/*
    * 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.File;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.RandomAccessFile;
  import java.io.Serializable;
  import java.lang.reflect.Method;
  import java.nio.ByteOrder;
  import java.nio.MappedByteBuffer;
  import java.nio.channels.FileChannel;
  import java.security.AccessController;
  import java.security.PrivilegedActionException;
  import java.security.PrivilegedExceptionAction;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Objects;
  
  import org.apache.logging.log4j.core.Layout;
  import org.apache.logging.log4j.core.util.Closer;
  import org.apache.logging.log4j.core.util.NullOutputStream;
  
  /**
   * Extends OutputStreamManager but instead of using a buffered output stream, this class maps a region of a file into
   * memory and writes to this memory region.
   * <p>
   * 
   * @see <a
   *      href="http://www.codeproject.com/Tips/683614/Things-to-Know-about-Memory-Mapped-File-in-Java">
   *        http://www.codeproject.com/Tips/683614/Things-to-Know-about-Memory-Mapped-File-in-Java</a>;
   * @see <a href="http://bugs.java.com/view_bug.do?bug_id=6893654">http://bugs.java.com/view_bug.do?bug_id=6893654</a>
   * @see <a href="http://bugs.java.com/view_bug.do?bug_id=4724038">http://bugs.java.com/view_bug.do?bug_id=4724038</a>
   * @see <a
   *      href="http://stackoverflow.com/questions/9261316/memory-mapped-mappedbytebuffer-or-direct-bytebuffer-for-db-implementation">
   *        http://stackoverflow.com/questions/9261316/memory-mapped-mappedbytebuffer-or-direct-bytebuffer-for-db-implementation</a>;
   * 
   * @since 2.1
   */
  public class MemoryMappedFileManager extends OutputStreamManager {
      /**
       * 
       */
      private static final int MAX_REMAP_COUNT = 10;
      static final int DEFAULT_REGION_LENGTH = 32 * 1024 * 1024;
      private static final MemoryMappedFileManagerFactory FACTORY = new MemoryMappedFileManagerFactory();
      private static final double NANOS_PER_MILLISEC = 1000.0 * 1000.0;
  
      private final boolean isForce;
      private final int regionLength;
      private final String advertiseURI;
      private final RandomAccessFile randomAccessFile;
      private final ThreadLocal<Boolean> isEndOfBatch = new ThreadLocal<>();
      private MappedByteBuffer mappedBuffer;
      private long mappingOffset;
  
      protected MemoryMappedFileManager(final RandomAccessFile file, final String fileName, final OutputStream os,
              final boolean force, final long position, final int regionLength, final String advertiseURI,
              final Layout<? extends Serializable> layout, final boolean writeHeader) throws IOException {
          super(os, fileName, layout, writeHeader);
          this.isForce = force;
          this.randomAccessFile = Objects.requireNonNull(file, "RandomAccessFile");
          this.regionLength = regionLength;
          this.advertiseURI = advertiseURI;
          this.isEndOfBatch.set(Boolean.FALSE);
          this.mappedBuffer = mmap(randomAccessFile.getChannel(), getFileName(), position, regionLength);
          this.mappingOffset = position;
      }
  
      /**
       * Returns the MemoryMappedFileManager.
       *
       * @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 isForce true if the contents should be flushed to disk on every write
       * @param regionLength The mapped region length.
       * @param advertiseURI the URI to use when advertising the file
       * @param layout The layout.
       * @return A MemoryMappedFileManager for the File.
       */
      public static MemoryMappedFileManager getFileManager(final String fileName, final boolean append,
              final boolean isForce, final int regionLength, final String advertiseURI,
              final Layout<? extends Serializable> layout) {
          return (MemoryMappedFileManager) getManager(fileName, new FactoryData(append, isForce, regionLength,
                 advertiseURI, layout), FACTORY);
     }
 
     public Boolean isEndOfBatch() {
         return isEndOfBatch.get();
     }
 
     public void setEndOfBatch(final boolean isEndOfBatch) {
         this.isEndOfBatch.set(Boolean.valueOf(isEndOfBatch));
     }
 
     @Override
     protected synchronized void write(final byte[] bytes, int offset, int length) {
         super.write(bytes, offset, length); // writes to dummy output stream
 
         while (length > mappedBuffer.remaining()) {
             final int chunk = mappedBuffer.remaining();
             mappedBuffer.put(bytes, offset, chunk);
             offset += chunk;
             length -= chunk;
             remap();
         }
         mappedBuffer.put(bytes, offset, length);
 
         // no need to call flush() if force is true,
         // already done in AbstractOutputStreamAppender.append
     }
 
     private synchronized void remap() {
         final long offset = this.mappingOffset + mappedBuffer.position();
         final int length = mappedBuffer.remaining() + regionLength;
         try {
             unsafeUnmap(mappedBuffer);
             final long fileLength = randomAccessFile.length() + regionLength;
             LOGGER.debug("MMapAppender extending {} by {} bytes to {}", getFileName(), regionLength, fileLength);
 
             final long startNanos = System.nanoTime();
             randomAccessFile.setLength(fileLength);
             final float millis = (float) ((System.nanoTime() - startNanos) / NANOS_PER_MILLISEC);
             LOGGER.debug("MMapAppender extended {} OK in {} millis", getFileName(), millis);
 
             mappedBuffer = mmap(randomAccessFile.getChannel(), getFileName(), offset, length);
             mappingOffset = offset;
         } catch (final Exception ex) {
             LOGGER.error("Unable to remap " + getName() + ". " + ex);
         }
     }
 
     @Override
     public synchronized void flush() {
         mappedBuffer.force();
     }
 
