/*******************************************************************************
 * Copyright (c) 2000, 2010 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
 *     Sergey Prigogin, Google
 *     Anton Leherbauer (Wind River Systems)
 *******************************************************************************/
package org.eclipse.cdt.internal.ui.text;

import java.util.Arrays;

import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.text.BadLocationException;
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.TypedRegion;

import org.eclipse.cdt.ui.text.ICPartitions;

/**
 * Utility methods for heuristic based C manipulations in an incomplete C source file.
 *
 * <p>An instance holds some internal position in the document and is therefore not thread-safe.</p>
 */
public final class CHeuristicScanner implements Symbols {
	/**
	 * Returned by all methods when the requested position could not be found, or if a
	 * {@link BadLocationException} was thrown while scanning.
	 */
	public static final int NOT_FOUND= -1;

	/**
	 * Special bound parameter that means either -1 (backward scanning) or
	 * <code>fDocument.getLength()</code> (forward scanning).
	 */
	public static final int UNBOUND= -2;


	/* character constants */
	private static final char LBRACE= '{';
	private static final char RBRACE= '}';
	private static final char LPAREN= '(';
	private static final char RPAREN= ')';
	private static final char SEMICOLON= ';';
	private static final char COLON= ':';
	private static final char COMMA= ',';
	private static final char LBRACKET= '[';
	private static final char RBRACKET= ']';
	private static final char QUESTIONMARK= '?';
	private static final char EQUAL= '=';
	private static final char LANGLE= '<';
	private static final char RANGLE= '>';
	private static final char DOT= '.';
	private static final char MINUS= '-';
	private static final char PLUS= '+';
	private static final char TILDE= '~';

	/**
	 * Specifies the stop condition, upon which the <code>scanXXX</code> methods will decide whether
	 * to keep scanning or not. This interface may implemented by clients.
	 */
	private static abstract class StopCondition {
		/**
		 * Instructs the scanner to return the current position.
		 *
		 * @param ch the char at the current position
		 * @param position the current position
		 * @param forward the iteration direction
		 * @return <code>true</code> if the stop condition is met.
		 */
		public abstract boolean stop(char ch, int position, boolean forward);

		/**
		 * Asks the condition to return the next position to query. The default
		 * is to return the next/previous position.
		 *
		 * @return the next position to scan
		 */
		public int nextPosition(int position, boolean forward) {
			return forward ? position + 1 : position - 1;
		}
	}

	/**
	 * Stops upon a non-whitespace (as defined by {@link Character#isWhitespace(char)}) character.
	 */
	private static class NonWhitespace extends StopCondition {
		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#stop(char)
		 */
		@Override
		public boolean stop(char ch, int position, boolean forward) {
			return !Character.isWhitespace(ch);
		}
	}

	/**
	 * Stops upon a non-whitespace character in the default partition.
	 *
	 * @see NonWhitespace
	 */
	private final class NonWhitespaceDefaultPartition extends NonWhitespace {
		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#stop(char)
		 */
		@Override
		public boolean stop(char ch, int position, boolean forward) {
			return super.stop(ch, position, true) && isDefaultPartition(position);
		}

		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#nextPosition(int, boolean)
		 */
		@Override
		public int nextPosition(int position, boolean forward) {
			ITypedRegion partition= getPartition(position);
			if (fPartition.equals(partition.getType()))
				return super.nextPosition(position, forward);

			if (forward) {
				int end= partition.getOffset() + partition.getLength();
				if (position < end)
					return end;
			} else {
				int offset= partition.getOffset();
				if (position > offset)
					return offset - 1;
			}
			return super.nextPosition(position, forward);
		}
	}

	/**
	 * Stops upon a non-java identifier (as defined by {@link Character#isJavaIdentifierPart(char)}) character.
	 */
	private static class NonJavaIdentifierPart extends StopCondition {
		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#stop(char)
		 */
		@Override
		public boolean stop(char ch, int position, boolean forward) {
			return !Character.isJavaIdentifierPart(ch);
		}
	}

	/**
	 * Stops upon a non-java identifier character in the default partition.
	 *
	 * @see NonJavaIdentifierPart
	 */
	private final class NonJavaIdentifierPartDefaultPartition extends NonJavaIdentifierPart {
		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#stop(char)
		 */
		@Override
		public boolean stop(char ch, int position, boolean forward) {
			return super.stop(ch, position, true) || !isDefaultPartition(position);
		}

		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#nextPosition(int, boolean)
		 */
		@Override
		public int nextPosition(int position, boolean forward) {
			ITypedRegion partition= getPartition(position);
			if (fPartition.equals(partition.getType()))
				return super.nextPosition(position, forward);

			if (forward) {
				int end= partition.getOffset() + partition.getLength();
				if (position < end)
					return end;
			} else {
				int offset= partition.getOffset();
				if (position > offset)
					return offset - 1;
			}
			return super.nextPosition(position, forward);
		}
	}

