package org.apache.maven.plugins.clean;
   
   /*
    * 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.File;
  import java.io.IOException;
  
  import org.apache.maven.plugin.logging.Log;
  import org.apache.maven.shared.utils.Os;
  import org.apache.maven.shared.utils.io.FileUtils;
  
  /**
   * Cleans directories.
   * 
   * @author Benjamin Bentmann
   */
  class Cleaner
  {
  
      private static final boolean ON_WINDOWS = Os.isFamily( Os.FAMILY_WINDOWS );
  
      private final Logger logDebug;
  
      private final Logger logInfo;
  
      private final Logger logVerbose;
  
      private final Logger logWarn;
  
      /**
       * Creates a new cleaner.
       * 
       * @param log The logger to use, may be <code>null</code> to disable logging.
       * @param verbose Whether to perform verbose logging.
       */
      public Cleaner( final Log log, boolean verbose )
      {
          logDebug = ( log == null || !log.isDebugEnabled() ) ? null : new Logger()
          {
              public void log( CharSequence message )
              {
                  log.debug( message );
              }
          };
  
          logInfo = ( log == null || !log.isInfoEnabled() ) ? null : new Logger()
          {
              public void log( CharSequence message )
              {
                  log.info( message );
              }
          };
  
          logWarn = ( log == null || !log.isWarnEnabled() ) ? null : new Logger()
          {
              public void log( CharSequence message )
              {
                  log.warn( message );
              }
          };
  
          logVerbose = verbose ? logInfo : logDebug;
      }
  
      /**
       * Deletes the specified directories and its contents.
       * 
       * @param basedir The directory to delete, must not be <code>null</code>. Non-existing directories will be silently
       *            ignored.
       * @param selector The selector used to determine what contents to delete, may be <code>null</code> to delete
       *            everything.
       * @param followSymlinks Whether to follow symlinks.
       * @param failOnError Whether to abort with an exception in case a selected file/directory could not be deleted.
       * @param retryOnError Whether to undertake additional delete attempts in case the first attempt failed.
       * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>.
       */
      public void delete( File basedir, Selector selector, boolean followSymlinks, boolean failOnError,
                          boolean retryOnError )
          throws IOException
      {
          if ( !basedir.isDirectory() )
          {
             if ( !basedir.exists() )
             {
                 if ( logDebug != null )
                 {
                     logDebug.log( "Skipping non-existing directory " + basedir );
                 }
                 return;
             }
             throw new IOException( "Invalid base directory " + basedir );
         }
 
         if ( logInfo != null )
         {
             logInfo.log( "Deleting " + basedir + ( selector != null ? " (" + selector + ")" : "" ) );
         }
 
         File file = followSymlinks ? basedir : basedir.getCanonicalFile();
 
         delete( file, "", selector, followSymlinks, failOnError, retryOnError );
     }
 
     /**
      * Deletes the specified file or directory.
      * 
      * @param file The file/directory to delete, must not be <code>null</code>. If <code>followSymlinks</code> is
      *            <code>false</code>, it is assumed that the parent file is canonical.
      * @param pathname The relative pathname of the file, using {@link File#separatorChar}, must not be
      *            <code>null</code>.
      * @param selector The selector used to determine what contents to delete, may be <code>null</code> to delete
      *            everything.
      * @param followSymlinks Whether to follow symlinks.
      * @param failOnError Whether to abort with an exception in case a selected file/directory could not be deleted.
      * @param retryOnError Whether to undertake additional delete attempts in case the first attempt failed.
      * @return The result of the cleaning, never <code>null</code>.
      * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>.
      */
     private Result delete( File file, String pathname, Selector selector, boolean followSymlinks, boolean failOnError,
                            boolean retryOnError )
         throws IOException
     {
         Result result = new Result();
 
         boolean isDirectory = file.isDirectory();
 
         if ( isDirectory )
         {
             if ( selector == null || selector.couldHoldSelected( pathname ) )
             {
                 final boolean isSymlink = FileUtils.isSymbolicLink( file );
                 File canonical = followSymlinks ? file : file.getCanonicalFile();
                 if ( followSymlinks || !isSymlink )
                 {
                     String[] filenames = canonical.list();
                     if ( filenames != null )
                     {
                         String prefix = pathname.length() > 0 ? pathname + File.separatorChar : "";
                         for ( int i = filenames.length - 1; i >= 0; i-- )
                         {
                             String filename = filenames[i];
                             File child = new File( canonical, filename );
                             result.update( delete( child, prefix + filename, selector, followSymlinks, failOnError,
                                                    retryOnError ) );
                         }
                     }
                 }
                 else if ( logDebug != null )
                 {
                     logDebug.log( "Not recursing into symlink " + file );
                 }
             }
             else if ( logDebug != null )
             {
                 logDebug.log( "Not recursing into directory without included files " + file );
             }
         }
 
         if ( !result.excluded && ( selector == null || selector.isSelected( pathname ) ) )
         {
             if ( logVerbose != null )
             {
                 if ( isDirectory )
                 {
                     logVerbose.log( "Deleting directory " + file );
                 }
                 else if ( file.exists() )
                 {
                     logVerbose.log( "Deleting file " + file );
                 }
                 else
                 {
                     logVerbose.log( "Deleting dangling symlink " + file );
                 }
             }
             result.failures += delete( file, failOnError, retryOnError );
         }
         else
         {
             result.excluded = true;
         }
 
         return result;
     }
 
     /**
      * Deletes the specified file, directory. If the path denotes a symlink, only the link is removed, its target is
      * left untouched.
      * 
      * @param file The file/directory to delete, must not be <code>null</code>.
      * @param failOnError Whether to abort with an exception in case the file/directory could not be deleted.
      * @param retryOnError Whether to undertake additional delete attempts in case the first attempt failed.
      * @return <code>0</code> if the file was deleted, <code>1</code> otherwise.
      * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>.
      */
     private int delete( File file, boolean failOnError, boolean retryOnError )
         throws IOException
     {
         if ( !file.delete() )
         {
             boolean deleted = false;
 
             if ( retryOnError )
             {
                 if ( ON_WINDOWS )
                 {
                     // try to release any locks held by non-closed files
                     System.gc();
                 }
 
                 final int[] delays = { 50, 250, 750 };
                 for ( int i = 0; !deleted && i < delays.length; i++ )
                 {
                     try
                     {
                         Thread.sleep( delays[i] );
                     }
                     catch ( InterruptedException e )
                     {
                         // ignore
                     }
                     deleted = file.delete() || !file.exists();
                 }
             }
             else
             {
                 deleted = !file.exists();
             }
 
             if ( !deleted )
             {
                 if ( failOnError )
                 {
                     throw new IOException( "Failed to delete " + file );
                 }
                 else
                 {
                     if ( logWarn != null )
                     {
                         logWarn.log( "Failed to delete " + file );
                     }
                     return 1;
                 }
             }
         }
 
         return 0;
     }
 
     private static class Result
     {
 
         private int failures;
 
         private boolean excluded;
 
         public void update( Result result )
         {
             failures += result.failures;
             excluded |= result.excluded;
         }
 
     }
 
     private interface Logger
     {
 
         void log( CharSequence message );
 
     }
 
 }