/*=============================================================================#
 # Copyright (c) 2009, 2017 Stephan Wahlbrink 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, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.internal.nico.ui.console;

import org.eclipse.jface.text.AbstractDocument;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IDocumentExtension4;
import org.eclipse.jface.text.IDocumentListener;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.ui.console.TextConsole;
import org.eclipse.ui.console.TextConsoleViewer;

import org.eclipse.statet.ecommons.ui.util.UIAccess;


public class OutputViewer extends TextConsoleViewer {
	
	
	/**
	 * will always scroll with output if value is true.
	 */
	private boolean autoScroll= true;
	
	private IDocumentListener documentListener;
	
	
	public OutputViewer(final Composite parent, final TextConsole console) {
		super(parent, console);
		setEditable(false);
	}
	
	
	public boolean isAutoScroll() {
		return this.autoScroll;
	}
	
	public void setAutoScroll(final boolean scroll) {
		this.autoScroll= scroll;
	}
	
	@Override
	public void setDocument(final IDocument document) {
		final IDocument oldDocument= getDocument();
		if (oldDocument != null) {
			oldDocument.removeDocumentListener(getDocumentListener());
		}
		
		super.setDocument(document);
		
		if (document != null) {
			document.addDocumentListener(getDocumentListener());
		}
	}
	
	private IDocumentListener getDocumentListener() {
		if (this.documentListener == null) {
			this.documentListener= new IDocumentListener() {
				@Override
				public void documentAboutToBeChanged(final DocumentEvent event) {
				}
				
				@Override
				public void documentChanged(final DocumentEvent event) {
					if (OutputViewer.this.autoScroll) {
						revealEndOfDocument();
					}
				}
			};
		}
		return this.documentListener;
	}
	
	@Override
	public void revealEndOfDocument() {
		final Display display= UIAccess.getDisplay();
		display.asyncExec(new Runnable() {
			@Override
			public void run() {
				final StyledText textWidget= getTextWidget();
				if (!UIAccess.isOkToUse(textWidget)) {
					return;
				}
				final AbstractDocument document= (AbstractDocument) getDocument();
				final long timestamp= document.getModificationStamp();
				final int lineCount= textWidget.getLineCount();
				final int lineToShow= ((lineCount > 1 && 
						textWidget.getCharCount() == textWidget.getOffsetAtLine(lineCount - 1)) ?
						(lineCount - 1) : (lineCount));
				final int visiblePixel= textWidget.getClientArea().height;
				final int linePixel= textWidget.getLineHeight();
				final int topPixel= (linePixel * (lineToShow - 1)) - visiblePixel + 2;
				if (topPixel + linePixel > 0) {
					if (topPixel < 0) {
						textWidget.setTopPixel(
								topPixel + linePixel );
					}
					else {
						final int[] move= new int[] {
								topPixel,
								topPixel + linePixel - 2,
								topPixel + linePixel - 1,
								topPixel + linePixel 
							};
						textWidget.setTopPixel(move[0]);
						final int[] state= new int[] { 1 };
						display.timerExec(75, new Runnable() {
							@Override
							public void run() {
								int i= state[0];
								if (!UIAccess.isOkToUse(textWidget)
										|| timestamp != ((IDocumentExtension4) getDocument()).getModificationStamp()
										|| move[i-1] != textWidget.getTopPixel()) {
									return;
								}
								textWidget.setTopPixel(move[i++]);
								if (i < move.length) {
									state[0]= i;
									display.timerExec(25, this);
								}
							}
						});
					}
				}
			}
		});
	}
	
}