org.eclipse.jface.text.tests/src/org/eclipse/jface/text/tests/UndoManagerTest.java

/*******************************************************************************
 * Copyright (c) 2000, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.text.tests;

import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Shell;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DefaultUndoManager;
import org.eclipse.jface.text.Document;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.IUndoManager;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.TextViewer;

import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;

/**
 * Test for DefaultUndoManager
 */
public class UndoManagerTest extends TestCase {

	/** The maximum undo level. */
	private static final int MAX_UNDO_LEVEL = 256;
	
	/** The shell. */
	private Shell fShell;
	/** The text viewer. */
	private ITextViewer fTextViewer;
	/** The undo manager. */
	private IUndoManager fUndoManager;

	public static Test suite() {
		return new TestSuite(UndoManagerTest.class);
	}
	
	/*
	 * @see TestCase#TestCase(String)
	 */
	public UndoManagerTest(final String name) {
		super(name);	
	}
	
	/*
	 *  @see TestCase#setUp()
	 */
	protected void setUp() {
		fShell = new Shell();	
		fUndoManager = new DefaultUndoManager(MAX_UNDO_LEVEL);
		fTextViewer = new TextViewer(fShell, SWT.NONE);
		fTextViewer.setUndoManager(fUndoManager);
		fUndoManager.connect(fTextViewer);
	}

	/**
	 * Test for line delimiter conversion.
	 */	
	public void testConvertLineDelimiters() {
		final String original= "a\r\nb\r\n";
		final IDocument document= new Document(original);		
		fTextViewer.setDocument(document);
		
		try {
			document.replace(1, 2, "\n");
			document.replace(3, 2, "\n");
		} catch (BadLocationException e) {
			assertTrue(false);
		}
		
		assertTrue(fUndoManager.undoable());
		fUndoManager.undo();
		assertTrue(fUndoManager.undoable());
		fUndoManager.undo();

		final String reverted= document.get();
		
		assertEquals(original, reverted);
	}

	/**
	 * Randomly applies document changes.
	 */
	public void testRandomAccess() {
		final int RANDOM_STRING_LENGTH= 50;
		final int RANDOM_REPLACE_COUNT= 100;
		
		assertTrue(RANDOM_REPLACE_COUNT >= 1);
		assertTrue(RANDOM_REPLACE_COUNT <= MAX_UNDO_LEVEL);
		
		String original= createRandomString(RANDOM_STRING_LENGTH);
		final IDocument document= new Document(original);
		fTextViewer.setDocument(document);
	
		doChange(document, RANDOM_REPLACE_COUNT);
		
		assertTrue(fUndoManager.undoable());
		while (fUndoManager.undoable())
			fUndoManager.undo();
			
		final String reverted= document.get();

		assertEquals(original, reverted);
	}
	
	private void doChange(IDocument document, int count) {
		try {
			for (int i= 0; i < count; i++) {
				final Position position= createRandomPositionPoisson(document.getLength());
				final String string= createRandomStringPoisson(4);
				document.replace(position.getOffset(), position.getLength(), string);
//				System.out.println("replace length = " + position.getLength());
//				System.out.println("string length = " + string.length());
			}
		} catch (BadLocationException e) {
			assertTrue(false);
		}
	}
	
	public void testRandomAccessAsCompound() {
		final int RANDOM_STRING_LENGTH= 50;
		final int RANDOM_REPLACE_COUNT= 100;
		
		assertTrue(RANDOM_REPLACE_COUNT >= 1);
		assertTrue(RANDOM_REPLACE_COUNT <= MAX_UNDO_LEVEL);
		
		String original= createRandomString(RANDOM_STRING_LENGTH);
		final IDocument document= new Document(original);
		fTextViewer.setDocument(document);

		fUndoManager.beginCompoundChange();		
		doChange(document, RANDOM_REPLACE_COUNT);
		fUndoManager.endCompoundChange();

		assertTrue(fUndoManager.undoable());
		while (fUndoManager.undoable())
			fUndoManager.undo();
		assertTrue(!fUndoManager.undoable());
			
		final String reverted= document.get();

		assertEquals(original, reverted);		
	}

	private static String createRandomString(int length) {
		final StringBuffer buffer= new StringBuffer();
		
		for (int i= 0; i < length; i++)
			buffer.append(getRandomCharacter());

		return buffer.toString();
	}
	
	private static final char getRandomCharacter() {
//		return Math.random() < 0.5
//			? '\r'
//			: '\n';
					
		// XXX must include \r, \n, \t
		return (char) (32 + 95 * Math.random());
	}
	
	private static String createRandomStringPoisson(int mean) {
		final int length= getRandomPoissonValue(2);
		return createRandomString(length);
	}
	
	private static Position createRandomPositionPoisson(int documentLength) {

		final float random= (float) Math.random();
		final int offset= (int) (random * (documentLength + 1));

		int length= getRandomPoissonValue(2);
		if (offset + length > documentLength)
			length= documentLength - offset;
			
		return new Position(offset, length);
	}
	
	private static int getRandomPoissonValue(int mean) {
		final int MAX_VALUE= 10;

		final float random= (float) Math.random();
		float probability= 0;
		int i= 0;
		while (probability < 1 && i < MAX_VALUE) {
			probability += getPoissonDistribution(mean, i);
			if (random <= probability)
				break;
			i++;
		}		
		return i;
	}

	private static float getPoissonDistribution(float lambda, int k) {
		return (float) (Math.exp(-lambda) * Math.pow(lambda, k) / faculty(k));
	}
	
	/**
	 * Returns the faculty of k.
	 */
	private static final int faculty(int k) {
		return k == 0
			? 1
			: k * faculty(k - 1);
	}
	
}