org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/java/JavaAutoIndentStrategy.java

/*******************************************************************************
 * Copyright (c) 2000, 2003 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
 *     Nikolay Metchev - Fixed bug 29909
 *******************************************************************************/
package org.eclipse.jdt.internal.ui.text.java;


import org.eclipse.jface.preference.IPreferenceStore;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DefaultAutoIndentStrategy;
import org.eclipse.jface.text.Document;
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.Region;
import org.eclipse.jface.text.TextUtilities;
import org.eclipse.jface.text.rules.DefaultPartitioner;

import org.eclipse.ui.IEditorPart;
import org.eclipse.ui.IWorkbenchPage;
import org.eclipse.ui.texteditor.ITextEditorExtension3;

import org.eclipse.jdt.core.ToolFactory;
import org.eclipse.jdt.core.compiler.IProblem;
import org.eclipse.jdt.core.compiler.IScanner;
import org.eclipse.jdt.core.compiler.ITerminalSymbols;
import org.eclipse.jdt.core.compiler.InvalidInputException;
import org.eclipse.jdt.core.dom.AST;
import org.eclipse.jdt.core.dom.ASTNode;
import org.eclipse.jdt.core.dom.CompilationUnit;
import org.eclipse.jdt.core.dom.DoStatement;
import org.eclipse.jdt.core.dom.Expression;
import org.eclipse.jdt.core.dom.ForStatement;
import org.eclipse.jdt.core.dom.IfStatement;
import org.eclipse.jdt.core.dom.Statement;
import org.eclipse.jdt.core.dom.WhileStatement;

import org.eclipse.jdt.ui.PreferenceConstants;

import org.eclipse.jdt.internal.corext.Assert;
import org.eclipse.jdt.internal.corext.dom.NodeFinder;
import org.eclipse.jdt.internal.ui.JavaPlugin;
import org.eclipse.jdt.internal.ui.text.FastJavaPartitionScanner;
import org.eclipse.jdt.internal.ui.text.IJavaPartitions;
import org.eclipse.jdt.internal.ui.text.JavaHeuristicScanner;
import org.eclipse.jdt.internal.ui.text.JavaIndenter;
import org.eclipse.jdt.internal.ui.text.Symbols;

/**
 * Auto indent strategy sensitive to brackets.
 */
public class JavaAutoIndentStrategy extends DefaultAutoIndentStrategy {
		
	/** The line comment introducer. Value is "{@value}" */
	private static final String LINE_COMMENT= "//"; //$NON-NLS-1$
	
		private static class CompilationUnitInfo {
			
			char[] buffer;
			int delta;
			
			CompilationUnitInfo(char[] buffer, int delta) {
				this.buffer= buffer;
				this.delta= delta;
			}
		}


	private boolean fCloseBrace;
	private boolean fIsSmartMode;

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

	private int getBracketCount(IDocument d, int startOffset, int endOffset, boolean ignoreCloseBrackets) throws BadLocationException {

		int bracketCount= 0;
		while (startOffset < endOffset) {
			char curr= d.getChar(startOffset);
			startOffset++;
			switch (curr) {
				case '/' :
					if (startOffset < endOffset) {
						char next= d.getChar(startOffset);
						if (next == '*') {
							// a comment starts, advance to the comment end
							startOffset= getCommentEnd(d, startOffset + 1, endOffset);
						} else if (next == '/') {
							// '//'-comment: nothing to do anymore on this line
							startOffset= endOffset;
						}
					}
					break;
				case '*' :
					if (startOffset < endOffset) {
						char next= d.getChar(startOffset);
						if (next == '/') {
							// we have been in a comment: forget what we read before
							bracketCount= 0;
							startOffset++;
						}
					}
					break;
				case '{' :
					bracketCount++;
					ignoreCloseBrackets= false;
					break;
				case '}' :
					if (!ignoreCloseBrackets) {
						bracketCount--;
					}
					break;
				case '"' :
				case '\'' :
					startOffset= getStringEnd(d, startOffset, endOffset, curr);
					break;
				default :
					}
		}
		return bracketCount;
	}

