/* (c) 2014 Open Source Geospatial Foundation - all rights reserved
 * (c) 2001 - 2013 OpenPlans
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geoserver.config.util;

import java.util.ArrayList;
import java.util.List;

import org.geoserver.platform.GeoServerExtensions;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

import com.thoughtworks.xstream.io.HierarchicalStreamDriver;
import com.thoughtworks.xstream.io.json.JettisonMappedXmlDriver;

/**
 * Factory for {@link XStreamPersister} instances.
 * <p>
 * This class is a singleton registered in a spring context. Any code that needs 
 * to create an XStreamPersister instance should do one of the following: 
 * <ol>
 *   <li>Use dependency injection via spring. Example:
 *     <pre>
 *       <bean id="myBean" class="com.xyz.MyBean">
 *         <constructor-arg ref="xstreamPersisterFactory"/>
 *       </bean>
 *     </pre>
 *   <li>Lookup via {@link GeoServerExtensions#bean(Class)}:
 *     <pre>
 *       XStreamPersisterFactory xpf = GeoServerExtension.bean(XStreamPeristerFactory.class);
 *     </pre>
 * </ol>
 * </p>
 * 
 * @author Justin Deoliveira, OpenGeo
 *
 */
public class XStreamPersisterFactory implements ApplicationContextAware {

    private List<XStreamPersisterInitializer> initializers;

    /**
     * Creates an instance configured to persist XML.
     */
    public XStreamPersister createXMLPersister() {
        return buildPersister(null);
    }

    /**
     * Creates an instance configured to persist JSON.
     */
    public XStreamPersister createJSONPersister() {
        return buildPersister(new JettisonMappedXmlDriver());
    }

    /**
     * Builds a persister and runs the initializers against it
     */
    private XStreamPersister buildPersister(HierarchicalStreamDriver driver) {
        XStreamPersister persister = new XStreamPersister(driver);

        // give the initializers a chance to register their own converters, aliases and so on
        for (XStreamPersisterInitializer initializer : getInitializers()) {
            initializer.init(persister);
        }

        return persister;
    }

    private List<XStreamPersisterInitializer> getInitializers() {
        if (initializers == null) {
            initializers = new ArrayList<XStreamPersisterInitializer>(
                    GeoServerExtensions.extensions(XStreamPersisterInitializer.class));
        }

        return initializers;
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        initializers = new ArrayList<XStreamPersisterInitializer>(GeoServerExtensions.extensions(
                XStreamPersisterInitializer.class, applicationContext));
    }

    /**
     * Programmatically adds a {@link XStreamPersisterInitializer} to the factory (initializers are
     * also automatically looked up from the Spring context, use this method only if you cannot
     * Declare your initializer as a spring bean)
     * 
     * @param initializer
     */
    public void addInitializer(XStreamPersisterInitializer initializer) {
        getInitializers().add(initializer);
    }

    /**
     * Removes an initializer
     * 
     * @return True if the initializer was found and removed, false otherwise
     */
    public boolean removeInitializer(XStreamPersisterInitializer initializer) {
        return getInitializers().remove(initializer);
    }
}