plugins/org.eclipse.app4mc.amalthea.model.editor.contribution/src/org/eclipse/app4mc/amalthea/model/editor/contribution/menu/MenuBuilder.java

/*********************************************************************************
 * Copyright (c) 2021 Robert Bosch GmbH and others.
 *
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     Robert Bosch GmbH - initial API and implementation
 ********************************************************************************
 */

package org.eclipse.app4mc.amalthea.model.editor.contribution.menu;

import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.StringTokenizer;

import org.eclipse.e4.ui.model.application.ui.menu.MHandledMenuItem;
import org.eclipse.e4.ui.model.application.ui.menu.MMenu;
import org.eclipse.e4.ui.model.application.ui.menu.MMenuElement;
import org.eclipse.e4.ui.model.application.ui.menu.MMenuFactory;

/**
 * Builds a hierarchical menu structure based on path description of added menu items.
 *
 * Path segments are separated by "|".
 *
 */
public class MenuBuilder {

	private Map<String, MenuBuilder> subMenus = new HashMap<>();
	private Map<String, MHandledMenuItem> menuItems = new HashMap<>();

	/**
	 * Adds a menu item to the menu.
	 *
	 * @param path		describes the position in the hierarchical menu (e.g. "Actions | Undo")
	 * @param menuItem	the configured menu item (the last segment of the path is set as label)
	 */
	public void addMenuItem(String path, MHandledMenuItem menuItem) {
		StringTokenizer tokenizer = new StringTokenizer(path, "|");
		addMenuItem(tokenizer, menuItem);
	}

	private void addMenuItem(StringTokenizer tokenizer, MHandledMenuItem menuItem) {
		String label = tokenizer.nextToken().trim();
		if (tokenizer.countTokens() == 0) {
			// last token -> add menu item
			menuItem.setLabel(label);
			menuItems.put(label, menuItem);
		} else {
			// intermediate token -> enter sub menu
			MenuBuilder builder = subMenus.computeIfAbsent(label, k -> new MenuBuilder());
			builder.addMenuItem(tokenizer, menuItem);
		}
	}

	/**
	 * Adds the menu structure (sub menus and menu items) to a given list of menu elements.
	 * <p>
	 * Order:
	 * <ul>
	 * <li>sub menus before menu entries</li>
	 * <li>sub menus in alphabetic order</li>
	 * <li>menu entries in alphabetic order</li>
	 * </ul>
	 *
	 * @param items
	 */
	public void populateMenuElementsList(List<MMenuElement> items) {
		// add sub menus
		subMenus.entrySet().stream()
			.sorted(Comparator.comparing(Entry::getKey))
			.forEachOrdered(e -> {
				MMenu subMenu = MMenuFactory.INSTANCE.createMenu();
				subMenu.setLabel(e.getKey());
				items.add(subMenu);
				e.getValue().populateMenuElementsList(subMenu.getChildren());
			});
		// add menu items
		menuItems.entrySet().stream()
		.sorted(Comparator.comparing(Entry::getKey))
		.forEachOrdered(e -> items.add(e.getValue()));
	}

}