package org.codehaus.plexus.util.interpolation;

 /*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you 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.

  */

 import org.codehaus.plexus.util.cli.CommandLineUtils;

 import java.io.IOException;

 import java.util.Properties;

 public class EnvarBasedValueSource

     implements ValueSource

 {

     private Properties envars;

     private final boolean caseSensitive;

     /**

      * Create a new value source for interpolation based on shell environment variables. In this

      * case, envar keys ARE CASE SENSITIVE.

      * 

      * @throws IOException

      */

     public EnvarBasedValueSource() throws IOException

     {

         this( true );

     }

     /**

      * Create a new value source for interpolation based on shell environment variables.

      * 

      * @param caseSensitive Whether the environment variable key should be treated in a 

      *                      case-sensitive manner for lookups

      * @throws IOException

      */

     public EnvarBasedValueSource( boolean caseSensitive ) throws IOException

     {

         this.caseSensitive = caseSensitive;

         envars = CommandLineUtils.getSystemEnvVars( caseSensitive );

     }

     public Object getValue( String expression )

     {

         String expr = expression;

         if ( expr.startsWith( "env." ) )

         {

             expr = expr.substring( "env.".length() );

         }

         if ( !caseSensitive )

         {

             expr = expr.toUpperCase();

         }

         return envars.getProperty( expr );

     }

 }