/*
 * 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.net.intent.impl;

import java.util.ArrayList;
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.onos.net.ConnectPoint;
import org.onlab.onos.net.DefaultEdgeLink;
import org.onlab.onos.net.DefaultPath;
import org.onlab.onos.net.Link;
import org.onlab.onos.net.Path;
import org.onlab.onos.net.intent.Intent;
import org.onlab.onos.net.intent.IntentCompiler;
import org.onlab.onos.net.intent.IntentExtensionService;
import org.onlab.onos.net.intent.PathIntent;
import org.onlab.onos.net.intent.PointToPointIntent;
import org.onlab.onos.net.provider.ProviderId;
import org.onlab.onos.net.resource.LinkResourceRequest;
import org.onlab.onos.net.topology.LinkWeight;
import org.onlab.onos.net.topology.Topology;
import org.onlab.onos.net.topology.TopologyEdge;
import org.onlab.onos.net.topology.TopologyService;

import static java.util.Arrays.asList;

/**
 * An intent compiler for {@link org.onlab.onos.net.intent.PointToPointIntent}.
 */
@Component(immediate = true)
public class PointToPointIntentCompiler
        implements IntentCompiler<PointToPointIntent> {

    private static final ProviderId PID = new ProviderId("core", "org.onlab.onos.core", true);
    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected IntentExtensionService intentManager;

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

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

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

    @Override
    public List<Intent> compile(PointToPointIntent intent) {
        Path path = getPath(intent.ingressPoint(), intent.egressPoint());

        List<Link> links = new ArrayList<>();
        links.add(DefaultEdgeLink.createEdgeLink(intent.ingressPoint(), true));
        links.addAll(path.links());
        links.add(DefaultEdgeLink.createEdgeLink(intent.egressPoint(), false));

        return asList(createPathIntent(new DefaultPath(PID, links, path.cost() + 2,
                path.annotations()), intent));
    }

    /**
     * Creates a path intent from the specified path and original
     * connectivity intent.
     *
     * @param path   path to create an intent for
     * @param intent original intent
     */
    private Intent createPathIntent(Path path,
                                    PointToPointIntent intent) {
        return new PathIntent(intent.appId(),
                              intent.selector(), intent.treatment(), path,
                              new LinkResourceRequest[0]);
    }

    /**
     * Computes a path between two ConnectPoints.
     *
     * @param one start of the path
     * @param two end of the path
     * @return Path between the two
     * @throws PathNotFoundException if a path cannot be found
     */
    private Path getPath(ConnectPoint one, ConnectPoint two) {
        Topology topology = topologyService.currentTopology();
        LinkWeight weight = new LinkWeight() {
            @Override
            public double weight(TopologyEdge edge) {
                return edge.link().type() == Link.Type.OPTICAL ? -1 : +1;
            }
        };

        Set<Path> paths = topologyService.getPaths(topology, one.deviceId(),
                                                   two.deviceId(), weight);
        if (paths.isEmpty()) {
            throw new PathNotFoundException("No packet path from " + one + " to " + two);
        }

        // TODO: let's be more intelligent about this eventually
        return paths.iterator().next();
    }
}