	// ----------- bracket counting ------------------------------------------------------

	private int getCommentEnd(IDocument d, int offset, int endOffset) throws BadLocationException {
		while (offset < endOffset) {
			char curr= d.getChar(offset);
			offset++;
			if (curr == '*') {
				if (offset < endOffset && d.getChar(offset) == '/') {
					return offset + 1;
				}
			}
		}
		return endOffset;
	}

	private String getIndentOfLine(IDocument d, int line) throws BadLocationException {
		if (line > -1) {
			int start= d.getLineOffset(line);
			int end= start + d.getLineLength(line) - 1;
			int whiteEnd= findEndOfWhiteSpace(d, start, end);
			return d.get(start, whiteEnd - start);
		} else {
			return ""; //$NON-NLS-1$
		}
	}

	private int getStringEnd(IDocument d, int offset, int endOffset, char ch) throws BadLocationException {
		while (offset < endOffset) {
			char curr= d.getChar(offset);
			offset++;
			if (curr == '\\') {
				// ignore escaped characters
				offset++;
			} else if (curr == ch) {
				return offset;
			}
		}
		return endOffset;
	}

	private void smartIndentAfterClosingBracket(IDocument d, DocumentCommand c) {
		if (c.offset == -1 || d.getLength() == 0)
			return;

		try {
			int p= (c.offset == d.getLength() ? c.offset - 1 : c.offset);
			int line= d.getLineOfOffset(p);
			int start= d.getLineOffset(line);
			int whiteend= findEndOfWhiteSpace(d, start, c.offset);
			
			JavaHeuristicScanner scanner= new JavaHeuristicScanner(d);
			JavaIndenter indenter= new JavaIndenter(d, scanner);

			// shift only when line does not contain any text up to the closing bracket
			if (whiteend == c.offset) {
				// evaluate the line with the opening bracket that matches out closing bracket
				int reference= indenter.findReferencePosition(c.offset, false, true, false, false);
				int indLine= d.getLineOfOffset(reference);
				if (indLine != -1 && indLine != line) {
					// take the indent of the found line
					StringBuffer replaceText= new StringBuffer(getIndentOfLine(d, indLine));
					// add the rest of the current line including the just added close bracket
					replaceText.append(d.get(whiteend, c.offset - whiteend));
					replaceText.append(c.text);
					// modify document command
					c.length += c.offset - start;
					c.offset= start;
					c.text= replaceText.toString();
				}
			}
		} catch (BadLocationException e) {
			JavaPlugin.log(e);
		}
	}
	
	private void smartIndentAfterOpeningBracket(IDocument d, DocumentCommand c) {
		if (c.offset < 1 || d.getLength() == 0)
			return;
			
		JavaHeuristicScanner scanner= new JavaHeuristicScanner(d);

		int p= (c.offset == d.getLength() ? c.offset - 1 : c.offset);
		
		try {
			// current line
			int line= d.getLineOfOffset(p);
			int lineOffset= d.getLineOffset(line);
			
			// line of last javacode
			int pos= scanner.findNonWhitespaceBackward(p, JavaHeuristicScanner.UNBOUND);
			if (pos == -1)
				return;
			int lastLine= d.getLineOfOffset(pos);
			
			// only shift if the last java line is further up and is a braceless block candidate
			if (lastLine < line) {
			
				JavaIndenter indenter= new JavaIndenter(d, scanner);
				StringBuffer indent= indenter.computeIndentation(p, true);
				if (indent != null) {
					c.text= indent.append(c.text).toString();
					c.length= indent.length();
					c.offset= lineOffset;
				}
			}
			
		} catch (BadLocationException e) {
			JavaPlugin.log(e);
		}
		
	}

	private void smartIndentAfterNewLine(IDocument d, DocumentCommand c) {
		JavaHeuristicScanner scanner= new JavaHeuristicScanner(d);
		JavaIndenter indenter= new JavaIndenter(d, scanner);
		StringBuffer indent= indenter.computeIndentation(c.offset);
		if (indent == null)
			indent= new StringBuffer(); //$NON-NLS-1$

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

		try {
			int p= (c.offset == docLength ? c.offset - 1 : c.offset);
			int line= d.getLineOfOffset(p);

			StringBuffer buf= new StringBuffer(c.text + indent);


			IRegion reg= d.getLineInformation(line);
			int lineEnd= reg.getOffset() + reg.getLength();

			int contentStart= findEndOfWhiteSpace(d, c.offset, lineEnd);
			c.length=  Math.max(contentStart - c.offset, 0);
		
			int start= reg.getOffset();
			ITypedRegion region= TextUtilities.getPartition(d, fPartitioning, start);
			if (IJavaPartitions.JAVA_DOC.equals(region.getType()))
				start= d.getLineInformationOfOffset(region.getOffset()).getOffset();
				
			if (getBracketCount(d, start, c.offset, true) > 0 && closeBrace() && !isClosed(d, c.offset, c.length)) {
				c.caretOffset= c.offset + buf.length();
				c.shiftsCaret= false;
				
