/*
* LensKit, an open source recommender systems toolkit.
* Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md.
* Work on LensKit has been funded by the National Science Foundation under
* grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This program 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
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.grouplens.lenskit.basic;
import it.unimi.dsi.fastutil.longs.LongSet;
import org.grouplens.lenskit.ItemRecommender;
import org.grouplens.lenskit.collections.LongUtils;
import org.grouplens.lenskit.scored.ScoredId;
import javax.annotation.Nullable;
import java.util.List;
import java.util.Set;
/**
* Base class for item recommenders. It implements all methods required by
* {@link ItemRecommender} by delegating them to general methods with
* fastutil-based interfaces.
*/
public abstract class AbstractItemRecommender implements ItemRecommender {
/**
* {@inheritDoc}
* <p>Delegates to {@link #recommend(long, int, LongSet, LongSet)}.
*/
@Override
public List<ScoredId> recommend(long user) {
return recommend(user, -1, null, null);
}
/**
* {@inheritDoc}
* <p>Delegates to {@link #recommend(long, int, LongSet, LongSet)}.
*/
@Override
public List<ScoredId> recommend(long user, int n) {
return recommend(user, n, null, null);
}
/**
* {@inheritDoc}
* <p>Delegates to {@link #recommend(long, int, LongSet, LongSet)}.
*/
@Override
public List<ScoredId> recommend(long user, Set<Long> candidates) {
return recommend(user, -1, candidates, null);
}
/**
* {@inheritDoc}
* <p>Delegates to {@link #recommend(long, int, LongSet, LongSet)}.
*/
@Override
public List<ScoredId> recommend(long user, int n,
@Nullable Set<Long> candidates,
@Nullable Set<Long> exclude) {
LongSet cs = LongUtils.asLongSet(candidates);
LongSet es = LongUtils.asLongSet(exclude);
return recommend(user, n, cs, es);
}
/**
* Implementation method for ID-based recommendation. All other ID-based methods are
* implemented in terms of this one.
*
* @param user The user ID.
* @param n The number of items to return, or negative to return all possible items.
* @param candidates The candidate set, or {@code null} to use a default set of candidates.
* @param exclude The set of excluded items, or {@code null} to use the default exclude set.
* @return A scored list of item IDs.
* @see ItemRecommender#recommend(long, int, Set, Set)
*/
protected abstract List<ScoredId> recommend(long user, int n,
@Nullable LongSet candidates,
@Nullable LongSet exclude);
}