/*
 * 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.queryparser.ext;

import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.search.Query;

/**
 * This class represents an extension base class to the Lucene standard {@link
 * org.apache.lucene.queryparser.classic.QueryParser}. The {@link
 * org.apache.lucene.queryparser.classic.QueryParser} is generated by the JavaCC parser generator.
 * Changing or adding functionality or syntax in the standard query parser requires changes to the
 * JavaCC source file. To enable extending the standard query parser without changing the JavaCC
 * sources and re-generate the parser the {@link ParserExtension} can be customized and plugged into
 * an instance of {@link ExtendableQueryParser}, a direct subclass of {@link
 * org.apache.lucene.queryparser.classic.QueryParser}.
 *
 * @see Extensions
 * @see ExtendableQueryParser
 */
public abstract class ParserExtension {

  /**
   * Processes the given {@link ExtensionQuery} and returns a corresponding {@link Query} instance.
   * Subclasses must either return a {@link Query} instance or raise a {@link ParseException}. This
   * method must not return <code>null</code>.
   *
   * @param query the extension query
   * @return a new query instance
   * @throws ParseException if the query can not be parsed.
   */
  public abstract Query parse(final ExtensionQuery query) throws ParseException;
}