	/**
	 * Stops upon a character in the default partition that matches the given character list.
	 */
	private final class CharacterMatch extends StopCondition {
		private final char[] fChars;

		/**
		 * Creates a new instance.
		 * @param ch the single character to match
		 */
		public CharacterMatch(char ch) {
			this(new char[] {ch});
		}

		/**
		 * Creates a new instance.
		 * @param chars the chars to match.
		 */
		public CharacterMatch(char[] chars) {
			Assert.isNotNull(chars);
			Assert.isTrue(chars.length > 0);
			fChars= chars;
			Arrays.sort(chars);
		}

		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#stop(char, int)
		 */
		@Override
		public boolean stop(char ch, int position, boolean forward) {
			return Arrays.binarySearch(fChars, ch) >= 0 && isDefaultPartition(position);
		}

		/*
		 * @see org.eclipse.cdt.internal.ui.text.CHeuristicScanner.StopCondition#nextPosition(int, boolean)
		 */
		@Override
		public int nextPosition(int position, boolean forward) {
			ITypedRegion partition= getPartition(position);
			if (fPartition.equals(partition.getType()))
				return super.nextPosition(position, forward);

			if (forward) {
				int end= partition.getOffset() + partition.getLength();
				if (position < end)
					return end;
			} else {
				int offset= partition.getOffset();
				if (position > offset)
					return offset - 1;
			}
			return super.nextPosition(position, forward);
		}
	}

	/** The document being scanned. */
	private final IDocument fDocument;
	/** The partitioning being used for scanning. */
	private final String fPartitioning;
	/** The partition to scan in. */
	private final String fPartition;

	/* internal scan state */

	/** the most recently read character. */
	private char fChar;
	/** the most recently read position. */
	private int fPos;
	/**
	 * The most recently used partition.
	 */
	private ITypedRegion fCachedPartition= new TypedRegion(-1, 0, "__no_partition_at_all"); //$NON-NLS-1$

	/* preset stop conditions */
	private final StopCondition fNonWSDefaultPart= new NonWhitespaceDefaultPartition();
	private static final StopCondition fNonWS= new NonWhitespace();
	private final StopCondition fNonIdent= new NonJavaIdentifierPartDefaultPartition();

	/**
	 * Creates a new instance.
	 *
	 * @param document the document to scan
	 * @param partitioning the partitioning to use for scanning
	 * @param partition the partition to scan in
	 */
	public CHeuristicScanner(IDocument document, String partitioning, String partition) {
		Assert.isLegal(document != null);
		Assert.isLegal(partitioning != null);
		Assert.isLegal(partition != null);
		fDocument= document;
		fPartitioning= partitioning;
		fPartition= partition;
	}

	/**
	 * Calls <code>this(document, ICPartitions.C_PARTITIONING, IDocument.DEFAULT_CONTENT_TYPE)</code>.
	 *
	 * @param document the document to scan.
	 */
	public CHeuristicScanner(IDocument document) {
		this(document, ICPartitions.C_PARTITIONING, IDocument.DEFAULT_CONTENT_TYPE);
	}

	/**
	 * Returns the most recent internal scan position.
	 *
	 * @return the most recent internal scan position.
	 */
	public int getPosition() {
		return fPos;
	}

	/**
	 * Returns the next token in forward direction, starting at <code>start</code>, and not extending
	 * further than <code>bound</code>. The return value is one of the constants defined in {@link Symbols}.
	 * After a call, {@link #getPosition()} will return the position just after the scanned token
	 * (i.e. the next position that will be scanned).
	 *
	 * @param start the first character position in the document to consider
	 * @param bound the first position not to consider any more
	 * @return a constant from {@link Symbols} describing the next token
	 */
	public int nextToken(int start, int bound) {
		int pos= scanForward(start, bound, fNonWS);
		if (pos == NOT_FOUND)
			return TokenEOF;
		try {
			// check for string or char literal
			char ch = fDocument.getChar(pos);
			if (ch == '"' || ch == '\'') {
				fChar= ch;
				fPos= fNonWSDefaultPart.nextPosition(pos, true);
				return TokenOTHER;
			}
		} catch (BadLocationException exc) {
		}
		pos= scanForward(pos, bound, fNonWSDefaultPart);
		if (pos == NOT_FOUND)
			return TokenEOF;

		fPos++;

