/*******************************************************************************
 * Copyright (c) 2004, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.internal;

import static org.eclipse.swt.events.SelectionListener.widgetSelectedAdapter;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.MenuItem;

/**
 * Represents a group of radio buttons in a menu. Each menu item is mapped onto
 * a particular value. The RadioMenu reports its state using the attached Model
 * object. That is, Model.getState() will return the value of the currently
 * selected radio button and Model.setState(value) will select the radio button
 * associated with the given value.
 */
public class RadioMenu implements IChangeListener {

	private Model data;

	private Menu parent;

	private List items = new ArrayList();

	SelectionListener selectionAdapter = widgetSelectedAdapter(e -> {
		Object newState = e.widget.getData();

		data.setState(newState, RadioMenu.this);
	});

	/**
	 * Creates a set of radio menu items on the given menu.
	 *
	 * @param parent  menu that will contain the menu items
	 * @param newData the model that will store the value of the currently selected
	 *                item
	 */
	public RadioMenu(Menu parent, Model newData) {
		this.parent = parent;
		this.data = newData;

		newData.addChangeListener(this);
	}

	/**
	 * Returns true iff the given values are considered equal.
	 *
	 * @param value1
	 * @param value2
	 * @return
	 */
	private static boolean isEqual(Object value1, Object value2) {
		if (value1 == null) {
			return value2 == null;
		} else if (value2 == null) {
			return false;
		}

		return value1.equals(value2);
	}

	/**
	 * Creates a new menu item with the given text and value. When the item is
	 * selected, the state of the model will change to match the given value.
	 *
	 * @param text
	 * @param value
	 */
	public void addMenuItem(String text, Object value) {
		MenuItem newItem = new MenuItem(parent, SWT.RADIO);

		newItem.setSelection(isEqual(data.getState(), value));
		newItem.setText(text);
		newItem.setData(value);
		items.add(newItem);

		newItem.addSelectionListener(selectionAdapter);
	}

	/**
	 * Disposes all menu items
	 */
	public void dispose() {
		Iterator iter = items.iterator();
		while (iter.hasNext()) {
			MenuItem next = (MenuItem) iter.next();

			if (!next.isDisposed()) {
				next.removeSelectionListener(selectionAdapter);
				next.dispose();
			}
		}

		items.clear();
	}

	/**
	 * Refreshes the selected menu items to match the current state of the model.
	 */
	private void refreshSelection() {
		Iterator iter = items.iterator();
		while (iter.hasNext()) {
			MenuItem next = (MenuItem) iter.next();

			if (!next.isDisposed()) {
				next.setSelection(isEqual(data.getState(), next.getData()));
			}
		}
	}

	@Override
	public void update(boolean changed) {
		refreshSelection();
	}

}