				// copy old content of line behind insertion point to new line
				// unless we think we are inserting an anonymous type definition
				if (c.offset == 0 || !(computeAnonymousPosition(d, c.offset - 1, fPartitioning, lineEnd) != -1)) {
					if (lineEnd - contentStart > 0) {
						c.length=  lineEnd - c.offset;
						buf.append(d.get(contentStart, lineEnd - contentStart).toCharArray());
					}
				}
			
				buf.append(getLineDelimiter(d));
				StringBuffer reference= indenter.getReferenceIndentation(c.offset);
				if (reference != null)
					buf.append(reference);
				buf.append('}');
			}
			c.text= buf.toString();

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

	/**
	 * Computes an insert position for an opening brace if <code>offset</code> maps to a position in
	 * <code>document</code> with a expression in parenthesis that will take a block after the closing parenthesis.
	 * 
	 * @param document the document being modified
	 * @param offset the offset of the caret position, relative to the line start.
	 * @param partitioning the document partitioning
	 * @param max the max position
	 * @return an insert position relative to the line start if <code>line</code> contains a parenthesized expression that can be followed by a block, -1 otherwise
	 */
	private static int computeAnonymousPosition(IDocument document, int offset, String partitioning,  int max) {
		// find the opening parenthesis for every closing parenthesis on the current line after offset
		// return the position behind the closing parenthesis if it looks like a method declaration
		// or an expression for an if, while, for, catch statement
		
		JavaHeuristicScanner scanner= new JavaHeuristicScanner(document);
		int pos= offset;
		int length= max;
		int scanTo= scanner.scanForward(pos, length, '}');
		if (scanTo == -1)
			scanTo= length;
			
		int closingParen= findClosingParenToLeft(scanner, pos) - 1;

		while (true) {
			int startScan= closingParen + 1;
			closingParen= scanner.scanForward(startScan, scanTo, ')');
			if (closingParen == -1)
				break;

			int openingParen= scanner.findOpeningPeer(closingParen - 1, '(', ')');

			// no way an expression at the beginning of the document can mean anything
			if (openingParen < 1)
				break;

			// only select insert positions for parenthesis currently embracing the caret
			if (openingParen > pos)
				continue;

			if (looksLikeAnonymousClassDef(document, partitioning, scanner, openingParen - 1))
				return closingParen + 1;

		}

		return -1;
	}

	/**
	 * Finds a closing parenthesis to the left of <code>position</code> in document, where that parenthesis is only
	 * separated by whitespace from <code>position</code>. If no such parenthesis can be found, <code>position</code> is returned.
	 * 
	 * @param document the document being modified
	 * @param position the first character position in <code>document</code> to be considered
	 * @param partitioning the document partitioning
	 * @return the position of a closing parenthesis left to <code>position</code> separated only by whitespace, or <code>position</code> if no parenthesis can be found
	 */
	private static int findClosingParenToLeft(JavaHeuristicScanner scanner, int position) {
		if (position < 1)
			return position;

		if (scanner.previousToken(position - 1, JavaHeuristicScanner.UNBOUND) == Symbols.TokenRPAREN)
			return scanner.getPosition() + 1;
		return position;
	}

	/**
	 * Checks whether the content of <code>document</code> in the range (<code>offset</code>, <code>length</code>)
	 * contains the <code>new</code> keyword.
	 * 
	 * @param document the document being modified
	 * @param offset the first character position in <code>document</code> to be considered
	 * @param length the length of the character range to be considered
	 * @param partitioning the document partitioning
	 * @return <code>true</code> if the specified character range contains a <code>new</code> keyword, <code>false</code> otherwise.
	 */
	private static boolean isNewMatch(IDocument document, int offset, int length, String partitioning) {
		Assert.isTrue(length >= 0);
		Assert.isTrue(offset >= 0);
		Assert.isTrue(offset + length < document.getLength() + 1);

		try {
			String text= document.get(offset, length);
			int pos= text.indexOf("new"); //$NON-NLS-1$
			
			while (pos != -1 && !isDefaultPartition(document, pos + offset, partitioning))
				pos= text.indexOf("new", pos + 2); //$NON-NLS-1$

			if (pos < 0)
				return false;

			if (pos != 0 && Character.isJavaIdentifierPart(text.charAt(pos - 1)))
				return false;

			if (pos + 3 < length && Character.isJavaIdentifierPart(text.charAt(pos + 3)))
				return false;
			
			return true;

