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Utility classes for OpenRDF/Sesame
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/*  Sesame - Storage and Querying architecture for RDF and RDF Schema
 *  Copyright (C) 2001-2006 Aduna
 *
 *  Contact: 
 *  	Aduna
 *  	Prinses Julianaplein 14 b
 *  	3817 CS Amersfoort
 *  	The Netherlands
 *  	tel. +33 (0)33 465 99 87
 *  	fax. +33 (0)33 465 99 87
 *
 *  	http://aduna-software.com/
 *  	http://www.openrdf.org/
 *  
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package org.openrdf.util;

public class StringUtil {

	/**
	 * Substitute String "old" by String "new" in String "text" everywhere.
	 *
	 * This is static util function that I could not place anywhere more
	 * appropriate. The name of this function is from the good-old awk time.
	 *
	 * @param olds	The String to be substituted.
	 * @param news	The String is the new content.
	 * @param text	The String in which the substitution is done.
	 * @return 		The result String containing the substitutions; if no
	 *              substitutions were made, the result is 'text'.
	 */
	public static String gsub(String olds, String news, String text) {
		if (olds == null || olds.length() == 0) {
			// Nothing to substitute.
			return text;
		}

		// Search for any occurences of 'olds'.
		int oldsIndex = text.indexOf(olds);

		if (oldsIndex == -1) {
			// Nothing to substitute.
			return text;
		}

		// We're going to do some substitutions.

		StringBuffer buf = new StringBuffer(text.length());
		int prevIndex = 0;

		while (oldsIndex >= 0) {
			// First, add the text between the previous and the current
			// occurence.
			buf.append(text.substring(prevIndex, oldsIndex));

			// Then add the substition pattern
			buf.append(news);

			// Remember the index for the next loop.
			prevIndex = oldsIndex + olds.length();

			// Search for the next occurence.
			oldsIndex = text.indexOf(olds, prevIndex);
		}

		// Add the part after the last occurence.
		buf.append(text.substring(prevIndex));

		return buf.toString();
	}

	/**
	 * Searches for the first occurrence of a word, which must be surrounded
	 * by whitespace characters, in a text.
	 **/
	public static int indexOfWord(String text, String word) {
		return indexOfWord(text, word, 0);
	}

	/**
	 * Searches for the first occurrence of a word, which must be surrounded
	 * by whitespace characters, that appears in a text after 'fromIndex'.
	 **/
	public static int indexOfWord(String text, String word, int fromIndex) {
		int wordIdx = fromIndex - 1;

		while (true) {
			wordIdx = text.indexOf(word, wordIdx + 1);

			if (wordIdx == -1) {
				// word not found
				break;
			}

			// Verify that the character before the word is whitespace
			int beforeIdx = wordIdx - 1;

			if (beforeIdx >= 0 &&
				!Character.isWhitespace(text.charAt(beforeIdx)))
			{
				// character was not whitespace
				continue;
			}

			// Verify that the character after the word is whitespace
			int afterIdx = wordIdx + word.length();

			if (afterIdx < text.length() &&
				!Character.isWhitespace(text.charAt(afterIdx)))
			{
				// character was not whitespace
				continue;
			}

			// All checks passed, 
			break;
		}

		return wordIdx;
	}

	/**
	 * Searches for the last occurrence of a word, which must be surrounded
	 * by whitespace characters, in a text.
	 **/
	public static int lastIndexOfWord(String text, String word) {
		return lastIndexOfWord(text, word, text.length());
	}

	/**
	 * Searches for the last occurrence of a word, which must be surrounded
	 * by whitespace characters, in a text. The algorithm searches the text
	 * backwards, starting from 'fromIndex'.
	 **/
	public static int lastIndexOfWord(String text, String word, int fromIndex) {
		int wordIdx = fromIndex + 1;

		while (true) {
			wordIdx = text.lastIndexOf(word, wordIdx - 1);

			if (wordIdx == -1) {
				// word not found
				break;
			}

			// Verify that the character before the word is whitespace
			int beforeIdx = wordIdx - 1;

			if (beforeIdx >= 0 &&
				!Character.isWhitespace(text.charAt(beforeIdx)))
			{
				// character was not whitespace
				continue;
			}

			// Verify that the character after the word is whitespace
			int afterIdx = wordIdx + word.length();

			if (afterIdx < text.length() &&
				!Character.isWhitespace(text.charAt(afterIdx)))
			{
				// character was not whitespace
				continue;
			}

			// All checks passed, 
			break;
		}

		return wordIdx;
	}

} //end class