/*
 * Copyright (c) 2010, grossmann
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * * Neither the name of the jo-widgets.org nor the
 *   names of its contributors may be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL jo-widgets.org BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

package org.jowidgets.api.toolkit;

import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ServiceLoader;

import org.jowidgets.classloading.api.SharedClassLoader;
import org.jowidgets.util.Assert;

/**
 * The toolkit interceptor accessor class
 */
public final class ToolkitInterceptor {

    private static CompositeToolkitInterceptorHolder compositeHolder;

    private ToolkitInterceptor() {}

    /**
     * Register a toolkit interceptor explicitly.
     * 
     * Only use this way of registration, if you are sure, that the toolkit that you are using was not already
     * created.
     * 
     * The recommended way is to use the Service Loader Mechanism for the {@link IToolkitInterceptorHolder} interface:
     * (http://docs.oracle.com/javase/6/docs/api/java/util/ServiceLoader.html)
     * 
     * @param holder The holder to register
     */
    public static synchronized void registerToolkitInterceptorHolder(final IToolkitInterceptorHolder holder) {
        Assert.paramNotNull(holder, "holder");
        getCompositeHolder().add(holder);
    }

    /**
     * @deprecated Use registerToolkitInterceptorHolder instead, because this method has a typo
     */
    @Deprecated
    public static synchronized void registerTollkitInterceptorHolder(final IToolkitInterceptorHolder holder) {
        registerToolkitInterceptorHolder(holder);
    }

    private static synchronized CompositeToolkitInterceptorHolder getCompositeHolder() {
        if (compositeHolder == null) {
            compositeHolder = new CompositeToolkitInterceptorHolder();
            final ServiceLoader<IToolkitInterceptorHolder> serviceLoader = ServiceLoader.load(
                    IToolkitInterceptorHolder.class,
                    SharedClassLoader.getCompositeClassLoader());
            final Iterator<IToolkitInterceptorHolder> iterator = serviceLoader.iterator();
            while (iterator.hasNext()) {
                compositeHolder.add(iterator.next());
            }
        }
        return compositeHolder;
    }

    /**
     * Gets the instance of the toolkit interceptor composite, that holds
     * all registered holders
     * 
     * @return The toolkit interceptor, never null
     */
    public static synchronized IToolkitInterceptor getInstance() {
        return getCompositeHolder().getToolkitInterceptor();
    }

    /**
     * This method should only be invoked by implementors of {@link IToolkit} after toolkit was created.
     * 
     * @param toolkit The toolkit that was created
     */
    public static void onToolkitCreate(final IToolkit toolkit) {
        getInstance().onToolkitCreate(toolkit);
    }

    private static class CompositeToolkitInterceptorHolder implements IToolkitInterceptorHolder {

        private final List<IToolkitInterceptorHolder> holders;

        private final IToolkitInterceptor toolkitInterceptor;

        CompositeToolkitInterceptorHolder() {
            this.holders = new LinkedList<IToolkitInterceptorHolder>();

            this.toolkitInterceptor = new IToolkitInterceptor() {

                @Override
                public void onToolkitCreate(final IToolkit toolkit) {
                    for (final IToolkitInterceptorHolder holder : holders) {
                        holder.getToolkitInterceptor().onToolkitCreate(toolkit);
                    }
                }
            };
        }

        void add(final IToolkitInterceptorHolder holder) {
            holders.add(holder);
            Collections.sort(holders, new Comparator<IToolkitInterceptorHolder>() {
                @Override
                public int compare(final IToolkitInterceptorHolder provider1, final IToolkitInterceptorHolder provider2) {
                    if (provider1 != null && provider2 != null) {
                        return provider1.getOrder() - provider2.getOrder();
                    }
                    return 0;
                }
            });
        }

        @Override
        public IToolkitInterceptor getToolkitInterceptor() {
            return toolkitInterceptor;
        }

        @Override
        public int getOrder() {
            return 0;
        }
    }

}