/*******************************************************************************
 * Copyright (c) 2000, 2018 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.jface.internal.text.html;

import java.io.IOException;
import java.io.StringReader;
import java.util.Iterator;

import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTError;
import org.eclipse.swt.browser.Browser;
import org.eclipse.swt.browser.LocationListener;
import org.eclipse.swt.browser.ProgressAdapter;
import org.eclipse.swt.browser.ProgressEvent;
import org.eclipse.swt.custom.StyleRange;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.graphics.TextLayout;
import org.eclipse.swt.graphics.TextStyle;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Slider;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.ListenerList;

import org.eclipse.jface.action.ToolBarManager;
import org.eclipse.jface.resource.JFaceResources;

import org.eclipse.jface.text.AbstractInformationControl;
import org.eclipse.jface.text.IDelayedInputChangeProvider;
import org.eclipse.jface.text.IInformationControlExtension2;
import org.eclipse.jface.text.IInputChangedListener;
import org.eclipse.jface.text.TextPresentation;


/**
 * Displays HTML information in a {@link org.eclipse.swt.browser.Browser} widget.
 * <p>
 * This {@link IInformationControlExtension2} expects {@link #setInput(Object)} to be called with an
 * argument of type {@link BrowserInformationControlInput}.
 * </p>
 * <p>
 * Moved into this package from <code>org.eclipse.jface.internal.text.revisions</code>.
 * </p>
 * <p>
 * This class may be instantiated; it is not intended to be subclassed.
 * </p>
 * <p>
 * Current problems:
 * <ul>
 * <li>the size computation is too small</li>
 * <li>focusLost event is not sent - see https://bugs.eclipse.org/bugs/show_bug.cgi?id=84532</li>
 * </ul>
 * </p>
 *
 * @since 3.2
 */
public class BrowserInformationControl extends AbstractInformationControl implements IInformationControlExtension2, IDelayedInputChangeProvider {


	/**
	 * Tells whether the SWT Browser widget and hence this information
	 * control is available.
	 *
	 * @param parent the parent component used for checking or <code>null</code> if none
	 * @return <code>true</code> if this control is available
	 */
	public static boolean isAvailable(Composite parent) {
		if (!fgAvailabilityChecked) {
			try {
				Browser browser= new Browser(parent, SWT.NONE);
				browser.dispose();
				fgIsAvailable= true;

				Slider sliderV= new Slider(parent, SWT.VERTICAL);
				Slider sliderH= new Slider(parent, SWT.HORIZONTAL);
				int width= sliderV.computeSize(SWT.DEFAULT, SWT.DEFAULT).x;
				int height= sliderH.computeSize(SWT.DEFAULT, SWT.DEFAULT).y;
				fgScrollBarSize= new Point(width, height);
				sliderV.dispose();
				sliderH.dispose();
			} catch (SWTError er) {
				fgIsAvailable= false;
			} finally {
				fgAvailabilityChecked= true;
			}
		}

		return fgIsAvailable;
	}


	/**
	 * Minimal size constraints.
	 * @since 3.2
	 */
	private static final int MIN_WIDTH= 80;

	private static final int MIN_HEIGHT= 50;


	/**
	 * Availability checking cache.
	 */
	private static boolean fgIsAvailable= false;

	private static boolean fgAvailabilityChecked= false;

	/**
	 * Cached scroll bar width and height
	 * @since 3.4
	 */
	private static Point fgScrollBarSize;

	/** The control's browser widget */
	private Browser fBrowser;

	/** Tells whether the browser has content */
	private boolean fBrowserHasContent;

	/** Text layout used to approximate size of content when rendered in browser */
	private TextLayout fTextLayout;

	/** Bold text style */
	private TextStyle fBoldStyle;

	private BrowserInformationControlInput fInput;

	/**
	 * <code>true</code> iff the browser has completed loading of the last
	 * input set via {@link #setInformation(String)}.
	 * @since 3.4
	 */
	private boolean fCompleted= false;

	/**
	 * The listener to be notified when a delayed location changing event happened.
	 * @since 3.4
	 */
	private IInputChangedListener fDelayedInputChangeListener;

	/**
	 * The listeners to be notified when the input changed.
	 * @since 3.4
	 */
	private ListenerList<IInputChangedListener> fInputChangeListeners= new ListenerList<>(ListenerList.IDENTITY);

	/**
	 * The symbolic name of the font used for size computations, or <code>null</code> to use dialog font.
	 * @since 3.4
	 */
	private final String fSymbolicFontName;


