/*
 * Copyright 2012-2017 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
 *
 *      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.springframework.boot.autoconfigure.hateoas;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
import org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration;
import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.hateoas.EntityLinks;
import org.springframework.hateoas.LinkDiscoverers;
import org.springframework.hateoas.Resource;
import org.springframework.hateoas.config.EnableEntityLinks;
import org.springframework.hateoas.config.EnableHypermediaSupport;
import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
import org.springframework.plugin.core.Plugin;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * {@link EnableAutoConfiguration Auto-configuration} for Spring HATEOAS's
 * {@link EnableHypermediaSupport}.
 *
 * @author Roy Clarkson
 * @author Oliver Gierke
 * @author Andy Wilkinson
 * @since 1.1.0
 */
@Configuration
@ConditionalOnClass({ Resource.class, RequestMapping.class, Plugin.class })
@ConditionalOnWebApplication
@AutoConfigureAfter({ WebMvcAutoConfiguration.class, JacksonAutoConfiguration.class,
		HttpMessageConvertersAutoConfiguration.class,
		RepositoryRestMvcAutoConfiguration.class })
@EnableConfigurationProperties(HateoasProperties.class)
@Import(HypermediaHttpMessageConverterConfiguration.class)
public class HypermediaAutoConfiguration {

	@Configuration
	@ConditionalOnMissingBean(LinkDiscoverers.class)
	@ConditionalOnClass(ObjectMapper.class)
	@EnableHypermediaSupport(type = HypermediaType.HAL)
	protected static class HypermediaConfiguration {

		@Bean
		public static HalObjectMapperConfigurer halObjectMapperConfigurer() {
			return new HalObjectMapperConfigurer();
		}

	}

	@Configuration
	@ConditionalOnMissingBean(EntityLinks.class)
	@EnableEntityLinks
	protected static class EntityLinksConfiguration {

	}

	/**
	 * {@link BeanPostProcessor} to apply any {@link Jackson2ObjectMapperBuilder}
	 * configuration to the HAL {@link ObjectMapper}.
	 */
	private static class HalObjectMapperConfigurer
			implements BeanPostProcessor, BeanFactoryAware {

		private BeanFactory beanFactory;

		@Override
		public Object postProcessBeforeInitialization(Object bean, String beanName)
				throws BeansException {
			if (bean instanceof ObjectMapper && "_halObjectMapper".equals(beanName)) {
				postProcessHalObjectMapper((ObjectMapper) bean);
			}
			return bean;
		}

		private void postProcessHalObjectMapper(ObjectMapper objectMapper) {
			try {
				Jackson2ObjectMapperBuilder builder = this.beanFactory
						.getBean(Jackson2ObjectMapperBuilder.class);
				builder.configure(objectMapper);
			}
			catch (NoSuchBeanDefinitionException ex) {
				// No Jackson configuration required
			}
		}

		@Override
		public Object postProcessAfterInitialization(Object bean, String beanName)
				throws BeansException {
			return bean;
		}

		@Override
		public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
			this.beanFactory = beanFactory;
		}

	}

}
