HelpButton.java

/*******************************************************************************
 * Copyright (c) 2012-2013 RelationWare, Benno Luthiger
 * 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:
 * RelationWare, Benno Luthiger
 ******************************************************************************/

package org.ripla.web.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import org.ripla.web.Activator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.vaadin.shared.ui.label.ContentMode;
import com.vaadin.ui.Alignment;
import com.vaadin.ui.Button;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.CustomComponent;
import com.vaadin.ui.HorizontalLayout;
import com.vaadin.ui.Label;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;
import com.vaadin.ui.Window;
import com.vaadin.ui.themes.BaseTheme;

/**
 * <p>
 * UI component that displays a <code>[Help]</code> link button. When clicked, a
 * window containing help text is displayed.
 * </p>
 * Usage:
 * 
 * <pre>
 * URL lHelpContent = this.getClass().getClassLoader().getResource("help.html");
 * layout.addComponent(new HelpButton("Help", lHelpContent, 700, 600));
 * </pre>
 * 
 * @author Luthiger
 */
@SuppressWarnings("serial")
public final class HelpButton extends CustomComponent {
	private static final Logger LOG = LoggerFactory.getLogger(HelpButton.class);

	private final static String NL = System.getProperty("line.separator"); //$NON-NLS-1$ // NOPMD 

	private final Map<URL, String> helpCache = new HashMap<URL, String>();

	/**
	 * HelpButton constructor.
	 * 
	 * @param inCaption
	 *            String the link button's caption
	 * @param inHelpContent
	 *            URL the file's url containing the html formatted help text to
	 *            display
	 * @param inWidth
	 *            int the popup windos's width
	 * @param inHeight
	 *            int the popup windos's height
	 */
	public HelpButton(final String inCaption, final URL inHelpContent,
			final int inWidth, final int inHeight) {
		super();

		final HorizontalLayout lLayout = new HorizontalLayout();
		lLayout.setStyleName("ripla-help"); //$NON-NLS-1$
		setCompositionRoot(lLayout);
		setWidth(SIZE_UNDEFINED, Unit.PIXELS);

		lLayout.setWidth(SIZE_UNDEFINED, Unit.PIXELS);
		Label lLabel = new Label("["); //$NON-NLS-1$
		RiplaViewHelper.makeUndefinedWidth(lLabel);
		lLayout.addComponent(lLabel);
		lLayout.addComponent(createLinkButton(inCaption, inHelpContent,
				inWidth, inHeight));
		lLabel = new Label("]"); //$NON-NLS-1$
		RiplaViewHelper.makeUndefinedWidth(lLabel);
		lLayout.addComponent(lLabel);
	}

	private Button createLinkButton(final String inCaption,
			final URL inHelpContent, final int inWidth, final int inHeight) {
		final Button outLink = new Button(inCaption);
		outLink.setStyleName(BaseTheme.BUTTON_LINK);
		outLink.addClickListener(new Button.ClickListener() {
			@Override
			public void buttonClick(final ClickEvent inEvent) {
				final HelpWindow lHelpWindow = new HelpWindow(Activator
						.getMessages().getMessage("help.window.title"), //$NON-NLS-1$
						getHelpText(inHelpContent), inWidth, inHeight);
				if (lHelpWindow.getParent() == null) {
					UI.getCurrent().addWindow(lHelpWindow);
				}
				lHelpWindow.setPosition(50, 50);
			}
		});
		return outLink;
	}

	private String getHelpText(final URL inHelpContent) {
		String out = helpCache.get(inHelpContent);
		if (out == null) {
			try {
				out = readHelpContent(inHelpContent);
			}
			catch (final IOException exc) {
				LOG.error("Problem reading from {}!", inHelpContent, exc); //$NON-NLS-1$
				out = String
						.format("<p>%s</p>", Activator.getMessages().getMessage("help.errormsg.readmsg")); //$NON-NLS-1$ //$NON-NLS-2$
			}
			helpCache.put(inHelpContent, out);
		}
		return out;
	}

	private String readHelpContent(final URL inHelpContent) throws IOException {
		final StringBuilder outHtml = new StringBuilder();
		InputStream lStream = null;
		InputStreamReader lReader = null;
		BufferedReader lBuffer = null;
		try {
			lStream = inHelpContent.openStream();
			lReader = new InputStreamReader(lStream);
			lBuffer = new BufferedReader(lReader);
			String lLine;
			while ((lLine = lBuffer.readLine()) != null) { // NOPMD
				outHtml.append(lLine).append(NL);
			}
		} finally {
			if (lBuffer != null) {
				try {
					lBuffer.close();
				}
				catch (final IOException exc) {
					LOG.error("Error encountered while closing the buffer!",
							exc);
				}
			}
			if (lReader != null) {
				try {
					lReader.close();
				}
				catch (final IOException exc) {
					LOG.error("Error encountered while closing the reader!",
							exc);
				}
			}
			if (lStream != null) {
				try {
					lStream.close();
				}
				catch (final IOException exc) {
					LOG.error("Error encountered while closing the stream!",
							exc);
				}
			}
		}
		return new String(outHtml);
	}

	// ---

	private static class HelpWindow extends Window {
		// private final transient Window helpWindow; // NOPMD by Luthiger on

		HelpWindow(final String inCaption, final String inHelpText,
				final int inWidth, final int inHeight) {
			super(inCaption);

			addStyleName("ripla-lookup"); //$NON-NLS-1$
			setWidth(inWidth, Unit.PIXELS);
			setHeight(inHeight, Unit.PIXELS);

			final VerticalLayout lLayout = new VerticalLayout();
			setContent(lLayout);
			lLayout.setSpacing(true);
			lLayout.setMargin(true);
			lLayout.setSpacing(true);
			lLayout.setSizeFull();
			lLayout.setStyleName("ripla-view"); //$NON-NLS-1$
			lLayout.addComponent(new Label(inHelpText, ContentMode.HTML));

			final Button lClose = new Button(Activator.getMessages()
					.getMessage("lookup.window.button.close"), //$NON-NLS-1$
					new Button.ClickListener() {
						@Override
						public void buttonClick(final ClickEvent inEvent) {
							UI.getCurrent().removeWindow(HelpWindow.this);
						}
					});
			lLayout.addComponent(lClose);
			lLayout.setComponentAlignment(lClose, Alignment.BOTTOM_RIGHT);
		}

		protected void setPosition(final int inPositionX, final int inPositionY) {
			setPositionX(inPositionX);
			setPositionX(inPositionY);
		}
	}

}