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

	/**
	 * Checks whether the content of <code>document</code> at <code>position</code> looks like an
	 * anonymous class definition. <code>position</code> must be to the left of the opening
	 * parenthesis of the definition's parameter list.
	 * 
	 * @param document the document being modified
	 * @param position the first character position in <code>document</code> to be considered
	 * @param partitioning the document partitioning
	 * @return <code>true</code> if the content of <code>document</code> looks like an anonymous class definition, <code>false</code> otherwise
	 */
	private static boolean looksLikeAnonymousClassDef(IDocument document, String partitioning, JavaHeuristicScanner scanner, int position) {
		int previousCommaOrParen= scanner.scanBackward(position - 1, JavaHeuristicScanner.UNBOUND, new char[] {',', '('});
		if (previousCommaOrParen == -1 || position < previousCommaOrParen + 5) // 2 for borders, 3 for "new"
			return false;

		if (isNewMatch(document, previousCommaOrParen + 1, position - previousCommaOrParen - 2, partitioning))
			return true;

		return false;
	}

	/**
	 * Checks whether <code>position</code> resides in a default (Java) partition of <code>document</code>.
	 * 
	 * @param document the document being modified
	 * @param position the position to be checked
	 * @param partitioning the document partitioning
	 * @return <code>true</code> if <code>position</code> is in the default partition of <code>document</code>, <code>false</code> otherwise
	 */
	private static boolean isDefaultPartition(IDocument document, int position, String partitioning) {
		Assert.isTrue(position >= 0);
		Assert.isTrue(position <= document.getLength());
		
		try {
			ITypedRegion region= TextUtilities.getPartition(document, partitioning, position);
			return region.getType().equals(IDocument.DEFAULT_CONTENT_TYPE);
			
		} catch (BadLocationException e) {
		}
		
		return false;
	}

	private boolean isClosed(IDocument document, int offset, int length) {
		
		CompilationUnitInfo info= getCompilationUnitForMethod(document, offset, fPartitioning);
		if (info == null)
			return false;
			
		CompilationUnit compilationUnit= null;
		try {
			compilationUnit= AST.parseCompilationUnit(info.buffer);
		} catch (ArrayIndexOutOfBoundsException x) {
			// work around for parser problem
			return false;
		}
		
		IProblem[] problems= compilationUnit.getProblems();
		for (int i= 0; i != problems.length; ++i) {
			if (problems[i].getID() == IProblem.UnmatchedBracket)
				return true;
		}
		
		final int relativeOffset= offset - info.delta;
		
		ASTNode node= NodeFinder.perform(compilationUnit, relativeOffset, length);
		if (node == null)
			return false;

		if (length == 0) {
			while (node != null && (relativeOffset == node.getStartPosition() || relativeOffset == node.getStartPosition() + node.getLength()))
				node= node.getParent();
		}
		
		switch (node.getNodeType()) {
		case ASTNode.BLOCK:
			return areBlocksConsistent(document, offset, fPartitioning);

		case ASTNode.IF_STATEMENT: 
			{
				IfStatement ifStatement= (IfStatement) node;
				Expression expression= ifStatement.getExpression();
				IRegion expressionRegion= createRegion(expression, info.delta);
				Statement thenStatement= ifStatement.getThenStatement();
				IRegion thenRegion= createRegion(thenStatement, info.delta);

				// between expression and then statement
				if (expressionRegion.getOffset() + expressionRegion.getLength() <= offset && offset + length <= thenRegion.getOffset())
					return thenStatement != null;
				

				Statement elseStatement= ifStatement.getElseStatement();
				IRegion elseRegion= createRegion(elseStatement, info.delta);
				
				IRegion elseToken= null;
				if (elseStatement != null) {
					int sourceOffset= thenRegion.getOffset() + thenRegion.getLength();
					int sourceLength= elseRegion.getOffset() - sourceOffset;
					elseToken= getToken(document, new Region(sourceOffset, sourceLength), ITerminalSymbols.TokenNameelse);
				}
				
				// between 'else' keyword and else statement				
				if (elseToken.getOffset() + elseToken.getLength() <= offset && offset + length < elseRegion.getOffset())
					return elseStatement != null;
			}
			break;

		case ASTNode.WHILE_STATEMENT:
		case ASTNode.FOR_STATEMENT:
			{
				Expression expression= node.getNodeType() == ASTNode.WHILE_STATEMENT ? ((WhileStatement) node).getExpression() : ((ForStatement) node).getExpression();
				IRegion expressionRegion= createRegion(expression, info.delta);
				Statement body= node.getNodeType() == ASTNode.WHILE_STATEMENT ? ((WhileStatement) node).getBody() : ((ForStatement) node).getBody();
				IRegion bodyRegion= createRegion(body, info.delta);
				
