/**
    * Copyright 2010-2014 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.common.util.spring.env;
  
  import java.util.Properties;
  
  import org.kuali.common.util.Ascii;
  import org.kuali.common.util.Assert;
  import org.kuali.common.util.FormatUtils;
  import org.kuali.common.util.PropertyUtils;
  import org.springframework.core.env.Environment;
  
  import com.google.common.base.Optional;
  
  public class EnvUtils {
  
  	public static final Optional<EnvironmentService> ABSENT = Optional.absent();
  
  	private static final String ENV_PREFIX = "env";
  
  	/**
  	 * If the environment contains a string under this key, convert it into a long signifying bytes
  	 * 
  	 * <pre>
  	 *   file.size=10m   (file that is 10 megabytes)
  	 *   disk.size=100g  (disk that is 100 gigabytes)
  	 * </pre>
  	 */
  	public static long getBytes(EnvironmentService env, String key, long provided) {
  		if (env.containsProperty(key)) {
  			String size = env.getString(key);
  			long bytes = FormatUtils.getBytes(size);
  			return bytes;
  		} else {
  			return provided;
  		}
  	}
  
  	private static Environment instance;
  
  	/**
  	 * Return an environment that uses system properties / environment variables
  	 */
  	public synchronized static Environment getDefaultEnvironment() {
  		if (instance == null) {
  			Properties global = PropertyUtils.getGlobalProperties();
  			instance = new PropertiesEnvironment(global);
  		}
  		return instance;
  	}
  
  	/**
  	 * <pre>
  	 *  foo.bar    -> env.FOO_BAR
  	 *  foo.barBaz -> env.FOO_BAR_BAZ
  	 * </pre>
  	 */
  	public static String getEnvironmentVariableKey(String key) {
  		Assert.noBlanks(key);
  		// Add a prefix, change to upper case and return
  		return ENV_PREFIX + "." + toUnderscore(key).toUpperCase();
  	}
  	
  	/**
  	 * <pre>
  	 *  foo.bar    -> foo_bar
  	 *  foo.barBaz -> foo_bar_baz
  	 * </pre>
  	 */
  	public static String toUnderscore(String key) {
  		char[] chars = key.toCharArray();
  		StringBuilder sb = new StringBuilder();
  		char prevChar = 0;
  		for (char c : chars) {
  			if (c == '.') {
  				// Convert dots into dashes
  				sb.append('_');
  			} else if (Ascii.isUpperCase(c) && Ascii.isLowerCase(prevChar)) {
  				// Insert an underscore every time there is a transition from a lower case char to an upper case char
  				sb.append('_');
  				sb.append(c);
  			} else {
  				// Just append the char
  				sb.append(c);
  			}
  			// Keep track of the previous char
 			prevChar = c;
 		}
 		return sb.toString();
 	}
 
 }