/*
 * Copyright 2013 Red Hat, Inc. and/or its affiliates.
 *
 * 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.kie.internal.runtime.cdi;

import java.util.LinkedList;
import java.util.List;
import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.event.Observes;
import javax.enterprise.inject.spi.AfterDeploymentValidation;
import javax.enterprise.inject.spi.Bean;
import javax.enterprise.inject.spi.BeanManager;
import javax.enterprise.inject.spi.Extension;
import javax.enterprise.inject.spi.ProcessBean;
import javax.inject.Singleton;

/**
 * CDI extension that is responsible to eagerly bootstrap CDI beans that
 * are annotated with <code>@BootOnLoad</code>. That mainly means that
 * beans annotated with <code>@BootOnLoad</code> will be invoked (their)
 * <code>@PostConstruct</code> method on CDI container initialization.
 * This extension will only take effect on beans marked as:
 * <ul>
 *  <li><code>@javax.enterprise.context.ApplicationScoped</code></li>
 *  <li><code>@javax.inject.Singleton</code></li>
 * </ul>
 */
public class BootOnLoadExtension implements Extension {

    private final List<Bean<?>> startupBootstrapBeans = new LinkedList<Bean<?>>();

    public <X> void processBean(@Observes final ProcessBean<X> event) {
        if (event.getAnnotated().isAnnotationPresent(BootOnLoad.class)
                && (event.getAnnotated().isAnnotationPresent(ApplicationScoped.class)
                        || event.getAnnotated().isAnnotationPresent(Singleton.class))) {
            startupBootstrapBeans.add(event.getBean());

        }
    }

    public void afterDeploymentValidation(
            final @Observes AfterDeploymentValidation event,
            final BeanManager manager) {
        // Force execution of Bootstrap bean's @PostConstruct methods first
        runPostConstruct(manager, startupBootstrapBeans);

    }

    private void runPostConstruct(final BeanManager manager,
            final List<Bean<?>> orderedBeans) {

        for (Bean<?> bean : orderedBeans) {
            // the call to toString() is a cheat to force the bean to be initialized
            manager.getReference(bean, bean.getBeanClass(),
                    manager.createCreationalContext(bean)).toString();
        }
    }


}
