/*
 Dandelion, a Lisp plugin for Eclipse.
 Copyright (C) 2007 Michael Bohn

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along
 with this program; if not, write to the Free Software Foundation, Inc.,
 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package de.defmacro.dandelion.internal.ui.text.rules;
/*******************************************************************************
 * 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
 *******************************************************************************/

import java.util.HashMap;
import java.util.Map;

import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.text.rules.ICharacterScanner;
import org.eclipse.jface.text.rules.IRule;
import org.eclipse.jface.text.rules.IToken;
import org.eclipse.jface.text.rules.IWordDetector;
import org.eclipse.jface.text.rules.Token;


/**
 * NOTIZ:
 * 'Strukturelle Nachahmung' der Klasse WordRule. 
 * AENDERUNG: Fuer das Lookup in der Word-Token Map wird der Buffer
 * in Lower-Case umgewandelt. Damit wird ein Case-Insensitive Matching
 * fuer Schluesselwoerter erreicht. Da fBuffer private ist, reicht
 * ein ueberschreiben der evaluate-Methode nicht aus. 
 * Ausserdem wurde Lookup-Map auf Generics umgestellt.
 * 
 * 
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * An implementation of <code>IRule</code> capable of detecting words
 * Word rules also allow for the association of tokens with specific words.
 * That is, not only can the rule be used to provide tokens for exact matches,
 * but also for the generalized notion of a word in the context in which it is used.
 * A word rules uses a word detector to determine what a word is.
 *
 * @see IWordDetector
 */
public class CaseInsensitiveWordRule implements IRule {

	/** Internal setting for the un-initialized column constraint */
	protected static final int UNDEFINED= -1;

	/** The word detector used by this rule */
	protected IWordDetector fDetector;
	/** The default token to be returned on success and if nothing else has been specified. */
	protected IToken fDefaultToken;
	/** The column constraint */
	protected int fColumn= UNDEFINED;
	/** The table of predefined words and token for this rule */
	protected Map<String, IToken> fWords= new HashMap<String, IToken>();
	/** Buffer used for pattern detection */
	private StringBuffer fBuffer= new StringBuffer();

	/**
	 * Creates a rule which, with the help of an word detector, will return the token
	 * associated with the detected word. If no token has been associated, the scanner
	 * will be rolled back and an undefined token will be returned in order to allow
	 * any subsequent rules to analyze the characters.
	 *
	 * @param detector the word detector to be used by this rule, may not be <code>null</code>
	 *
	 * @see #addWord(String, IToken)
	 */
	public CaseInsensitiveWordRule(IWordDetector detector) {
		this(detector, Token.UNDEFINED);
	}

	/**
	 * Creates a rule which, with the help of a word detector, will return the token
	 * associated with the detected word. If no token has been associated, the
	 * specified default token will be returned.
	 *
	 * @param detector the word detector to be used by this rule, may not be <code>null</code>
	 * @param defaultToken the default token to be returned on success
	 *		if nothing else is specified, may not be <code>null</code>
	 *
	 * @see #addWord(String, IToken)
	 */
	public CaseInsensitiveWordRule(IWordDetector detector, IToken defaultToken) {

		Assert.isNotNull(detector);
		Assert.isNotNull(defaultToken);

		fDetector= detector;
		fDefaultToken= defaultToken;
	}

	/**
	 * Adds a word and the token to be returned if it is detected.
	 *
	 * @param word the word this rule will search for, may not be <code>null</code>
	 * @param token the token to be returned if the word has been found, may not be <code>null</code>
	 */
	public void addWord(String word, IToken token) {
		Assert.isNotNull(word);
		Assert.isNotNull(token);

		fWords.put(word, token);
	}

	/**
	 * Sets a column constraint for this rule. If set, the rule's token
	 * will only be returned if the pattern is detected starting at the
	 * specified column. If the column is smaller then 0, the column
	 * constraint is considered removed.
	 *
	 * @param column the column in which the pattern starts
	 */
	public void setColumnConstraint(int column) {
		if (column < 0)
			column= UNDEFINED;
		fColumn= column;
	}

	/*
	 * @see IRule#evaluate(ICharacterScanner)
	 */
	//Schluesselwoerter in Lisp bestehen nur aus ASCII-Zeichen, deshalb
	//toLowerCase ohne Local-Methode problemlos verwendbar
	@edu.umd.cs.findbugs.annotations.SuppressWarnings("DM")
	public IToken evaluate(ICharacterScanner scanner) {
		int c= scanner.read();
		if (fDetector.isWordStart((char) c)) {
			if (fColumn == UNDEFINED || (fColumn == scanner.getColumn() - 1)) {

				fBuffer.setLength(0);
				do {
					fBuffer.append((char) c);
					c= scanner.read();
				} while (c != ICharacterScanner.EOF && fDetector.isWordPart((char) c));
				scanner.unread();

				IToken token= fWords.get(fBuffer.toString().toLowerCase());
				if (token != null)
					return token;

				if (fDefaultToken.isUndefined())
					unreadBuffer(scanner);

				return fDefaultToken;
			}
		}

		scanner.unread();
		return Token.UNDEFINED;
	}

	/**
	 * Returns the characters in the buffer to the scanner.
	 *
	 * @param scanner the scanner to be used
	 */
	protected void unreadBuffer(ICharacterScanner scanner) {
		for (int i= fBuffer.length() - 1; i >= 0; i--)
			scanner.unread();
	}
}

