/*
 * Copyright 2002-2017 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.context.support;

import java.util.Locale;

import org.springframework.context.HierarchicalMessageSource;
import org.springframework.context.MessageSource;
import org.springframework.context.MessageSourceResolvable;
import org.springframework.context.NoSuchMessageException;
import org.springframework.lang.Nullable;

Empty MessageSource that delegates all calls to the parent MessageSource. If no parent is available, it simply won't resolve any message. 
Used as placeholder by AbstractApplicationContext, if the context doesn't
define its own MessageSource. Not intended for direct use in applications.
Author:
Juergen Hoeller
See Also:
AbstractApplicationContext
Since:
1.1.5/**
 * Empty {@link MessageSource} that delegates all calls to the parent MessageSource.
 * If no parent is available, it simply won't resolve any message.
 *
 * <p>Used as placeholder by AbstractApplicationContext, if the context doesn't
 * define its own MessageSource. Not intended for direct use in applications.
 *
 * @author Juergen Hoeller
 * @since 1.1.5
 * @see AbstractApplicationContext
 */
public class DelegatingMessageSource extends MessageSourceSupport implements HierarchicalMessageSource {

	@Nullable
	private MessageSource parentMessageSource;


	@Override
	public void setParentMessageSource(@Nullable MessageSource parent) {
		this.parentMessageSource = parent;
	}

	@Override
	@Nullable
	public MessageSource getParentMessageSource() {
		return this.parentMessageSource;
	}


	@Override
	@Nullable
	public String getMessage(String code, @Nullable Object[] args, @Nullable String defaultMessage, Locale locale) {
		if (this.parentMessageSource != null) {
			return this.parentMessageSource.getMessage(code, args, defaultMessage, locale);
		}
		else if (defaultMessage != null) {
			return renderDefaultMessage(defaultMessage, args, locale);
		}
		else {
			return null;
		}
	}

	@Override
	public String getMessage(String code, @Nullable Object[] args, Locale locale) throws NoSuchMessageException {
		if (this.parentMessageSource != null) {
			return this.parentMessageSource.getMessage(code, args, locale);
		}
		else {
			throw new NoSuchMessageException(code, locale);
		}
	}

	@Override
	public String getMessage(MessageSourceResolvable resolvable, Locale locale) throws NoSuchMessageException {
		if (this.parentMessageSource != null) {
			return this.parentMessageSource.getMessage(resolvable, locale);
		}
		else {
			if (resolvable.getDefaultMessage() != null) {
				return renderDefaultMessage(resolvable.getDefaultMessage(), resolvable.getArguments(), locale);
			}
			String[] codes = resolvable.getCodes();
			String code = (codes != null && codes.length > 0 ? codes[0] : "");
			throw new NoSuchMessageException(code, locale);
		}
	}


	@Override
	public String toString() {
		return this.parentMessageSource != null ? this.parentMessageSource.toString() : "Empty MessageSource";
	}

}