//
//  Copyright (C) 2014 Tom Beckmann
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program 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 General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
//

namespace Gala {
    public enum PluginFunction {
        ADDITION,
        WINDOW_SWITCHER,
        DESKTOP,
        WORKSPACE_VIEW,
        WINDOW_OVERVIEW
    }

    public enum LoadPriority {
        /**
         * Have your plugin loaded immediately once gala has started
         */
        IMMEDIATE,
        /**
         * Allow gala to defer loading your plugin once it got the
         * major part of the initialization done
         */
        DEFERRED
    }

    public struct PluginInfo {
        string name;
        string author;

        /**
         * Type of your plugin class, has to be derived from the Plugin class.
         */
        Type plugin_type;

        /**
         * This property allows you to override default functionality of gala
         * so systems won't be instantiated next to each other. Use
         * PluginFunction.ADDITION if no special component is overridden.
         */
        PluginFunction provides;

        /**
         * Give gala a hint for when to load your plugin. Especially use DEFERRED
         * if you're adding a completely new ui component that's not directly
         * related to the wm.
         */
        LoadPriority load_priority;

        /**
         * You don't have to fill this field, it will be filled by gala with
         * the filename in which your module was found.
         */
        string module_name;
    }

    /**
     * This class has to be implemented by every plugin.
     * Additionally, the plugin module is required to have a register_plugin
     * function which returns a PluginInfo struct.
     * The plugin_type field has to be the type of your plugin class derived
     * from this class.
     */
    public abstract class Plugin : Object {
        /**
         * Emitted when update_region is called. Mainly for internal purposes.
         */
        public signal void region_changed ();

        /**
         * The region indicates an area where mouse events should be sent to
         * the stage, which means your actors, instead of the windows.
         *
         * It is calculated by the system whenever update_region is called.
         * You can influce it with the custom_region and the track_actor function.
         */
        public Meta.Rectangle[] region { get; private set; }

        /**
         * This list will be merged with the region property. See region for
         * more details. Changing this property will cause update_region to be
         * called. Default to null.
         */
        protected Meta.Rectangle[]? custom_region {
            get {
                return _custom_region;
            }
            protected set {
                _custom_region = value;
                update_region ();
            }
        }

        /**
         * Set this property to true while animating an actor if you have tracked
         * actors to prevent constant recalculations of the regions during an
         * animation.
         */
        protected bool freeze_track {
            get {
                return _freeze_track;
            }
            set {
                _freeze_track = value;

                if (!_freeze_track)
                  update_region ();
            }
        }

        private bool _freeze_track = false;
        private Meta.Rectangle[]? _custom_region = null;
        private List<Clutter.Actor> tracked_actors = new List<Clutter.Actor> ();

        /**
         * Once this method is called you can start adding actors to the stage
         * via the windowmanager instance that is given to you.
         *
         * @param wm The window manager.
         */
        public abstract void initialize (WindowManager wm);

        /**
         * This method is currently not called in the code, however you should
         * still implement it to be compatible whenever we decide to use it.
         * It should make sure that everything your plugin added to the stage
         * is cleaned up.
         */
        public abstract void destroy ();

        /**
         * Listen to changes to the allocation of actor and update the region
         * accordingly. You may add multiple actors, their shapes will be
         * combined when one of them changes.
         *
         * @param actor The actor to be tracked
         */
        public void track_actor (Clutter.Actor actor) {
            tracked_actors.prepend (actor);
            actor.allocation_changed.connect (actor_allocation_changed);

            update_region ();
        }

        /**
         * Stop listening to allocation changes and remove the actor's
         * allocation from the region array.
         *
         * @param actor The actor to stop listening the changes on
         */
        public void untrack_actor (Clutter.Actor actor) {
            tracked_actors.remove (actor);
            actor.allocation_changed.disconnect (actor_allocation_changed);
        }

        /**
         * You can call this method to force the system to update the region that
         * is used by the window manager. It will automatically upon changes to
         * the custom_region property and when a tracked actor's allocation changes
         * unless freeze_track is set to true. You may need to call this function
         * after setting freeze_track back to false after an animation to make the
         * wm aware of the new position of the actor in question.
         */
        public void update_region () {
            var has_custom = custom_region != null;
            var len = tracked_actors.length () + (has_custom ? custom_region.length : 0);

            Meta.Rectangle[] regions = new Meta.Rectangle[len];
            var i = 0;

            if (has_custom) {
                for (var j = 0; j < custom_region.length; j++) {
                    regions[i++] = custom_region[j];
                }
            }

            foreach (var actor in tracked_actors) {
                float x, y, w, h;
                actor.get_transformed_position (out x, out y);
                actor.get_transformed_size (out w, out h);

                if (w == 0 || h == 0)
                    continue;

                regions[i++] = { (int) x, (int) y, (int) w, (int) h };
            }

            region = regions;

            region_changed ();
        }

        private void actor_allocation_changed (Clutter.ActorBox box, Clutter.AllocationFlags f) {
            if (!freeze_track)
                update_region ();
        }
    }
}