/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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.suggest.document;
import java.io.IOException;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.TokenStreamToAutomaton;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.PayloadAttribute;
import org.apache.lucene.analysis.tokenattributes.TermToBytesRefAttribute;
import org.apache.lucene.util.AttributeImpl;
import org.apache.lucene.util.AttributeReflector;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.BytesRefBuilder;
import org.apache.lucene.util.CharsRefBuilder;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.IntsRef;
import org.apache.lucene.util.automaton.Automaton;
import org.apache.lucene.util.automaton.FiniteStringsIterator;
import org.apache.lucene.util.automaton.LimitedFiniteStringsIterator;
import org.apache.lucene.util.automaton.Operations;
import org.apache.lucene.util.automaton.Transition;
import org.apache.lucene.util.fst.Util;
import static org.apache.lucene.search.suggest.document.CompletionAnalyzer.DEFAULT_MAX_GRAPH_EXPANSIONS;
import static org.apache.lucene.search.suggest.document.CompletionAnalyzer.DEFAULT_PRESERVE_POSITION_INCREMENTS;
import static org.apache.lucene.search.suggest.document.CompletionAnalyzer.DEFAULT_PRESERVE_SEP;
import static org.apache.lucene.search.suggest.document.CompletionAnalyzer.SEP_LABEL;
/**
* Token stream which converts a provided token stream to an automaton.
* The accepted strings enumeration from the automaton are available through the
* {@link org.apache.lucene.analysis.tokenattributes.TermToBytesRefAttribute} attribute
* The token stream uses a {@link org.apache.lucene.analysis.tokenattributes.PayloadAttribute} to store
* a completion's payload (see {@link CompletionTokenStream#setPayload(org.apache.lucene.util.BytesRef)})
*
* @lucene.experimental
*/
public final class CompletionTokenStream extends TokenStream {
private final PayloadAttribute payloadAttr = addAttribute(PayloadAttribute.class);
private final BytesRefBuilderTermAttribute bytesAtt = addAttribute(BytesRefBuilderTermAttribute.class);
final TokenStream inputTokenStream;
final boolean preserveSep;
final boolean preservePositionIncrements;
final int maxGraphExpansions;
private FiniteStringsIterator finiteStrings;
private BytesRef payload;
private CharTermAttribute charTermAttribute;
/**
* Creates a token stream to convert <code>input</code> to a token stream
* of accepted strings by its automaton.
* <p>
* The token stream <code>input</code> is converted to an automaton
* with the default settings of {@link org.apache.lucene.search.suggest.document.CompletionAnalyzer}
*/
CompletionTokenStream(TokenStream inputTokenStream) {
this(inputTokenStream, DEFAULT_PRESERVE_SEP, DEFAULT_PRESERVE_POSITION_INCREMENTS, DEFAULT_MAX_GRAPH_EXPANSIONS);
}
CompletionTokenStream(TokenStream inputTokenStream, boolean preserveSep, boolean preservePositionIncrements, int maxGraphExpansions) {
// Don't call the super(input) ctor - this is a true delegate and has a new attribute source since we consume
// the input stream entirely in the first call to incrementToken
this.inputTokenStream = inputTokenStream;
this.preserveSep = preserveSep;
this.preservePositionIncrements = preservePositionIncrements;
this.maxGraphExpansions = maxGraphExpansions;
}
/**
* Sets a payload available throughout successive token stream enumeration
*/
public void setPayload(BytesRef payload) {
this.payload = payload;
}
@Override
public boolean incrementToken() throws IOException {
clearAttributes();
if (finiteStrings == null) {
Automaton automaton = toAutomaton();
finiteStrings = new LimitedFiniteStringsIterator(automaton, maxGraphExpansions);
}
IntsRef string = finiteStrings.next();
if (string == null) {
return false;
}
Util.toBytesRef(string, bytesAtt.builder()); // now we have UTF-8
if (charTermAttribute != null) {
charTermAttribute.setLength(0);
charTermAttribute.append(bytesAtt.toUTF16());
}
if (payload != null) {
payloadAttr.setPayload(this.payload);
}
return true;
}
@Override
public void end() throws IOException {
super.end();
if (finiteStrings == null) {
inputTokenStream.end();
}
}
@Override
public void close() throws IOException {
if (finiteStrings == null) {
inputTokenStream.close();
}
}
@Override
public void reset() throws IOException {
super.reset();
if (hasAttribute(CharTermAttribute.class)) {
// we only create this if we really need it to safe the UTF-8 to UTF-16 conversion
charTermAttribute = getAttribute(CharTermAttribute.class);
}
finiteStrings = null;
}
/**
* Converts the token stream to an automaton,
* treating the transition labels as utf-8
*/
public Automaton toAutomaton() throws IOException {
return toAutomaton(false);
}
/**
* Converts the tokenStream to an automaton
*/
public Automaton toAutomaton(boolean unicodeAware) throws IOException {
// TODO refactor this
// maybe we could hook up a modified automaton from TermAutomatonQuery here?
