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/*
 * Copyright (c) 2008, Christophe Delory
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY CHRISTOPHE DELORY ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL CHRISTOPHE DELORY BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package chameleon.content;

import java.util.ServiceLoader;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Fills the metadata of a given {@link Content content} through {@link ContentMetadataProvider metadata providers}.
 * These metadata should be:
 * 
 * The content {@link Content#setDuration duration}
 * The content {@link Content#setWidth width} and {@link Content#setHeight height}
 * 
 * @version $Revision: 92 $
 * @author Christophe Delory
 * @since 1.0.0
 */
public final class ContentMetadataCenter
{
    /**
     * The singleton instance.
     */
    private static ContentMetadataCenter _instance = null;

    /**
     * Returns the unique class instance.
     * @return an instance of this class. Shall not be null.
     */
    public static ContentMetadataCenter getInstance()
    {
        synchronized(ContentMetadataCenter.class)
        {
            if (_instance == null)
            {
                _instance = new ContentMetadataCenter();
            }
        }

        return _instance;
    }

    /**
     * The associated service provider loader.
     */
    private final ServiceLoader _serviceLoader;

    /**
     * The logger attached to this instance.
     */
    private final Log _logger;

    /**
     * Builds a new content metadata center.
     */
    private ContentMetadataCenter()
    {
        _logger = LogFactory.getLog(getClass()); // May throw LogConfigurationException.
        _serviceLoader = ServiceLoader.load(ContentMetadataProvider.class);
    }

    /**
     * Refreshes the list of providers managed by this center.
     * If new providers are added after the instantiation of this class, you will need to call this method manually.
     */
    public void reloadProviders()
    {
        _serviceLoader.reload();
    }

    /**
     * Fills if possible the metadata of the specified content.
     * @param content a content. Shall not be null.
     * @return true if a provider recognized the format, false otherwise.
     * @throws NullPointerException if content is null.
     * @see ContentMetadataProvider#fillMetadata
     */
    public boolean fillMetadata(final Content content)
    {
        boolean ret = false;

        for (ContentMetadataProvider service : _serviceLoader)
        {
            try
            {
                service.fillMetadata(content, _logger); // Throws NullPointerException if content is null. May throw Exception.

                // If we reached this point, it's OK.
                ret = true;
                break;
            }
            catch (Throwable e)
            {
                // Ignore it.
                if (_logger.isTraceEnabled())
                {
                    _logger.trace("Metadata provider " + service + " cannot handle content <" + content + ">", e);
                }
                else if (_logger.isDebugEnabled())
                {
                    _logger.debug("Metadata provider " + service + " cannot handle content <" + content + ">: " + e);
                }
            }
        }

        return ret;
    }
}