/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2011 by Rapid-I and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapid-i.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero 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 Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.tools;

import java.lang.ref.SoftReference;
import java.util.Map;
import java.util.WeakHashMap;

import com.rapidminer.ObjectVisualizer;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.gui.DummyObjectVisualizer;
import com.rapidminer.gui.ExampleVisualizer;

/**
 * This class provides the management of {@link ObjectVisualizer}s. The visualizer are remembered per object using a
 * weak hash map and WeakReferences. Hence if the object isn't in ordinary use any more, the visualizer will be
 * discarded also.
 * 
 * @author Ingo Mierswa, Sebastian Land
 */
public class ObjectVisualizerService {

    private static final DummyObjectVisualizer DUMMY_VISUALIZER = new DummyObjectVisualizer();

    private static final Map<Object, SoftReference<ObjectVisualizer>> visualizerMap = new WeakHashMap<Object, SoftReference<ObjectVisualizer>>();

    /**
     * This method adds the given visualizer for the target object. Please not that only one visualizer per object is
     * allowed. The subsequent added visualizer will overwrite the first.
     * 
     * The targets will be remembered using a weak reference, so that they don't pose a memory leak: If the object isn't
     * referenced anywhere else, it will be deleted.
     */
    public static void addObjectVisualizer(Object target, ObjectVisualizer visualizer) {
        visualizerMap.put(target, new SoftReference<ObjectVisualizer>(visualizer));
    }

    /**
     * Returns the object visualizer registered for this targetObject. If the targetObject is of type ExampleSet and
     * there's no special visualizer registered, it will return an new ExampleVisualizer.
     */
    public static ObjectVisualizer getVisualizerForObject(Object targetObject) {
        ObjectVisualizer capableVisualizer = null;
        SoftReference<ObjectVisualizer> visualizerReference = visualizerMap.get(targetObject);
        if (visualizerReference != null) {
            capableVisualizer = visualizerReference.get();
        }
        if (capableVisualizer == null) {
            if (targetObject instanceof ExampleSet) {
                ObjectVisualizer visualizer = new ExampleVisualizer((ExampleSet) targetObject);
                addObjectVisualizer(targetObject, visualizer);
                return visualizer;
            }
            return DUMMY_VISUALIZER;
        }
        return capableVisualizer;
    }
}