				// between expression and body statement
				if (expressionRegion.getOffset() + expressionRegion.getLength() <= offset && offset + length <= bodyRegion.getOffset())
					return body != null;
			}
			break;

		case ASTNode.DO_STATEMENT:
			{
				DoStatement doStatement= (DoStatement) node;
				IRegion doRegion= createRegion(doStatement, info.delta);
				Statement body= doStatement.getBody();
				IRegion bodyRegion= createRegion(body, info.delta);

				if (doRegion.getOffset() + doRegion.getLength() <= offset && offset + length <= bodyRegion.getOffset())
					return body != null;
			}
			break;
		}
		
		return true;
	}

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

		return System.getProperty("line.separator"); //$NON-NLS-1$
	}
	
	/**
	 * Installs a java partitioner with <code>document</code>.
	 * 
	 * @param document the document
	 */
	private static void installJavaStuff(Document document) {
		String[] types= new String[] {
									  IJavaPartitions.JAVA_DOC,
									  IJavaPartitions.JAVA_MULTI_LINE_COMMENT,
									  IJavaPartitions.JAVA_SINGLE_LINE_COMMENT,
									  IJavaPartitions.JAVA_STRING,
									  IJavaPartitions.JAVA_CHARACTER,
									  IDocument.DEFAULT_CONTENT_TYPE
		};
		DefaultPartitioner partitioner= new DefaultPartitioner(new FastJavaPartitionScanner(), types);
		partitioner.connect(document);
		document.setDocumentPartitioner(IJavaPartitions.JAVA_PARTITIONING, partitioner);
	}

	private static void smartPaste(IDocument document, DocumentCommand command) {
		try {
			JavaHeuristicScanner scanner= new JavaHeuristicScanner(document);
			JavaIndenter indenter= new JavaIndenter(document, scanner);
			int offset= command.offset;
			
			// reference position to get the indent from
			int refOffset= indenter.findReferencePosition(offset);
			if (refOffset == JavaHeuristicScanner.NOT_FOUND)
				return;
			int peerOffset= getPeerPosition(document, command);
			peerOffset= indenter.findReferencePosition(peerOffset);
			refOffset= Math.min(refOffset, peerOffset);
			
			// eat any WS before the insertion to the beginning of the line 
			IRegion line= document.getLineInformationOfOffset(offset);
			String notSelected= document.get(line.getOffset(), offset - line.getOffset());
			if (notSelected.trim().length() == 0) {
				command.length += notSelected.length();
				command.offset= line.getOffset();
			}
			
			// prefix: the part we need for formatting but won't paste
			IRegion refLine= document.getLineInformationOfOffset(refOffset);
			String prefix= document.get(refLine.getOffset(), command.offset - refLine.getOffset());
			
			// handle the indentation computation inside a temporary document
			Document temp= new Document(prefix + command.text);
			scanner= new JavaHeuristicScanner(temp);
			indenter= new JavaIndenter(temp, scanner);
			installJavaStuff(temp);
			
			// indent the first and second line
			// compute the relative indentation difference from the second line
			// (as the first might be partially selected) and use the value to
			// indent all other lines.
			boolean isIndentDetected= false;
			StringBuffer addition= new StringBuffer();
			int insertLength= 0;
			int first= document.computeNumberOfLines(prefix);
			int lines= temp.getNumberOfLines();
			for (int l= first; l < lines; l++) { // we don't change the number of lines while adding indents
				
				IRegion r= temp.getLineInformation(l);
				int lineOffset= r.getOffset();
				int lineLength= r.getLength();
				
				if (lineLength == 0) // don't modify empty lines
					continue;
				
				if (!isIndentDetected){
					
					// indent the first pasted line
					String current= getCurrentIndent(temp, l);
					StringBuffer correct= indenter.computeIndentation(lineOffset);
					if (correct == null)
						return; // bail out
					
					insertLength= subtractIndent(correct, current, addition);
					if (l != first)
						isIndentDetected= true;
				}
				
				// relatively indent all pasted lines 
				if (insertLength > 0)
					addIndent(temp, l, addition);
				else if (insertLength < 0)
					cutIndent(temp, l, -insertLength);
				
			}
			
			// modify the command
			command.text= temp.get(prefix.length(), temp.getLength() - prefix.length());
			
		} catch (BadLocationException e) {
			JavaPlugin.log(e);
		}

	}

	/**
	 * Returns the indentation of the line <code>line</code> in <code>document</code>.
	 * The returned string may contain pairs of leading slashes that are considered
	 * part of the indentation. The space before the asterix in a javadoc-like
	 * comment is not considered part of the indentation.
	 * 
	 * @param document the document
	 * @param line the line
	 * @return the indentation of <code>line</code> in <code>document</code>
	 * @throws BadLocationException if the document is changed concurrently
	 */
	private static String getCurrentIndent(Document document, int line) throws BadLocationException {
		IRegion region= document.getLineInformation(line);
		int from= region.getOffset();
		int endOffset= region.getOffset() + region.getLength();
		
		// go behind line comments
		int to= from;
		while (to < endOffset - 2 && document.get(to, 2).equals(LINE_COMMENT))
			to += 2;
		
		while (to < endOffset) {
			char ch= document.getChar(to);
			if (!Character.isWhitespace(ch))
				break;
			to++;
		}
		
