text/phpdoc/JavaDocAutoIndentStrategy.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 net.sourceforge.phpdt.internal.ui.text.phpdoc;

import java.text.BreakIterator;

import net.sourceforge.phpdt.core.ICompilationUnit;
import net.sourceforge.phpdt.core.IJavaElement;
import net.sourceforge.phpdt.core.IMethod;
import net.sourceforge.phpdt.core.ISourceRange;
import net.sourceforge.phpdt.core.IType;
import net.sourceforge.phpdt.internal.corext.util.Strings;
import net.sourceforge.phpdt.ui.CodeGeneration;
import net.sourceforge.phpdt.ui.IWorkingCopyManager;
import net.sourceforge.phpdt.ui.PreferenceConstants;
import net.sourceforge.phpeclipse.PHPeclipsePlugin;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.Preferences;
import org.eclipse.jface.preference.IPreferenceStore;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DefaultIndentLineAutoEditStrategy;
import org.eclipse.jface.text.DocumentCommand;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.text.TextUtilities;
import org.eclipse.ui.IEditorPart;
import org.eclipse.ui.IWorkbenchPage;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.texteditor.AbstractDecoratedTextEditorPreferenceConstants;
import org.eclipse.ui.texteditor.ITextEditorExtension3;

/**
 * Auto indent strategy for java doc comments
 */
public class JavaDocAutoIndentStrategy extends
		DefaultIndentLineAutoEditStrategy {

	private String fPartitioning;

	/**
	 * Creates a new Javadoc auto indent strategy for the given document
	 * partitioning.
	 *
	 * @param partitioning
	 *            the document partitioning
	 */
	public JavaDocAutoIndentStrategy(String partitioning) {
		fPartitioning = partitioning;
	}

	private static String getLineDelimiter(IDocument document) {
		try {
			if (document.getNumberOfLines() > 1)
				return document.getLineDelimiter(0);
		} catch (BadLocationException e) {
			PHPeclipsePlugin.log(e);
		}

		return System.getProperty("line.separator"); //$NON-NLS-1$
	}

	/**
	 * Copies the indentation of the previous line and add a star. If the
	 * javadoc just started on this line add standard method tags and close the
	 * javadoc.
	 *
	 * @param d
	 *            the document to work on
	 * @param c
	 *            the command to deal with
	 */
	private void jdocIndentAfterNewLine(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) { // 1GEYL1R: ITPJUI:ALL - java doc edit smartness
								// not work for class comments
				// append to input
				String indentation = jdocExtractLinePrefix(d, d
						.getLineOfOffset(c.offset));
				buf.append(indentation);
				if (end < c.offset) {
					if (d.getChar(end) == '/') {
						// javadoc started on this line
						buf.append(" * "); //$NON-NLS-1$

						if (PHPeclipsePlugin
								.getDefault()
								.getPreferenceStore()
								.getBoolean(
										PreferenceConstants.EDITOR_CLOSE_JAVADOCS)
								&& isNewComment(d, c.offset, fPartitioning)) {
							String lineDelimiter = getLineDelimiter(d);

							String endTag = lineDelimiter + indentation + " */"; //$NON-NLS-1$
							d.replace(c.offset, 0, endTag); //$NON-NLS-1$
							// evaluate method signature
							ICompilationUnit unit = getCompilationUnit();

							// if
							// (PHPeclipsePlugin.getDefault().getPreferenceStore().getBoolean(PreferenceConstants.EDITOR_ADD_JAVADOC_TAGS)
							// &&
							// unit != null)
							// {
							// try {
							// JavaModelUtil.reconcile(unit);
							// String string= createJavaDocTags(d, c,
							// indentation, lineDelimiter, unit);
							// if (string != null) {
							// d.replace(c.offset, 0, string);
							// }
							// } catch (CoreException e) {
							// // ignore
							// }
							// }
						}

					}
				}
			}

			c.text = buf.toString();

