/**
 * 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.utils;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;

/**
 * Provides base functionality for a static reference bean locator. Used by legacy code that is not
 * managed within spring, avoids direct use of PortalApplicationContextLocator by client code and in
 * the case of an already created ApplicationConext uses the bean refernce injected by the context.
 *
 */
public abstract class AbstractBeanLocator<T> implements DisposableBean, InitializingBean {
    protected final Log logger = LogFactory.getLog(AbstractBeanLocator.class);

    private final T instance;

    public AbstractBeanLocator(T instance, Class<T> type) {
        Assert.notNull(instance, "instance must not be null");
        Assert.notNull(type, "type must not be null");
        Assert.isInstanceOf(type, instance, instance + " must implement " + type);

        this.instance = instance;
    }

    protected abstract void setLocator(AbstractBeanLocator<T> locator);

    protected abstract AbstractBeanLocator<T> getLocator();

    public final T getInstance() {
        return this.instance;
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
     */
    @Override
    public final void afterPropertiesSet() throws Exception {
        if (this.getLocator() != null) {
            this.logger.warn(
                    "Static "
                            + this.getClass().getName()
                            + " reference has already been set and setInstance is being called");
        }
        this.setLocator(this);
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.DisposableBean#destroy()
     */
    @Override
    public final void destroy() throws Exception {
        if (this.getLocator() == null) {
            this.logger.warn(
                    "Static "
                            + this.getClass().getName()
                            + " reference is already null and destroy is being called");
        }
        this.setLocator(null);
    }
}