		switch (fChar) {
			case LBRACE:
				return TokenLBRACE;
			case RBRACE:
				return TokenRBRACE;
			case LBRACKET:
				return TokenLBRACKET;
			case RBRACKET:
				return TokenRBRACKET;
			case LPAREN:
				return TokenLPAREN;
			case RPAREN:
				return TokenRPAREN;
			case SEMICOLON:
				return TokenSEMICOLON;
			case COLON:
				switch (peekNextChar()) {
				case COLON:
					++fPos;
					return TokenDOUBLECOLON;
				}
				return TokenCOLON;
			case COMMA:
				return TokenCOMMA;
			case QUESTIONMARK:
				return TokenQUESTIONMARK;
			case EQUAL:
				return TokenEQUAL;
			case LANGLE:
				switch (peekNextChar()) {
				case LANGLE:
					++fPos;
					return TokenSHIFTLEFT;
				case EQUAL:
					++fPos;
					return TokenOTHER;
				}
				return TokenLESSTHAN;
			case RANGLE:
				switch (peekNextChar()) {
				case RANGLE:
					++fPos;
					return TokenSHIFTRIGHT;
				case EQUAL:
					++fPos;
					return TokenOTHER;
				}
				return TokenGREATERTHAN;
			case DOT:
				return TokenDOT;
			case MINUS:
				switch (peekNextChar()) {
				case RANGLE:
					++fPos;
					return TokenARROW;
				}
				return TokenMINUS;
			case PLUS:
				return TokenPLUS;
			case TILDE:
				return TokenTILDE;
		}

		// else
		if (Character.isJavaIdentifierPart(fChar)) {
			// assume an identifier or keyword
			int from= pos, to;
			pos= scanForward(pos + 1, bound, fNonIdent);
			if (pos == NOT_FOUND)
				to= bound == UNBOUND ? fDocument.getLength() : bound;
			else
				to= pos;

			String identOrKeyword;
			try {
				identOrKeyword= fDocument.get(from, to - from);
			} catch (BadLocationException e) {
				return TokenEOF;
			}

			return getToken(identOrKeyword);


		}
		// operators, number literals etc
		return TokenOTHER;
	}

	/**
	 * Returns the next token in backward direction, starting at <code>start</code>, and not extending
	 * further than <code>bound</code>. The return value is one of the constants defined in {@link Symbols}.
	 * After a call, {@link #getPosition()} will return the position just before the scanned token
	 * starts (i.e. the next position that will be scanned).
	 *
	 * @param start the first character position in the document to consider
	 * @param bound the first position not to consider any more
	 * @return a constant from {@link Symbols} describing the previous token
	 */
	public int previousToken(int start, int bound) {
		int pos= scanBackward(start, bound, fNonWSDefaultPart);
		if (pos == NOT_FOUND)
			return TokenEOF;

		fPos--;

		switch (fChar) {
			case LBRACE:
				return TokenLBRACE;
			case RBRACE:
				return TokenRBRACE;
			case LBRACKET:
				return TokenLBRACKET;
			case RBRACKET:
				return TokenRBRACKET;
			case LPAREN:
				return TokenLPAREN;
			case RPAREN:
				return TokenRPAREN;
			case SEMICOLON:
				return TokenSEMICOLON;
			case COLON:
				switch (peekPreviousChar()) {
				case COLON:
					--fPos;
					return TokenDOUBLECOLON;
				}
				return TokenCOLON;
			case COMMA:
				return TokenCOMMA;
			case QUESTIONMARK:
				return TokenQUESTIONMARK;
			case EQUAL:
				switch (peekPreviousChar()) {
				case RANGLE:
				case LANGLE:
					--fPos;
					return TokenOTHER;
				}
				return TokenEQUAL;
			case LANGLE:
				switch (peekPreviousChar()) {
				case LANGLE:
					--fPos;
					return TokenSHIFTLEFT;
				}
				return TokenLESSTHAN;
			case RANGLE:
				switch (peekPreviousChar()) {
				case RANGLE:
					--fPos;
					return TokenSHIFTRIGHT;
				case MINUS:
					--fPos;
					return TokenARROW;
				}
				return TokenGREATERTHAN;
			case DOT:
				return TokenDOT;
			case MINUS:
				return TokenMINUS;
			case PLUS:
				return TokenPLUS;
			case TILDE:
				return TokenTILDE;
		}

		// else
		if (Character.isJavaIdentifierPart(fChar)) {
			// assume an ident or keyword
			int from, to= pos + 1;
			pos= scanBackward(pos - 1, bound, fNonIdent);
			if (pos == NOT_FOUND)
				from= bound == UNBOUND ? 0 : bound + 1;
			else
				from= pos + 1;

			String identOrKeyword;
			try {
				identOrKeyword= fDocument.get(from, to - from);
			} catch (BadLocationException e) {
				return TokenEOF;
			}

			return getToken(identOrKeyword);
		}
		// operators, number literals etc
		return TokenOTHER;
	}

	/**
	 * @return the next char without shifting the position
	 */
	private char peekNextChar() {
		if (fPos + 1 < fDocument.getLength()) {
			try {
				return fDocument.getChar(fPos + 1);
			} catch (BadLocationException exc) {
			}
		}
		return (char)-1;
	}

	/**
	 * @return the previous char without shifting the position
	 */
	private char peekPreviousChar() {
		if (fPos >= 0) {
			try {
				return fDocument.getChar(fPos);
			} catch (BadLocationException e) {
			}
		}
		return (char)-1;
	}

