/*******************************************************************************
 * Copyright (c) 2005, 2007 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
 *     Bjorn Freeman-Benson - initial API and implementation
 *******************************************************************************/
package org.eclipse.debug.examples.ui.pda.editor;

import org.eclipse.debug.examples.ui.pda.DebugUIPlugin;
import org.eclipse.jface.text.TextAttribute;
import org.eclipse.jface.text.rules.BufferedRuleBasedScanner;
import org.eclipse.jface.text.rules.IRule;
import org.eclipse.jface.text.rules.IWordDetector;
import org.eclipse.jface.text.rules.Token;
import org.eclipse.jface.text.rules.WordRule;


/**
 * PDA editor keyword scanner.
 */
public class PDAScanner extends BufferedRuleBasedScanner {
    
    /**
     * PDA keywods
     */
    public static final String[] fgKeywords = new String[] {
        "add", "branch_not_zero", "call", "dec", "dup",
        "halt", "output", "pop", "push", "return", "var"
    };
    
    /**
     * Detects potential keywords
     */
    class PDAWordDetector implements IWordDetector {

        /* (non-Javadoc)
         * @see org.eclipse.jface.text.rules.IWordDetector#isWordStart(char)
         */
        public boolean isWordStart(char c) {
            return Character.isLetter(c);
        }

        /* (non-Javadoc)
         * @see org.eclipse.jface.text.rules.IWordDetector#isWordPart(char)
         */
        public boolean isWordPart(char c) {
            return Character.isLetter(c) || c == '_';
        }
    }
    
    /**
     * Detects PDA branch labels
     */
    class PDALabelDetector extends PDAWordDetector {
        
        /* (non-Javadoc)
         * @see org.eclipse.jface.text.rules.IWordDetector#isWordStart(char)
         */
        public boolean isWordStart(char c) {
            return c == ':';
        }
        
        /* (non-Javadoc)
         * @see org.eclipse.jface.text.rules.IWordDetector#isWordPart(char)
         */
        public boolean isWordPart(char c) {
            return super.isWordPart(c) || Character.isDigit(c);
        }
    }

    /**
     * Constructs a scanner that identifies PDA keywords.
     */
    public PDAScanner() {
        // keywords
        Token token = new Token(new TextAttribute(DebugUIPlugin.getDefault().getColor(DebugUIPlugin.KEYWORD)));
        WordRule keywords = new WordRule(new PDAWordDetector());
        for (int i = 0; i < fgKeywords.length; i++) {
            String keyword = fgKeywords[i];
            keywords.addWord(keyword, token);
        }
        // labels
        token = new Token(new TextAttribute(DebugUIPlugin.getDefault().getColor(DebugUIPlugin.LABEL)));
        WordRule labels = new WordRule(new PDALabelDetector(), token); 
        setRules(new IRule[]{keywords, labels});
    }
}