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package org.avaje.metric.agent.offline;


/**
 * Utility String class that supports String manipulation functions.
 */
public class StringReplace {


	/**
	 * This method takes a String and will replace all occurrences of the match
	 * String with that of the replace String.
	 * 
	 * @param source
	 *            the source string
	 * @param match
	 *            the string used to find a match
	 * @param replace
	 *            the string used to replace match with
	 * @return the source string after the search and replace
	 */
	public static String replace(String source, String match, String replace) {
		return replaceString(source, match, replace, 30, 0, source.length());
	}

	/**
	 * Additionally specify the additionalSize to add to the buffer. This will
	 * make the buffer bigger so that it doesn't have to grow when replacement
	 * occurs.
	 */
	private static String replaceString(String source, String match, String replace,
			int additionalSize, int startPos, int endPos) {

		char match0 = match.charAt(0);
		
		int matchLength = match.length();

		if (matchLength == 1 && replace.length() == 1) {
			char replace0 = replace.charAt(0);
			return source.replace(match0, replace0);
		}
		if (matchLength >= replace.length()) {
			additionalSize = 0;
		}


		int sourceLength = source.length();
		int lastMatch = endPos - matchLength;

		StringBuilder sb = new StringBuilder(sourceLength + additionalSize);

		if (startPos > 0) {
			sb.append(source.substring(0, startPos));
		}

		char sourceChar;
		boolean isMatch;
		int sourceMatchPos;

		for (int i = startPos; i < sourceLength; i++) {
			sourceChar = source.charAt(i);
			if (i > lastMatch || sourceChar != match0) {
				sb.append(sourceChar);

			} else {
				// check to see if this is a match
				isMatch = true;
				sourceMatchPos = i;
				
				// check each following character...
				for (int j = 1; j < matchLength; j++) {
					sourceMatchPos++;
					if (source.charAt(sourceMatchPos) != match.charAt(j)) {
						isMatch = false;
						break;
					}
				}
				if (isMatch) {
					i = i + matchLength - 1;
					sb.append(replace);
				} else {
					// was not a match
					sb.append(sourceChar);
				}
			}
		}

		return sb.toString();
	}


}