/*******************************************************************************
 * Copyright (c) 2005, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.ui.internal.menus;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionDelta;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.IRegistryChangeEvent;
import org.eclipse.core.runtime.Platform;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.internal.registry.IWorkbenchRegistryConstants;
import org.eclipse.ui.internal.services.RegistryPersistence;
import org.eclipse.ui.menus.AbstractContributionFactory;

/**
 * <p>
 * A static class for accessing the registry.
 * </p>
 * <p>
 * This class is not intended for use outside of the
 * <code>org.eclipse.ui.workbench</code> plug-in.
 * </p>
 * 
 * @since 3.2
 */
final class MenuPersistence extends RegistryPersistence {

	private final WorkbenchMenuService menuService;

	/**
	 * Constructs a new instance of {@link MenuPersistence}.
	 * 
	 * @param workbenchMenuService
	 * 
	 * @param workbenchMenuService
	 *            The menu service which should be populated with the values
	 *            from the registry; must not be <code>null</code>.
	 */
	MenuPersistence(final WorkbenchMenuService workbenchMenuService) {
		if (workbenchMenuService == null) {
			throw new NullPointerException("The menu service cannot be null"); //$NON-NLS-1$
		}

		this.menuService = workbenchMenuService;
	}

	public final void dispose() {
		super.dispose();
	}

	protected final boolean isChangeImportant(final IRegistryChangeEvent event) {
		/*
		 * TODO Menus will need to be re-read (i.e., re-verified) if any of the
		 * menu extensions change (i.e., menus), or if any of the command
		 * extensions change (i.e., action definitions).
		 */
		return false;
	}

	public boolean menusNeedUpdating(final IRegistryChangeEvent event) {
		final IExtensionDelta[] menuDeltas = event.getExtensionDeltas(
				PlatformUI.PLUGIN_ID, IWorkbenchRegistryConstants.PL_MENUS);
		if (menuDeltas.length == 0) {
			return false;
		}

		return true;
	}

	/**
	 * <p>
	 * Reads all of the menu elements and action sets from the registry.
	 * </p>
	 * <p>
	 * TODO Add support for modifications.
	 * </p>
	 */
	protected final void read() {
		super.read();

		// Read legacy 3.2 'trim' additions
		readTrimAdditions();

		// read the 3.3 menu additions
		readAdditions();
	}

	//
	// 3.3 menu extension code
	// 

	public void readTrimAdditions() {
		if (menuService == null)
			return;

		final IExtensionRegistry registry = Platform.getExtensionRegistry();
		final IConfigurationElement[] configElements = registry
				.getConfigurationElementsFor(EXTENSION_MENUS);

		// Create a cache entry for every menu addition
		for (int i = 0; i < configElements.length; i++) {
			// Only process 'group' entries
			if (!TAG_GROUP.equals(configElements[i].getName()))
				continue;

			String id = configElements[i]
					.getAttribute(IWorkbenchRegistryConstants.ATT_ID);

			// Define the initial URI spec
			String uriSpec = "toolbar:" + id; //$NON-NLS-1$
			if (configElements[i].getChildren(TAG_LOCATION).length > 0) {
				IConfigurationElement location = configElements[i]
						.getChildren(TAG_LOCATION)[0];
				if (location.getChildren(TAG_ORDER).length > 0) {
					IConfigurationElement order = location
							.getChildren(TAG_ORDER)[0];

					String pos = order
							.getAttribute(IWorkbenchRegistryConstants.ATT_POSITION);
					String relTo = order
							.getAttribute(IWorkbenchRegistryConstants.ATT_RELATIVE_TO);
					uriSpec += "?" + pos + "=" + relTo; //$NON-NLS-1$ //$NON-NLS-2$

					// HACK! We expect that the new trim group is -always-
					// relative to
					// one of the 'default' groups; indicating which trim area
					// they're in
					MenuLocationURI uri = new MenuLocationURI(
							"toolbar:" + relTo); //$NON-NLS-1$
					List trimAdditions = menuService.getAdditionsForURI(uri);

					//
					// TODO convert the TrimAdditionCacheEntry over to use the
					// new MenuCacheEntry and addCacheForURI(*)
					// OK, add the addition to this area
					uri = new MenuLocationURI(uriSpec);
					trimAdditions.add(new TrimAdditionCacheEntry(
							configElements[i], uri, menuService));
				} else {
					// Must be a default group; make a new entry cache
					MenuLocationURI uri = new MenuLocationURI(uriSpec);

					// NOTE: 'getAdditionsForURI' forces creation
					menuService.getAdditionsForURI(uri);
				}
			}
		}
	}

	public void readAdditions() {
		final IExtensionRegistry registry = Platform.getExtensionRegistry();
		ArrayList configElements = new ArrayList();

		final IConfigurationElement[] menusExtensionPoint = registry
				.getConfigurationElementsFor(EXTENSION_MENUS);

		// Create a cache entry for every menu addition;
		for (int i = 0; i < menusExtensionPoint.length; i++) {
			if (PL_MENU_CONTRIBUTION.equals(menusExtensionPoint[i].getName())) {
				configElements.add(menusExtensionPoint[i]);
			}
		}
		Comparator comparer = new Comparator() {
			public int compare(Object o1, Object o2) {
				IConfigurationElement c1 = (IConfigurationElement) o1;
				IConfigurationElement c2 = (IConfigurationElement) o2;
				return c1.getNamespaceIdentifier().compareToIgnoreCase(
						c2.getNamespaceIdentifier());
			}
		};
		Collections.sort(configElements, comparer);

		Iterator i = configElements.iterator();
		while (i.hasNext()) {
			final IConfigurationElement configElement = (IConfigurationElement) i
					.next();
			
			AbstractContributionFactory newFactory = null;
			
			if (isProgramaticContribution(configElement))
				newFactory = new ProxyMenuAdditionCacheEntry(
						configElement
								.getAttribute(IWorkbenchRegistryConstants.TAG_LOCATION_URI),
								configElement.getNamespaceIdentifier(), configElement);

			else
				newFactory = new MenuAdditionCacheEntry(
						menuService,
						configElement,
						configElement
								.getAttribute(IWorkbenchRegistryConstants.TAG_LOCATION_URI),
								configElement.getNamespaceIdentifier());

			if (newFactory != null)
				menuService.addContributionFactory(newFactory);
			
		}
	}
	
	/**
	 * Return whether or not this contribution is programmatic (ie: has a class attribute).
	 * 
	 * @param menuAddition
	 * @return whether or not this contribution is programamtic
	 * @since 3.5
	 */
	private boolean isProgramaticContribution(IConfigurationElement menuAddition) {
		return menuAddition.getAttribute(IWorkbenchRegistryConstants.ATT_CLASS) != null;
	}
}