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/*
 * Copyright (c) 2010-2021 Haifeng Li. All rights reserved.
 *
 * Smile is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Smile is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Smile.  If not, see .
 */

package smile.taxonomy;

import java.util.Iterator;
import java.util.List;
import smile.math.distance.Distance;

/**
 * The distance between concepts in a taxonomy.
 * The distance between two concepts a and b is defined by the length of the
 * path from a to their lowest common ancestor and then to b.
 *
 * @author Haifeng Li
 */
public class TaxonomicDistance implements Distance {
    /**
     * The taxonomy basis to calculate the distance.
     */
    private final Taxonomy taxonomy;

    /**
     * Constructor.
     * 
     * @param taxonomy the taxonomy that this distance is associated with.
     */
    public TaxonomicDistance(Taxonomy taxonomy) {
        this.taxonomy = taxonomy;
    }

    @Override
    public String toString() {
        return String.format("Taxonomic distance on %s", taxonomy);
    }

    /**
     * Computes the distance between two concepts in a taxonomy.
     * @param x a concept.
     * @param y the other concept.
     * @return the distance.
     */
    public double d(String x, String y) {
        return d(taxonomy.getConcept(x), taxonomy.getConcept(y));
    }

    /**
     * Computes the distance between two concepts in a taxonomy.
     */
    @Override
    public double d(Concept x, Concept y) {
        if (x.taxonomy != y.taxonomy) {
            throw new IllegalArgumentException("Concepts are not from the same taxonomy.");
        }

        List xPath = x.getPathFromRoot();
        List yPath = y.getPathFromRoot();

        Iterator xIter = xPath.iterator();
        Iterator yIter = yPath.iterator();

        int depth = 0;
        while (xIter.hasNext() && yIter.hasNext()) {
            if (xIter.next() != yIter.next()) {
                break;
            }

            depth++;
        }

        return xPath.size() - depth + yPath.size() - depth;
    }
}