	/**
	 * Returns one of the keyword constants or <code>TokenIDENT</code> for a scanned identifier.
	 *
	 * @param s a scanned identifier
	 * @return one of the constants defined in {@link Symbols}
	 */
	private int getToken(String s) {
		Assert.isNotNull(s);

		switch (s.length()) {
			case 2:
				if ("if".equals(s)) //$NON-NLS-1$
					return TokenIF;
				if ("do".equals(s)) //$NON-NLS-1$
					return TokenDO;
				break;
			case 3:
				if ("for".equals(s)) //$NON-NLS-1$
					return TokenFOR;
				if ("try".equals(s)) //$NON-NLS-1$
					return TokenTRY;
				if ("new".equals(s)) //$NON-NLS-1$
					return TokenNEW;
				break;
			case 4:
				if ("case".equals(s)) //$NON-NLS-1$
					return TokenCASE;
				if ("else".equals(s)) //$NON-NLS-1$
					return TokenELSE;
				if ("enum".equals(s)) //$NON-NLS-1$
					return TokenENUM;
				if ("goto".equals(s)) //$NON-NLS-1$
					return TokenGOTO;
				break;
			case 5:
				if ("break".equals(s)) //$NON-NLS-1$
					return TokenBREAK;
				if ("catch".equals(s)) //$NON-NLS-1$
					return TokenCATCH;
				if ("class".equals(s)) //$NON-NLS-1$
					return TokenCLASS;
				if ("const".equals(s)) //$NON-NLS-1$
					return TokenCONST;
				if ("while".equals(s)) //$NON-NLS-1$
					return TokenWHILE;
				if ("union".equals(s)) //$NON-NLS-1$
					return TokenUNION;
				if ("using".equals(s)) //$NON-NLS-1$
					return TokenUSING;
				if ("throw".equals(s)) //$NON-NLS-1$
					return TokenTHROW;
				break;
			case 6:
				if ("delete".equals(s)) //$NON-NLS-1$
					return TokenDELETE;
				if ("public".equals(s)) //$NON-NLS-1$
					return TokenPUBLIC;
				if ("return".equals(s)) //$NON-NLS-1$
					return TokenRETURN;
				if ("static".equals(s)) //$NON-NLS-1$
					return TokenSTATIC;
				if ("struct".equals(s)) //$NON-NLS-1$
					return TokenSTRUCT;
				if ("switch".equals(s)) //$NON-NLS-1$
					return TokenSWITCH;
				if ("extern".equals(s)) //$NON-NLS-1$
					return TokenEXTERN;
				break;
			case 7:
				if ("default".equals(s)) //$NON-NLS-1$
					return TokenDEFAULT;
				if ("private".equals(s)) //$NON-NLS-1$
					return TokenPRIVATE;
				if ("typedef".equals(s)) //$NON-NLS-1$
					return TokenTYPEDEF;
				if ("virtual".equals(s)) //$NON-NLS-1$
					return TokenVIRTUAL;
				break;
			case 8:
				if ("operator".equals(s)) //$NON-NLS-1$
					return TokenOPERATOR;
				if ("template".equals(s)) //$NON-NLS-1$
					return TokenTEMPLATE;
				if ("typename".equals(s)) //$NON-NLS-1$
					return TokenTYPENAME;
				break;
			case 9:
				if ("namespace".equals(s)) //$NON-NLS-1$
					return TokenNAMESPACE;
				if ("protected".equals(s)) //$NON-NLS-1$
					return TokenPROTECTED;
		}
		return TokenIDENT;
	}

	/**
	 * Returns the position of the closing peer character (forward search). Any scopes introduced
	 * by opening peers are skipped. All peers accounted for must reside in the default partition.
	 *
	 * <p>Note that <code>start</code> must not point to the opening peer, but to the first
	 * character being searched.</p>
	 *
	 * @param start the start position
	 * @param openingPeer the opening peer character (e.g. '{')
	 * @param closingPeer the closing peer character (e.g. '}')
	 * @return the matching peer character position, or <code>NOT_FOUND</code>
	 */
	public int findClosingPeer(int start, final char openingPeer, final char closingPeer) {
		return findClosingPeer(start, UNBOUND, openingPeer, closingPeer);
	}

	/**
	 * Returns the position of the closing peer character (forward search). Any scopes introduced by opening peers
	 * are skipped. All peers accounted for must reside in the default partition.
	 *
	 * <p>Note that <code>start</code> must not point to the opening peer, but to the first
	 * character being searched.</p>
	 *
	 * @param start the start position
	 * @param bound the bound
	 * @param openingPeer the opening peer character (e.g. '{')
	 * @param closingPeer the closing peer character (e.g. '}')
	 * @return the matching peer character position, or <code>NOT_FOUND</code>
	 */
	public int findClosingPeer(int start, int bound, final char openingPeer, final char closingPeer) {
		Assert.isLegal(start >= 0);

		try {
			int depth= 1;
			start -= 1;
			while (true) {
				start= scanForward(start + 1, bound, new CharacterMatch(new char[] {openingPeer, closingPeer}));
				if (start == NOT_FOUND)
					return NOT_FOUND;

