/*
    * 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.logging.log4j.core.appender;
  
  import java.io.BufferedOutputStream;
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.nio.channels.FileChannel;
  import java.nio.channels.FileLock;
  import java.util.HashMap;
  import java.util.Map;
  
  
  /**
   * Manages actual File I/O for File Appenders.
   */
  public class FileManager extends OutputStreamManager {
  
      private static final FileManagerFactory FACTORY = new FileManagerFactory();
  
      private final boolean isAppend;
      private final boolean isLocking;
      private final String advertiseURI;
  
      protected FileManager(final String fileName, final OutputStream os, final boolean append, final boolean locking, String advertiseURI) {
          super(os, fileName);
          this.isAppend = append;
          this.isLocking = locking;
          this.advertiseURI = advertiseURI;
      }
  
      /**
       * Returns the FileManager.
       * @param fileName The name of the file to manage.
       * @param append true if the file should be appended to, false if it should be overwritten.
       * @param locking true if the file should be locked while writing, false otherwise.
       * @param bufferedIO true if the contents should be buffered as they are written.
       * @param advertiseURI the URI to use when advertising the file
       * @return A FileManager for the File.
       */
      public static FileManager getFileManager(final String fileName, final boolean append, boolean locking,
                                               final boolean bufferedIO, String advertiseURI) {
  
          if (locking && bufferedIO) {
              locking = false;
          }
          return (FileManager) getManager(fileName, new FactoryData(append, locking, bufferedIO, advertiseURI), FACTORY);
      }
  
      @Override
      protected synchronized void write(final byte[] bytes, final int offset, final int length)  {
  
          if (isLocking) {
              final FileChannel channel = ((FileOutputStream) getOutputStream()).getChannel();
              try {
                  /* Lock the whole file. This could be optimized to only lock from the current file
                     position. Note that locking may be advisory on some systems and mandatory on others,
                     so locking just from the current position would allow reading on systems where
                     locking is mandatory.  Also, Java 6 will throw an exception if the region of the
                     file is already locked by another FileChannel in the same JVM. Hopefully, that will
                     be avoided since every file should have a single file manager - unless two different
                     files strings are configured that somehow map to the same file.*/
                  final FileLock lock = channel.lock(0, Long.MAX_VALUE, false);
                  try {
                      super.write(bytes, offset, length);
                  } finally {
                      lock.release();
                  }
              } catch (final IOException ex) {
                  throw new AppenderRuntimeException("Unable to obtain lock on " + getName(), ex);
              }
  
          } else {
              super.write(bytes, offset, length);
          }
      }
  
      /**
       * Returns the name of the File being managed.
       * @return The name of the File being managed.
       */
      public String getFileName() {
         return getName();
     }
 
     /**
      * Returns the append status.
      * @return true if the file will be appended to, false if it is overwritten.
      */
     public boolean isAppend() {
         return isAppend;
     }
 
     /**
      * Returns the lock status.
      * @return true if the file will be locked when writing, false otherwise.
      */
     public boolean isLocking() {
         return isLocking;
     }
 
     /**
      * FileManager's content format is specified by:<p/>
      * Key: "fileURI" Value: provided "advertiseURI" param
      * @return Map of content format keys supporting FileManager
      */
     public Map<String, String> getContentFormat()
     {
         Map<String, String> result = new HashMap<String, String>(super.getContentFormat());
         result.put("fileURI", advertiseURI);
         return result;
     }
 
     /**
      * Factory Data.
      */
     private static class FactoryData {
         private final boolean append;
         private final boolean locking;
         private final boolean bufferedIO;
         private final String advertiseURI;
 
         /**
          * Constructor.
          * @param append Append status.
          * @param locking Locking status.
          * @param bufferedIO Buffering flag.
          * @param advertiseURI the URI to use when advertising the file
          */
         public FactoryData(final boolean append, final boolean locking, final boolean bufferedIO, String advertiseURI) {
             this.append = append;
             this.locking = locking;
             this.bufferedIO = bufferedIO;
             this.advertiseURI = advertiseURI;
         }
     }
 
     /**
      * Factory to create a FileManager.
      */
     private static class FileManagerFactory implements ManagerFactory<FileManager, FactoryData> {
 
         /**
          * Create a FileManager.
          * @param name The name of the File.
          * @param data The FactoryData
          * @return The FileManager for the File.
          */
         public FileManager createManager(final String name, final FactoryData data) {
             final File file = new File(name);
             final File parent = file.getParentFile();
             if (null != parent && !parent.exists()) {
                 parent.mkdirs();
             }
 
             OutputStream os;
             try {
                 os = new FileOutputStream(name, data.append);
                 if (data.bufferedIO) {
                     os = new BufferedOutputStream(os);
                 }
                 return new FileManager(name, os, data.append, data.locking, data.advertiseURI);
             } catch (final FileNotFoundException ex) {
                 LOGGER.error("FileManager (" + name + ") " + ex);
             }
             return null;
         }
     }
 
 }