/*
* Copyright (c) 2011 LinkedIn, Inc
*
* 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 com.flaptor.indextank.index.term.query;
import java.util.List;
import com.flaptor.indextank.index.term.DocTermMatch;
import com.flaptor.indextank.util.AbstractSkippableIterable;
import com.flaptor.indextank.util.AbstractSkippableIterator;
import com.flaptor.indextank.util.IdentityIntersection;
import com.flaptor.indextank.util.Intersection;
import com.flaptor.indextank.util.PeekingSkippableIterator;
import com.flaptor.indextank.util.SkippableIterable;
import com.flaptor.indextank.util.SkippableIterator;
import com.flaptor.indextank.util.Skippables;
import com.flaptor.util.CollectionsUtil.PeekingIterator;
import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.primitives.Ints;
final class PhraseMerger extends AbstractSkippableIterable<RawMatch> {
private Iterable<SkippableIterable<DocTermMatch>> cursors;
private int[] termPositions;
private double boost;
PhraseMerger(Iterable<SkippableIterable<DocTermMatch>> cursors, int[] termPositions, double boost) {
this.cursors = cursors;
this.termPositions = termPositions;
this.boost = boost;
}
@Override
public SkippableIterator<RawMatch> iterator() {
return new AbstractSkippableIterator<RawMatch>() {
private List<PeekingSkippableIterator<DocTermMatch>> iterators = Lists.newArrayList(Iterables.transform(cursors, Intersection.<DocTermMatch>peekingIteratorFunction()));
@Override
protected RawMatch computeNext() {
int current = -1;
while (true) {
boolean found = true;
for (PeekingSkippableIterator<DocTermMatch> it : iterators) {
while (it.hasNext() && current != -1 && it.peek().getRawId() < current) {
it.skipTo(current);
it.next();
}
if (!it.hasNext()) {
return endOfData();
}
if (current != -1 && it.peek().getRawId() == current) {
continue;
} else {
found = false;
current = it.peek().getRawId();
}
}
if (found) {
RawMatch r = tryMatch(current, peekedItems());
for (PeekingIterator<DocTermMatch> it : iterators) {
it.next();
}
if (r != null)
return r;
}
}
}
private List<DocTermMatch> peekedItems() {
return Lists.transform(iterators, Intersection.<DocTermMatch>peekFunction());
}
@Override
public void skipTo(int i) {
for (PeekingSkippableIterator<DocTermMatch> it : iterators) {
it.skipTo(i);
}
}
};
}
public static <T> Function<PeekingIterator<T>, T> peekFunction() {
return new Function<PeekingIterator<T>, T>() {
@Override
public T apply(PeekingIterator<T> it) {
return it.peek();
}
};
}
public static <T> Function<SkippableIterable<T>, PeekingSkippableIterator<T>> peekingIteratorFunction() {
return new Function<SkippableIterable<T>, PeekingSkippableIterator<T>>() {
@Override
public PeekingSkippableIterator<T> apply(SkippableIterable<T> ts) {
return new PeekingSkippableIterator<T>(ts.iterator());
}
};
}
protected RawMatch tryMatch(int id, List<DocTermMatch> items) {
List<SkippableIterable<Integer>> positionsList = Lists.newArrayList();
for (int i = 0; i < items.size(); i++) {
DocTermMatch m = items.get(i);
List<Integer> positions = Ints.asList(m.getPositions()).subList(0, m.getPositionsLength());
positionsList.add(Skippables.fromIterable(Iterables.transform(positions, addFunction(-this.termPositions[i]))));
}
boolean matches = new IdentityIntersection<Integer>(positionsList).iterator().hasNext();
if (matches) {
double score = 1.0;
for (DocTermMatch p : items) {
score += p.getTermScore();
}
return new RawMatch(id, score, boost);
} else {
return null;
}
}
private static Function<Integer, Integer> addFunction(final int delta) {
return new Function<Integer, Integer>() {
@Override
public Integer apply(Integer i) {
return i + delta;
}
};
}
}