/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2011 by Rapid-I and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapid-i.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.tools;

import java.util.Stack;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

/**
 * This class provides the functionality to translate a GLOB expression into 
 * a standard regular expression. 
 * 
 * GLOB provides a subset of the functionality of regular expressions:
 * '?'  Matches one unknown character
 * '*'  Matches any number of unknown characters
 * '[abc]' Matches a, b or c, or more general any inserted character
 * '{abc,def}' Matches abc or def.
 * 
 * @author Sebastian Land
 * 
 */
public class GlobCompiler {
	private enum Commands {
		UNBRACED,
		SQUARE_BRACKETS,
		CURLY_BRACKETS
	}
	

	public static Pattern compileGlob(final String glob) throws PatternSyntaxException {
		// use stack to keep track if inside braces. Start unbraced...
		Stack<Commands> currentMode = new Stack<Commands>();
		currentMode.push(Commands.UNBRACED);

		int globLength = glob.length();
		int currentIndex = 0;

		/* equivalent REGEX expression to be compiled */
		StringBuffer buffer = new StringBuffer();

		while (currentIndex < globLength) {
			char c = glob.charAt(currentIndex++);
			if (c == '\\') {
				if (currentIndex == globLength) {
					// no characters left, so treat '\' as literal char 
					buffer.append(Pattern.quote("\\"));
				} else {
					// read next character 
					String s = glob.charAt(currentIndex) + "";
					if ((Commands.UNBRACED == currentMode.peek() && "\\[]{}?*".contains(s)) || (Commands.SQUARE_BRACKETS == currentMode.peek() && "\\[]{}?*!-".contains(s)) || (Commands.CURLY_BRACKETS == currentMode.peek()) && "\\[]{}?*,".contains(s)) {
						// escape the construct char
						currentIndex++;
						buffer.append(Pattern.quote(s));
					} else {
						// treat '\' as literal char
						buffer.append(Pattern.quote("\\"));
					}
				}
			} else if (c == '*') {
				// *
				buffer.append(".*");
			} else if (c == '?') {
				// .
				buffer.append('.');
			// [...]
			} else if (c == '[') {
				buffer.append('[');
				currentMode.push(Commands.SQUARE_BRACKETS);
				// check for negation character '!' immediately after the opening bracket '[' 
				if ((currentIndex < globLength) && (glob.charAt(currentIndex) == '!')) {
					currentIndex++;
					buffer.append('^');
				}
			} else if ((c == ']') && Commands.SQUARE_BRACKETS == (currentMode.peek())) {
				buffer.append(']');
				currentMode.pop();
			} else if ((c == '-') && Commands.SQUARE_BRACKETS == (currentMode.peek())) {
				// character range '-' in "[...]" 
				buffer.append('-');
			// {...}
			} else if (c == '{') {
				buffer.append("(?:(?:");
				currentMode.push(Commands.CURLY_BRACKETS);
			} else if ((c == '}') && Commands.CURLY_BRACKETS == (currentMode.peek())) {
				buffer.append("))");
				currentMode.pop();
			} else if ((c == ',') && Commands.CURLY_BRACKETS == (currentMode.peek())) {
				// comma between strings in "{...}"
				buffer.append(")|(?:");
			} else {
				// simple literal
				buffer.append(Pattern.quote(c + ""));
			}
		}
	
		// finally check for mismatched [...] or {...} 
		if ("[]".equals(currentMode.peek()))
			throw new PatternSyntaxException("Cannot find matching closing square bracket ] in GLOB expression", glob, -1);

		if ("{}".equals(currentMode.peek()))
			throw new PatternSyntaxException("Cannot find matching closing curly brace } in GLOB expression", glob, -1);
		return Pattern.compile(buffer.toString());
	}
}