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.StringUtils;

 import java.util.ArrayList;

 import java.util.Iterator;

 import java.util.List;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 public class RegexBasedInterpolator

 {

     private List valueSources;

     public RegexBasedInterpolator()

     {

         valueSources = new ArrayList();

     }

     public RegexBasedInterpolator( List valueSources )

     {

         this.valueSources = new ArrayList( valueSources );

     }

     public void addValueSource( ValueSource valueSource )

     {

         this.valueSources.add( valueSource );

     }

     public void removeValuesSource( ValueSource valueSource )

     {

         this.valueSources.remove( valueSource );

     }

     public String interpolate( String input, String thisPrefixPattern )

     {

         String result = input;

         Pattern expressionPattern = Pattern.compile( "\\$\\{(" + thisPrefixPattern + ")?([^}]+)\\}" );

         Matcher matcher = expressionPattern.matcher( result );

         while ( matcher.find() )

         {

             String wholeExpr = matcher.group( 0 );

             String realExpr = matcher.group( 2 );

             if ( realExpr.startsWith( "." ) )

             {

                 realExpr = realExpr.substring( 1 );

             }

             Object value = null;

             for ( Iterator it = valueSources.iterator(); it.hasNext() && value == null; )

             {

                 ValueSource vs = (ValueSource) it.next();

                 value = vs.getValue( realExpr );

             }

             // if the expression refers to itself, die.

             if ( wholeExpr.equals( value ) )

             {

                 throw new IllegalArgumentException( "Expression: \'" + wholeExpr + "\' references itself." );

             }

             if ( value != null )

             {

                 result = StringUtils.replace( result, wholeExpr, String.valueOf( value ) );

                 // could use:

                 // result = matcher.replaceFirst( stringValue );

                 // but this could result in multiple lookups of stringValue, and replaceAll is not correct behaviour

                 matcher.reset( result );

             }

         }

         return result;

     }

 }