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

	private String createJavaDocTags(IDocument document,
			DocumentCommand command, String indentation, String lineDelimiter,
			ICompilationUnit unit) throws CoreException, BadLocationException {
		IJavaElement element = unit.getElementAt(command.offset);
		if (element == null)
			return null;

		switch (element.getElementType()) {
		case IJavaElement.TYPE:
			return createTypeTags(document, command, indentation,
					lineDelimiter, (IType) element);

		case IJavaElement.METHOD:
			return createMethodTags(document, command, indentation,
					lineDelimiter, (IMethod) element);

		default:
			return null;
		}
	}

	/*
	 * Removes start and end of a comment and corrects indentation and line
	 * delimiters.
	 */
	private String prepareTemplateComment(String comment, String indentation,
			String lineDelimiter) {
		// trim comment start and end if any
		if (comment.endsWith("*/")) //$NON-NLS-1$
			comment = comment.substring(0, comment.length() - 2);
		comment = comment.trim();
		if (comment.startsWith("/*")) { //$NON-NLS-1$
			if (comment.length() > 2 && comment.charAt(2) == '*') {
				comment = comment.substring(3); // remove '/**'
			} else {
				comment = comment.substring(2); // remove '/*'
			}
		}
		// return Strings.changeIndent(comment, 0,
		// CodeFormatterUtil.getTabWidth(), indentation, lineDelimiter);
		return Strings.changeIndent(comment, 0, getTabWidth(), indentation,
				lineDelimiter);
	}

	public static int getTabWidth() {
		Preferences preferences = PHPeclipsePlugin.getDefault()
				.getPluginPreferences();
		return preferences
				.getInt(AbstractDecoratedTextEditorPreferenceConstants.EDITOR_TAB_WIDTH);
	}

	private String createTypeTags(IDocument document, DocumentCommand command,
			String indentation, String lineDelimiter, IType type)
			throws CoreException {
		String comment = CodeGeneration.getTypeComment(type
				.getCompilationUnit(), type.getTypeQualifiedName('.'),
				lineDelimiter);
		if (comment != null) {
			return prepareTemplateComment(comment.trim(), indentation,
					lineDelimiter);
		}
		return null;
	}

	private String createMethodTags(IDocument document,
			DocumentCommand command, String indentation, String lineDelimiter,
			IMethod method) throws CoreException, BadLocationException {
		IRegion partition = TextUtilities.getPartition(document, fPartitioning,
				command.offset, false);
		ISourceRange sourceRange = method.getSourceRange();
		if (sourceRange == null
				|| sourceRange.getOffset() != partition.getOffset())
			return null;

		// IMethod inheritedMethod= getInheritedMethod(method);
		// String comment= CodeGeneration.getMethodComment(method,
		// inheritedMethod, lineDelimiter);
		// if (comment != null) {
		// comment= comment.trim();
		// boolean javadocComment= comment.startsWith("/**"); //$NON-NLS-1$
		// boolean isJavaDoc= partition.getLength() >= 3 &&
		// document.get(partition.getOffset(), 3).equals("/**"); //$NON-NLS-1$
		// if (javadocComment == isJavaDoc) {
		// return prepareTemplateComment(comment, indentation, lineDelimiter);
		// }
		// }
		return null;
	}

	/**
	 * Returns the method inherited from, <code>null</code> if method is newly
	 * defined.
	 */
	// private static IMethod getInheritedMethod(IMethod method) throws
	// JavaModelException {
	// IType declaringType= method.getDeclaringType();
	// ITypeHierarchy typeHierarchy=
	// SuperTypeHierarchyCache.getTypeHierarchy(declaringType);
	// return JavaModelUtil.findMethodDeclarationInHierarchy(typeHierarchy,
	// declaringType,
	// method.getElementName(), method.getParameterTypes(),
	// method.isConstructor());
	// }
	protected void jdocIndentForCommentEnd(IDocument d, DocumentCommand c) {
		if (c.offset < 2 || d.getLength() == 0) {
			return;
		}
		try {
			if ("* ".equals(d.get(c.offset - 2, 2))) { //$NON-NLS-1$
				// modify document command
				c.length++;
				c.offset--;
			}
		} catch (BadLocationException excp) {
			// stop work
		}
	}

