/**
 * Licensed to Apereo under one or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information regarding copyright ownership. Apereo
 * licenses this file to you 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 the
 * following location:
 *
 * <p>http://www.apache.org/licenses/LICENSE-2.0
 *
 * <p>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.apereo.portal.spring.beans.factory;

import java.util.List;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.config.AbstractFactoryBean;
import org.springframework.util.Assert;

/**
 * Takes a list of bean names and attempts to load each in order. If the loading of a bean throws an
 * Exception it is logged and the next bean name in the list is tried. If no beans can be loaded a
 * {@link BeanCreationException} is thrown.
 */
public class MediatingFactoryBean<T> extends AbstractFactoryBean<T> implements BeanFactoryAware {
    private List<String> delegateBeanNames;
    private Class<T> type = null;

    /** @return the delegateBeanNames */
    public List<String> getDelegateBeanNames() {
        return this.delegateBeanNames;
    }

    /** @param delegateBeanNames the delegateBeanNames to set */
    public void setDelegateBeanNames(List<String> delegateBeanNames) {
        this.delegateBeanNames = delegateBeanNames;
    }

    /** @return the type */
    public Class<T> getType() {
        return this.type;
    }

    /** @param type the type to set */
    public void setType(Class<T> type) {
        this.type = type;
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.config.AbstractFactoryBean#afterPropertiesSet()
     */
    @Override
    public void afterPropertiesSet() throws Exception {
        Assert.notEmpty(this.delegateBeanNames, "delegateBeanNames list cannot be empty");

        super.afterPropertiesSet();
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.config.AbstractFactoryBean#createInstance()
     */
    @Override
    protected T createInstance() throws Exception {
        for (final String beanName : this.delegateBeanNames) {
            try {
                final T bean;
                if (this.type == null) {
                    bean = (T) this.getBeanFactory().getBean(beanName);
                } else {
                    bean = this.getBeanFactory().getBean(beanName, this.type);
                }

                if (this.logger.isInfoEnabled()) {
                    this.logger.info("Loaded bean for name " + beanName);
                }

                return bean;
            } catch (final Exception e) {
                final String msg =
                        "Failed to load bean '"
                                + beanName
                                + "' from ApplicationContext"
                                + (this.type != null ? " expecting type: " + this.type : "")
                                + ". Will try to load the next bean in the list instead. Error message from the attempt to load this bean ('"
                                + beanName
                                + "'): ";

                if (this.logger.isDebugEnabled()) {
                    this.logger.debug(msg, e);
                } else if (this.logger.isInfoEnabled()) {
                    this.logger.info(
                            msg + " " + e.getMessage() + " (enable debug for stack trace)");
                }
            }
        }

        throw new BeanCreationException(
                "None of the configured bean names could be loaded. BeanNames: "
                        + this.delegateBeanNames);
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.config.AbstractFactoryBean#getObjectType()
     */
    @Override
    public Class<?> getObjectType() {
        return this.type;
    }
}