/*

 * Copyright (C) 2005-2010 Alfresco Software Limited.

 *

 * This file is part of Alfresco

 *

 * Alfresco is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * Alfresco is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.

 */

package org.alfresco.repo.management.subsystems;



import java.io.IOException;

import java.util.Collections;

import java.util.Set;



import org.springframework.context.ApplicationContext;



/**

 * A configurable proxy for a set of {@link ApplicationContextFactory} beans that allows dynamic selection of one or

 * more alternative subsystems via a <code>sourceBeanName</code> property. As with other {@link PropertyBackedBean}s,

 * can be stopped, reconfigured, started and tested.

 */

public class SwitchableApplicationContextFactory extends AbstractPropertyBackedBean implements

        ApplicationContextFactory

{



    /** The name of the property holding the bean name of the source {@link ApplicationContextFactory}. */

    private static final String SOURCE_BEAN_PROPERTY = "sourceBeanName";



    /** The default bean name of the source {@link ApplicationContextFactory}. */

    private String sourceBeanName;



    /**

     * Sets the default bean name of the source {@link ApplicationContextFactory}.

     * 

     * @param sourceBeanName

     *            the bean name

     */

    public void setSourceBeanName(String sourceBeanName)

    {

        this.sourceBeanName = sourceBeanName;

    }



    /*

     * (non-Javadoc)

     * @see org.alfresco.repo.management.subsystems.ApplicationContextFactory#getApplicationContext()

     */

    public ApplicationContext getApplicationContext()

    {

        this.lock.readLock().lock();

        try

        {

            return ((SwitchableState) getState(true)).getApplicationContext();

        }

        finally

        {

            this.lock.readLock().unlock();

        }

    }



    /*

     * (non-Javadoc)

     * @see org.alfresco.repo.management.subsystems.AbstractPropertyBackedBean#createInitialState()

     */

    @Override

    protected PropertyBackedBeanState createInitialState() throws IOException

    {

        return new SwitchableState(this.sourceBeanName);

    }



    /**

     * Represents the state of a {@link SwitchableApplicationContextFactory}.

     */

    protected class SwitchableState implements PropertyBackedBeanState

    {



        /** The current source application context factory. */

        private ApplicationContextFactory sourceApplicationContextFactory;



        /** The bean name of the source {@link ApplicationContextFactory}. */

        private String sourceBeanName;



        /**

         * Instantiates a new switchable state.

         * 

         * @param sourceBeanName

         *            the source bean name

         */

        protected SwitchableState(String sourceBeanName)

        {

            this.sourceBeanName = sourceBeanName;

        }



        /*

         * (non-Javadoc)

         * @see org.alfresco.enterprise.repo.management.ConfigurableBean#onStart()

         */

        public void start()

        {

            if (this.sourceApplicationContextFactory == null)

            {

                this.sourceApplicationContextFactory = (ApplicationContextFactory) getParent().getBean(

                        this.sourceBeanName);

                this.sourceApplicationContextFactory.start();

            }

        }



        /*

         * (non-Javadoc)

         * @see org.alfresco.repo.management.SelfDescribingBean#onStop()

         */

        public void stop()

        {

            if (this.sourceApplicationContextFactory != null)

            {

                try

                {

                    this.sourceApplicationContextFactory.stop();

                }

                catch (Exception e)

                {

                    throw new RuntimeException(e);

                }

            }

            this.sourceApplicationContextFactory = null;

        }



        /**

         * Gets the application context.

         * 

         * @return the application context

         */

        public ApplicationContext getApplicationContext()

        {

            if (this.sourceApplicationContextFactory == null)

            {

                start();

            }

            return this.sourceApplicationContextFactory.getApplicationContext();

        }



        /*

         * (non-Javadoc)

         * @see org.alfresco.repo.management.subsystems.PropertyBackedBean#getProperty(java.lang.String)

         */

        public String getProperty(String name)

        {

            if (!name.equals(SwitchableApplicationContextFactory.SOURCE_BEAN_PROPERTY))

            {

                return null;

            }

            return this.sourceBeanName;

        }



        /*

         * (non-Javadoc)

         * @see org.alfresco.repo.management.subsystems.PropertyBackedBean#getPropertyNames()

         */

        public Set<String> getPropertyNames()

        {

            return Collections.singleton(SwitchableApplicationContextFactory.SOURCE_BEAN_PROPERTY);

        }



        /*

         * (non-Javadoc)

         * @see org.alfresco.repo.management.subsystems.PropertyBackedBean#setProperty(java.lang.String,

         * java.lang.String)

         */

        public void setProperty(String name, String value)

        {

            if (!name.equals(SwitchableApplicationContextFactory.SOURCE_BEAN_PROPERTY))

            {

                throw new IllegalStateException("Illegal attempt to write to property \"" + name + "\"");

            }

            if (!getParent().containsBean(value))

            {

                throw new IllegalStateException("\"" + value + "\" is not a valid bean name");

            }

            if (this.sourceApplicationContextFactory != null)

            {

                stop();

                this.sourceBeanName = value;

                start();

            }

            else

            {

                this.sourceBeanName = value;

            }

        }



    }

}