// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
/**
 * pluginmanager.h
 *
 * Copyright (C)  2004  Zack Rusin <zack@kde.org>
 * Copyright (C)  2003  Martijn Klingens <klingens@kde.org>
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
 * 02111-1307  USA
 */

#ifndef KOMPOSER_PLUGINMANAGER_H
#define KOMPOSER_PLUGINMANAGER_H

#include <qmap.h>
#include <qobject.h>
#include <qstring.h>
#include <qstringlist.h>
#include <qvaluelist.h>

class KPluginInfo;

namespace Komposer
{

  class Plugin;

  class PluginManager : public QObject
  {
    Q_OBJECT

  public:
    PluginManager( QObject* );

    ~PluginManager();

    /**
     * Returns a list of all available plugins for the given category.
     * Currently there are two categories, "Plugins" and "Editors", but
     * you can add your own categories if you want.
     *
     * If you pass an empty string you get the complete list of ALL plugins.
     *
     * You can query all information on the plugins through the @ref KPluginInfo
     * interface.
     */
    QValueList<KPluginInfo*> availablePlugins( const QString& category
                                               = QString::null ) const;

    /**
     * Returns a list of all plugins that are actually loaded.
     * If you omit the category you get all, otherwise it's a filtered list.
     * See also @ref availablePlugins().
     */
    QMap<KPluginInfo*, Plugin*> loadedPlugins( const QString& category
                                               = QString::null ) const;

    /**
     * @brief Search by plugin name. This is the key used as X-KDE-PluginInfo-Name in
     * the .desktop file, e.g. "komposer_attachment"
     *
     * @return The @ref Plugin object found by the search, or a null
     * pointer if the plugin is not loaded.
     *
     * If you want to also load the plugin you can better use @ref loadPlugin, which returns
     * the pointer to the plugin if it's already loaded.
     */
    Plugin* plugin( const QString& pluginName ) const;

    /**
     * @brief Return the short user-visible name of the plugin.
     *
     * If you want to have the internal name, use @ref pluginId() instead.
     *
     * @return The name of the protocol, in the user's locale.
     */
    QString pluginName( const Plugin* plugin ) const;

    /**
     * @brief Return the internal name of the plugin.
     *
     * You cannot display this name on the screen, it's used internally for
     * passing around IDs. Use @ref pluginName() for a string ready for display.
     *
     * @return The name of the protocol, in the user's locale.
     */
    QString pluginId( const Plugin* plugin ) const;

    /**
     * @brief Unload the plugin specified by @p pluginName
     */
    bool unloadPlugin( const QString& pluginName );

    /**
     * @brief Retrieve the name of the icon for a @ref Plugin.
     *
     * @return An empty string if the given plugin is not loaded
     * or the filename of the icon to use.
     */
    QString pluginIcon( const Plugin* plugin ) const;

    /**
     * Shuts down the plugin manager on Komposer shutdown, but first
     * unloads all plugins asynchronously.
     *
     * After 3 seconds all plugins should be removed; what's still left
     * by then is unloaded through a hard delete instead.
     *
     * Note that this call also derefs the plugin manager from the event
     * loop, so do NOT call this method when not terminating Komposer!
     */
    void shutdown();

    /**
     * Enable a plugin.
     *
     * This marks a plugin as enabled in the config file, so loadAll()
     * can pick it up later.
     *
     * This method does not actually load a plugin, it only edits the
     * config file.
     *
     * @param name is the name of the plugin as it is listed in the .desktop
     * file in the X-KDE-Library field.
     *
     * Returns false when no appropriate plugin can be found.
     */
    bool setPluginEnabled( const QString& name, bool enabled = true );

    /**
     * Plugin loading mode. Used by @loadPlugin. Code that doesn't want to block
     * the GUI and/or lot a lot of plugins at once should use Async loading.
     * The default is sync loading.
     */
    enum PluginLoadMode { LoadSync, LoadAsync };

  public slots:
    /**
     * @brief Load a single plugin by plugin name. Returns an existing plugin
     * if one is already loaded in memory.
     *
     * If mode is set to Async, the plugin will be queued and loaded in
     * the background. This method will return a null pointer. To get
     * the loaded plugin you can track the @ref pluginLoaded() signal.
     *
     * See also @ref plugin().
     */
    Plugin* loadPlugin( const QString& pluginId, PluginLoadMode mode = LoadSync );

    /**
     * @brief Loads all the enabled plugins. Also used to reread the
     * config file when the configuration has changed.
     */
    void loadAllPlugins();

  signals:
    /**
     * @brief Signals a new plugin has just been loaded.
     */
    void pluginLoaded( Plugin* plugin );

    /**
     * @brief All plugins have been loaded by the plugin manager.
     *
     * This signal is emitted exactly ONCE, when the plugin manager has emptied
     * its plugin queue for the first time. This means that if you call an async
     * loadPlugin() before loadAllPlugins() this signal is probably emitted after
     * the initial call completes, unless you are quick enough to fill the queue
     * before it completes, which is a dangerous race you shouldn't count upon :)
     *
     * The signal is delayed one event loop iteration through a singleShot timer,
     * but that is not guaranteed to be enough for account instantiation. You may
     * need an additional timer for it in the code if you want to programmatically
     * act on it.
     *
     * If you use the signal for enabling/disabling GUI objects there is little
     * chance a user is able to activate them in the short while that's remaining,
     * the slow part of the code is over now and the remaining processing time
     * is neglectable for the user.
     */
    void allPluginsLoaded();

  private slots:
    /**
     * @brief Cleans up some references if the plugin is destroyed
     */
    void slotPluginDestroyed( QObject* plugin );

    /**
     * shutdown() starts a timer, when it fires we force all plugins
     * to be unloaded here by deref()-ing the event loop to trigger the plugin
     * manager's destruction
     */
    void slotShutdownTimeout();

    /**
     * Common entry point to deref() the KApplication. Used both by the clean
     * shutdown and the timeout condition of slotShutdownTimeout()
     */
    void slotShutdownDone();

    /**
     * Emitted by a Plugin when it's ready for unload
     */
    void slotPluginReadyForUnload();

    /**
     * Load a plugin from our queue. Does nothing if the queue is empty.
     * Schedules itself again if more plugins are pending.
     */
    void slotLoadNextPlugin();

  private:
    /**
     * @internal
     *
     * The internal method for loading plugins.
     * Called by @ref loadPlugin directly or through the queue for async plugin
     * loading.
     */
    Plugin * loadPluginInternal( const QString &pluginId );

    /**
     * @internal
     *
     * Find the KPluginInfo structure by key. Reduces some code duplication.
     *
     * Returns a null pointer when no plugin info is found.
     */
    KPluginInfo* infoForPluginId( const QString& pluginId ) const;
  private:
    class Private;
    Private* d;
  };

}

#endif // KOMPOSER_PLUGINMANAGER_H
