/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.log4j.or;

import org.apache.log4j.spi.RendererSupport;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.helpers.Loader;
import org.apache.log4j.helpers.OptionConverter;
import java.util.Hashtable;

/**
 * Map class objects to an {@link ObjectRenderer}.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @since version 1.0
 */
public class RendererMap {

    Hashtable map;

    static ObjectRenderer defaultRenderer = new DefaultRenderer();

    public RendererMap() {
	map = new Hashtable();
    }

    /**
     * Add a renderer to a hierarchy passed as parameter.
     */
    static public void addRenderer(RendererSupport repository, String renderedClassName, String renderingClassName) {
	LogLog.debug("Rendering class: [" + renderingClassName + "], Rendered class: [" + renderedClassName + "].");
	ObjectRenderer renderer = (ObjectRenderer) OptionConverter.instantiateByClassName(renderingClassName,
		ObjectRenderer.class, null);
	if (renderer == null) {
	    LogLog.error("Could not instantiate renderer [" + renderingClassName + "].");
	    return;
	} else {
	    try {
		Class renderedClass = Loader.loadClass(renderedClassName);
		repository.setRenderer(renderedClass, renderer);
	    } catch (ClassNotFoundException e) {
		LogLog.error("Could not find class [" + renderedClassName + "].", e);
	    }
	}
    }

    /**
     * Find the appropriate renderer for the class type of the <code>o</code>
     * parameter. This is accomplished by calling the {@link #get(Class)} method.
     * Once a renderer is found, it is applied on the object <code>o</code> and the
     * result is returned as a {@link String}.
     */
    public String findAndRender(Object o) {
	if (o == null)
	    return null;
	else
	    return get(o.getClass()).doRender(o);
    }

    /**
     * Syntactic sugar method that calls {@link #get(Class)} with the class of the
     * object parameter.
     */
    public ObjectRenderer get(Object o) {
	if (o == null)
	    return null;
	else
	    return get(o.getClass());
    }

    /**
     * Search the parents of <code>clazz</code> for a renderer. The renderer closest
     * in the hierarchy will be returned. If no renderers could be found, then the
     * default renderer is returned.
     * 
     * <p>
     * The search first looks for a renderer configured for <code>clazz</code>. If a
     * renderer could not be found, then the search continues by looking at all the
     * interfaces implemented by <code>clazz</code> including the super-interfaces
     * of each interface. If a renderer cannot be found, then the search looks for a
     * renderer defined for the parent (superclass) of <code>clazz</code>. If that
     * fails, then all the interfaces implemented by the parent of
     * <code>clazz</code> are searched and so on.
     * 
     * <p>
     * For example, if A0, A1, A2 are classes and X0, X1, X2, Y0, Y1 are interfaces
     * where A2 extends A1 which in turn extends A0 and similarly X2 extends X1
     * which extends X0 and Y1 extends Y0. Let us also assume that A1 implements the
     * Y0 interface and that A2 implements the X2 interface.
     * 
     * <p>
     * The table below shows the results returned by the <code>get(A2.class)</code>
     * method depending on the renderers added to the map.
     * 
     * <p>
     * <table border="1">
     * <tr>
     * <th>Added renderers</th>
     * <th>Value returned by <code>get(A2.class)</code></th>
     * 
     * <tr>
     * <td><code>A0Renderer</code>
     * <td align="center"><code>A0Renderer</code>
     * 
     * <tr>
     * <td><code>A0Renderer, A1Renderer</code>
     * <td align="center"><code>A1Renderer</code>
     * 
     * <tr>
     * <td><code>X0Renderer</code>
     * <td align="center"><code>X0Renderer</code>
     * 
     * <tr>
     * <td><code>A1Renderer, X0Renderer</code>
     * <td align="center"><code>X0Renderer</code>
     * 
     * </table>
     * 
     * <p>
     * This search algorithm is not the most natural, although it is particularly
     * easy to implement. Future log4j versions <em>may</em> implement a more
     * intuitive search algorithm. However, the present algorithm should be
     * acceptable in the vast majority of circumstances.
     * 
     */
    public ObjectRenderer get(Class clazz) {
	// System.out.println("\nget: "+clazz);
	ObjectRenderer r = null;
	for (Class c = clazz; c != null; c = c.getSuperclass()) {
	    // System.out.println("Searching for class: "+c);
	    r = (ObjectRenderer) map.get(c);
	    if (r != null) {
		return r;
	    }
	    r = searchInterfaces(c);
	    if (r != null)
		return r;
	}
	return defaultRenderer;
    }

    ObjectRenderer searchInterfaces(Class c) {
	// System.out.println("Searching interfaces of class: "+c);

	ObjectRenderer r = (ObjectRenderer) map.get(c);
	if (r != null) {
	    return r;
	} else {
	    Class[] ia = c.getInterfaces();
	    for (int i = 0; i < ia.length; i++) {
		r = searchInterfaces(ia[i]);
		if (r != null)
		    return r;
	    }
	}
	return null;
    }

    public ObjectRenderer getDefaultRenderer() {
	return defaultRenderer;
    }

    public void clear() {
	map.clear();
    }

    /**
     * Register an {@link ObjectRenderer} for <code>clazz</code>.
     */
    public void put(Class clazz, ObjectRenderer or) {
	map.put(clazz, or);
    }
}