	/**
	 * Guesses if the command operates within a newly created javadoc comment or
	 * not. If in doubt, it will assume that the javadoc is new.
	 */
	private static boolean isNewComment(IDocument document, int commandOffset,
			String partitioning) {

		try {
			int lineIndex = document.getLineOfOffset(commandOffset) + 1;
			if (lineIndex >= document.getNumberOfLines())
				return true;

			IRegion line = document.getLineInformation(lineIndex);
			ITypedRegion partition = TextUtilities.getPartition(document,
					partitioning, commandOffset, false);
			int partitionEnd = partition.getOffset() + partition.getLength();
			if (line.getOffset() >= partitionEnd)
				return false;

			if (document.getLength() == partitionEnd)
				return true; // partition goes to end of document - probably
								// a new comment

			String comment = document.get(partition.getOffset(), partition
					.getLength());
			if (comment.indexOf("/*", 2) != -1) //$NON-NLS-1$
				return true; // enclosed another comment -> probably a new
								// comment

			return false;

		} catch (BadLocationException e) {
			return false;
		}
	}

	private boolean isSmartMode() {
		IWorkbenchPage page = PHPeclipsePlugin.getActivePage();
		if (page != null) {
			IEditorPart part = page.getActiveEditor();
			if (part instanceof ITextEditorExtension3) {
				ITextEditorExtension3 extension = (ITextEditorExtension3) part;
				return extension.getInsertMode() == ITextEditorExtension3.SMART_INSERT;
			}
		}
		return false;
	}

	/*
	 * @see IAutoIndentStrategy#customizeDocumentCommand
	 */
	public void customizeDocumentCommand(IDocument document,
			DocumentCommand command) {

		if (!isSmartMode())
			return;

		try {

			if (command.text != null && command.length == 0) {
				String[] lineDelimiters = document.getLegalLineDelimiters();
				int index = TextUtilities
						.endsWith(lineDelimiters, command.text);
				if (index > -1) {
					// ends with line delimiter
					if (lineDelimiters[index].equals(command.text))
						// just the line delimiter
						jdocIndentAfterNewLine(document, command);
					return;
				}
			}

			if (command.text != null && command.text.equals("/")) { //$NON-NLS-1$
				jdocIndentForCommentEnd(document, command);
				return;
			}

			ITypedRegion partition = TextUtilities.getPartition(document,
					fPartitioning, command.offset, true);
			int partitionStart = partition.getOffset();
			int partitionEnd = partition.getLength() + partitionStart;

			String text = command.text;
			int offset = command.offset;
			int length = command.length;

			// partition change
			final int PREFIX_LENGTH = "/*".length(); //$NON-NLS-1$
			final int POSTFIX_LENGTH = "*/".length(); //$NON-NLS-1$
			if ((offset < partitionStart + PREFIX_LENGTH || offset + length > partitionEnd
					- POSTFIX_LENGTH)
					|| text != null
					&& text.length() >= 2
					&& ((text.indexOf("*/") != -1) || (document.getChar(offset) == '*' && text.startsWith("/")))) //$NON-NLS-1$ //$NON-NLS-2$
				return;

			if (command.text == null || command.text.length() == 0)
				jdocHandleBackspaceDelete(document, command);

			else if (command.text != null && command.length == 0
					&& command.text.length() > 0)
				jdocWrapParagraphOnInsert(document, command);

		} catch (BadLocationException e) {
			PHPeclipsePlugin.log(e);
		}
	}

	private void flushCommand(IDocument document, DocumentCommand command)
			throws BadLocationException {

		if (!command.doit)
			return;

		document.replace(command.offset, command.length, command.text);

		command.doit = false;
		if (command.text != null)
			command.offset += command.text.length();
		command.length = 0;
		command.text = null;
	}

	protected void jdocWrapParagraphOnInsert(IDocument document,
			DocumentCommand command) throws BadLocationException {

