/*
* Copyright Myrrix Ltd
*
* 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 net.myrrix.online;
import java.util.Iterator;
import org.apache.mahout.cf.taste.recommender.IDRescorer;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import net.myrrix.common.LangUtils;
import net.myrrix.common.MutableRecommendedItem;
import net.myrrix.common.collection.FastByIDFloatMap;
/**
* Used by {@link net.myrrix.common.MyrrixRecommender#mostPopularItems(int)}.
*
* @author Sean Owen
*/
final class MostPopularItemsIterator implements Iterator<RecommendedItem> {
private final MutableRecommendedItem delegate;
private final Iterator<FastByIDFloatMap.MapEntry> countsIterator;
private final IDRescorer rescorer;
MostPopularItemsIterator(Iterator<FastByIDFloatMap.MapEntry> countsIterator, IDRescorer rescorer) {
delegate = new MutableRecommendedItem();
this.countsIterator = countsIterator;
this.rescorer = rescorer;
}
@Override
public boolean hasNext() {
return countsIterator.hasNext();
}
@Override
public RecommendedItem next() {
FastByIDFloatMap.MapEntry entry = countsIterator.next();
long id = entry.getKey();
float value = entry.getValue();
IDRescorer theRescorer = rescorer;
if (theRescorer != null) {
if (theRescorer.isFiltered(id)) {
return null;
}
value = (float) theRescorer.rescore(id, value);
if (!LangUtils.isFinite(value)) {
return null;
}
}
delegate.set(id, value);
return delegate;
}
/**
* @throws UnsupportedOperationException
*/
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}