package org.eclipse.aether.internal.impl;
   
   /*
    * 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.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.Closeable;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.RandomAccessFile;
  import java.util.Map;
  import java.util.Properties;
  
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Manages access to a properties file.
   */
  @Singleton
  @Named
  public final class DefaultTrackingFileManager
      implements TrackingFileManager
  {
      private static final Logger LOGGER = LoggerFactory.getLogger( DefaultTrackingFileManager.class );
  
      @Override
      public Properties read( File file )
      {
          FileInputStream stream = null;
          try
          {
              if ( !file.exists() )
              {
                  return null;
              }
  
              stream = new FileInputStream( file );
  
              Properties props = new Properties();
              props.load( stream );
  
              return props;
          }
          catch ( IOException e )
          {
              LOGGER.warn( "Failed to read tracking file {}", file, e );
          }
          finally
          {
              close( stream, file );
          }
  
          return null;
      }
  
      @Override
      public Properties update( File file, Map<String, String> updates )
      {
          Properties props = new Properties();
  
          File directory = file.getParentFile();
          if ( !directory.mkdirs() && !directory.exists() )
          {
              LOGGER.warn( "Failed to create parent directories for tracking file {}", file );
              return props;
          }
  
          RandomAccessFile raf = null;
          try
          {
              raf = new RandomAccessFile( file, "rw" );
  
              if ( file.canRead() )
              {
                  byte[] buffer = new byte[(int) raf.length()];
  
                  raf.readFully( buffer );
 
                 ByteArrayInputStream stream = new ByteArrayInputStream( buffer );
 
                 props.load( stream );
             }
 
             for ( Map.Entry<String, String> update : updates.entrySet() )
             {
                 if ( update.getValue() == null )
                 {
                     props.remove( update.getKey() );
                 }
                 else
                 {
                     props.setProperty( update.getKey(), update.getValue() );
                 }
             }
 
             ByteArrayOutputStream stream = new ByteArrayOutputStream( 1024 * 2 );
 
             LOGGER.debug( "Writing tracking file {}", file );
             props.store( stream, "NOTE: This is a Maven Resolver internal implementation file"
                 + ", its format can be changed without prior notice." );
 
             raf.seek( 0 );
             raf.write( stream.toByteArray() );
             raf.setLength( raf.getFilePointer() );
         }
         catch ( IOException e )
         {
             LOGGER.warn( "Failed to write tracking file {}", file, e );
         }
         finally
         {
             close( raf, file );
         }
 
         return props;
     }
 
     private void close( Closeable closeable, File file )
     {
         if ( closeable != null )
         {
             try
             {
                 closeable.close();
             }
             catch ( IOException e )
             {
                 LOGGER.warn( "Error closing tracking file {}", file, e );
             }
         }
     }
 
 }