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package com.openexchange.file.storage.osgi;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;
import org.osgi.util.tracker.ServiceTrackerCustomizer;
import com.openexchange.file.storage.FileStorageException;
import com.openexchange.file.storage.FileStorageExceptionCodes;
import com.openexchange.file.storage.FileStorageService;
import com.openexchange.file.storage.registry.FileStorageServiceRegistry;

/**
 * {@link OSGIFileStorageServiceRegistry}
 * 
 * @author <a href="mailto:francisco.laguna@open-xchange.com">Francisco Laguna</a>
 * @author <a href="mailto:thorben.betten@open-xchange.com">Thorben Betten</a>
 * @since Open-Xchange v6.18.2
 */
public class OSGIFileStorageServiceRegistry implements FileStorageServiceRegistry {

    /**
     * The backing map.
     */
    final ConcurrentMap<String, FileStorageService> map;

    /**
     * The tracker instance.
     */
    private ServiceTracker tracker;

    /**
     * Initializes a new {@link OSGIFileStorageServiceRegistry}.
     */
    public OSGIFileStorageServiceRegistry() {
        super();
        map = new ConcurrentHashMap<String, FileStorageService>(8);
    }

    /**
     * Starts the tracker.
     * 
     * @param context The bundle context
     */
    public void start(final BundleContext context) {
        if (null == tracker) {
            tracker = new ServiceTracker(context, FileStorageService.class.getName(), new Customizer(context));
            tracker.open();
        }
    }

    /**
     * Stops the tracker.
     */
    public void stop() {
        if (null != tracker) {
            tracker.close();
            tracker = null;
        }
    }

    public List<FileStorageService> getAllServices() throws FileStorageException {
        return new ArrayList<FileStorageService>(map.values());
    }

    public FileStorageService getFileStorageService(final String id) throws FileStorageException {
        final FileStorageService filestorageService = map.get(id);
        if (null == filestorageService) {
            throw FileStorageExceptionCodes.UNKNOWN_FILE_STORAGE_SERVICE.create(id);
        }
        return filestorageService;
    }

    public boolean containsFileStorageService(final String id) {
        return null == id ? false : map.containsKey(id);
    }

    private final class Customizer implements ServiceTrackerCustomizer {

        private final BundleContext context;

        Customizer(final BundleContext context) {
            super();
            this.context = context;
        }

        public Object addingService(final ServiceReference reference) {
            final Object service = context.getService(reference);
            if ((service instanceof FileStorageService)) {
                final FileStorageService addMe = (FileStorageService) service;
                if (null == map.putIfAbsent(addMe.getId(), addMe)) {
                    return service;
                }
                final org.apache.commons.logging.Log logger =
                    org.apache.commons.logging.LogFactory.getLog(OSGIFileStorageServiceRegistry.Customizer.class);
                if (logger.isWarnEnabled()) {
                    logger.warn(new StringBuilder(128).append("File storage service ").append(addMe.getDisplayName()).append(
                        " could not be added to registry. Another service is already registered with identifier: ").append(addMe.getId()).toString());
                }
            }
            /*
             * Adding to registry failed
             */
            context.ungetService(reference);
            return null;
        }

        public void modifiedService(final ServiceReference reference, final Object service) {
            // Nothing to do
        }

        public void removedService(final ServiceReference reference, final Object service) {
            if (null != service) {
                try {
                    if (service instanceof FileStorageService) {
                        final FileStorageService removeMe = (FileStorageService) service;
                        map.remove(removeMe.getId());
                    }
                } finally {
                    context.ungetService(reference);
                }
            }
        }
    } // End of Customizer class

}
