package org.apache.maven.shared.filtering;

 /*

  * 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.IOUtil;

 import org.codehaus.plexus.util.StringUtils;

 import java.io.File;

 import java.io.FileInputStream;

 import java.io.FileNotFoundException;

 import java.io.IOException;

 import java.util.Iterator;

 import java.util.Properties;

 /**

  * @author <a href="mailto:kenney@neonics.com">Kenney Westerhof</a>

  * @author William Ferguson

  *

  */

 public final class PropertyUtils

 {

     /**

      * Private empty constructor to prevent instantiation.

      */

     private PropertyUtils()

     {

         // prevent instantiation

     }

     /**

      * Reads a property file, resolving all internal variables, using the supplied base properties.

      * <p>

      * The properties are resolved iteratively, so if the value of property A refers to property B, 

      * then after resolution the value of property B will contain the value of property B.

      * </p>

      * 

      * @param propFile The property file to load.

      * @param baseProps Properties containing the initial values to substitute into the properties file.

      * @return Properties object containing the properties in the file with their values fully resolved.

      * @throws IOException if profile does not exist, or cannot be read.

      */

     public static Properties loadPropertyFile( File propFile, Properties baseProps )

         throws IOException

     {

         if ( !propFile.exists() )

         {

             throw new FileNotFoundException( propFile.toString() );

         }

         final Properties fileProps = new Properties();

         final FileInputStream inStream = new FileInputStream( propFile );

         try

         {

             fileProps.load( inStream );

         }

         finally

         {

             IOUtil.close( inStream );

         }

         final Properties combinedProps = new Properties();

         combinedProps.putAll( baseProps == null ? new Properties() : baseProps );

         combinedProps.putAll( fileProps );

         // The algorithm iterates only over the fileProps which is all that is required to resolve

         // the properties defined within the file. This is slightly different to current, however

         // I suspect that this was the actual original intent.

         // 

         // The difference is that #loadPropertyFile(File, boolean, boolean) also resolves System properties

         // whose values contain expressions. I believe this is unexpected and is not validated by the test cases,

         // as can be verified by replacing the implementation of #loadPropertyFile(File, boolean, boolean)

         // with the commented variant I have provided that reuses this method.

         for ( Iterator iter = fileProps.keySet().iterator(); iter.hasNext(); )

         {

             final String k = (String) iter.next();

             final String propValue = getPropertyValue( k, combinedProps );

             fileProps.setProperty( k, propValue );

         }

         return fileProps;

     }

     /**

      * Reads a property file, resolving all internal variables.

      *

      * @param propfile The property file to load

      * @param fail whether to throw an exception when the file cannot be loaded or to return null

      * @param useSystemProps whether to incorporate System.getProperties settings into the returned Properties object.

      * @return the loaded and fully resolved Properties object

      * @throws IOException if profile does not exist, or cannot be read.

      */

     public static Properties loadPropertyFile( File propfile, boolean fail, boolean useSystemProps )

         throws IOException

     {

         final Properties baseProps = new Properties();

         if ( useSystemProps )

         {

             baseProps.putAll( System.getProperties() );

         }

         final Properties resolvedProps = new Properties();

         try

         {

             resolvedProps.putAll( loadPropertyFile( propfile, baseProps ) );

         }

         catch ( FileNotFoundException e )

         {

             if ( fail )

             {

                 throw new FileNotFoundException( propfile.toString() );

             }

         }

         if ( useSystemProps )

         {

             resolvedProps.putAll( baseProps );

         }

         return resolvedProps;

     }

     /**

      * Retrieves a property value, replacing values like ${token}

      * using the Properties to look them up.

      *

      * It will leave unresolved properties alone, trying for System

      * properties, and implements reparsing (in the case that

      * the value of a property contains a key), and will

      * not loop endlessly on a pair like

      * test = ${test}.

      *

      * @param k

      * @param p

      * @return The filtered property value.

      */

     private static String getPropertyValue( String k, Properties p )

     {

         // This can also be done using InterpolationFilterReader,

         // but it requires reparsing the file over and over until

         // it doesn't change.

         String v = p.getProperty( k );

         String ret = "";

         int idx, idx2;

         while ( ( idx = v.indexOf( "${" ) ) >= 0 )

         {

             // append prefix to result

             ret += v.substring( 0, idx );

             // strip prefix from original

             v = v.substring( idx + 2 );

             // if no matching } then bail

             if ( ( idx2 = v.indexOf( '}' ) ) < 0 )

             {

                 break;

             }

             // strip out the key and resolve it

             // resolve the key/value for the ${statement}

             String nk = v.substring( 0, idx2 );

             v = v.substring( idx2 + 1 );

             String nv = p.getProperty( nk );

             // try global environment..

             if ( nv == null && !StringUtils.isEmpty( nk ) )

             {

                 nv = System.getProperty( nk );

             }

             // if the key cannot be resolved,

             // leave it alone ( and don't parse again )

             // else prefix the original string with the

             // resolved property ( so it can be parsed further )

             // taking recursion into account.

             if ( nv == null || nv.equals( k ) || k.equals( nk ) )

             {

                 ret += "${" + nk + "}";

             }

             else

             {

                 v = nv + v;

             }

         }

         return ret + v;

     }

 }