		// don't count the space before javadoc like, asterix-style comment lines
		if (to > from && to < endOffset - 1 && document.get(to - 1, 2).equals(" *")) { //$NON-NLS-1$
			String type= TextUtilities.getContentType(document, IJavaPartitions.JAVA_PARTITIONING, to);
			if (type.equals(IJavaPartitions.JAVA_DOC) || type.equals(IJavaPartitions.JAVA_MULTI_LINE_COMMENT))
				to--;
		}
		
		return document.get(from, to - from);
	}

	/**
	 * Computes the difference of two indentations and returns the difference in
	 * length of current and correct. If the return value is positive, <code>addition</code>
	 * is initialized with a substring of that length of <code>correct</code>.
	 * 
	 * @param correct the correct indentation
	 * @param current the current indentation (migth contain non-whitespace)
	 * @param difference a string buffer - if the return value is positive, it will be cleared and set to the substring of <code>current</code> of that length
	 * @return the difference in lenght of <code>correct</code> and <code>current</code> 
	 */
	private static int subtractIndent(CharSequence correct, CharSequence current, StringBuffer difference) {
		int c1= computeVisualLength(correct);
		int c2= computeVisualLength(current);
		int diff= c1 - c2;
		if (diff <= 0)
			return diff;
		
		difference.setLength(0);
		int len= 0, i= 0;
		while (len < diff) {
			char c= correct.charAt(i++);
			difference.append(c);
			len += computeVisualLength(c);
		}
		
		
		return diff;
	}

	/**
	 * Indents line <code>line</code> in <code>document</code> with <code>indent</code>.
	 * Leaves leading comment signs alone.
	 * 
	 * @param document the document
	 * @param line the line
	 * @param indent the indentation to insert
	 * @throws BadLocationException on concurrent document modification
	 */
	private static void addIndent(Document document, int line, CharSequence indent) throws BadLocationException {
		IRegion region= document.getLineInformation(line);
		int insert= region.getOffset();
		int endOffset= region.getOffset() + region.getLength();
		
		// go behind line comments
		while (insert < endOffset - 2 && document.get(insert, 2).equals(LINE_COMMENT))
			insert += 2;
		
		// insert indent
		document.replace(insert, 0, indent.toString());
	}

	/**
	 * Cuts the visual equivalent of <code>toDelete</code> characters out of the
	 * indentation of line <code>line</code> in <code>document</code>. Leaves
	 * leading comment signs alone.
	 * 
	 * @param document the document
	 * @param line the line
	 * @param toDelete the number of space equivalents to delete.
	 * @throws BadLocationException on concurrent document modification
	 */
	private static void cutIndent(Document document, int line, int toDelete) throws BadLocationException {
		IRegion region= document.getLineInformation(line);
		int from= region.getOffset();
		int endOffset= region.getOffset() + region.getLength();
		
		// go behind line comments
		while (from < endOffset - 2 && document.get(from, 2).equals(LINE_COMMENT))
			from += 2;
		
		int to= from;
		while (toDelete > 0 && to < endOffset) {
			char ch= document.getChar(to);
			if (!Character.isWhitespace(ch))
				break;
			toDelete -= computeVisualLength(ch);
			to++;
		}
		
		document.replace(from, to - from, null);
	}

	/**
	 * Returns the visual length of a given <code>CharSequence</code> taking into
	 * account the visual tabulator length.
	 * 
	 * @param seq the string to measure
	 * @return the visual length of <code>seq</code>
	 */
	private static int computeVisualLength(CharSequence seq) {
		int size= 0;
		int tablen= getVisualTabLengthPreference();
		
		for (int i= 0; i < seq.length(); i++) {
			char ch= seq.charAt(i);
			if (ch == '\t')
				size += tablen - size % tablen;
			else
				size++;
		}
		return size;
	}
	
	/**
	 * Returns the visual length of a given character taking into
	 * account the visual tabulator length.
	 * 
	 * @param ch the character to measure
	 * @return the visual length of <code>ch</code>
	 */
	private static int computeVisualLength(char ch) {
		if (ch == '\t')
			return getVisualTabLengthPreference();
		else
			return 1;
	}

	/**
	 * The preference setting for the visual tabulator display.
	 *  
	 * @return the number of spaces displayed for a tabulator in the editor
	 */
	private static int getVisualTabLengthPreference() {
		return JavaPlugin.getDefault().getPreferenceStore().getInt(PreferenceConstants.EDITOR_TAB_WIDTH);
	}

	private static int getPeerPosition(IDocument document, DocumentCommand command) {
    	/*
    	 * Search for scope closers in the pasted text and find their opening peers
    	 * in the document. 
    	 */
    	Document pasted= new Document(command.text);
    	installJavaStuff(pasted);
    	int firstPeer= command.offset;
    	