	/**
	 * Creates a browser information control with the given shell as parent.
	 *
	 * @param parent the parent shell
	 * @param symbolicFontName the symbolic name of the font used for size computations
	 * @param resizable <code>true</code> if the control should be resizable
	 * @since 3.4
	 */
	public BrowserInformationControl(Shell parent, String symbolicFontName, boolean resizable) {
		super(parent, resizable);
		fSymbolicFontName= symbolicFontName;
		create();
	}

	/**
	 * Creates a browser information control with the given shell as parent.
	 *
	 * @param parent the parent shell
	 * @param symbolicFontName the symbolic name of the font used for size computations
	 * @param statusFieldText the text to be used in the optional status field
	 *            or <code>null</code> if the status field should be hidden
	 * @since 3.4
	 */
	public BrowserInformationControl(Shell parent, String symbolicFontName, String statusFieldText) {
		super(parent, statusFieldText);
		fSymbolicFontName= symbolicFontName;
		create();
	}

	/**
	 * Creates a browser information control with the given shell as parent.
	 *
	 * @param parent the parent shell
	 * @param symbolicFontName the symbolic name of the font used for size computations
	 * @param toolBarManager the manager or <code>null</code> if toolbar is not desired
	 * @since 3.4
	 */
	public BrowserInformationControl(Shell parent, String symbolicFontName, ToolBarManager toolBarManager) {
		super(parent, toolBarManager);
		fSymbolicFontName= symbolicFontName;
		create();
	}

	@Override
	protected void createContent(Composite parent) {
		fBrowser= new Browser(parent, SWT.NONE);
		fBrowser.setJavascriptEnabled(false);

		Display display= getShell().getDisplay();
		fBrowser.setForeground(display.getSystemColor(SWT.COLOR_INFO_FOREGROUND));
		fBrowser.setBackground(display.getSystemColor(SWT.COLOR_INFO_BACKGROUND));

		fBrowser.addProgressListener(new ProgressAdapter() {
			@Override
			public void completed(ProgressEvent event) {
				fCompleted= true;
			}
		});
		// Cancel opening of new windows
		fBrowser.addOpenWindowListener(event -> event.required= true);

		// Replace browser's built-in context menu with none
		fBrowser.setMenu(new Menu(getShell(), SWT.NONE));

		createTextLayout();
	}

	/**
	 * {@inheritDoc}
	 * @deprecated use {@link #setInput(Object)}
	 */
	@Deprecated
	@Override
	public void setInformation(final String content) {
		setInput(new BrowserInformationControlInput(null) {
			@Override
			public String getHtml() {
				return content;
			}

			@Override
			public String getInputName() {
				return ""; //$NON-NLS-1$
			}

			@Override
			public Object getInputElement() {
				return content;
			}
		});
	}

	/**
	 * {@inheritDoc} This control can handle {@link String} and
	 * {@link BrowserInformationControlInput}.
	 */
	@Override
	public void setInput(Object input) {
		Assert.isLegal(input == null || input instanceof String || input instanceof BrowserInformationControlInput, input != null ? input.getClass().getName() : "null"); //$NON-NLS-1$

		if (input instanceof String) {
			setInformation((String)input);
			return;
		}

		fInput= (BrowserInformationControlInput)input;

		String content= null;
		if (fInput != null)
			content= fInput.getHtml();

		fBrowserHasContent= content != null && content.length() > 0;

		if (!fBrowserHasContent)
			content= "<html><body ></html>"; //$NON-NLS-1$

		boolean RTL= (getShell().getStyle() & SWT.RIGHT_TO_LEFT) != 0;
		boolean resizable= isResizable();

		// The default "overflow:auto" would not result in a predictable width for the client area
		// and the re-wrapping would cause visual noise
		String[] styles= null;
		if (RTL && resizable)
			styles= new String[] { "direction:rtl;", "overflow:scroll;", "word-wrap:break-word;" }; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
		else if (RTL && !resizable)
			styles= new String[] { "direction:rtl;", "overflow:hidden;", "word-wrap:break-word;" }; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
		else if (!resizable)
			//XXX: In IE, "word-wrap: break-word;" causes bogus wrapping even in non-broken words :-(see e.g. Javadoc of String).
			// Re-check whether we really still need this now that the Javadoc Hover header already sets this style.
			styles= new String[] { "overflow:hidden;"/*, "word-wrap: break-word;"*/}; //$NON-NLS-1$
		else
			styles= new String[] { "overflow:scroll;" }; //$NON-NLS-1$

