/*
* 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.QueryParser;
import org.apache.lucene.queryparser.classic.QueryParserBase;
import java.util.HashMap;
import java.util.Map;
/**
* The {@link Extensions} class represents an extension mapping to associate
* {@link ParserExtension} instances with extension keys. An extension key is a
* string encoded into a Lucene standard query parser field symbol recognized by
* {@link ExtendableQueryParser}. The query parser passes each extension field
* token to {@link #splitExtensionField(String, String)} to separate the
* extension key from the field identifier.
* <p>
* In addition to the key to extension mapping this class also defines the field
* name overloading scheme. {@link ExtendableQueryParser} uses the given
* extension to split the actual field name and extension key by calling
* {@link #splitExtensionField(String, String)}. To change the order or the key
* / field name encoding scheme users can subclass {@link Extensions} to
* implement their own.
*
* @see ExtendableQueryParser
* @see ParserExtension
*/
public class Extensions {
private final Map<String,ParserExtension> extensions = new HashMap<>();
private final char extensionFieldDelimiter;
/**
* The default extension field delimiter character. This constant is set to
* ':'
*/
public static final char DEFAULT_EXTENSION_FIELD_DELIMITER = ':';
/**
* Creates a new {@link Extensions} instance with the
* {@link #DEFAULT_EXTENSION_FIELD_DELIMITER} as a delimiter character.
*/
public Extensions() {
this(DEFAULT_EXTENSION_FIELD_DELIMITER);
}
/**
* Creates a new {@link Extensions} instance
*
* @param extensionFieldDelimiter
* the extensions field delimiter character
*/
public Extensions(char extensionFieldDelimiter) {
this.extensionFieldDelimiter = extensionFieldDelimiter;
}
/**
* Adds a new {@link ParserExtension} instance associated with the given key.
*
* @param key
* the parser extension key
* @param extension
* the parser extension
*/
public void add(String key, ParserExtension extension) {
this.extensions.put(key, extension);
}
/**
* Returns the {@link ParserExtension} instance for the given key or
* <code>null</code> if no extension can be found for the key.
*
* @param key
* the extension key
* @return the {@link ParserExtension} instance for the given key or
* <code>null</code> if no extension can be found for the key.
*/
public final ParserExtension getExtension(String key) {
return this.extensions.get(key);
}
/**
* Returns the extension field delimiter
*
* @return the extension field delimiter
*/
public char getExtensionFieldDelimiter() {
return extensionFieldDelimiter;
}
/**
* Splits a extension field and returns the field / extension part as a
* {@link Pair}. This method tries to split on the first occurrence of the
* extension field delimiter, if the delimiter is not present in the string
* the result will contain a <code>null</code> value for the extension key and
* the given field string as the field value. If the given extension field
* string contains no field identifier the result pair will carry the given
* default field as the field value.
*
* @param defaultField
* the default query field
* @param field
* the extension field string
* @return a {@link Pair} with the field name as the {@link Pair#cur} and the
* extension key as the {@link Pair#cud}
*/
public Pair<String,String> splitExtensionField(String defaultField,
String field) {
int indexOf = field.indexOf(this.extensionFieldDelimiter);
if (indexOf < 0)
return new Pair<>(field, null);
final String indexField = indexOf == 0 ? defaultField : field.substring(0,
indexOf);
final String extensionKey = field.substring(indexOf + 1);
return new Pair<>(indexField, extensionKey);
}
/**
* Escapes an extension field. The default implementation is equivalent to
* {@link QueryParser#escape(String)}.
*
* @param extfield
* the extension field identifier
* @return the extension field identifier with all special chars escaped with
* a backslash character.
*/
public String escapeExtensionField(String extfield) {
return QueryParserBase.escape(extfield);
}
/**
* Builds an extension field string from a given extension key and the default
* query field. The default field and the key are delimited with the extension
* field delimiter character. This method makes no assumption about the order
* of the extension key and the field. By default the extension key is
* appended to the end of the returned string while the field is added to the
* beginning. Special Query characters are escaped in the result.
* <p>
* Note: {@link Extensions} subclasses must maintain the contract between
* {@link #buildExtensionField(String)} and
* {@link #splitExtensionField(String, String)} where the latter inverts the
* former.
* </p>
*/
public String buildExtensionField(String extensionKey) {
return buildExtensionField(extensionKey, "");
}
/**
* Builds an extension field string from a given extension key and the
* extensions field. The field and the key are delimited with the extension
* field delimiter character. This method makes no assumption about the order
* of the extension key and the field. By default the extension key is
* appended to the end of the returned string while the field is added to the
* beginning. Special Query characters are escaped in the result.
* <p>
* Note: {@link Extensions} subclasses must maintain the contract between
* {@link #buildExtensionField(String, String)} and
* {@link #splitExtensionField(String, String)} where the latter inverts the
* former.
* </p>
*
* @param extensionKey
* the extension key
* @param field
* the field to apply the extension on.
* @return escaped extension field identifier
* @see #buildExtensionField(String) to use the default query field
*/
public String buildExtensionField(String extensionKey, String field) {
StringBuilder builder = new StringBuilder(field);
builder.append(this.extensionFieldDelimiter);
builder.append(extensionKey);
return escapeExtensionField(builder.toString());
}
/**
* This class represents a generic pair.
*
* @param <Cur>
* the pairs first element
* @param <Cud>
* the pairs last element of the pair.
*/
public static class Pair<Cur,Cud> {
public final Cur cur;
public final Cud cud;
/**
* Creates a new Pair
*
* @param cur
* the pairs first element
* @param cud
* the pairs last element
*/
public Pair(Cur cur, Cud cud) {
this.cur = cur;
this.cud = cud;
}
}
}