    	JavaHeuristicScanner pScanner= new JavaHeuristicScanner(pasted);
    	JavaHeuristicScanner dScanner= new JavaHeuristicScanner(document);
    	
    	// add scope relevant after context to peer search
    	int afterToken= dScanner.nextToken(command.offset + command.length, JavaHeuristicScanner.UNBOUND);
    	try {
			switch (afterToken) {
			case Symbols.TokenRBRACE:
				pasted.replace(pasted.getLength(), 0, "}"); //$NON-NLS-1$
				break;
			case Symbols.TokenRPAREN:
				pasted.replace(pasted.getLength(), 0, ")"); //$NON-NLS-1$
				break;
			case Symbols.TokenRBRACKET:
				pasted.replace(pasted.getLength(), 0, "]"); //$NON-NLS-1$
				break;
			}
		} catch (BadLocationException e) {
			// cannot happen
			Assert.isTrue(false);
		}
    	
    	int pPos= 0; // paste text position (increasing from 0)
    	int dPos= Math.max(0, command.offset - 1); // document position (decreasing from paste offset)
    	while (true) {
    		int token= pScanner.nextToken(pPos, JavaHeuristicScanner.UNBOUND);
   			pPos= pScanner.getPosition();
    		switch (token) {
    			case Symbols.TokenLBRACE:
    			case Symbols.TokenLBRACKET:
    			case Symbols.TokenLPAREN:
    				pPos= skipScope(pScanner, pPos, token);
    				if (pPos == JavaHeuristicScanner.NOT_FOUND)
    					return firstPeer;
    				break; // closed scope -> keep searching
    			case Symbols.TokenRBRACE:
    				int peer= dScanner.findOpeningPeer(dPos, '{', '}');
    				dPos= peer - 1; 
    				if (peer == JavaHeuristicScanner.NOT_FOUND)
    					return firstPeer;
    				firstPeer= peer;
    				break; // keep searching
    			case Symbols.TokenRBRACKET:
    				peer= dScanner.findOpeningPeer(dPos, '[', ']');
    				dPos= peer - 1; 
    				if (peer == JavaHeuristicScanner.NOT_FOUND)
    					return firstPeer;
    				firstPeer= peer;
    				break; // keep searching
    			case Symbols.TokenRPAREN:
    				peer= dScanner.findOpeningPeer(dPos, '(', ')');
    				dPos= peer - 1; 
    				if (peer == JavaHeuristicScanner.NOT_FOUND)
    					return firstPeer;
    				firstPeer= peer;
    				break; // keep searching
    			case Symbols.TokenCASE:
    			case Symbols.TokenDEFAULT:
    				JavaIndenter indenter= new JavaIndenter(document, dScanner);
    				peer= indenter.findReferencePosition(dPos, false, false, false, true);
    				if (peer == JavaHeuristicScanner.NOT_FOUND)
    					return firstPeer;
    				firstPeer= peer;
    				break; // keep searching
    				
    			case Symbols.TokenEOF:
    				return firstPeer;
    			default:
    				// keep searching
    		}
    	}
    }

    /**
     * Skips the scope opened by <code>token</code> in <code>document</code>,
     * returns either the position of the 
     * @param pos
     * @param token
     * @return
     */
    private static int skipScope(JavaHeuristicScanner scanner, int pos, int token) {
    	int openToken= token;
    	int closeToken;
    	switch (token) {
    		case Symbols.TokenLPAREN:
    			closeToken= Symbols.TokenRPAREN;
    			break;
    		case Symbols.TokenLBRACKET:
    			closeToken= Symbols.TokenRBRACKET;
    			break;
    		case Symbols.TokenLBRACE:
    			closeToken= Symbols.TokenRBRACE;
    			break;
    		default:
    			Assert.isTrue(false);
    			return -1; // dummy
    	}
    	
    	int depth= 1;
    	int p= pos;

    	while (true) {
    		int tok= scanner.nextToken(p, JavaHeuristicScanner.UNBOUND);
    		p= scanner.getPosition();
    		
    		if (tok == openToken) {
    			depth++;
    		} else if (tok == closeToken) {
    			depth--;
    			if (depth == 0)
    				return p + 1;
    		} else if (tok == Symbols.TokenEOF) {
    			return JavaHeuristicScanner.NOT_FOUND;
    		}
    	}
    }

    private boolean isLineDelimiter(IDocument document, String text) {
		String[] delimiters= document.getLegalLineDelimiters();
		if (delimiters != null)
			return TextUtilities.equals(delimiters, text) > -1;
		return false;
	}

	private void smartIndentAfterBlockDelimiter(IDocument document, DocumentCommand command) {
		if (command.text.charAt(0) == '}')
			smartIndentAfterClosingBracket(document, command);
		else if (command.text.charAt(0) == '{')
			smartIndentAfterOpeningBracket(document, command);
	}

