/*******************************************************************************

 * Copyright (c) 2006 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.actions;

import java.util.ArrayList;

import java.util.List;

import org.eclipse.jface.action.IMenuManager;

import org.eclipse.jface.action.MenuManager;

import org.eclipse.swt.custom.StyledText;

import org.eclipse.swt.graphics.GC;

import org.eclipse.swt.graphics.Point;

import org.eclipse.swt.graphics.Rectangle;

import org.eclipse.swt.widgets.Control;

import org.eclipse.swt.widgets.Display;

import org.eclipse.swt.widgets.Menu;

import org.eclipse.swt.widgets.Table;

import org.eclipse.swt.widgets.TableItem;

import org.eclipse.swt.widgets.Tree;

import org.eclipse.swt.widgets.TreeItem;

/**

 * Abstract class that is capable of creating a context menu under the mouse

 * pointer.

 * 

 * @since 3.3

 */

public abstract class QuickMenuCreator {

	private static final int CHAR_INDENT = 3;

	private Menu quickMenu;

	/**

	 * Create the context menu.

	 */

	public void createMenu() {

		Display display = Display.getCurrent();

		if (display == null) {

			return;

		}

		Control focus = display.getFocusControl();

		if (focus == null || focus.isDisposed()) {

			return;

		}

		MenuManager menu = new MenuManager();

		fillMenu(menu);

		if (quickMenu != null) {

			quickMenu.dispose();

			quickMenu = null;

		}

		quickMenu = menu.createContextMenu(focus.getShell());

		Point location = computeMenuLocation(focus);

		if (location == null) {

			return;

		}

		quickMenu.setLocation(location);

		quickMenu.setVisible(true);

	}

	/**

	 * Create the contents of the context menu.

	 * 

	 * @param menu

	 *            the menu to fill

	 */

	protected abstract void fillMenu(IMenuManager menu);

	/**

	 * Determine the optimal point for this menu to appear.

	 * 

	 * @param focus

	 *            the focus control

	 * @return the optimal placement

	 */

	private Point computeMenuLocation(Control focus) {

		Point cursorLocation = focus.getDisplay().getCursorLocation();

		Rectangle clientArea = null;

		Point result = null;

		if (focus instanceof StyledText) {

			StyledText styledText = (StyledText) focus;

			clientArea = styledText.getClientArea();

			result = computeMenuLocation(styledText);

		} else if (focus instanceof Tree) {

			Tree tree = (Tree) focus;

			clientArea = tree.getClientArea();

			result = computeMenuLocation(tree);

		} else if (focus instanceof Table) {

			Table table = (Table) focus;

			clientArea = table.getClientArea();

			result = computeMenuLocation(table);

		}

		if (result == null) {

			result = focus.toControl(cursorLocation);

		}

		if (clientArea != null && !clientArea.contains(result)) {

			result = new Point(clientArea.x + clientArea.width / 2,

					clientArea.y + clientArea.height / 2);

		}

		Rectangle shellArea = focus.getShell().getClientArea();

		if (!shellArea.contains(focus.getShell().toControl(

				focus.toDisplay(result)))) {

			result = new Point(shellArea.x + shellArea.width / 2, shellArea.y

					+ shellArea.height / 2);

		}

		return focus.toDisplay(result);

	}

	/**

	 * Hook to compute the menu location if the focus widget is a styled text

	 * widget.

	 * 

	 * @param text

	 *            the styled text widget that has the focus

	 * 

	 * @return a widget relative position of the menu to pop up or

	 *         <code>null</code> if now position inside the widget can be

	 *         computed

	 */

	private Point computeMenuLocation(StyledText text) {

		Point result = text.getLocationAtOffset(text.getCaretOffset());

		result.y += text.getLineHeight();

		if (!text.getClientArea().contains(result)) {

			return null;

		}

		return result;

	}

	/**

	 * Hook to compute the menu location if the focus widget is a tree widget.

