/*
 * 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.core.config;

import java.util.LinkedList;

import org.apache.lucene.queryparser.flexible.core.processors.QueryNodeProcessor;
import org.apache.lucene.queryparser.flexible.core.util.StringUtils;

This class can be used to hold any query configuration and no field configuration. For field configuration, it creates an empty FieldConfig object and delegate it to field config listeners, these are responsible for setting up all the field configuration. QueryConfigHandler should be extended by classes that intends to provide configuration to QueryNodeProcessor objects. The class that extends QueryConfigHandler should also provide FieldConfig objects for each collection field. 
See Also:
FieldConfig
FieldConfigListener
QueryConfigHandler/**
 * This class can be used to hold any query configuration and no field
 * configuration. For field configuration, it creates an empty
 * {@link FieldConfig} object and delegate it to field config listeners, 
 * these are responsible for setting up all the field configuration.
 * 
 * {@link QueryConfigHandler} should be extended by classes that intends to
 * provide configuration to {@link QueryNodeProcessor} objects.
 * 
 * The class that extends {@link QueryConfigHandler} should also provide
 * {@link FieldConfig} objects for each collection field.
 * 
 * @see FieldConfig
 * @see FieldConfigListener
 * @see QueryConfigHandler
 */
public abstract class QueryConfigHandler extends AbstractQueryConfig {
  
  final private LinkedList<FieldConfigListener> listeners = new LinkedList<>();

  
Returns an implementation of FieldConfig for a specific field name. If the implemented QueryConfigHandler does not know a specific field name, it may return null, indicating there is no configuration for that
field.
Params:
fieldName – 
         the field name
Returns:
a FieldConfig object containing the field name configuration or null, if the implemented QueryConfigHandler has no configuration for that field/**
   * Returns an implementation of
   * {@link FieldConfig} for a specific field name. If the implemented
   * {@link QueryConfigHandler} does not know a specific field name, it may
   * return <code>null</code>, indicating there is no configuration for that
   * field.
   * 
   * @param fieldName
   *          the field name
   * @return a {@link FieldConfig} object containing the field name
   *         configuration or <code>null</code>, if the implemented
   *         {@link QueryConfigHandler} has no configuration for that field
   */
  public FieldConfig getFieldConfig(String fieldName) {
    FieldConfig fieldConfig = new FieldConfig(StringUtils.toString(fieldName));

    for (FieldConfigListener listener : this.listeners) {
      listener.buildFieldConfig(fieldConfig);
    }

    return fieldConfig;

  }

  
Adds a listener. The added listeners are called in the order they are
added.
Params:
listener – 
         the listener to be added/**
   * Adds a listener. The added listeners are called in the order they are
   * added.
   * 
   * @param listener
   *          the listener to be added
   */
  public void addFieldConfigListener(FieldConfigListener listener) {
    this.listeners.add(listener);
  }
  
}