		// Assert.isTrue(command.length == 0);
		// Assert.isTrue(command.text != null && command.text.length() == 1);

		if (!getPreferenceStore().getBoolean(
				PreferenceConstants.EDITOR_FORMAT_JAVADOCS))
			return;

		int line = document.getLineOfOffset(command.offset);
		IRegion region = document.getLineInformation(line);
		int lineOffset = region.getOffset();
		int lineLength = region.getLength();

		String lineContents = document.get(lineOffset, lineLength);
		StringBuffer buffer = new StringBuffer(lineContents);
		int start = command.offset - lineOffset;
		int end = command.length + start;
		buffer.replace(start, end, command.text);

		// handle whitespace
		if (command.text != null && command.text.length() != 0
				&& command.text.trim().length() == 0) {

			String endOfLine = document.get(command.offset, lineOffset
					+ lineLength - command.offset);

			// end of line
			if (endOfLine.length() == 0) {
				// move caret to next line
				flushCommand(document, command);

				if (isLineTooShort(document, line)) {
					int[] caretOffset = { command.offset };
					jdocWrapParagraphFromLine(document, line, caretOffset,
							false);
					command.offset = caretOffset[0];
					return;
				}

				// move caret to next line if possible
				if (line < document.getNumberOfLines() - 1
						&& isJavaDocLine(document, line + 1)) {
					String lineDelimiter = document.getLineDelimiter(line);
					String nextLinePrefix = jdocExtractLinePrefix(document,
							line + 1);
					command.offset += lineDelimiter.length()
							+ nextLinePrefix.length();
				}
				return;

				// inside whitespace at end of line
			} else if (endOfLine.trim().length() == 0) {
				// simply insert space
				return;
			}
		}

		// change in prefix region
		String prefix = jdocExtractLinePrefix(document, line);
		boolean wrapAlways = command.offset >= lineOffset
				&& command.offset <= lineOffset + prefix.length();

		// must insert the text now because it may include whitepace
		flushCommand(document, command);

		if (wrapAlways
				|| calculateDisplayedWidth(buffer.toString()) > getMargin()
				|| isLineTooShort(document, line)) {
			int[] caretOffset = { command.offset };
			jdocWrapParagraphFromLine(document, line, caretOffset, wrapAlways);

			if (!wrapAlways)
				command.offset = caretOffset[0];
		}
	}

	/**
	 * Method jdocWrapParagraphFromLine.
	 *
	 * @param document
	 * @param line
	 * @param always
	 */
	private void jdocWrapParagraphFromLine(IDocument document, int line,
			int[] caretOffset, boolean always) throws BadLocationException {

		String indent = jdocExtractLinePrefix(document, line);
		if (!always) {
			if (!indent.trim().startsWith("*")) //$NON-NLS-1$
				return;

			if (indent.trim().startsWith("*/")) //$NON-NLS-1$
				return;

			if (!isLineTooLong(document, line)
					&& !isLineTooShort(document, line))
				return;
		}

		boolean caretRelativeToParagraphOffset = false;
		int caret = caretOffset[0];

		int caretLine = document.getLineOfOffset(caret);
		int lineOffset = document.getLineOffset(line);
		int paragraphOffset = lineOffset + indent.length();
		if (paragraphOffset < caret) {
			caret -= paragraphOffset;
			caretRelativeToParagraphOffset = true;
		} else {
			caret -= lineOffset;
		}

		StringBuffer buffer = new StringBuffer();
		int currentLine = line;
		while (line == currentLine || isJavaDocLine(document, currentLine)) {

			if (buffer.length() != 0
					&& !Character.isWhitespace(buffer
							.charAt(buffer.length() - 1))) {
				buffer.append(' ');
				if (currentLine <= caretLine) {
					// in this case caretRelativeToParagraphOffset is always
					// true
					++caret;
				}
			}