     @Override
     public synchronized void close() {
         final long position = mappedBuffer.position();
         final long length = mappingOffset + position;
         try {
             unsafeUnmap(mappedBuffer);
         } catch (final Exception ex) {
             LOGGER.error("Unable to unmap MappedBuffer " + getName() + ". " + ex);
         }
         try {
             LOGGER.debug("MMapAppender closing. Setting {} length to {} (offset {} + position {})", getFileName(),
                     length, mappingOffset, position);
             randomAccessFile.setLength(length);
             randomAccessFile.close();
         } catch (final IOException ex) {
             LOGGER.error("Unable to close MemoryMappedFile " + getName() + ". " + ex);
         }
     }
 
     public static MappedByteBuffer mmap(final FileChannel fileChannel, final String fileName, final long start,
             final int size) throws IOException {
         for (int i = 1;; i++) {
             try {
                 LOGGER.debug("MMapAppender remapping {} start={}, size={}", fileName, start, size);
 
                 final long startNanos = System.nanoTime();
                 final MappedByteBuffer map = fileChannel.map(FileChannel.MapMode.READ_WRITE, start, size);
                 map.order(ByteOrder.nativeOrder());
 
                 final float millis = (float) ((System.nanoTime() - startNanos) / NANOS_PER_MILLISEC);
                 LOGGER.debug("MMapAppender remapped {} OK in {} millis", fileName, millis);
 
                 return map;
             } catch (final IOException e) {
                 if (e.getMessage() == null || !e.getMessage().endsWith("user-mapped section open")) {
                     throw e;
                 }
                 LOGGER.debug("Remap attempt {}/{} failed. Retrying...", i, MAX_REMAP_COUNT, e);
                 if (i < MAX_REMAP_COUNT) {
                     Thread.yield();
                 } else {
                     try {
                         Thread.sleep(1);
                     } catch (final InterruptedException ignored) {
                         Thread.currentThread().interrupt();
                         throw e;
                     }
                 }
             }
         }
     }
 
     private static void unsafeUnmap(final MappedByteBuffer mbb) throws PrivilegedActionException {
         LOGGER.debug("MMapAppender unmapping old buffer...");
         final long startNanos = System.nanoTime();
         AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
             @Override
             public Object run() throws Exception {
                 final Method getCleanerMethod = mbb.getClass().getMethod("cleaner");
                 getCleanerMethod.setAccessible(true);
                 final Object cleaner = getCleanerMethod.invoke(mbb); // sun.misc.Cleaner instance
                 final Method cleanMethod = cleaner.getClass().getMethod("clean");
                 cleanMethod.invoke(cleaner);
                 return null;
             }
         });
         final float millis = (float) ((System.nanoTime() - startNanos) / NANOS_PER_MILLISEC);
         LOGGER.debug("MMapAppender unmapped buffer OK in {} millis", millis);
     }
 
     /**
      * Returns the name of the File being managed.
      *
      * @return The name of the File being managed.
      */
     public String getFileName() {
         return getName();
     }
 
     /**
      * Returns the length of the memory mapped region.
      * 
      * @return the length of the mapped region
      */
     public int getRegionLength() {
         return regionLength;
     }
 
     /**
      * Returns {@code true} if the content of the buffer should be forced to the storage device on every write,
      * {@code false} otherwise.
      * 
      * @return whether each write should be force-sync'ed
      */
     public boolean isImmediateFlush() {
         return isForce;
     }
 
     /**
      * Gets this FileManager's content format specified by:
      * <p>
      * Key: "fileURI" Value: provided "advertiseURI" param.
      * </p>
      * 
      * @return Map of content format keys supporting FileManager
      */
     @Override
     public Map<String, String> getContentFormat() {
         final Map<String, String> result = new HashMap<>(super.getContentFormat());
         result.put("fileURI", advertiseURI);
         return result;
     }
 
     /**
      * Factory Data.
      */
     private static class FactoryData {
         private final boolean append;
         private final boolean force;
         private final int regionLength;
         private final String advertiseURI;
         private final Layout<? extends Serializable> layout;
 
         /**
          * Constructor.
          *
          * @param append Append to existing file or truncate.
          * @param force forces the memory content to be written to the storage device on every event
          * @param regionLength length of the mapped region
          */
         public FactoryData(final boolean append, final boolean force, final int regionLength,
                 final String advertiseURI, final Layout<? extends Serializable> layout) {
             this.append = append;
             this.force = force;
             this.regionLength = regionLength;
             this.advertiseURI = advertiseURI;
             this.layout = layout;
         }
     }
 
     /**
      * Factory to create a MemoryMappedFileManager.
      */
     private static class MemoryMappedFileManagerFactory 
             implements ManagerFactory<MemoryMappedFileManager, FactoryData> {
 
         /**
          * Create a MemoryMappedFileManager.
          *
          * @param name The name of the File.
          * @param data The FactoryData
          * @return The MemoryMappedFileManager for the File.
          */
         @SuppressWarnings("resource")
         @Override
         public MemoryMappedFileManager 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();
             }
             if (!data.append) {
                 file.delete();
             }
 
             final boolean writeHeader = !data.append || !file.exists();
             final OutputStream os = NullOutputStream.NULL_OUTPUT_STREAM;
             RandomAccessFile raf = null;
             try {
                 raf = new RandomAccessFile(name, "rw");
                 final long position = (data.append) ? raf.length() : 0;
                 raf.setLength(position + data.regionLength);
                 return new MemoryMappedFileManager(raf, name, os, data.force, position, data.regionLength,
                         data.advertiseURI, data.layout, writeHeader);
             } catch (final Exception ex) {
                 LOGGER.error("MemoryMappedFileManager (" + name + ") " + ex);
                 Closer.closeSilently(raf);
             }
             return null;
         }
     }
 }