				if (fDocument.getChar(start) == openingPeer)
					depth++;
				else
					depth--;

				if (depth == 0)
					return start;
			}

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

	/**
	 * Returns the position of the opening peer character (backward search). Any scopes introduced by closing peers
	 * are skipped. All peers accounted for must reside in the default partition.
	 *
	 * <p>Note that <code>start</code> must not point to the closing peer, but to the first
	 * character being searched.</p>
	 *
	 * @param start the start position
	 * @param openingPeer the opening peer character (e.g. '{')
	 * @param closingPeer the closing peer character (e.g. '}')
	 * @return the matching peer character position, or <code>NOT_FOUND</code>
	 */
	public int findOpeningPeer(int start, char openingPeer, char closingPeer) {
		return findOpeningPeer(start, CHeuristicScanner.UNBOUND, openingPeer, closingPeer);
	}

	/**
	 * Returns the position of the opening peer character (backward search). Any scopes introduced by closing peers
	 * are skipped. All peers accounted for must reside in the default partition.
	 *
	 * <p>Note that <code>start</code> must not point to the closing peer, but to the first
	 * character being searched.</p>
	 *
	 * @param start the start position
	 * @param bound the bound
	 * @param openingPeer the opening peer character (e.g. '{')
	 * @param closingPeer the closing peer character (e.g. '}')
	 * @return the matching peer character position, or <code>NOT_FOUND</code>
	 */
	public int findOpeningPeer(int start, int bound, char openingPeer, char closingPeer) {
		Assert.isLegal(start < fDocument.getLength());

		try {
			final CharacterMatch match= new CharacterMatch(new char[] {openingPeer, closingPeer});
			int depth= 1;
			start += 1;
			while (true) {
				start= scanBackward(start - 1, bound, match);
				if (start == NOT_FOUND)
					return NOT_FOUND;

				if (fDocument.getChar(start) == closingPeer)
					depth++;
				else
					depth--;

				if (depth == 0)
					return start;
			}

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

	/**
	 * Computes the surrounding block around <code>offset</code>. The search is started at the
	 * beginning of <code>offset</code>, i.e. an opening brace at <code>offset</code> will not be
	 * part of the surrounding block, but a closing brace will.
	 *
	 * @param offset the offset for which the surrounding block is computed
	 * @return a region describing the surrounding block, or <code>null</code> if none can be found
	 */
	public IRegion findSurroundingBlock(int offset) {
		if (offset < 1 || offset >= fDocument.getLength())
			return null;

		int begin= findOpeningPeer(offset - 1, CHeuristicScanner.UNBOUND, LBRACE, RBRACE);
		int end= findClosingPeer(offset, UNBOUND, LBRACE, RBRACE);
		if (begin == NOT_FOUND || end == NOT_FOUND)
			return null;
		return new Region(begin, end + 1 - begin);
	}

	/**
	 * Finds the smallest position in <code>fDocument</code> such that the position is &gt;= <code>position</code>
	 * and &lt; <code>bound</code> and <code>Character.isWhitespace(fDocument.getChar(pos))</code> evaluates to <code>false</code>
	 * and the position is in the default partition.
	 *
	 * @param position the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &gt; <code>position</code>, or <code>UNBOUND</code>
	 * @return the smallest position of a non-whitespace character in [<code>position</code>, <code>bound</code>) that resides in a C partition, or <code>NOT_FOUND</code> if none can be found
	 */
	public int findNonWhitespaceForward(int position, int bound) {
		return scanForward(position, bound, fNonWSDefaultPart);
	}

	/**
	 * Finds the smallest position in <code>fDocument</code> such that the position is &gt;= <code>position</code>
	 * and &lt; <code>bound</code> and <code>Character.isWhitespace(fDocument.getChar(pos))</code> evaluates to <code>false</code>.
	 *
	 * @param position the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &gt; <code>position</code>, or <code>UNBOUND</code>
	 * @return the smallest position of a non-whitespace character in [<code>position</code>, <code>bound</code>), or <code>NOT_FOUND</code> if none can be found
	 */
	public int findNonWhitespaceForwardInAnyPartition(int position, int bound) {
		return scanForward(position, bound, fNonWS);
	}

	/**
	 * Finds the highest position in <code>fDocument</code> such that the position is &lt;= <code>position</code>
	 * and &gt; <code>bound</code> and <code>Character.isWhitespace(fDocument.getChar(pos))</code> evaluates to <code>false</code>
	 * and the position is in the default partition.
	 *
	 * @param position the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &lt; <code>position</code>, or <code>UNBOUND</code>
	 * @return the highest position of a non-whitespace character in (<code>bound</code>, <code>position</code>] that resides in a C partition, or <code>NOT_FOUND</code> if none can be found
	 */
	public int findNonWhitespaceBackward(int position, int bound) {
		return scanBackward(position, bound, fNonWSDefaultPart);
	}

