/*
 * Jitsi, the OpenSource Java VoIP and Instant Messaging client.
 *
 * Copyright @ 2015 Atlassian Pty Ltd
 *
 * Licensed 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
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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 net.java.sip.communicator.service.systray;

import net.java.sip.communicator.service.systray.event.*;
import net.java.sip.communicator.util.*;
import org.jitsi.service.configuration.*;
import org.osgi.framework.*;

import java.util.*;

/**
 * Base implementation of {@link SystrayService}. Manages
 * <tt>PopupMessageHandler</tt>s and <tt>SystrayPopupMessageListener</tt>s.
 *
 * @author Nicolas Chamouard
 * @author Yana Stamcheva
 * @author Lyubomir Marinov
 * @author Symphorien Wanko
 * @author Pawel Domas
 */
public abstract class AbstractSystrayService
    implements SystrayService
{

    /**
     * The logger
     */
    private final Logger logger
            = Logger.getLogger(AbstractSystrayService.class);

    /**
     * OSGI bundle context
     */
    private final BundleContext bundleContext;

    /**
     * The popup handler currently used to show popup messages
     */
    private PopupMessageHandler activePopupHandler;

    /**
     * A set of usable <tt>PopupMessageHandler</tt>
     */
    private final Hashtable<String, PopupMessageHandler> popupHandlerSet
            = new Hashtable<String, PopupMessageHandler>();

    /**
     * List of listeners from early received calls to addPopupMessageListener.
     * Calls to addPopupMessageListener before the UIService is registered.
     */
    private List<SystrayPopupMessageListener> earlyAddedListeners = null;

    /**
     * Creates new instance of <tt>AbstractSystrayService</tt>.
     * @param bundleContext OSGI bundle context that will be used by this
     *                      instance
     */
    public AbstractSystrayService(BundleContext bundleContext)
    {
        this.bundleContext = bundleContext;
    }

    /**
     * Registers given <tt>PopupMessageHandler</tt>.
     * @param handler the <tt>PopupMessageHandler</tt> to be registered.
     */
    protected void addPopupHandler(PopupMessageHandler handler)
    {
        popupHandlerSet.put(handler.getClass().getName(), handler);
    }

    /**
     * Removes given <tt>PopupMessageHandler</tt>.
     * @param handler the <tt>PopupMessageHandler</tt> to be removed.
     */
    protected void removePopupHandler(PopupMessageHandler handler)
    {
        popupHandlerSet.remove(handler.getClass().getName());
    }

    /**
     * Checks if given <tt>handlerClass</tt> is registered as a handler.
     * @param handlerClass the class name to be checked.
     * @return <tt>true</tt> if given <tt>handlerClass</tt> is already
     *         registered as a handler.
     */
    protected boolean containsHandler(String handlerClass)
    {
        return popupHandlerSet.contains(handlerClass);
    }

    /**
     * Returns active <tt>PopupMessageHandler</tt>.
     * @return active <tt>PopupMessageHandler</tt>.
     */
    protected PopupMessageHandler getActivePopupHandler()
    {
        return activePopupHandler;
    }

    /**
     * Implements <tt>SystraService#showPopupMessage()</tt>
     *
     * @param popupMessage the message we will show
     */
    public void showPopupMessage(PopupMessage popupMessage)
    {
        // since popup handler could be loaded and unloader on the fly,
        // we have to check if we currently have a valid one.
        if (activePopupHandler != null)
            activePopupHandler.showPopupMessage(popupMessage);
    }

    /**
     * Stub method that does nothing.
     * @param count ignored 
     */
    @Override
    public void setNotificationCount(int count)
    {
    }

    /**
     * Implements the <tt>SystrayService.addPopupMessageListener</tt> method.
     * If <tt>activePopupHandler</tt> is still not available record the listener
     * so we can add him later.
     *
     * @param listener the listener to add
     */
    public void addPopupMessageListener(SystrayPopupMessageListener listener)
    {
        if (activePopupHandler != null)
            activePopupHandler.addPopupMessageListener(listener);
        else
        {
            if(earlyAddedListeners == null)
                earlyAddedListeners =
                        new ArrayList<SystrayPopupMessageListener>();

            earlyAddedListeners.add(listener);
        }
    }

    /**
     * Implements the <tt>SystrayService.removePopupMessageListener</tt> method.
     *
     * @param listener the listener to remove
     */
    public void removePopupMessageListener(SystrayPopupMessageListener listener)
    {
        if (activePopupHandler != null)
            activePopupHandler.removePopupMessageListener(listener);
    }

    /**
     * Set the handler which will be used for popup message
     * @param newHandler the handler to set. providing a null handler is like
     * disabling popup.
     * @return the previously used popup handler
     */
    public PopupMessageHandler setActivePopupMessageHandler(
            PopupMessageHandler newHandler)
    {
        PopupMessageHandler oldHandler = activePopupHandler;

        if (logger.isInfoEnabled())
        {
            logger.info(
                    "setting the following popup handler as active: "
                            + newHandler);
        }
        activePopupHandler = newHandler;
        // if we have received calls to addPopupMessageListener before
        // the UIService is registered we should add those listeners
        if(earlyAddedListeners != null)
        {
            for(SystrayPopupMessageListener l : earlyAddedListeners)
                activePopupHandler.addPopupMessageListener(l);

            earlyAddedListeners.clear();
            earlyAddedListeners = null;
        }

        return oldHandler;
    }

    /**
     * Get the handler currently used by this implementation to popup message
     * @return the current handler
     */
    public PopupMessageHandler getActivePopupMessageHandler()
    {
        return activePopupHandler;
    }

