content: /*******************************************************************************
   * Copyright (c) 2000, 2008 IBM Corporation and others.
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *     IBM Corporation - initial API and implementation
   *     Christian Plesner Hansen (plesner@quenta.org) - changed implementation to use DefaultCharacterPairMatcher
   *******************************************************************************/
  package org.eclipse.wst.jsdt.internal.ui.text;
  
  import org.eclipse.jface.text.BadLocationException;
  import org.eclipse.jface.text.IDocument;
  import org.eclipse.jface.text.IRegion;
  import org.eclipse.jface.text.TextUtilities;
  import org.eclipse.jface.text.source.DefaultCharacterPairMatcher;
  import org.eclipse.wst.jsdt.core.JavaScriptCore;
  import org.eclipse.wst.jsdt.ui.text.IJavaScriptPartitions;
  
  /**
   * Helper class for match pairs of characters.
   */
  public final class JavaPairMatcher extends DefaultCharacterPairMatcher implements ISourceVersionDependent {
  
  	/**
  	 * Stores the source version state.
  	 * 
  	 */
  	private boolean fHighlightAngularBrackets= false;
  
  
  	public JavaPairMatcher(char[] pairs) {
  		super(pairs, IJavaScriptPartitions.JAVA_PARTITIONING);
  	}
  
  	/* @see ICharacterPairMatcher#match(IDocument, int) */
  	public IRegion match(IDocument document, int offset) {
  		try {
  			return performMatch(document, offset);
  		} catch (BadLocationException ble) {
  			return null;
  		}
  	}
  	
  	/*
  	 * Performs the actual work of matching for #match(IDocument, int).
  	 */ 
  	private IRegion performMatch(IDocument document, int offset) throws BadLocationException {
  		if (offset < 0 || document == null) return null;
  		final char prevChar= document.getChar(Math.max(offset - 1, 0));
  		if ((prevChar == '<' || prevChar == '>') && !fHighlightAngularBrackets)
  			return null;
  		if (prevChar == '<' && isLessThanOperator(document, offset - 1))
  			return null;
  		final IRegion region= super.match(document, offset);
  		if (region == null) return region;
  		if (prevChar == '>') {
  			final int peer= region.getOffset();
  			if (isLessThanOperator(document, peer)) return null;
  		}
  		return region;
  	}
  
  	/**
  	 * Returns true if the character at the specified offset is a
  	 * less-than sign, rather than an type parameter list open
  	 * angle bracket.
  	 * 
  	 * @param document a document
  	 * @param offset an offset within the document
  	 * @return true if the character at the specified offset is not
  	 *   a type parameter start bracket
  	 * @throws BadLocationException
  	 */
  	private boolean isLessThanOperator(IDocument document, int offset) throws BadLocationException {
  		if (offset < 0) return false;
  		JavaHeuristicScanner scanner= new JavaHeuristicScanner(document, IJavaScriptPartitions.JAVA_PARTITIONING, TextUtilities.getContentType(document, IJavaScriptPartitions.JAVA_PARTITIONING, offset, false));
  		return !isTypeParameterBracket(offset, document, scanner);
  	}
  
  	/**
  	 * Checks if the angular bracket at <code>offset</code> is a type
  	 * parameter bracket.
  	 *
  	 * @param offset the offset of the opening bracket
  	 * @param document the document
  	 * @param scanner a java heuristic scanner on <code>document</code>
  	 * @return <code>true</code> if the bracket is part of a type parameter,
  	 *         <code>false</code> otherwise
  	 * 
  	 */
  	private boolean isTypeParameterBracket(int offset, IDocument document, JavaHeuristicScanner scanner) {
  		/*
  		 * type parameter come after braces (closing or opening), semicolons, or after
  		 * a Type name (heuristic: starts with capital character, or after a modifier
  		 * keyword in a method declaration (visibility, static, synchronized, final)
  		 */
  
  		try {
  			IRegion line= document.getLineInformationOfOffset(offset);
  
  			int prevToken= scanner.previousToken(offset - 1, line.getOffset());
  			int prevTokenOffset= scanner.getPosition() + 1;
  			String previous= prevToken == Symbols.TokenEOF ? null : document.get(prevTokenOffset, offset - prevTokenOffset).trim();
  
  			if (	   prevToken == Symbols.TokenLBRACE
  					|| prevToken == Symbols.TokenRBRACE
  					|| prevToken == Symbols.TokenSEMICOLON
  					|| prevToken == Symbols.TokenSYNCHRONIZED
  					|| prevToken == Symbols.TokenSTATIC
  					|| (prevToken == Symbols.TokenIDENT && isTypeParameterIntroducer(previous))
  					|| prevToken == Symbols.TokenEOF)
  				return true;
  		} catch (BadLocationException e) {
  			return false;
  		}
  
  		return false;
  	}
  
  	/**
  	 * Returns <code>true</code> if <code>identifier</code> is an identifier
  	 * that could come right before a type parameter list. It uses a heuristic:
  	 * if the identifier starts with an upper case, it is assumed a type name.
  	 * Also, if <code>identifier</code> is a method modifier, it is assumed
  	 * that the angular bracket is part of the generic type parameter of a
  	 * method.
  	 *
  	 * @param identifier the identifier to check
  	 * @return <code>true</code> if the identifier could introduce a type
  	 *         parameter list
  	 * 
  	 */
  	private boolean isTypeParameterIntroducer(String identifier) {
  		return identifier.length() > 0
  				&& (Character.isUpperCase(identifier.charAt(0))
  						|| identifier.startsWith("final") //$NON-NLS-1$
  						|| identifier.startsWith("public") //$NON-NLS-1$
  						|| identifier.startsWith("public") //$NON-NLS-1$
  						|| identifier.startsWith("protected") //$NON-NLS-1$
  						|| identifier.startsWith("private")); //$NON-NLS-1$
  	}
  
  	/*
  	 * @see org.eclipse.wst.jsdt.internal.ui.text.ISourceVersionDependent#setSourceVersion(java.lang.String)
  	 */
  	public void setSourceVersion(String version) {
  		if (JavaScriptCore.VERSION_1_5.compareTo(version) <= 0)
  			fHighlightAngularBrackets= true;
  		else
  			fHighlightAngularBrackets= false;
  	}
  }
  