core/api/src/main/java/org/onosproject/net/topology/HopCountLinkWeight.java

/*
 * Copyright 2015-present 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.topology;

import static org.onosproject.net.Link.State.ACTIVE;
import static org.onosproject.net.Link.Type.INDIRECT;

/**
 * Link weight for measuring link cost as hop count with indirect links
 * being as expensive as traversing the entire graph to assume the worst.
 */
public class HopCountLinkWeight implements LinkWeight {
    private final int indirectLinkCost;

    /**
     * Creates a new hop-count weight.
     */
    public HopCountLinkWeight() {
        this.indirectLinkCost = Short.MAX_VALUE;
    }

    /**
     * Creates a new hop-count weight with the specified cost of indirect links.
     *
     * @param indirectLinkCost indirect link cost
     */
    public HopCountLinkWeight(int indirectLinkCost) {
        this.indirectLinkCost = indirectLinkCost;
    }

    @Override
    public double weight(TopologyEdge edge) {
        // To force preference to use direct paths first, make indirect
        // links as expensive as the linear vertex traversal.
        return edge.link().state() ==
                ACTIVE ? (edge.link().type() ==
                INDIRECT ? indirectLinkCost : 1) : -1;
    }
}