/*
 * Copyright (c) 2012, 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.model.item;

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.api.command.IAction;
import org.jowidgets.classloading.api.SharedClassLoader;
import org.jowidgets.util.Assert;
import org.jowidgets.util.priority.IPriorityValue;
import org.jowidgets.util.priority.LowHighPriority;
import org.jowidgets.util.priority.PrioritizedResultCreator;

public final class ActionItemVisibilityAspectPlugin {

    private static PluginComposite pluginComposite;

    private ActionItemVisibilityAspectPlugin() {}

    /**
     * Gets the visibility for an action
     * 
     * @param action The action to get visibility for
     * 
     * @return The visibility for the action, may be null
     */
    public static IPriorityValue<Boolean, LowHighPriority> getVisibility(final IAction action) {
        return getPluginCompositeImpl().getVisibility(action);
    }

    /**
     * Registers a IActionItemVisibilityAspectPlugin
     * 
     * @param plugin the plugin to register
     */
    public static void registerPlugin(final IActionItemVisibilityAspectPlugin plugin) {
        Assert.paramNotNull(plugin, "plugin");
        getPluginCompositeImpl().addPlugin(plugin);
    }

    private static synchronized PluginComposite getPluginCompositeImpl() {
        if (pluginComposite == null) {
            pluginComposite = new PluginComposite();
        }
        return pluginComposite;
    }

    private static final class PluginComposite {

        private final List<IActionItemVisibilityAspectPlugin> allPlugins;

        private PluginComposite() {
            this.allPlugins = new LinkedList<IActionItemVisibilityAspectPlugin>();
            this.allPlugins.addAll(getRegisteredPlugins());
            sortPlugins(allPlugins);
        }

        private IPriorityValue<Boolean, LowHighPriority> getVisibility(final IAction action) {
            return getVisibility(action, allPlugins);
        }

        private IPriorityValue<Boolean, LowHighPriority> getVisibility(
            final IAction action,
            final List<IActionItemVisibilityAspectPlugin> plugins) {
            if (plugins.size() > 0) {
                final PrioritizedResultCreator<Boolean, LowHighPriority> resultCreator;
                resultCreator = new PrioritizedResultCreator<Boolean, LowHighPriority>(LowHighPriority.HIGH);
                final Iterator<IActionItemVisibilityAspectPlugin> iterator = plugins.iterator();
                while (iterator.hasNext() && !resultCreator.hasMaxPrio()) {
                    resultCreator.addResult(iterator.next().getVisibilityAspect().getVisibility(action));
                }
                return resultCreator.getResult();
            }
            else {
                return null;
            }
        }

        private void addPlugin(final IActionItemVisibilityAspectPlugin plugin) {
            allPlugins.add(plugin);
            sortPlugins(allPlugins);
        }

        private void sortPlugins(final List<IActionItemVisibilityAspectPlugin> plugins) {
            Collections.sort(plugins, new Comparator<IActionItemVisibilityAspectPlugin>() {
                @Override
                public int compare(
                    final IActionItemVisibilityAspectPlugin plugin1,
                    final IActionItemVisibilityAspectPlugin plugin2) {
                    if (plugin1 != null && plugin2 != null) {
                        //add plugins with higher order before plugins with lower order
                        //because evaluation end, if max prio is reached
                        return plugin1.getOrder() - plugin2.getOrder();
                    }
                    return 0;
                }
            });
        }

        private List<IActionItemVisibilityAspectPlugin> getRegisteredPlugins() {
            final List<IActionItemVisibilityAspectPlugin> result = new LinkedList<IActionItemVisibilityAspectPlugin>();
            final ServiceLoader<IActionItemVisibilityAspectPlugin> service = ServiceLoader.load(
                    IActionItemVisibilityAspectPlugin.class,
                    SharedClassLoader.getCompositeClassLoader());
            if (service != null) {
                final Iterator<IActionItemVisibilityAspectPlugin> iterator = service.iterator();
                while (iterator.hasNext()) {
                    result.add(iterator.next());
                }
            }
            return result;
        }
    }
}