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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you 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 org.apache.lucene.search.uhighlight;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.PrefixQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.spans.SpanMultiTermQueryWrapper;
import org.apache.lucene.search.spans.SpanNearQuery;
import org.apache.lucene.search.spans.SpanOrQuery;
import org.apache.lucene.search.spans.SpanQuery;
import org.apache.lucene.search.spans.SpanTermQuery;
import org.apache.lucene.util.BytesRef;
import org.elasticsearch.common.Nullable;
import org.elasticsearch.common.lucene.search.MultiPhrasePrefixQuery;
import java.io.IOException;
import java.text.BreakIterator;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.function.Predicate;
/**
* Subclass of the {@link UnifiedHighlighter} that works for a single field in a single document.
* Uses a custom {@link PassageFormatter}. Accepts field content as a constructor
* argument, given that loadings field value can be done reading from _source field.
* Supports using different {@link BreakIterator} to break the text into fragments. Considers every distinct field
* value as a discrete passage for highlighting (unless the whole content needs to be highlighted).
* Supports both returning empty snippets and non highlighted snippets when no highlighting can be performed.
*/
public class CustomUnifiedHighlighter extends UnifiedHighlighter {
public static final char MULTIVAL_SEP_CHAR = (char) 0;
private static final Snippet[] EMPTY_SNIPPET = new Snippet[0];
private final OffsetSource offsetSource;
private final String fieldValue;
private final PassageFormatter passageFormatter;
private final BreakIterator breakIterator;
private final Locale breakIteratorLocale;
private final int noMatchSize;
/**
* Creates a new instance of {@link CustomUnifiedHighlighter}
*
* @param analyzer the analyzer used for the field at index time, used for multi term queries internally.
* @param passageFormatter our own {@link CustomPassageFormatter}
* which generates snippets in forms of {@link Snippet} objects.
* @param offsetSource the {@link OffsetSource} to used for offsets retrieval.
* @param breakIteratorLocale the {@link Locale} to use for dividing text into passages.
* If null {@link Locale#ROOT} is used.
* @param breakIterator the {@link BreakIterator} to use for dividing text into passages.
* If null {@link BreakIterator#getSentenceInstance(Locale)} is used.
* @param fieldValue the original field values delimited by MULTIVAL_SEP_CHAR.
* @param noMatchSize The size of the text that should be returned when no highlighting can be performed.
*/
public CustomUnifiedHighlighter(IndexSearcher searcher,
Analyzer analyzer,
OffsetSource offsetSource,
PassageFormatter passageFormatter,
@Nullable Locale breakIteratorLocale,
@Nullable BreakIterator breakIterator,
String fieldValue,
int noMatchSize) {
super(searcher, analyzer);
this.offsetSource = offsetSource;
this.breakIterator = breakIterator;
this.breakIteratorLocale = breakIteratorLocale == null ? Locale.ROOT : breakIteratorLocale;
this.passageFormatter = passageFormatter;
this.fieldValue = fieldValue;
this.noMatchSize = noMatchSize;
}
/**
* Highlights terms extracted from the provided query within the content of the provided field name
*/
public Snippet[] highlightField(String field, Query query, int docId, int maxPassages) throws IOException {
Map fieldsAsObjects = super.highlightFieldsAsObjects(new String[]{field}, query,
new int[]{docId}, new int[]{maxPassages});
Object[] snippetObjects = fieldsAsObjects.get(field);
if (snippetObjects != null) {
//one single document at a time
assert snippetObjects.length == 1;
Object snippetObject = snippetObjects[0];
if (snippetObject != null && snippetObject instanceof Snippet[]) {
return (Snippet[]) snippetObject;
}
}
return EMPTY_SNIPPET;
}
@Override
protected List loadFieldValues(String[] fields, DocIdSetIterator docIter,
int cacheCharsThreshold) throws IOException {
// we only highlight one field, one document at a time
return Collections.singletonList(new String[]{fieldValue});
}
@Override
protected BreakIterator getBreakIterator(String field) {
return breakIterator;
}
@Override
protected PassageFormatter getFormatter(String field) {
return passageFormatter;
}
@Override
protected FieldHighlighter getFieldHighlighter(String field, Query query, Set allTerms, int maxPassages) {
Predicate fieldMatcher = getFieldMatcher(field);
BytesRef[] terms = filterExtractedTerms(fieldMatcher, allTerms);
Set highlightFlags = getFlags(field);
PhraseHelper phraseHelper = getPhraseHelper(field, query, highlightFlags);
LabelledCharArrayMatcher[] automata = getAutomata(field, query, highlightFlags);
UHComponents components = new UHComponents(field, fieldMatcher, query, terms, phraseHelper, automata, false , highlightFlags);
OffsetSource offsetSource = getOptimizedOffsetSource(components);
BreakIterator breakIterator = new SplittingBreakIterator(getBreakIterator(field),
UnifiedHighlighter.MULTIVAL_SEP_CHAR);
FieldOffsetStrategy strategy = getOffsetStrategy(offsetSource, components);
return new CustomFieldHighlighter(field, strategy, breakIteratorLocale, breakIterator,
getScorer(field), maxPassages, (noMatchSize > 0 ? 1 : 0), getFormatter(field), noMatchSize, fieldValue);
}
@Override
protected Collection preSpanQueryRewrite(Query query) {
return rewriteCustomQuery(query);
}
/**
* Translate custom queries in queries that are supported by the unified highlighter.
*/
private Collection rewriteCustomQuery(Query query) {
if (query instanceof MultiPhrasePrefixQuery) {
MultiPhrasePrefixQuery mpq = (MultiPhrasePrefixQuery) query;
Term[][] terms = mpq.getTerms();
int[] positions = mpq.getPositions();
SpanQuery[] positionSpanQueries = new SpanQuery[positions.length];
int sizeMinus1 = terms.length - 1;
for (int i = 0; i < positions.length; i++) {
SpanQuery[] innerQueries = new SpanQuery[terms[i].length];
for (int j = 0; j < terms[i].length; j++) {
if (i == sizeMinus1) {
innerQueries[j] = new SpanMultiTermQueryWrapper<>(new PrefixQuery(terms[i][j]));
} else {
innerQueries[j] = new SpanTermQuery(terms[i][j]);
}
}
if (innerQueries.length > 1) {
positionSpanQueries[i] = new SpanOrQuery(innerQueries);
} else {
positionSpanQueries[i] = innerQueries[0];
}
}
if (positionSpanQueries.length == 1) {
return Collections.singletonList(positionSpanQueries[0]);
}
// sum position increments beyond 1
int positionGaps = 0;
if (positions.length >= 2) {
// positions are in increasing order. max(0,...) is just a safeguard.
positionGaps = Math.max(0, positions[positions.length - 1] - positions[0] - positions.length + 1);
}
//if original slop is 0 then require inOrder
boolean inorder = (mpq.getSlop() == 0);
return Collections.singletonList(new SpanNearQuery(positionSpanQueries,
mpq.getSlop() + positionGaps, inorder));
} else {
return null;
}
}
/**
* Forces the offset source for this highlighter
*/
@Override
protected OffsetSource getOffsetSource(String field) {
if (offsetSource == null) {
return super.getOffsetSource(field);
}
return offsetSource;
}
}