		StringBuilder buffer= new StringBuilder(content);
		HTMLPrinter.insertStyles(buffer, styles);
		content= buffer.toString();

		/*
		 * XXX: Should add some JavaScript here that shows something like
		 * "(continued...)" or "..." at the end of the visible area when the page overflowed
		 * with "overflow:hidden;".
		 */

		fCompleted= false;
		fBrowser.setText(content);

		for (IInputChangedListener listener : fInputChangeListeners) {
			listener.inputChanged(fInput);
		}
	}

	@Override
	public void setVisible(boolean visible) {
		Shell shell= getShell();
		if (shell.isVisible() == visible)
			return;

		if (!visible) {
			super.setVisible(false);
			setInput(null);
			return;
		}

		/*
		 * The Browser widget flickers when made visible while it is not completely loaded.
		 * The fix is to delay the call to setVisible until either loading is completed
		 * (see ProgressListener in constructor), or a timeout has been reached.
		 */
		final Display display= shell.getDisplay();

		// Make sure the display wakes from sleep after timeout:
		display.timerExec(100, () -> fCompleted= true);

		while (!fCompleted) {
			// Drive the event loop to process the events required to load the browser widget's contents:
			if (!display.readAndDispatch()) {
				display.sleep();
			}
		}

		shell= getShell();
		if (shell == null || shell.isDisposed())
			return;

		/*
		 * Avoids flickering when replacing hovers, especially on Vista in ON_CLICK mode.
		 * Causes flickering on GTK. Carbon does not care.
		 */
		if ("win32".equals(SWT.getPlatform())) //$NON-NLS-1$
			shell.moveAbove(null);

		super.setVisible(true);
	}

	@Override
	public void setSize(int width, int height) {
		fBrowser.setRedraw(false); // avoid flickering
		try {
			super.setSize(width, height);
		} finally {
			fBrowser.setRedraw(true);
		}
	}

	/**
	 * Creates and initializes the text layout used
	 * to compute the size hint.
	 *
	 * @since 3.2
	 */
	private void createTextLayout() {
		fTextLayout= new TextLayout(fBrowser.getDisplay());

		// Initialize fonts
		String symbolicFontName= fSymbolicFontName == null ? JFaceResources.DIALOG_FONT : fSymbolicFontName;
		Font font= JFaceResources.getFont(symbolicFontName);
		fTextLayout.setFont(font);
		fTextLayout.setWidth(-1);
		font= JFaceResources.getFontRegistry().getBold(symbolicFontName);
		fBoldStyle= new TextStyle(font, null, null);

		// Compute and set tab width
		fTextLayout.setText("    "); //$NON-NLS-1$
		int tabWidth= fTextLayout.getBounds().width;
		fTextLayout.setTabs(new int[] { tabWidth });
		fTextLayout.setText(""); //$NON-NLS-1$
	}

	@Override
	protected void handleDispose() {
		if (fTextLayout != null) {
			fTextLayout.dispose();
			fTextLayout= null;
		}
		fBrowser= null;

		super.handleDispose();
	}

	@Override
	public Point computeSizeHint() {
		Point sizeConstraints= getSizeConstraints();
		Rectangle trim= computeTrim();
		int height= trim.height;

		//FIXME: The HTML2TextReader does not render <p> like a browser.
		// Instead of inserting an empty line, it just adds a single line break.
		// Furthermore, the indentation of <dl><dd> elements is too small (e.g with a long @see line)
		TextPresentation presentation= new TextPresentation();
		String text;
		try (HTML2TextReader reader= new HTML2TextReader(new StringReader(fInput.getHtml()), presentation)) {
			text= reader.getString();
		} catch (IOException e) {
			text= ""; //$NON-NLS-1$
		}

		fTextLayout.setText(text);
		fTextLayout.setWidth(sizeConstraints == null ? SWT.DEFAULT : sizeConstraints.x - trim.width);
		Iterator<StyleRange> iter= presentation.getAllStyleRangeIterator();
		while (iter.hasNext()) {
			StyleRange sr= iter.next();
			if (sr.fontStyle == SWT.BOLD)
				fTextLayout.setStyle(fBoldStyle, sr.start, sr.start + sr.length - 1);
		}

		Rectangle bounds= fTextLayout.getBounds(); // does not return minimum width, see https://bugs.eclipse.org/bugs/show_bug.cgi?id=217446
		int lineCount= fTextLayout.getLineCount();
		int textWidth= 0;
		for (int i= 0; i < lineCount; i++) {
			Rectangle rect= fTextLayout.getLineBounds(i);
			int lineWidth= rect.x + rect.width;
			if (i == 0)
				lineWidth+= fInput.getLeadingImageWidth();
			textWidth= Math.max(textWidth, lineWidth);
		}
		bounds.width= textWidth;
		fTextLayout.setText(""); //$NON-NLS-1$

		int minWidth= bounds.width;
		height= height + bounds.height;