	/**
	 * Finds the lowest position <code>p</code> in <code>fDocument</code> such that <code>start</code> &lt;= p &lt;
	 * <code>bound</code> and <code>condition.stop(fDocument.getChar(p), p)</code> evaluates to <code>true</code>.
	 *
	 * @param start the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &gt; <code>start</code>, or <code>UNBOUND</code>
	 * @param condition the <code>StopCondition</code> to check
	 * @return the lowest position in [<code>start</code>, <code>bound</code>) for which <code>condition</code> holds, or <code>NOT_FOUND</code> if none can be found
	 */
	public int scanForward(int start, int bound, StopCondition condition) {
		Assert.isLegal(start >= 0);

		if (bound == UNBOUND)
			bound= fDocument.getLength();

		Assert.isLegal(bound <= fDocument.getLength());

		try {
			fPos= start;
			while (fPos < bound) {

				fChar= fDocument.getChar(fPos);
				if (condition.stop(fChar, fPos, true))
					return fPos;

				fPos= condition.nextPosition(fPos, true);
			}
		} catch (BadLocationException e) {
		}
		return NOT_FOUND;
	}


	/**
	 * Finds the lowest position in <code>fDocument</code> such that the position is &gt;= <code>position</code>
	 * and &lt; <code>bound</code> and <code>fDocument.getChar(position) == ch</code> evaluates to <code>true</code>
	 * and the position is in the default partition.
	 *
	 * @param position the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &gt; <code>position</code>, or <code>UNBOUND</code>
	 * @param ch the <code>char</code> to search for
	 * @return the lowest position of <code>ch</code> in (<code>bound</code>, <code>position</code>] that resides in a C partition, or <code>NOT_FOUND</code> if none can be found
	 */
	public int scanForward(int position, int bound, char ch) {
		return scanForward(position, bound, new CharacterMatch(ch));
	}

	/**
	 * Finds the lowest position in <code>fDocument</code> such that the position is &gt;= <code>position</code>
	 * and &lt; <code>bound</code> and <code>fDocument.getChar(position) == ch</code> evaluates to <code>true</code> for at least one
	 * ch in <code>chars</code> and the position is in the default partition.
	 *
	 * @param position the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &gt; <code>position</code>, or <code>UNBOUND</code>
	 * @param chars an array of <code>char</code> to search for
	 * @return the lowest position of a non-whitespace character in [<code>position</code>, <code>bound</code>) that resides in a C partition, or <code>NOT_FOUND</code> if none can be found
	 */
	public int scanForward(int position, int bound, char[] chars) {
		return scanForward(position, bound, new CharacterMatch(chars));
	}

	/**
	 * Finds the highest position <code>p</code> in <code>fDocument</code> such that <code>bound</code> &lt; <code>p</code> &lt;= <code>start</code>
	 * and <code>condition.stop(fDocument.getChar(p), p)</code> evaluates to <code>true</code>.
	 *
	 * @param start the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &lt; <code>start</code>, or <code>UNBOUND</code>
	 * @param condition the <code>StopCondition</code> to check
	 * @return the highest position in (<code>bound</code>, <code>start</code> for which <code>condition</code> holds, or <code>NOT_FOUND</code> if none can be found
	 */
	public int scanBackward(int start, int bound, StopCondition condition) {
		if (bound == UNBOUND)
			bound= -1;

		Assert.isLegal(bound >= -1);
		Assert.isLegal(start < fDocument.getLength() );

		try {
			fPos= start;
			while (fPos > bound) {

				fChar= fDocument.getChar(fPos);
				if (condition.stop(fChar, fPos, false))
					return fPos;

				fPos= condition.nextPosition(fPos, false);
			}
		} catch (BadLocationException e) {
		}
		return NOT_FOUND;
	}

	/**
	 * Finds the highest position in <code>fDocument</code> such that the position is &lt;= <code>position</code>
	 * and &gt; <code>bound</code> and <code>fDocument.getChar(position) == ch</code> evaluates to <code>true</code>
	 * and the position is in the default partition.
	 *
	 * @param position the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &lt; <code>position</code>, or <code>UNBOUND</code>
	 * @param ch the <code>char</code> to search for
	 * @return the highest position of one element in <code>chars</code> in (<code>bound</code>, <code>position</code>] that resides in a C partition, or <code>NOT_FOUND</code> if none can be found
	 */
	public int scanBackward(int position, int bound, char ch) {
		return scanBackward(position, bound, new CharacterMatch(ch));
	}

	/**
	 * Finds the highest position in <code>fDocument</code> such that the position is &lt;= <code>position</code>
	 * and &gt; <code>bound</code> and <code>fDocument.getChar(position) == ch</code> evaluates to <code>true</code> for at least one
	 * ch in <code>chars</code> and the position is in the default partition.
	 *
	 * @param position the first character position in <code>fDocument</code> to be considered
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with <code>bound</code> &lt; <code>position</code>, or <code>UNBOUND</code>
	 * @param chars an array of <code>char</code> to search for
	 * @return the highest position of one element in <code>chars</code> in (<code>bound</code>, <code>position</code>] that resides in a C partition, or <code>NOT_FOUND</code> if none can be found
	 */
	public int scanBackward(int position, int bound, char[] chars) {
		return scanBackward(position, bound, new CharacterMatch(chars));
	}

