/*
 * Copyright 2012-2018 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.actuate.autoconfigure.metrics.export;

import java.util.Arrays;

import io.micrometer.core.instrument.Clock;
import io.micrometer.core.instrument.MeterRegistry;
import io.micrometer.core.instrument.composite.CompositeMeterRegistry;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.ConstructorArgumentValues;
import org.springframework.beans.factory.config.ConstructorArgumentValues.ValueHolder;
import org.springframework.beans.factory.config.RuntimeBeanReference;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.beans.factory.support.ManagedList;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.util.ObjectUtils;

/**
 * {@link BeanFactoryPostProcessor} to register a {@link CompositeMeterRegistry} when
 * necessary.
 *
 * @author Jon Schneider
 * @author Phillip Webb
 */
@Order(Ordered.LOWEST_PRECEDENCE - 1)
class CompositeMeterRegistryPostProcessor
		implements BeanDefinitionRegistryPostProcessor, BeanFactoryAware {

	private static final String COMPOSITE_BEAN_NAME = "compositeMeterRegistry";

	private ConfigurableListableBeanFactory beanFactory;

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

	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
			throws BeansException {
	}

	@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
			throws BeansException {
		if (this.beanFactory == null) {
			return;
		}
		String[] registryBeans = this.beanFactory.getBeanNamesForType(MeterRegistry.class,
				true, false);
		registerCompositeIfNecessary(registry, registryBeans);
	}

	private void registerCompositeIfNecessary(BeanDefinitionRegistry registry,
			String[] registryBeans) {
		if (ObjectUtils.isEmpty(registryBeans)) {
			registerNoOpMeterRegistry(registry);
		}
		if (registryBeans.length > 1 && !hasPrimaryDefinition(registryBeans)) {
			registerPrimaryCompositeMeterRegistry(registry, registryBeans);
		}
	}

	private boolean hasPrimaryDefinition(String[] registryBeans) {
		return Arrays.stream(registryBeans).map(this.beanFactory::getBeanDefinition)
				.anyMatch(BeanDefinition::isPrimary);
	}

	private void registerNoOpMeterRegistry(BeanDefinitionRegistry registry) {
		// If there are no meter registries configured, we register an empty composite
		// that effectively no-ops metrics instrumentation throughout the app.
		GenericBeanDefinition definition = new GenericBeanDefinition();
		definition.setBeanClass(CompositeMeterRegistry.class);
		registry.registerBeanDefinition(COMPOSITE_BEAN_NAME, definition);
	}

	private void registerPrimaryCompositeMeterRegistry(BeanDefinitionRegistry registry,
			String[] registryBeans) {
		GenericBeanDefinition definition = new GenericBeanDefinition();
		definition.setBeanClass(CompositeMeterRegistry.class);
		definition.setPrimary(true);
		ConstructorArgumentValues arguments = new ConstructorArgumentValues();
		arguments.addIndexedArgumentValue(0,
				new ValueHolder(null, Clock.class.getName()));
		arguments.addIndexedArgumentValue(1, getBeanReferences(registryBeans));
		definition.setConstructorArgumentValues(arguments);
		registry.registerBeanDefinition(COMPOSITE_BEAN_NAME, definition);
	}

	private ManagedList<RuntimeBeanReference> getBeanReferences(String[] names) {
		ManagedList<RuntimeBeanReference> references = new ManagedList<>(names.length);
		Arrays.stream(names).map(RuntimeBeanReference::new).forEach(references::add);
		return references;
	}

}
