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/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.text;


/**
 * This strategy always copies the indentation of the previous line.
 * 
 * This class is not intended to be subclassed.
 *
 * @since 3.1
 */
public class DefaultIndentLineAutoEditStrategy implements IAutoEditStrategy {

	/**
	 * Creates a new indent line auto edit strategy which can be installed on
	 * text viewers.
	 */
	public DefaultIndentLineAutoEditStrategy() {
	}

	/**
	 * Returns the first offset greater than offset and smaller than
	 * end whose character is not a space or tab character. If no such
	 * offset is found, end is returned.
	 *
	 * @param document the document to search in
	 * @param offset the offset at which searching start
	 * @param end the offset at which searching stops
	 * @return the offset in the specified range whose character is not a space or tab
	 * @exception BadLocationException if position is an invalid range in the given document
	 */
	protected int findEndOfWhiteSpace(IDocument document, int offset, int end) throws BadLocationException {
		while (offset < end) {
			char c= document.getChar(offset);
			if (c != ' ' && c != '\t') {
				return offset;
			}
			offset++;
		}
		return end;
	}

	/**
	 * Copies the indentation of the previous line.
	 *
	 * @param d the document to work on
	 * @param c the command to deal with
	 */
	private void autoIndentAfterNewLine(IDocument d, DocumentCommand c) {

		if (c.offset == -1 || d.getLength() == 0)
			return;

		try {
			// find start of line
			int p= (c.offset == d.getLength() ? c.offset  - 1 : c.offset);
			IRegion info= d.getLineInformationOfOffset(p);
			int start= info.getOffset();

			// find white spaces
			int end= findEndOfWhiteSpace(d, start, c.offset);

			StringBuffer buf= new StringBuffer(c.text);
			if (end > start) {
				// append to input
				buf.append(d.get(start, end - start));
			}

			c.text= buf.toString();

		} catch (BadLocationException excp) {
			// stop work
		}
	}

	/*
	 * @see org.eclipse.jface.text.IAutoEditStrategy#customizeDocumentCommand(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.DocumentCommand)
	 */
	public void customizeDocumentCommand(IDocument d, DocumentCommand c) {
		if (c.length == 0 && c.text != null && TextUtilities.endsWith(d.getLegalLineDelimiters(), c.text) != -1)
			autoIndentAfterNewLine(d, c);
	}
}