package org.apache.maven.plugins.shade.resource;
   
   /*
    * 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 java.io.BufferedReader;
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.io.StringReader;
  import java.nio.charset.StandardCharsets;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.jar.JarEntry;
  import java.util.jar.JarOutputStream;
  
  import org.apache.commons.io.IOUtils;
  import org.apache.maven.plugins.shade.relocation.Relocator;
  
  import com.google.common.io.LineReader;
  
  /**
   * Resources transformer that relocates classes in META-INF/services and appends entries in META-INF/services resources
   * into a single resource. For example, if there are several META-INF/services/org.apache.maven.project.ProjectBuilder
   * resources spread across many JARs the individual entries will all be concatenated into a single
   * META-INF/services/org.apache.maven.project.ProjectBuilder resource packaged into the resultant JAR produced by the
   * shading process.
   */
  public class ServicesResourceTransformer
      implements ResourceTransformer
  {
  
      private static final String SERVICES_PATH = "META-INF/services";
  
      private Map<String, ServiceStream> serviceEntries = new HashMap<>();
  
      private List<Relocator> relocators;
  
      public boolean canTransformResource( String resource )
      {
          if ( resource.startsWith( SERVICES_PATH ) )
          {
              return true;
          }
  
          return false;
      }
  
      public void processResource( String resource, InputStream is, final List<Relocator> relocators )
          throws IOException
      {
          ServiceStream out = serviceEntries.get( resource );
          if ( out == null )
          {
              out = new ServiceStream();
              serviceEntries.put( resource, out );
          }
  
          final ServiceStream fout = out;
  
          final String content = IOUtils.toString( is );
          StringReader reader = new StringReader( content );
          LineReader lineReader = new LineReader( reader );
          String line;
          while ( ( line = lineReader.readLine() ) != null )
          {
              String relContent = line;
              for ( Relocator relocator : relocators )
              {
                  if ( relocator.canRelocateClass( relContent ) )
                  {
                      relContent = relocator.applyToSourceContent( relContent );
                  }
              }
              fout.append( relContent + "\n" );
          }
  
          if ( this.relocators == null )
          {
             this.relocators = relocators;
         }
     }
     public boolean hasTransformedResource()
     {
         return serviceEntries.size() > 0;
     }
 
     public void modifyOutputStream( JarOutputStream jos )
         throws IOException
     {
         for ( Map.Entry<String, ServiceStream> entry : serviceEntries.entrySet() )
         {
             String key = entry.getKey();
             ServiceStream data = entry.getValue();
 
             if ( relocators != null )
             {
                 key = key.substring( SERVICES_PATH.length() + 1 );
                 for ( Relocator relocator : relocators )
                 {
                     if ( relocator.canRelocateClass( key ) )
                     {
                         key = relocator.relocateClass( key );
                         break;
                     }
                 }
 
                 key = SERVICES_PATH + '/' + key;
             }
 
             jos.putNextEntry( new JarEntry( key ) );
 
 
             //read the content of service file for candidate classes for relocation
             PrintWriter writer = new PrintWriter( jos );
             InputStreamReader streamReader = new InputStreamReader( data.toInputStream() );
             BufferedReader reader = new BufferedReader( streamReader );
             String className;
 
             while ( ( className = reader.readLine() ) != null )
             {
                 writer.println( className );
                 writer.flush();
             }
 
             reader.close();
             data.reset();
         }
     }
 
     static class ServiceStream
         extends ByteArrayOutputStream
     {
 
         ServiceStream()
         {
             super( 1024 );
         }
 
         public void append( String content )
             throws IOException
         {
             if ( count > 0 && buf[count - 1] != '\n' && buf[count - 1] != '\r' )
             {
                 write( '\n' );
             }
 
             byte[] contentBytes = content.getBytes( StandardCharsets.UTF_8 );
             this.write( contentBytes );
         }
 
         public InputStream toInputStream()
         {
             return new ByteArrayInputStream( buf, 0, count );
         }
 
     }
 
 }