/**
* Copyright 2014 National University of Ireland, Galway.
*
* This file is part of the SIREn project. Project and contact information:
*
* https://github.com/rdelbru/SIREn
*
* 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 org.sindice.siren.search.node;
import java.io.IOException;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.search.RegexpQuery;
import org.apache.lucene.util.AttributeSource;
import org.apache.lucene.util.ToStringUtils;
import org.apache.lucene.util.automaton.Automaton;
import org.apache.lucene.util.automaton.BasicOperations;
import org.apache.lucene.util.automaton.CompiledAutomaton;
/**
* A {@link MultiNodeTermQuery} that will match terms against a finite-state
* machine.
*
* <p>
*
* This query will match documents that contain terms accepted by a given
* finite-state machine. The automaton can be constructed with the
* {@link org.apache.lucene.util.automaton} API. Alternatively, it can be
* created from a regular expression with {@link RegexpQuery} or from
* the standard Lucene wildcard syntax with {@link NodeWildcardQuery}.
*
* <p>
*
* When the query is executed, it will create an equivalent DFA of the
* finite-state machine, and will enumerate the term dictionary in an
* intelligent way to reduce the number of comparisons. For example: the regular
* expression of <code>[dl]og?</code> will make approximately four comparisons:
* do, dog, lo, and log.
*/
public class NodeAutomatonQuery extends MultiNodeTermQuery {
/** the automaton to match index terms against */
protected final Automaton automaton;
protected final CompiledAutomaton compiled;
/** term containing the field, and possibly some pattern structure */
protected final Term term;
/**
* Create a new AutomatonQuery from an {@link Automaton}.
*
* @param term Term containing field and possibly some pattern structure. The
* term text is ignored.
* @param automaton Automaton to run, terms that are accepted are considered a
* match.
*/
public NodeAutomatonQuery(final Term term, final Automaton automaton) {
super(term.field());
this.term = term;
this.automaton = automaton;
this.compiled = new CompiledAutomaton(automaton);
}
@Override
protected TermsEnum getTermsEnum(final Terms terms, final AttributeSource atts) throws IOException {
return compiled.getTermsEnum(terms);
}
@Override
public int hashCode() {
final int prime = 31;
int result = super.hashCode();
if (automaton != null) {
// we already minimized the automaton in the ctor, so
// this hash code will be the same for automata that
// are the same:
int automatonHashCode = automaton.getNumberOfStates() * 3 + automaton.getNumberOfTransitions() * 2;
if (automatonHashCode == 0) {
automatonHashCode = 1;
}
result = prime * result + automatonHashCode;
}
result = prime * result + ((term == null) ? 0 : term.hashCode());
return result;
}
@Override
public boolean equals(final Object obj) {
if (this == obj)
return true;
if (!super.equals(obj))
return false;
if (this.getClass() != obj.getClass())
return false;
final NodeAutomatonQuery other = (NodeAutomatonQuery) obj;
if (automaton == null) {
if (other.automaton != null)
return false;
} else if (!BasicOperations.sameLanguage(automaton, other.automaton))
return false;
if (term == null) {
if (other.term != null)
return false;
} else if (!term.equals(other.term))
return false;
return true;
}
@Override
public String toString(final String field) {
final StringBuilder buffer = new StringBuilder();
buffer.append(this.getClass().getSimpleName());
buffer.append(" {");
buffer.append('\n');
buffer.append(automaton.toString());
buffer.append("}");
buffer.append(ToStringUtils.boost(this.getBoost()));
return buffer.toString();
}
}