    /**
     * Sets activePopupHandler to be the one with the highest preference index.
     */
    public void selectBestPopupMessageHandler()
    {
        PopupMessageHandler preferredHandler = null;
        int highestPrefIndex = 0;

        if (!popupHandlerSet.isEmpty())
        {
            Enumeration<String> keys = popupHandlerSet.keys();

            while (keys.hasMoreElements())
            {
                String handlerName = keys.nextElement();
                PopupMessageHandler h = popupHandlerSet.get(handlerName);

                if (h.getPreferenceIndex() > highestPrefIndex)
                {
                    highestPrefIndex = h.getPreferenceIndex();
                    preferredHandler = h;
                }
            }
            setActivePopupMessageHandler(preferredHandler);
        }
    }

    /**
     * Initializes popup handler by searching registered services for class
     * <tt>PopupMessageHandler</tt>.
     */
    protected void initHandlers()
    {
        // Listens for new popup handlers
        try
        {
            bundleContext.addServiceListener(
                    new ServiceListenerImpl(),
                    "(objectclass=" + PopupMessageHandler.class.getName()
                        + ")");
        }
        catch (Exception e)
        {
            logger.warn(e);
        }

        // now we look if some handler has been registered before we start
        // to listen
        Collection<ServiceReference<PopupMessageHandler>> handlerRefs
            = ServiceUtils.getServiceReferences(
                    bundleContext,
                    PopupMessageHandler.class);

        if (!handlerRefs.isEmpty())
        {
            ConfigurationService config
                = ServiceUtils.getService(
                        bundleContext,
                        ConfigurationService.class);
            String configuredHandler
                = config.getString("systray.POPUP_HANDLER");

            for (ServiceReference<PopupMessageHandler> handlerRef : handlerRefs)
            {
                PopupMessageHandler handler
                    = bundleContext.getService(handlerRef);
                String handlerName = handler.getClass().getName();

                if (!containsHandler(handlerName))
                {
                    addPopupHandler(handler);
                    if (logger.isInfoEnabled())
                    {
                        logger.info(
                                "added the following popup handler : "
                                        + handler);
                    }
                    if ((configuredHandler != null)
                            && configuredHandler.equals(
                                    handler.getClass().getName()))
                    {
                        setActivePopupMessageHandler(handler);
                    }
                }
            }

            if (configuredHandler == null)
                selectBestPopupMessageHandler();
        }
    }

    /** An implementation of <tt>ServiceListener</tt> we will use */
    private class ServiceListenerImpl
        implements ServiceListener
    {

        /**
         * implements <tt>ServiceListener.serviceChanged</tt>
         * @param serviceEvent
         */
        public void serviceChanged(ServiceEvent serviceEvent)
        {
            try
            {
                Object service
                    = bundleContext.getService(
                            serviceEvent.getServiceReference());
                // Event filters don't work on Android
                if(!(service instanceof PopupMessageHandler))
                    return;

                PopupMessageHandler handler
                    = (PopupMessageHandler)
                        bundleContext.getService(
                                serviceEvent.getServiceReference());

                if (serviceEvent.getType() == ServiceEvent.REGISTERED)
                {
                    if (!containsHandler(handler.getClass().getName()))
                    {
                        if (logger.isInfoEnabled())
                            logger.info("adding the following popup handler : "
                                                + handler);
                        addPopupHandler(handler);
                    }
                    else
                        logger.warn("the following popup handler has not " +
                                    "been added since it is already known : "
                                            + handler);

                    ConfigurationService cfg
                        = ServiceUtils.getService( bundleContext,
                                                   ConfigurationService.class);
                    String configuredHandler
                        = cfg.getString("systray.POPUP_HANDLER");

                    if ((configuredHandler == null)
                            && ((getActivePopupHandler() == null)
                            || (handler.getPreferenceIndex()
                            > getActivePopupHandler().getPreferenceIndex())))
                    {
                        // The user doesn't have a preferred handler set and new
                        // handler with better preference index has arrived,
                        // thus setting it as active.
                        setActivePopupMessageHandler(handler);
                    }
                    if ((configuredHandler != null)
                            && configuredHandler.equals(
                            handler.getClass().getName()))
                    {
                        // The user has a preferred handler set and it just
                        // became available, thus setting it as active
                        setActivePopupMessageHandler(handler);
                    }
                }
                else if (serviceEvent.getType() == ServiceEvent.UNREGISTERING)
                {
                    if (logger.isInfoEnabled())
                        logger.info("removing the following popup handler : "
                                            + handler);
                    removePopupHandler(handler);
                    PopupMessageHandler activeHandler = getActivePopupHandler();
                    if (activeHandler == handler)
                    {
                        setActivePopupMessageHandler(null);

                        // We just lost our default handler, so we replace it
                        // with the one that has the highest preference index.
                        selectBestPopupMessageHandler();
                    }
                }
            }
            catch (IllegalStateException e)
            {
                if (logger.isDebugEnabled())
                    logger.debug(e);
            }
        }
    }
}