	/**
	 * Checks whether <code>position</code> resides in a default (C) partition of <code>fDocument</code>.
	 *
	 * @param position the position to be checked
	 * @return <code>true</code> if <code>position</code> is in the default partition of <code>fDocument</code>, <code>false</code> otherwise
	 */
	public boolean isDefaultPartition(int position) {
		return fPartition.equals(getPartition(position).getType());
	}

	/**
	 * Returns the partition at <code>position</code>.
	 *
	 * @param position the position to get the partition for
	 * @return the partition at <code>position</code> or a dummy zero-length
	 *         partition if accessing the document fails
	 */
	private ITypedRegion getPartition(int position) {
		if (!contains(fCachedPartition, position)) {
			Assert.isTrue(position >= 0);
			Assert.isTrue(position <= fDocument.getLength());
			
			try {
				fCachedPartition= TextUtilities.getPartition(fDocument, fPartitioning, position, false);
			} catch (BadLocationException e) {
				fCachedPartition= new TypedRegion(position, 0, "__no_partition_at_all"); //$NON-NLS-1$
			}
		}

		return fCachedPartition;
	}

	/**
	 * Returns <code>true</code> if <code>region</code> contains <code>position</code>.
	 * 
	 * @param region a region
	 * @param position an offset
	 * @return <code>true</code> if <code>region</code> contains <code>position</code>
	 */
	private boolean contains(IRegion region, int position) {
		int offset= region.getOffset();
		return offset <= position && position < offset + region.getLength();
	}

	/**
	 * Checks if the line seems to be an open condition not followed by a block (i.e. an if, while,
	 * or for statement with just one following statement, see example below).
	 *
	 * <pre>
	 * if (condition)
	 *     doStuff();
	 * </pre>
	 *
	 * <p>Algorithm: if the last non-WS, non-Comment code on the line is an if (condition), while (condition),
	 * for( expression), do, else, and there is no statement after that </p>
	 *
	 * @param position the insert position of the new character
	 * @param bound the lowest position to consider
	 * @return <code>true</code> if the code is a conditional statement or loop without a block, <code>false</code> otherwise
	 */
	public boolean isBracelessBlockStart(int position, int bound) {
		if (position < 1)
			return false;

		switch (previousToken(position, bound)) {
			case TokenDO:
			case TokenELSE:
				return true;
			case TokenRPAREN:
				position= findOpeningPeer(fPos, CHeuristicScanner.UNBOUND, LPAREN, RPAREN);
				if (position > 0) {
					switch (previousToken(position - 1, bound)) {
						case TokenIF:
						case TokenFOR:
						case TokenWHILE:
							return true;
					}
				}
		}

		return false;
	}
	
	/**
	 * Returns <code>true</code> if the document, when scanned backwards from <code>start</code>
	 * appears to contain a class instance creation, i.e. a possibly qualified name preceded by a
	 * <code>new</code> keyword. The <code>start</code> must be at the end of the type name, and
	 * before any generic signature or constructor parameter list. The heuristic will return
	 * <code>true</code> if <code>start</code> is at the following positions (|):
	 * 
	 * <pre>
	 *  new std::vector&lt;std::string&gt;|(10)
	 *  new str_vector |(10)
	 *  new / * comment * / str_vector |(10)
	 * </pre>
	 * 
	 * but not the following:
	 * 
	 * <pre>
	 *  new std::vector&lt;std::string&gt;(10)|
	 *  new std::vector&lt;std::string&gt;|(10)
	 *  new vector (10)|
	 *  vector |(10)
	 * </pre>
	 * 
	 * @param start the position where the type name of the class instance creation supposedly ends
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with
	 *        <code>bound</code> &lt; <code>start</code>, or <code>UNBOUND</code>
	 * @return <code>true</code> if the current position looks like after the type name of a class
	 *         instance creation
	 */
	public boolean looksLikeClassInstanceCreationBackward(int start, int bound) {
		int token= previousToken(start - 1, bound);
		if (token == Symbols.TokenIDENT) { // type name
			token= previousToken(getPosition(), bound);
			while (token == Symbols.TokenDOUBLECOLON) { // qualification
				token= previousToken(getPosition(), bound);
				if (token != Symbols.TokenIDENT) // qualification name
					return false;
				token= previousToken(getPosition(), bound);
			}
			return token == Symbols.TokenNEW;
		}
		return false;
	}