			String string = getLineContents(document, currentLine);
			buffer.append(string);
			currentLine++;
		}
		String paragraph = buffer.toString();

		if (paragraph.trim().length() == 0)
			return;

		caretOffset[0] = caretRelativeToParagraphOffset ? caret : 0;
		String delimiter = document.getLineDelimiter(0);
		String wrapped = formatParagraph(paragraph, caretOffset, indent,
				delimiter, getMargin());

		int beginning = document.getLineOffset(line);
		int end = document.getLineOffset(currentLine);
		document.replace(beginning, end - beginning, wrapped.toString());

		caretOffset[0] = caretRelativeToParagraphOffset ? caretOffset[0]
				+ beginning : caret + beginning;
	}

	/**
	 * Line break iterator to handle whitespaces as first class citizens.
	 */
	private static class LineBreakIterator {

		private final String fString;

		private final BreakIterator fIterator = BreakIterator.getLineInstance();

		private int fStart;

		private int fEnd;

		private int fBufferedEnd;

		public LineBreakIterator(String string) {
			fString = string;
			fIterator.setText(string);
		}

		public int first() {
			fBufferedEnd = -1;
			fStart = fIterator.first();
			return fStart;
		}

		public int next() {

			if (fBufferedEnd != -1) {
				fStart = fEnd;
				fEnd = fBufferedEnd;
				fBufferedEnd = -1;
				return fEnd;
			}

			fStart = fEnd;
			fEnd = fIterator.next();

			if (fEnd == BreakIterator.DONE)
				return fEnd;

			final String string = fString.substring(fStart, fEnd);

			// whitespace
			if (string.trim().length() == 0)
				return fEnd;

			final String word = string.trim();
			if (word.length() == string.length())
				return fEnd;

			// suspected whitespace
			fBufferedEnd = fEnd;
			return fStart + word.length();
		}
	}

	/**
	 * Formats a paragraph, using break iterator.
	 *
	 * @param offset
	 *            an offset within the paragraph, which will be updated with
	 *            respect to formatting.
	 */
	private static String formatParagraph(String paragraph, int[] offset,
			String prefix, String lineDelimiter, int margin) {

		LineBreakIterator iterator = new LineBreakIterator(paragraph);

		StringBuffer paragraphBuffer = new StringBuffer();
		StringBuffer lineBuffer = new StringBuffer();
		StringBuffer whiteSpaceBuffer = new StringBuffer();

		int index = offset[0];
		int indexBuffer = -1;

		// line delimiter could be null
		if (lineDelimiter == null)
			lineDelimiter = ""; //$NON-NLS-1$

		for (int start = iterator.first(), end = iterator.next(); end != BreakIterator.DONE; start = end, end = iterator
				.next()) {

			String word = paragraph.substring(start, end);

			// word is whitespace
			if (word.trim().length() == 0) {
				whiteSpaceBuffer.append(word);

				// first word of line is always appended
			} else if (lineBuffer.length() == 0) {
				lineBuffer.append(prefix);
				lineBuffer.append(whiteSpaceBuffer.toString());
				lineBuffer.append(word);

			} else {
				String line = lineBuffer.toString()
						+ whiteSpaceBuffer.toString() + word.toString();

				// margin exceeded
				if (calculateDisplayedWidth(line) > margin) {
					// flush line buffer and wrap paragraph
					paragraphBuffer.append(lineBuffer.toString());
					paragraphBuffer.append(lineDelimiter);
					lineBuffer.setLength(0);
					lineBuffer.append(prefix);
					lineBuffer.append(word);

					// flush index buffer
					if (indexBuffer != -1) {
						offset[0] = indexBuffer;
						// correct for caret in whitespace at the end of line
						if (whiteSpaceBuffer.length() != 0 && index < start
								&& index >= start - whiteSpaceBuffer.length())
							offset[0] -= (index - (start - whiteSpaceBuffer
									.length()));
						indexBuffer = -1;
					}

					whiteSpaceBuffer.setLength(0);

					// margin not exceeded
				} else {
					lineBuffer.append(whiteSpaceBuffer.toString());
					lineBuffer.append(word);
					whiteSpaceBuffer.setLength(0);
				}
			}

			if (index >= start && index < end) {
				indexBuffer = paragraphBuffer.length() + lineBuffer.length()
						+ (index - start);
				if (word.trim().length() != 0)
					indexBuffer -= word.length();
			}
		}

