/*
    * 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.
   */
  package org.apache.commons.vfs2.impl;
  
  import java.io.File;
  import java.security.AccessController;
  import java.security.PrivilegedAction;
  import java.security.PrivilegedActionException;
  import java.security.PrivilegedExceptionAction;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.vfs2.FileObject;
  import org.apache.commons.vfs2.FileSelector;
  import org.apache.commons.vfs2.FileSystemException;
  import org.apache.commons.vfs2.provider.FileReplicator;
  import org.apache.commons.vfs2.provider.VfsComponent;
  import org.apache.commons.vfs2.provider.VfsComponentContext;
  
  /**
   * A file replicator that wraps another file replicator, performing the replication as a privileged action.
   */
  public class PrivilegedFileReplicator implements FileReplicator, VfsComponent {
  
      /**
       * An action that closes the wrapped replicator.
       */
      private final class CloseAction implements PrivilegedAction<Object> {
          /**
           * Performs the action.
           */
          @Override
          public Object run() {
              replicatorComponent.close();
              return null;
          }
      }
      /**
       * An action that initializes the wrapped replicator.
       */
      private final class InitAction implements PrivilegedExceptionAction<Object> {
          /**
           * Performs the action.
           */
          @Override
          public Object run() throws Exception {
              replicatorComponent.init();
              return null;
          }
      }
  
      /**
       * An action that replicates a file using the wrapped replicator.
       */
      private final class ReplicateAction implements PrivilegedExceptionAction<File> {
          private final FileObject srcFile;
          private final FileSelector selector;
  
          ReplicateAction(final FileObject srcFile, final FileSelector selector) {
              this.srcFile = srcFile;
              this.selector = selector;
          }
  
          /**
           * Performs the action.
           *
           * @throws Exception if an error occurs.
           */
          @Override
          public File run() throws Exception {
              // TODO - Do not pass the selector through. It is untrusted
              // TODO - Need to determine which files can be read
              return replicator.replicateFile(srcFile, selector);
          }
      }
  
      private final FileReplicator replicator;
  
      private final VfsComponent replicatorComponent;
  
      /**
       * Constructs a new instance.
       *
       * @param replicator The replicator.
       */
      public PrivilegedFileReplicator(final FileReplicator replicator) {
         this.replicator = replicator;
         if (replicator instanceof VfsComponent) {
             replicatorComponent = (VfsComponent) replicator;
         } else {
             replicatorComponent = null;
         }
     }
 
     /**
      * Closes the replicator.
      */
     @Override
     public void close() {
         if (replicatorComponent != null) {
             AccessController.doPrivileged(new CloseAction());
         }
     }
 
     /**
      * Initializes the component.
      *
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public void init() throws FileSystemException {
         if (replicatorComponent != null) {
             try {
                 AccessController.doPrivileged(new InitAction());
             } catch (final PrivilegedActionException e) {
                 throw new FileSystemException("vfs.impl/init-replicator.error", e);
             }
         }
     }
 
     /**
      * Creates a local copy of the file, and all its descendants.
      *
      * @param srcFile The source FileObject.
      * @param selector The file selector.
      * @return The replicated file.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public File replicateFile(final FileObject srcFile, final FileSelector selector) throws FileSystemException {
         try {
             final ReplicateAction action = new ReplicateAction(srcFile, selector);
             return AccessController.doPrivileged(action);
         } catch (final PrivilegedActionException e) {
             throw new FileSystemException("vfs.impl/replicate-file.error", e, srcFile.getName());
         }
     }
 
     /**
      * Sets the context for the replicator.
      *
      * @param context The component context.
      */
     @Override
     public void setContext(final VfsComponentContext context) {
         if (replicatorComponent != null) {
             replicatorComponent.setContext(context);
         }
     }
 
     /**
      * Sets the Logger to use for the component.
      *
      * @param logger The logger.
      */
     @Override
     public void setLogger(final Log logger) {
         if (replicatorComponent != null) {
             replicatorComponent.setLogger(logger);
         }
     }
 }