	/**
	 * Returns <code>true</code> if the document, when scanned backwards from <code>start</code>
	 * appears to contain a field reference, i.e. a (optional) name preceded by a <code>.</code> 
	 * or <code>-&gt;</code> or <code>::</code>.
	 * 
	 * @param start the position after the field reference operator.
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with
	 *        <code>bound</code> &lt; <code>start</code>, or <code>UNBOUND</code>
	 * @return <code>true</code> if the current position looks like a field reference
	 */
	public boolean looksLikeFieldReferenceBackward(int start, int bound) {
		int token= previousToken(start - 1, bound);
		if (token == Symbols.TokenIDENT) { // field name
			token= previousToken(getPosition(), bound);
		}
		if (token == Symbols.TokenDOT) {
			return true;
		}
		if (token == Symbols.TokenARROW) {
			return true;
		} else if (token == Symbols.TokenDOUBLECOLON) {
			return true;
		}
		return false;
	}
	
	/**
	 * Returns <code>true</code> if the document, when scanned backwards from <code>start</code>
	 * appears to be a composite type (class, struct, union) or enum definition. Examples:
	 * 
	 * <pre>
	 * class A {
	 * struct A {
	 * class A : B {
	 * class A : virtual public B, protected C&lt;T&gt; {
	 * enum E {
	 * </pre>
	 * 
	 * @param start the position of the opening brace.
	 * @param bound the first position in <code>fDocument</code> to not consider any more, with
	 *        <code>bound</code> &lt; <code>start</code>, or <code>UNBOUND</code>
	 * @return <code>true</code> if the current position looks like a composite type definition
	 */
	public boolean looksLikeCompositeTypeDefinitionBackward(int start, int bound) {
		int token= previousToken(start - 1, bound);
		switch (token) {
		case Symbols.TokenSTRUCT:
		case Symbols.TokenUNION:
		case Symbols.TokenENUM:
			return true; // anonymous
		case Symbols.TokenIDENT:
			token= previousToken(getPosition(), bound);
			switch (token) {
			case Symbols.TokenCLASS:
			case Symbols.TokenSTRUCT:
			case Symbols.TokenUNION:
			case Symbols.TokenENUM:
				return true; // no base-clause
			default:
				// backtrack
				token= previousToken(start - 1, bound);
			}
			break;
		default:
			// backtrack
			token= previousToken(start - 1, bound);
			break;
		}
		// match base-clause
		if (token == Symbols.TokenGREATERTHAN) {
			findOpeningPeer(getPosition(), bound, '<', '>');
			token= previousToken(getPosition(), bound);
			if (token != Symbols.TokenLESSTHAN) {
				return false;
			}
			token= previousToken(getPosition(), bound);
		}
		outerWhile: while (token == Symbols.TokenIDENT) {// type name or base type
			token= previousToken(getPosition(), bound);
			// match nested-name-specifier
			while (token == Symbols.TokenCOLON) { // colon of qualification
				token= previousToken(getPosition(), bound);
				if (token != Symbols.TokenCOLON) { // second colon of qualification
					break outerWhile;
				}
				token= previousToken(getPosition(), bound);
				if (token != Symbols.TokenIDENT) // qualification name?
					break;
				token= previousToken(getPosition(), bound);
			}
			switch (token) {
			case Symbols.TokenVIRTUAL:
				token= previousToken(getPosition(), bound);
				//$FALL-THROUGH$
			case Symbols.TokenPUBLIC:
			case Symbols.TokenPROTECTED:
			case Symbols.TokenPRIVATE:
				token= previousToken(getPosition(), bound);
				if (token == Symbols.TokenVIRTUAL) {
					token= previousToken(getPosition(), bound);
				}
				if (token == Symbols.TokenCOMMA) {
					token= previousToken(getPosition(), bound);
					if (token == Symbols.TokenGREATERTHAN) {
						findOpeningPeer(getPosition(), bound, '<', '>');
						token= previousToken(getPosition(), bound);
						if (token != Symbols.TokenLESSTHAN) {
							return false;
						}
						token= previousToken(getPosition(), bound);
					}
					continue; // another base type
				}
				if (token != Symbols.TokenCOLON) // colon after class def identifier
					return false;
				//$FALL-THROUGH$
			case Symbols.TokenCOLON:
				token= previousToken(getPosition(), bound);
				break outerWhile;
			case Symbols.TokenCOMMA:
				token= previousToken(getPosition(), bound);
				if (token == Symbols.TokenGREATERTHAN) {
					findOpeningPeer(getPosition(), bound, '<', '>');
					token= previousToken(getPosition(), bound);
					if (token != Symbols.TokenLESSTHAN) {
						return false;
					}
					token= previousToken(getPosition(), bound);
				}
				continue; // another base type
			case Symbols.TokenIDENT:
				break outerWhile;
			default:
				return false;
			}
		}
		if (token != Symbols.TokenIDENT) {
			return false;
		}
		token= previousToken(getPosition(), bound);
		switch (token) {
		case Symbols.TokenCLASS:
		case Symbols.TokenSTRUCT:
		case Symbols.TokenUNION:
		case Symbols.TokenENUM:  // enum is actually not valid here
			return true;
		default:
			return false;
		}
	}

}