Automaton automaton = null;
try {
// Create corresponding automaton: labels are bytes
// from each analyzed token, with byte 0 used as
// separator between tokens:
final TokenStreamToAutomaton tsta;
if (preserveSep) {
tsta = new EscapingTokenStreamToAutomaton((char) SEP_LABEL);
} else {
// When we're not preserving sep, we don't steal 0xff
// byte, so we don't need to do any escaping:
tsta = new TokenStreamToAutomaton();
}
tsta.setPreservePositionIncrements(preservePositionIncrements);
tsta.setUnicodeArcs(unicodeAware);
automaton = tsta.toAutomaton(inputTokenStream);
} finally {
IOUtils.closeWhileHandlingException(inputTokenStream);
}
// TODO: we can optimize this somewhat by determinizing
// while we convert
automaton = replaceSep(automaton, preserveSep, SEP_LABEL);
// This automaton should not blow up during determinize:
return Operations.determinize(automaton, maxGraphExpansions);
}
/**
* Just escapes the 0xff byte (which we still for SEP).
*/
private static final class EscapingTokenStreamToAutomaton extends TokenStreamToAutomaton {
final BytesRefBuilder spare = new BytesRefBuilder();
private char sepLabel;
public EscapingTokenStreamToAutomaton(char sepLabel) {
this.sepLabel = sepLabel;
}
@Override
protected BytesRef changeToken(BytesRef in) {
int upto = 0;
for (int i = 0; i < in.length; i++) {
byte b = in.bytes[in.offset + i];
if (b == (byte) sepLabel) {
spare.grow(upto + 2);
spare.setByteAt(upto++, (byte) sepLabel);
spare.setByteAt(upto++, b);
} else {
spare.grow(upto + 1);
spare.setByteAt(upto++, b);
}
}
spare.setLength(upto);
return spare.get();
}
}
// Replaces SEP with epsilon or remaps them if
// we were asked to preserve them:
private static Automaton replaceSep(Automaton a, boolean preserveSep, int sepLabel) {
Automaton result = new Automaton();
// Copy all states over
int numStates = a.getNumStates();
for (int s = 0; s < numStates; s++) {
result.createState();
result.setAccept(s, a.isAccept(s));
}
// Go in reverse topo sort so we know we only have to
// make one pass:
Transition t = new Transition();
int[] topoSortStates = Operations.topoSortStates(a);
for (int i = 0; i < topoSortStates.length; i++) {
int state = topoSortStates[topoSortStates.length - 1 - i];
int count = a.initTransition(state, t);
for (int j = 0; j < count; j++) {
a.getNextTransition(t);
if (t.min == TokenStreamToAutomaton.POS_SEP) {
assert t.max == TokenStreamToAutomaton.POS_SEP;
if (preserveSep) {
// Remap to SEP_LABEL:
result.addTransition(state, t.dest, sepLabel);
} else {
result.addEpsilon(state, t.dest);
}
} else if (t.min == TokenStreamToAutomaton.HOLE) {
assert t.max == TokenStreamToAutomaton.HOLE;
// Just remove the hole: there will then be two
// SEP tokens next to each other, which will only
// match another hole at search time. Note that
// it will also match an empty-string token ... if
// that's somehow a problem we can always map HOLE
// to a dedicated byte (and escape it in the
// input).
result.addEpsilon(state, t.dest);
} else {
result.addTransition(state, t.dest, t.min, t.max);
}
}
}
result.finishState();
return result;
}
/**
* Attribute providing access to the term builder and UTF-16 conversion
*/
public interface BytesRefBuilderTermAttribute extends TermToBytesRefAttribute {
/**
* Returns the builder from which the term is derived.
*/
BytesRefBuilder builder();
/**
* Returns the term represented as UTF-16
*/
CharSequence toUTF16();
}
/**
* Custom attribute implementation for completion token stream
*/
public static final class BytesRefBuilderTermAttributeImpl extends AttributeImpl implements BytesRefBuilderTermAttribute, TermToBytesRefAttribute {
private final BytesRefBuilder bytes = new BytesRefBuilder();
private transient CharsRefBuilder charsRef;
/**
* Sole constructor
* no-op
*/
public BytesRefBuilderTermAttributeImpl() {
}
@Override
public BytesRefBuilder builder() {
return bytes;
}
@Override
public BytesRef getBytesRef() {
return bytes.get();
}
@Override
public void clear() {
bytes.clear();
}
@Override
public void copyTo(AttributeImpl target) {
BytesRefBuilderTermAttributeImpl other = (BytesRefBuilderTermAttributeImpl) target;
other.bytes.copyBytes(bytes);
}
@Override
public AttributeImpl clone() {
BytesRefBuilderTermAttributeImpl other = new BytesRefBuilderTermAttributeImpl();
copyTo(other);
return other;
}
@Override
public void reflectWith(AttributeReflector reflector) {
reflector.reflect(TermToBytesRefAttribute.class, "bytes", getBytesRef());
}
@Override
public CharSequence toUTF16() {
if (charsRef == null) {
charsRef = new CharsRefBuilder();
}
charsRef.copyUTF8Bytes(getBytesRef());
return charsRef.get();
}
}
}