/*
    * 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.util;
  
  import java.io.BufferedOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.apache.commons.vfs2.FileSystemException;
  
  /**
   * An OutputStream that provides buffering and end-of-stream monitoring.
   */
  public class MonitorOutputStream extends BufferedOutputStream {
  
      private final AtomicBoolean closed = new AtomicBoolean();
  
      /**
       * Constructs a MonitorOutputStream from the passed OutputStream.
       *
       * @param out The output stream to wrap.
       */
      public MonitorOutputStream(final OutputStream out) {
          super(out);
      }
  
      /**
       * Constructs a MonitorOutputStream from the passed OutputStream and with the specified buffer size.
       *
       * @param out The output stream to wrap.
       * @param bufferSize The buffer size to use.
       * @since 2.4
       */
      public MonitorOutputStream(final OutputStream out, final int bufferSize) {
          super(out, bufferSize);
      }
  
      /**
       * Check if file is still open.
       * <p>
       * This is a workaround for an oddity with Java's BufferedOutputStream where you can write to even if the stream has
       * been closed.
       * </p>
       *
       * @throws FileSystemException if already closed.
       * @since 2.0
       */
      protected void assertOpen() throws FileSystemException {
          if (isClosed()) {
              throw new FileSystemException("vfs.provider/closed.error");
          }
      }
  
      /**
       * Closes this output stream.
       * <p>
       * This makes sure the buffers are flushed, close the output stream and it will call {@link #onClose()} and re-throw
       * last exception from any of the three.
       * </p>
       * <p>
       * This does nothing if the stream is closed already.
       * </p>
       *
       * @throws IOException if an IO error occurs.
       */
      @Override
      public void close() throws IOException {
          // do not use super.close()
          // on Java 8 it might throw self suppression, see JDK-8042377
          // in older Java it silently ignores flush() errors
          if (closed.getAndSet(true)) {
              return;
          }
  
          IOException exc = null;
  
          // flush the buffer and out stream
          try {
              super.flush();
          } catch (final IOException ioe) {
              exc = ioe;
          }
  
          // close the out stream without using super.close()
         try {
             super.out.close();
         } catch (final IOException ioe) {
             exc = ioe;
         }
 
         // Notify of end of output
         try {
             onClose();
         } catch (final IOException ioe) {
             exc = ioe;
         }
 
         if (exc != null) {
             throw exc;
         }
     }
 
     /**
      * @throws IOException if an error occurs.
      * @since 2.0
      */
     @Override
     public synchronized void flush() throws IOException {
         if (isClosed()) {
             return;
         }
         super.flush();
     }
 
     private boolean isClosed() {
         return closed.get();
     }
 
     /**
      * Called after this stream is closed.
      * <p>
      * This implementation does nothing.
      * </p>
      *
      * @throws IOException if an error occurs.
      */
     // IOException is needed because subclasses may need to throw it
     protected void onClose() throws IOException {
     }
 
     /**
      * @param b The byte array.
      * @throws IOException if an error occurs.
      * @since 2.0
      */
     @Override
     public void write(final byte[] b) throws IOException {
         assertOpen();
         super.write(b);
     }
 
     /**
      * @param b The byte array.
      * @param off The offset into the array.
      * @param len The number of bytes to write.
      * @throws IOException if an error occurs.
      * @since 2.0
      */
     @Override
     public synchronized void write(final byte[] b, final int off, final int len) throws IOException {
         assertOpen();
         super.write(b, off, len);
     }
 
     /**
      * @param b The character to write.
      * @throws IOException if an error occurs.
      * @since 2.0
      */
     @Override
     public synchronized void write(final int b) throws IOException {
         assertOpen();
         super.write(b);
     }
 }