	 * 

	 * @param tree

	 *            the tree widget that has the focus

	 * 

	 * @return a widget relative position of the menu to pop up or

	 *         <code>null</code> if now position inside the widget can be

	 *         computed

	 */

	private Point computeMenuLocation(Tree tree) {

		TreeItem[] items = tree.getSelection();

		Rectangle clientArea = tree.getClientArea();

		switch (items.length) {

		case 0:

			return null;

		case 1:

			Rectangle bounds = items[0].getBounds();

			Rectangle intersect = clientArea.intersection(bounds);

			if (intersect != null && intersect.height == bounds.height) {

				return new Point(Math.max(0, bounds.x

						+ getAvarageCharWith(tree) * CHAR_INDENT), bounds.y

						+ bounds.height);

			}

			return null;

		default:

			Rectangle[] rectangles = new Rectangle[items.length];

			for (int i = 0; i < rectangles.length; i++) {

				rectangles[i] = items[i].getBounds();

			}

			Point cursorLocation = tree.getDisplay().getCursorLocation();

			Point result = findBestLocation(getIncludedPositions(rectangles,

					clientArea), tree.toControl(cursorLocation));

			if (result != null) {

				result.x = result.x + getAvarageCharWith(tree) * CHAR_INDENT;

			}

			return result;

		}

	}

	/**

	 * Hook to compute the menu location if the focus widget is a table widget.

	 * 

	 * @param table

	 *            the table widget that has the focus

	 * 

	 * @return a widget relative position of the menu to pop up or

	 *         <code>null</code> if now position inside the widget can be

	 *         computed

	 */

	private Point computeMenuLocation(Table table) {

		TableItem[] items = table.getSelection();

		Rectangle clientArea = table.getClientArea();

		switch (items.length) {

		case 0: {

			return null;

		}

		case 1: {

			Rectangle bounds = items[0].getBounds(0);

			Rectangle iBounds = items[0].getImageBounds(0);

			Rectangle intersect = clientArea.intersection(bounds);

			if (intersect != null && intersect.height == bounds.height) {

				return new Point(Math.max(0, bounds.x + iBounds.width

						+ getAvarageCharWith(table) * CHAR_INDENT), bounds.y

						+ bounds.height);

			}

			return null;

		}

		default: {

			Rectangle[] rectangles = new Rectangle[items.length];

			for (int i = 0; i < rectangles.length; i++) {

				rectangles[i] = items[i].getBounds(0);

			}

			Rectangle iBounds = items[0].getImageBounds(0);

			Point cursorLocation = table.getDisplay().getCursorLocation();

			Point result = findBestLocation(getIncludedPositions(rectangles,

					clientArea), table.toControl(cursorLocation));

			if (result != null) {

				result.x = result.x + iBounds.width + getAvarageCharWith(table)

						* CHAR_INDENT;

			}

			return result;

		}

		}

	}

	private Point[] getIncludedPositions(Rectangle[] rectangles,

			Rectangle widgetBounds) {

		List result = new ArrayList();

		for (int i = 0; i < rectangles.length; i++) {

			Rectangle rectangle = rectangles[i];

			Rectangle intersect = widgetBounds.intersection(rectangle);

			if (intersect != null && intersect.height == rectangle.height) {

				result.add(new Point(intersect.x, intersect.y

						+ intersect.height));

			}

		}

		return (Point[]) result.toArray(new Point[result.size()]);

	}

	private Point findBestLocation(Point[] points, Point relativeCursor) {

		Point result = null;

		double bestDist = Double.MAX_VALUE;

		for (int i = 0; i < points.length; i++) {

			Point point = points[i];

			int a = 0;

			int b = 0;

			if (point.x > relativeCursor.x) {

				a = point.x - relativeCursor.x;

			} else {

				a = relativeCursor.x - point.x;

			}

			if (point.y > relativeCursor.y) {

				b = point.y - relativeCursor.y;

			} else {

				b = relativeCursor.y - point.y;

			}

			double dist = Math.sqrt(a * a + b * b);

			if (dist < bestDist) {

				result = point;

				bestDist = dist;

			}

		}

		return result;

	}

	private int getAvarageCharWith(Control control) {

		GC gc = null;

		try {

			gc = new GC(control);

			return gc.getFontMetrics().getAverageCharWidth();

		} finally {

			if (gc != null) {

				gc.dispose();

			}

		}

	}

	/**

	 * Dispose of this quick menu creator. Subclasses should ensure that they

	 * call this method.

	 */

	public void dispose() {

		if (quickMenu != null) {

			quickMenu.dispose();

			quickMenu = null;

		}

	}

}

import org.eclipse.ui.actions.QuickMenuCreator;