		// flush line buffer
		paragraphBuffer.append(lineBuffer.toString());
		paragraphBuffer.append(lineDelimiter);

		// flush index buffer
		if (indexBuffer != -1)
			offset[0] = indexBuffer;

		// last position is not returned by break iterator
		else if (offset[0] == paragraph.length())
			offset[0] = paragraphBuffer.length() - lineDelimiter.length();

		return paragraphBuffer.toString();
	}

	private static IPreferenceStore getPreferenceStore() {
		return PHPeclipsePlugin.getDefault().getPreferenceStore();
	}

	/**
	 * Returns the displayed width of a string, taking in account the displayed
	 * tab width. The result can be compared against the print margin.
	 */
	private static int calculateDisplayedWidth(String string) {

		int tabWidth = getPreferenceStore()
				.getInt(
						AbstractDecoratedTextEditorPreferenceConstants.EDITOR_TAB_WIDTH);
		if (tabWidth <= 0) {
			tabWidth = 2;
		}
		int column = 0;
		for (int i = 0; i < string.length(); i++)
			if ('\t' == string.charAt(i))
				column += tabWidth - (column % tabWidth);
			else
				column++;

		return column;
	}

	private String jdocExtractLinePrefix(IDocument d, int line)
			throws BadLocationException {

		IRegion region = d.getLineInformation(line);
		int lineOffset = region.getOffset();
		int index = findEndOfWhiteSpace(d, lineOffset, lineOffset
				+ d.getLineLength(line));
		if (d.getChar(index) == '*') {
			index++;
			if (index != lineOffset + region.getLength()
					&& d.getChar(index) == ' ')
				index++;
		}
		return d.get(lineOffset, index - lineOffset);
	}

	private String getLineContents(IDocument d, int line)
			throws BadLocationException {
		int offset = d.getLineOffset(line);
		int length = d.getLineLength(line);
		String lineDelimiter = d.getLineDelimiter(line);
		if (lineDelimiter != null)
			length = length - lineDelimiter.length();
		String lineContents = d.get(offset, length);
		int trim = jdocExtractLinePrefix(d, line).length();
		return lineContents.substring(trim);
	}

	private static String getLine(IDocument document, int line)
			throws BadLocationException {
		IRegion region = document.getLineInformation(line);
		return document.get(region.getOffset(), region.getLength());
	}

	/**
	 * Returns <code>true</code> if the javadoc line is too short,
	 * <code>false</code> otherwise.
	 */
	private boolean isLineTooShort(IDocument document, int line)
			throws BadLocationException {

		if (!isJavaDocLine(document, line + 1))
			return false;

		String nextLine = getLineContents(document, line + 1);
		if (nextLine.trim().length() == 0)
			return false;

		return true;
	}

	/**
	 * Returns <code>true</code> if the line is too long, <code>false</code>
	 * otherwise.
	 */
	private boolean isLineTooLong(IDocument document, int line)
			throws BadLocationException {
		String lineContents = getLine(document, line);
		return calculateDisplayedWidth(lineContents) > getMargin();
	}

	private static int getMargin() {
		return getPreferenceStore()
				.getInt(
						AbstractDecoratedTextEditorPreferenceConstants.EDITOR_PRINT_MARGIN_COLUMN);
	}

	private static final String[] fgInlineTags = {
			"<b>", "<i>", "<em>", "<strong>", "<code>" //$NON-NLS-1$  //$NON-NLS-2$  //$NON-NLS-3$  //$NON-NLS-4$ //$NON-NLS-5$
	};

	private boolean isInlineTag(String string) {
		for (int i = 0; i < fgInlineTags.length; i++)
			if (string.startsWith(fgInlineTags[i]))
				return true;
		return false;
	}

