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package com.github.javaclub.configcenter.spring.config;

import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.EnvironmentAware;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;
import org.springframework.core.env.CompositePropertySource;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.Environment;
import org.springframework.core.env.MutablePropertySources;
import org.springframework.core.env.PropertySource;

import com.github.javaclub.configcenter.ConfigServerConstants.BootConfig;
import com.github.javaclub.configcenter.client.AppConfig;
import com.github.javaclub.configcenter.client.ConfigService;
import com.github.javaclub.configcenter.spring.property.AutoUpdateConfigChangeListener;
import com.github.javaclub.configcenter.spring.utils.SpringInjector;
import com.google.common.collect.ImmutableSortedSet;
import com.google.common.collect.LinkedHashMultimap;
import com.google.common.collect.Multimap;
import com.google.common.collect.Sets;
import com.google.common.eventbus.EventBus;

/**
 * ConfigCenter Property Sources processor for Spring Annotation Based
 * Application. 

 * 

 *
 * The reason why PropertySourcesProcessor implements
 * {@link BeanFactoryPostProcessor} instead of
 * {@link org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor}
 * is that lower versions of Spring (e.g. 3.1.1) doesn't support registering
 * BeanDefinitionRegistryPostProcessor in ImportBeanDefinitionRegistrar -
 * {@link com.github.javaclub.configcenter.spring.annotation.ConfigServerRegistrar}
 *
 */
public class PropertySourcesProcessor implements BeanFactoryPostProcessor, EnvironmentAware, PriorityOrdered {
	
	private static final Multimap NAMESPACE_NAMES = LinkedHashMultimap.create();
	private static final Set AUTO_UPDATE_INITIALIZED_BEAN_FACTORIES = Sets.newConcurrentHashSet();

	protected final EventBus eventBus = SpringInjector.getInstance(EventBus.class);
	protected final ConfigPropertySourceFactory configPropertySourceFactory = SpringInjector.getInstance(ConfigPropertySourceFactory.class);

	private ConfigurableEnvironment environment;
	
	public static boolean addNamespaces(Collection namespaces, int order) {
		return NAMESPACE_NAMES.putAll(order, namespaces);
	}
	
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		eventBus.register(this);
		initializePropertySources();
		initializeAutoUpdatePropertiesFeature(beanFactory);
	}

	private void initializePropertySources() {
		if (environment.getPropertySources().contains(BootConfig.CONFIGSERVER_PROPERTY_SOURCE_NAME)) {
			// already initialized
			return;
		}
		CompositePropertySource composite = new CompositePropertySource(BootConfig.CONFIGSERVER_PROPERTY_SOURCE_NAME);

		// sort by order asc
		ImmutableSortedSet orders = ImmutableSortedSet.copyOf(NAMESPACE_NAMES.keySet());
		Iterator iterator = orders.iterator();

		while (iterator.hasNext()) {
			int order = iterator.next();
			for (String namespace : NAMESPACE_NAMES.get(order)) {
				AppConfig config = ConfigService.getAppConfig();
				composite.addPropertySource(configPropertySourceFactory.getConfigPropertySource(namespace, config));
			}
		}

		// clean up
		NAMESPACE_NAMES.clear();

		// add after the bootstrap property source or to the first
		if (environment.getPropertySources().contains(BootConfig.CONFIGSERVER_BOOTSTRAP_PROPERTY_SOURCE_NAME)) {

			// ensure ConfigserverBootstrapPropertySources is still the first
			ensureBootstrapPropertyPrecedence(environment);

			environment.getPropertySources().addAfter(BootConfig.CONFIGSERVER_BOOTSTRAP_PROPERTY_SOURCE_NAME,
					composite);
		} else {
			environment.getPropertySources().addFirst(composite);
		}
	}

	private void ensureBootstrapPropertyPrecedence(ConfigurableEnvironment environment) {
		MutablePropertySources propertySources = environment.getPropertySources();

		PropertySource bootstrapPropertySource = propertySources.get(BootConfig.CONFIGSERVER_BOOTSTRAP_PROPERTY_SOURCE_NAME);

		// not exists or already in the first place
		if (bootstrapPropertySource == null || propertySources.precedenceOf(bootstrapPropertySource) == 0) {
			return;
		}

		propertySources.remove(BootConfig.CONFIGSERVER_BOOTSTRAP_PROPERTY_SOURCE_NAME);
		propertySources.addFirst(bootstrapPropertySource);
	}

	private void initializeAutoUpdatePropertiesFeature(ConfigurableListableBeanFactory beanFactory) {
		if (!AUTO_UPDATE_INITIALIZED_BEAN_FACTORIES.add(beanFactory)) {
			return;
		}

		AutoUpdateConfigChangeListener autoUpdateConfigChangeListener = new AutoUpdateConfigChangeListener(environment,
				beanFactory);

		List configPropertySources = configPropertySourceFactory.getAllConfigPropertySources();
		for (ConfigPropertySource configPropertySource : configPropertySources) {
			configPropertySource.addChangeListener(autoUpdateConfigChangeListener);
		}
	}

	@Override
	public void setEnvironment(Environment environment) {
		// it is safe enough to cast as all known environment is derived from ConfigurableEnvironment
		this.environment = (ConfigurableEnvironment) environment;
	}

	@Override
	public int getOrder() {
		// make it as early as possible
		return Ordered.HIGHEST_PRECEDENCE;
	}

}