		// Add some air to accommodate for different browser renderings
		minWidth+= 15;
		height+= 15;


		// Apply max size constraints
		if (sizeConstraints != null) {
			if (sizeConstraints.x != SWT.DEFAULT)
				minWidth= Math.min(sizeConstraints.x, minWidth + trim.width);
			if (sizeConstraints.y != SWT.DEFAULT)
				height= Math.min(sizeConstraints.y, height);
		}

		// Ensure minimal size
		int width= Math.max(MIN_WIDTH, minWidth);
		height= Math.max(MIN_HEIGHT, height);

		return new Point(width, height);
	}

	@Override
	public Rectangle computeTrim() {
		Rectangle trim= super.computeTrim();
		if (isResizable()) {
			boolean RTL= (getShell().getStyle() & SWT.RIGHT_TO_LEFT) != 0;
			if (RTL) {
				trim.x-= fgScrollBarSize.x;
			}
			trim.width+= fgScrollBarSize.x;
			trim.height+= fgScrollBarSize.y;
		}
		return trim;
	}

	/**
	 * Adds the listener to the collection of listeners who will be
	 * notified when the current location has changed or is about to change.
	 *
	 * @param listener the location listener
	 * @since 3.4
	 */
	public void addLocationListener(LocationListener listener) {
		fBrowser.addLocationListener(listener);
	}

	@Override
	public void setForegroundColor(Color foreground) {
		super.setForegroundColor(foreground);
		fBrowser.setForeground(foreground);
	}

	@Override
	public void setBackgroundColor(Color background) {
		super.setBackgroundColor(background);
		fBrowser.setBackground(background);
	}

	@Override
	public boolean hasContents() {
		return fBrowserHasContent;
	}

	/**
	 * Adds a listener for input changes to this input change provider.
	 * Has no effect if an identical listener is already registered.
	 *
	 * @param inputChangeListener the listener to add
	 * @since 3.4
	 */
	public void addInputChangeListener(IInputChangedListener inputChangeListener) {
		Assert.isNotNull(inputChangeListener);
		fInputChangeListeners.add(inputChangeListener);
	}

	/**
	 * Removes the given input change listener from this input change provider.
	 * Has no effect if an identical listener is not registered.
	 *
	 * @param inputChangeListener the listener to remove
	 * @since 3.4
	 */
	public void removeInputChangeListener(IInputChangedListener inputChangeListener) {
		fInputChangeListeners.remove(inputChangeListener);
	}

	@Override
	public void setDelayedInputChangeListener(IInputChangedListener inputChangeListener) {
		fDelayedInputChangeListener= inputChangeListener;
	}

	/**
	 * Tells whether a delayed input change listener is registered.
	 *
	 * @return <code>true</code> iff a delayed input change
	 *         listener is currently registered
	 * @since 3.4
	 */
	public boolean hasDelayedInputChangeListener() {
		return fDelayedInputChangeListener != null;
	}

	/**
	 * Notifies listeners of a delayed input change.
	 *
	 * @param newInput the new input, or <code>null</code> to request cancellation
	 * @since 3.4
	 */
	public void notifyDelayedInputChange(Object newInput) {
		if (fDelayedInputChangeListener != null)
			fDelayedInputChangeListener.inputChanged(newInput);
	}

	@Override
	public String toString() {
		String style= (getShell().getStyle() & SWT.RESIZE) == 0 ? "fixed" : "resizeable"; //$NON-NLS-1$ //$NON-NLS-2$
		return super.toString() + " -  style: " + style; //$NON-NLS-1$
	}

	/**
	 * @return the current browser input or <code>null</code>
	 */
	public BrowserInformationControlInput getInput() {
		return fInput;
	}

	@Override
	public Point computeSizeConstraints(int widthInChars, int heightInChars) {
		if (fSymbolicFontName == null)
			return null;

		GC gc= new GC(fBrowser);
		Font font= JFaceResources.getFont(fSymbolicFontName);
		gc.setFont(font);
		double width= gc.getFontMetrics().getAverageCharacterWidth();
		int height= gc.getFontMetrics().getHeight();
		gc.dispose();

		return new Point((int) (widthInChars * width), heightInChars * height);
	}

}
