/*
 *  Copyright 2008 biaoping.yin
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.frameworkset.util;

/**
 * <p>Title: SystemPropertyUtils.java</p> 
 * <p>Description: </p>
 * <p>bboss workgroup</p>
 * <p>Copyright (c) 2008</p>
 * @Date 2010-10-14
 * @author biaoping.yin
 * @version 1.0
 */
public abstract class SystemPropertyUtils {
	/** Prefix for system property placeholders: "${" */
	public static final String PLACEHOLDER_PREFIX = "${";

	/** Suffix for system property placeholders: "}" */
	public static final String PLACEHOLDER_SUFFIX = "}";


	/**
	 * Resolve ${...} placeholders in the given text,
	 * replacing them with corresponding system property values.
	 * @param text the String to resolve
	 * @return the resolved String
	 * @see #PLACEHOLDER_PREFIX
	 * @see #PLACEHOLDER_SUFFIX
	 */
	public static String resolvePlaceholders(String text) {
		StringBuffer buf = new StringBuffer(text);

		int startIndex = buf.indexOf(PLACEHOLDER_PREFIX);
		while (startIndex != -1) {
			int endIndex = buf.indexOf(PLACEHOLDER_SUFFIX, startIndex + PLACEHOLDER_PREFIX.length());
			if (endIndex != -1) {
				String placeholder = buf.substring(startIndex + PLACEHOLDER_PREFIX.length(), endIndex);
				int nextIndex = endIndex + PLACEHOLDER_SUFFIX.length();
				try {
					String propVal = System.getProperty(placeholder);
					if (propVal == null) {
						// Fall back to searching the system environment.
						propVal = System.getenv(placeholder);
					}
					if (propVal != null) {
						buf.replace(startIndex, endIndex + PLACEHOLDER_SUFFIX.length(), propVal);
						nextIndex = startIndex + propVal.length();
					}
					else {
						System.err.println("Could not resolve placeholder '" + placeholder + "' in [" + text +
								"] as system property: neither system property nor environment variable found");
					}
				}
				catch (Throwable ex) {
					System.err.println("Could not resolve placeholder '" + placeholder + "' in [" + text +
							"] as system property: " + ex);
				}
				startIndex = buf.indexOf(PLACEHOLDER_PREFIX, nextIndex);
			}
			else {
				startIndex = -1;
			}
		}

		return buf.toString();
	}

}
