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/*
 * GraphGrowthRule.java
 * Created on Jun 8, 2012
 */
package com.googlecode.blaisemath.graph.query;

/*
 * #%L
 * BlaiseGraphTheory
 * --
 * Copyright (C) 2009 - 2016 Elisha Peterson
 * --
 * 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.
 * #L%
 */

import java.util.HashSet;
import java.util.Set;
import com.googlecode.blaisemath.graph.Graph;
import com.googlecode.blaisemath.graph.GraphUtils;

/**
 * A "growth rule" to make a (small) subgraph larger.
 *
 * @author petereb1
 */
public interface GraphGrowthRule {

    /**
     * Name of rule for display
     * @return name
     */
    String getName();

    /**
     * Grows a subset of a graph based on some rule. While the resulting set is
     * generally expected to be a superset of the input set, this is not enforced.
     * @param graph the entire graph
     * @param seed the seed input set, a subset of nodes of the graph
     * @return larger subset of the graph
     */
    Set grow(Graph graph, Set seed);



    //
    //
    // IMPLEMENTATIONS
    //

    /**
     * Construct larger graph by hops.
     */
    public static class HopGrowthRule implements GraphGrowthRule {

        private int n;
        private boolean directed;

        public HopGrowthRule() {
            this(2);
        }

        public HopGrowthRule(int n) {
            this.n = n;
        }

        @Override
        public String getName() {
            return n + "-Hop";
        }

        public int getN() {
            return n;
        }

        public void setN(int n) {
            this.n = Math.max(0, n);
        }

        public boolean isDirected() {
            return directed;
        }

        public void setDirected(boolean directed) {
            this.directed = directed;
        }

        @Override
        public Set grow(Graph graph, Set seed) {
            return grow(directed || !graph.isDirected() ? graph : GraphUtils.copyAsUndirectedSparseGraph(graph), seed, n);
        }

        /**
         * Grows the seed set by n hops
         * @param graph graph
         * @param seed seed nodes
         * @param n # of steps to grow
         * @return nodes in grown set
         */
        public Set grow(Graph graph, Set seed, int n) {
            if (n == 0) {
                return seed;
            }
            Set grown = grow1(graph, seed);
            if (grown.containsAll(seed) && seed.containsAll(grown)) {
                return seed;
            } else {
                return grow(graph, grown, n - 1);
            }
        }

        /**
         * Grows the seed set by 1 hop
         * @param graph graph
         * @param seed seed nodes
         * @return nodes in grown set
         */
        public Set grow1(Graph graph, Set seed) {
            Set result = new HashSet();
            result.addAll(seed);
            for (Object o : seed) {
                result.addAll(graph.neighbors(o));
            }
            return result;
        }
    }

    //

}