceType;
import org.onosproject.net.topology.LinkWeight;
import org.onosproject.net.topology.Topology;
import org.onosproject.net.topology.TopologyEdge;
import org.onosproject.net.topology.TopologyService;

import com.google.common.collect.ImmutableList;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * An intent compiler for {@link org.onosproject.net.intent.OpticalConnectivityIntent}.
 */
@Component(immediate = true)
public class OpticalConnectivityIntentCompiler implements IntentCompiler<OpticalConnectivityIntent> {

    private static final GridType DEFAULT_OCH_GRIDTYPE = GridType.DWDM;
    private static final ChannelSpacing DEFAULT_CHANNEL_SPACING = ChannelSpacing.CHL_50GHZ;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected IntentExtensionService intentManager;

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

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected LinkResourceService linkResourceService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected DeviceResourceService deviceResourceService;

    @Activate
    public void activate() {
        intentManager.registerCompiler(OpticalConnectivityIntent.class, this);
    }

    @Deactivate
    public void deactivate() {
        intentManager.unregisterCompiler(OpticalConnectivityIntent.class);
    }

    @Override
    public List<Intent> compile(OpticalConnectivityIntent intent,
                                List<Intent> installable,
                                Set<LinkResourceAllocations> resources) {
        // Check if source and destination are optical OCh ports
        ConnectPoint src = intent.getSrc();
        ConnectPoint dst = intent.getDst();
        Port srcPort = deviceService.getPort(src.deviceId(), src.port());
        Port dstPort = deviceService.getPort(dst.deviceId(), dst.port());
        checkArgument(srcPort instanceof OchPort);
        checkArgument(dstPort instanceof OchPort);

        // Calculate available light paths
        Set<Path> paths = getOpticalPaths(intent);

        // Use first path that can be successfully reserved
        for (Path path : paths) {
            // Request and reserve lambda on path
            LinkResourceAllocations linkAllocs = assignWavelength(intent, path);
            if (linkAllocs == null) {
                continue;
            }

            OmsPort omsPort = (OmsPort) deviceService.getPort(path.src().deviceId(), path.src().port());

            // Try to reserve port resources, roll back if unsuccessful
            Set<Port> portAllocs = deviceResourceService.requestPorts(intent);
            if (portAllocs == null) {
                linkResourceService.releaseResources(linkAllocs);
                continue;
            }

            // Create installable optical path intent
            LambdaResourceAllocation lambdaAlloc = getWavelength(path, linkAllocs);
            OchSignal ochSignal = getOchSignal(lambdaAlloc, omsPort.minFrequency(), omsPort.grid());

            Intent newIntent = OpticalPathIntent.builder()
                    .appId(intent.appId())
                    .src(intent.getSrc())
                    .dst(intent.getDst())
                    .path(path)
                    .lambda(ochSignal)
                    .build();

            return ImmutableList.of(newIntent);
        }

        return Collections.emptyList();
    }

    /**
     * Find the lambda allocated to the path.
     *
     * @param path the path
     * @param linkAllocs the link allocations
     * @return
     */
    private LambdaResourceAllocation getWavelength(Path path, LinkResourceAllocations linkAllocs) {
        for (Link link : path.links()) {
            for (ResourceAllocation alloc : linkAllocs.getResourceAllocation(link)) {
                if (alloc.type() == ResourceType.LAMBDA) {
                    return (LambdaResourceAllocation) alloc;
                }
            }
        }

        return null;
    }

    /**
     * Request and reserve first available wavelength across path.
     *
     * @param path path in WDM topology
     * @return first available lambda resource allocation
     */
    private LinkResourceAllocations assignWavelength(Intent intent, Path path) {
        LinkResourceRequest.Builder request =
                DefaultLinkResourceRequest.builder(intent.id(), path.links())
                .addLambdaRequest();

        LinkResourceAllocations allocations = linkResourceService.requestResources(request.build());

        checkWavelengthContinuity(allocations, path);

        return allocations;
    }

    /**
     * Checks wavelength continuity constraint across path, i.e., an identical lambda is used on all links.
     * @return true if wavelength continuity is met, false otherwise
     */
    private boolean checkWavelengthContinuity(LinkResourceAllocations allocations, Path path) {
        if (allocations == null) {
            return false;
        }

        LambdaResource lambda = null;

        for (Link link : path.links()) {
            for (ResourceAllocation alloc : allocations.getResourceAllocation(link)) {
                if (alloc.type() == ResourceType.LAMBDA) {
                    LambdaResource nextLambda = ((LambdaResourceAllocation) alloc).lambda();
                    if (nextLambda == null) {
                        return false;
                    }
                    if (lambda == null) {
                        lambda = nextLambda;
                        continue;
                    }
                    if (!lambda.equals(nextLambda)) {
                        return false;
                    }
                }
            }
        }

        return true;
    }

    /**
     * Convert lambda resource allocation in OCh signal.
     *
     * @param alloc lambda resource allocation
     * @param minFrequency minimum frequency
     * @param grid grid spacing frequency
     * @return OCh signal
     */
    private OchSignal getOchSignal(LambdaResourceAllocation alloc, Frequency minFrequency, Frequency grid) {
        int channel = alloc.lambda().toInt();

        // Calculate center frequency
        Frequency centerFrequency = minFrequency.add(grid.multiply(channel)).add(grid.floorDivision(2));

        // Build OCh signal object
        int spacingMultiplier = (int) (centerFrequency.subtract(OchSignal.CENTER_FREQUENCY).asHz() / grid.asHz());
        int slotGranularity = (int) (grid.asHz() / ChannelSpacing.CHL_12P5GHZ.frequency().asHz());
        OchSignal ochSignal = new OchSignal(DEFAULT_OCH_GRIDTYPE, DEFAULT_CHANNEL_SPACING,
                spacingMultiplier, slotGranularity);

        return ochSignal;
    }

    /**
     * Calculates optical paths in WDM topology.
     *
     * @param intent optical connectivity intent
     * @return set of paths in WDM topology
     */
    private Set<Path> getOpticalPaths(OpticalConnectivityIntent intent) {
        // Route in WDM topology
        Topology topology = topologyService.currentTopology();
        LinkWeight weight = new LinkWeight() {
            @Override
            public double weight(TopologyEdge edge) {
                if (edge.link().state() == Link.State.INACTIVE) {
                    return -1;
                }
                if (edge.link().type() != Link.Type.OPTICAL) {
                    return -1;
                }
                return edge.link().annotations().value("optical.type").equals("WDM") ? +1 : -1;
            }
        };

        ConnectPoint start = intent.getSrc();
        ConnectPoint end = intent.getDst();
        Set<Path> paths = topologyService.getPaths(topology, start.deviceId(),
                end.deviceId(), weight);

        return paths;
    }
}