	/**
	 * returns true if the specified line is part of a paragraph and should be
	 * merged with the previous line.
	 */
	private boolean isJavaDocLine(IDocument document, int line)
			throws BadLocationException {

		if (document.getNumberOfLines() < line)
			return false;

		int offset = document.getLineOffset(line);
		int length = document.getLineLength(line);
		int firstChar = findEndOfWhiteSpace(document, offset, offset + length);
		length -= firstChar - offset;
		String lineContents = document.get(firstChar, length);

		String prefix = lineContents.trim();
		if (!prefix.startsWith("*") || prefix.startsWith("*/")) //$NON-NLS-1$ //$NON-NLS-2$
			return false;

		lineContents = lineContents.substring(1).trim().toLowerCase();

		// preserve empty lines
		if (lineContents.length() == 0)
			return false;

		// preserve @TAGS
		if (lineContents.startsWith("@")) //$NON-NLS-1$
			return false;

		// preserve HTML tags which are not inline
		if (lineContents.startsWith("<") && !isInlineTag(lineContents)) //$NON-NLS-1$
			return false;

		return true;
	}

	protected void jdocHandleBackspaceDelete(IDocument document,
			DocumentCommand c) {

		if (!getPreferenceStore().getBoolean(
				PreferenceConstants.EDITOR_FORMAT_JAVADOCS))
			return;

		try {
			String text = document.get(c.offset, c.length);
			int line = document.getLineOfOffset(c.offset);
			int lineOffset = document.getLineOffset(line);

			// erase line delimiter
			String lineDelimiter = document.getLineDelimiter(line);
			if (lineDelimiter != null && lineDelimiter.equals(text)) {

				String prefix = jdocExtractLinePrefix(document, line + 1);

				// strip prefix if any
				if (prefix.length() > 0) {
					int length = document.getLineDelimiter(line).length()
							+ prefix.length();
					document.replace(c.offset, length, null);

					c.doit = false;
					c.length = 0;
					return;
				}

				// backspace: beginning of a javadoc line
			} else if (document.getChar(c.offset - 1) == '*'
					&& jdocExtractLinePrefix(document, line).length() - 1 >= c.offset
							- lineOffset) {

				lineDelimiter = document.getLineDelimiter(line - 1);
				String prefix = jdocExtractLinePrefix(document, line);
				int length = (lineDelimiter != null ? lineDelimiter.length()
						: 0)
						+ prefix.length();
				document.replace(c.offset - length + 1, length, null);

				c.doit = false;
				c.offset -= length - 1;
				c.length = 0;
				return;

			} else {
				document.replace(c.offset, c.length, null);
				c.doit = false;
				c.length = 0;
			}

		} catch (BadLocationException e) {
			PHPeclipsePlugin.log(e);
		}

		try {
			int line = document.getLineOfOffset(c.offset);
			int lineOffset = document.getLineOffset(line);
			String prefix = jdocExtractLinePrefix(document, line);
			boolean always = c.offset > lineOffset
					&& c.offset <= lineOffset + prefix.length();
			int[] caretOffset = { c.offset };
			jdocWrapParagraphFromLine(document, document
					.getLineOfOffset(c.offset), caretOffset, always);
			c.offset = caretOffset[0];

		} catch (BadLocationException e) {
			PHPeclipsePlugin.log(e);
		}
	}

	/**
	 * Returns the compilation unit of the CompilationUnitEditor invoking the
	 * AutoIndentStrategy, might return <code>null</code> on error.
	 */
	private static ICompilationUnit getCompilationUnit() {

		IWorkbenchWindow window = PlatformUI.getWorkbench()
				.getActiveWorkbenchWindow();
		if (window == null)
			return null;

		IWorkbenchPage page = window.getActivePage();
		if (page == null)
			return null;

		IEditorPart editor = page.getActiveEditor();
		if (editor == null)
			return null;

		IWorkingCopyManager manager = PHPeclipsePlugin.getDefault()
				.getWorkingCopyManager();
		ICompilationUnit unit = manager.getWorkingCopy(editor.getEditorInput());
		if (unit == null)
			return null;

		return unit;
	}

}