UndoCollector.java

/*******************************************************************************
 * Copyright (c) 2012-2015 Codenvy, S.A.
 * 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:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.ide.ext.java.jdt.text.edits;

import org.eclipse.che.ide.api.editor.text.BadLocationException;
import org.eclipse.che.ide.ext.java.jdt.text.Document;
import org.eclipse.che.ide.ext.java.jdt.text.DocumentEvent;
import org.eclipse.che.ide.ext.java.jdt.text.DocumentListener;
import org.eclipse.che.ide.runtime.Assert;

class UndoCollector implements DocumentListener {

    protected UndoEdit undo;

    private int fOffset;

    private int fLength;

    private String fLastCurrentText;

    public UndoCollector(TextEdit root) {
        fOffset = root.getOffset();
        fLength = root.getLength();
    }

    public void connect(Document document) {
        document.addDocumentListener(this);
        undo = new UndoEdit();
    }

    public void disconnect(Document document) {
        if (undo != null) {
            document.removeDocumentListener(this);
            undo.defineRegion(fOffset, fLength);
        }
    }

    /** {@inheritDoc} */
    @Override
    public void documentChanged(DocumentEvent event) {
        fLength += getDelta(event);
    }

    private static int getDelta(DocumentEvent event) {
        String text = event.getText();
        return text == null ? -event.getLength() : (text.length() - event.getLength());
    }

    /** {@inheritDoc} */
    @Override
    public void documentAboutToBeChanged(DocumentEvent event) {
        int offset = event.getOffset();
        int currentLength = event.getLength();
        String currentText = null;
        try {
            currentText = event.getDocument().get(offset, currentLength);
        } catch (BadLocationException cannotHappen) {
            Assert.isTrue(false, "Can't happen"); //$NON-NLS-1$
        }

    /*
    * see https://bugs.eclipse.org/bugs/show_bug.cgi?id=93634
    * If the same string is replaced on many documents (e.g. rename
    * package), the size of the undo can be reduced by using the same
    * String instance in all edits, instead of using the unique String
    * returned from IDocument.get(int, int).
    */
        if (fLastCurrentText != null && fLastCurrentText.equals(currentText))
            currentText = fLastCurrentText;
        else
            fLastCurrentText = currentText;

        String newText = event.getText();
        undo.add(new ReplaceEdit(offset, newText != null ? newText.length() : 0, currentText));
    }
}