/*
 * 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.flexible.standard.processors;

import java.util.List;

import org.apache.lucene.queryparser.flexible.messages.MessageImpl;
import org.apache.lucene.queryparser.flexible.core.QueryNodeException;
import org.apache.lucene.queryparser.flexible.core.config.QueryConfigHandler;
import org.apache.lucene.queryparser.flexible.core.messages.QueryParserMessages;
import org.apache.lucene.queryparser.flexible.core.nodes.QueryNode;
import org.apache.lucene.queryparser.flexible.core.processors.QueryNodeProcessorImpl;
import org.apache.lucene.queryparser.flexible.core.util.UnescapedCharSequence;
import org.apache.lucene.queryparser.flexible.standard.config.StandardQueryConfigHandler.ConfigurationKeys;
import org.apache.lucene.queryparser.flexible.standard.nodes.WildcardQueryNode;
import org.apache.lucene.queryparser.flexible.standard.parser.EscapeQuerySyntaxImpl;

This processor verifies if ConfigurationKeys.ALLOW_LEADING_WILDCARD is defined in the QueryConfigHandler. If it is and leading wildcard is not allowed, it looks for every WildcardQueryNode contained in the query node tree and throws an exception if any of them has a leading wildcard ('*' or '?'). 
See Also:
ConfigurationKeys.ALLOW_LEADING_WILDCARD/**
 * This processor verifies if
 * {@link ConfigurationKeys#ALLOW_LEADING_WILDCARD} is defined in the
 * {@link QueryConfigHandler}. If it is and leading wildcard is not allowed, it
 * looks for every {@link WildcardQueryNode} contained in the query node tree
 * and throws an exception if any of them has a leading wildcard ('*' or '?').
 * 
 * @see ConfigurationKeys#ALLOW_LEADING_WILDCARD
 */
public class AllowLeadingWildcardProcessor extends QueryNodeProcessorImpl {

  public AllowLeadingWildcardProcessor() {
    // empty constructor
  }

  @Override
  public QueryNode process(QueryNode queryTree) throws QueryNodeException {
    Boolean allowsLeadingWildcard = getQueryConfigHandler().get(ConfigurationKeys.ALLOW_LEADING_WILDCARD);

    if (allowsLeadingWildcard != null) {

      if (!allowsLeadingWildcard) {
        return super.process(queryTree);
      }

    }

    return queryTree;
  }

  @Override
  protected QueryNode postProcessNode(QueryNode node) throws QueryNodeException {

    if (node instanceof WildcardQueryNode) {
      WildcardQueryNode wildcardNode = (WildcardQueryNode) node;

      if (wildcardNode.getText().length() > 0) {
        
        // Validate if the wildcard was escaped
        if (UnescapedCharSequence.wasEscaped(wildcardNode.getText(), 0))
          return node;
        
        switch (wildcardNode.getText().charAt(0)) {    
          case '*':
          case '?':
            throw new QueryNodeException(new MessageImpl(
                QueryParserMessages.LEADING_WILDCARD_NOT_ALLOWED, node
                    .toQueryString(new EscapeQuerySyntaxImpl())));    
        }
      }

    }

    return node;

  }

  @Override
  protected QueryNode preProcessNode(QueryNode node) throws QueryNodeException {

    return node;

  }

  @Override
  protected List<QueryNode> setChildrenOrder(List<QueryNode> children)
      throws QueryNodeException {

    return children;

  }

}