	/*
	 * @see org.eclipse.jface.text.IAutoIndentStrategy#customizeDocumentCommand(org.eclipse.jface.text.IDocument, org.eclipse.jface.text.DocumentCommand)
	 */
	public void customizeDocumentCommand(IDocument d, DocumentCommand c) {
		
		clearCachedValues();
		if (!isSmartMode() || c.doit == false)
			return;
		
		if (c.length == 0 && c.text != null && isLineDelimiter(d, c.text))
			smartIndentAfterNewLine(d, c);
		else if (c.text.length() == 1)
			smartIndentAfterBlockDelimiter(d, c);
		else if (c.text.length() > 1 && getPreferenceStore().getBoolean(PreferenceConstants.EDITOR_SMART_PASTE))
			smartPaste(d, c);
		
	}
	
	private static IPreferenceStore getPreferenceStore() {
		return JavaPlugin.getDefault().getPreferenceStore();
	}
	
	private boolean closeBrace() {
		return fCloseBrace;
	}

	private boolean isSmartMode() {
		return fIsSmartMode;
	}
	
	private void clearCachedValues() {
        IPreferenceStore preferenceStore= getPreferenceStore();
		fCloseBrace= preferenceStore.getBoolean(PreferenceConstants.EDITOR_CLOSE_BRACES);
		fIsSmartMode= computeSmartMode();
	}
	
	private boolean computeSmartMode() {
		IWorkbenchPage page= JavaPlugin.getActivePage();
		if (page != null)  {
			IEditorPart part= page.getActiveEditor(); 
			if (part instanceof ITextEditorExtension3) {
				ITextEditorExtension3 extension= (ITextEditorExtension3) part;
				return extension.getInsertMode() == ITextEditorExtension3.SMART_INSERT;
			}
		}
		return false;
	}

	private static CompilationUnitInfo getCompilationUnitForMethod(IDocument document, int offset, String partitioning) {
		try {
			JavaHeuristicScanner scanner= new JavaHeuristicScanner(document);
			
			IRegion sourceRange= scanner.findSurroundingBlock(offset);
			if (sourceRange == null)
				return null;
			String source= document.get(sourceRange.getOffset(), sourceRange.getLength());
	
			StringBuffer contents= new StringBuffer();
			contents.append("class ____C{void ____m()"); //$NON-NLS-1$
			final int methodOffset= contents.length();
			contents.append(source);
			contents.append('}');
			
			char[] buffer= contents.toString().toCharArray();
	
			return new CompilationUnitInfo(buffer, sourceRange.getOffset() - methodOffset);
	
		} catch (BadLocationException e) {
			JavaPlugin.log(e);
		}
	
		return null;
	}
	
	private static boolean areBlocksConsistent(IDocument document, int offset, String partitioning) {
		if (offset < 1 || offset >= document.getLength())
			return false;
		
		int begin= offset;
		int end= offset - 1;
		
		JavaHeuristicScanner scanner= new JavaHeuristicScanner(document);
		
		while (true) {
			begin= scanner.findOpeningPeer(begin - 1, '{', '}');
			end= scanner.findClosingPeer(end + 1, '{', '}');
			if (begin == -1 && end == -1)
				return true;
			if (begin == -1 || end == -1)
				return false;
		}		
	}
	
	private static IRegion createRegion(ASTNode node, int delta) {
		return node == null ? null : new Region(node.getStartPosition() + delta, node.getLength());
	}
	
	private static IRegion getToken(IDocument document, IRegion scanRegion, int tokenId)  {

		try {
			
			final String source= document.get(scanRegion.getOffset(), scanRegion.getLength());
	
			IScanner scanner= ToolFactory.createScanner(false, false, false, false);
			scanner.setSource(source.toCharArray());

			int id= scanner.getNextToken();
			while (id != ITerminalSymbols.TokenNameEOF && id != tokenId)
				id= scanner.getNextToken();

			if (id == ITerminalSymbols.TokenNameEOF)
				return null;

			int tokenOffset= scanner.getCurrentTokenStartPosition();
			int tokenLength= scanner.getCurrentTokenEndPosition() + 1 - tokenOffset; // inclusive end
			return new Region(tokenOffset + scanRegion.getOffset(), tokenLength);

		} catch (InvalidInputException x) {
			return null;
		} catch (BadLocationException x) {
			return null;
		}
	}
}