package org.apache.archiva.common.filelock;
   
   /*
    * 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 org.apache.commons.lang3.time.StopWatch;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.stereotype.Service;
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.nio.channels.ClosedChannelException;
  import java.nio.file.Files;
  import java.nio.file.NoSuchFileException;
  import java.nio.file.Path;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * @author Olivier Lamy
   * @since 2.0.0
   */
  @Service("fileLockManager#default")
  public class DefaultFileLockManager
      implements FileLockManager
  {
      // TODO currently we create lock for read and write!!
      // the idea could be to store lock here with various clients read/write
      // only read could be a more simple lock and acquire a write lock means waiting the end of all reading threads
      private static final ConcurrentMap<Path, Lock> lockFiles = new ConcurrentHashMap<Path, Lock>( 64 );
  
      private boolean skipLocking = true;
  
      private Logger log = LoggerFactory.getLogger( getClass() );
  
      private int timeout = 0;
  
  
      @Override
      public Lock readFileLock( Path file )
          throws FileLockException, FileLockTimeoutException
      {
          if ( skipLocking )
          {
              return new Lock( file );
  
          }
          StopWatch stopWatch = new StopWatch();
          boolean acquired = false;
          try {
              mkdirs(file.getParent());
          } catch (IOException e) {
              throw new FileLockException("Could not create directories "+file.getParent(), e);
          }
  
          Lock lock = null;
  
          stopWatch.start();
  
          while ( !acquired )
          {
              // Make sure that not a bad lock is returned, if a exception was thrown.
              lock = null;
  
              if ( timeout > 0 )
              {
                  long delta = stopWatch.getTime();
                  log.debug( "delta {}, timeout {}", delta, timeout );
                  if ( delta > timeout )
                  {
                      log.warn( "Cannot acquire read lock within {} millis. Will skip the file: {}", timeout, file );
                      // we could not get the lock within the timeout period, so  throw  FileLockTimeoutException
                      throw new FileLockTimeoutException();
                  }
              }
  
              Lock current = lockFiles.get( file );
  
              if ( current != null )
              {
                  log.trace( "read lock file exist continue wait" );
                  continue;
             }
 
             try
             {
                 lock = new Lock( file, false );
                 createNewFileQuietly( file );
                 lock.openLock( false, timeout > 0 );
                 // We are not returning an existing lock. If the lock is not
                 // exclusive, another thread may release the lock and the client
                 // knows nothing about it.
                 // The only atomic operation is the putIfAbsent operation, so if
                 // this returns null everything is OK, otherwise we should start at
                 // the beginning.
                 current = lockFiles.putIfAbsent( file, lock );
                 if ( current == null )
                 {
                     // Success
                     acquired = true;
                 } else {
                     // We try again
                     lock.close();
                     lock=null;
                 }
             }
             catch ( FileNotFoundException | NoSuchFileException e )
             {
 
                 log.debug( "read Lock skip: {} try to create file", e.getMessage() );
                 createNewFileQuietly( file );
             }
             catch ( IOException e )
             {
                 throw new FileLockException( e.getMessage(), e );
             }
             catch ( IllegalStateException e )
             {
                 log.trace( "openLock {}:{}", e.getClass(), e.getMessage() );
             }
         }
 
         return lock;
 
     }
 
 
     @Override
     public Lock writeFileLock( Path file )
         throws FileLockException, FileLockTimeoutException
     {
         if ( skipLocking )
         {
             return new Lock( file );
         }
 
         try {
             mkdirs( file.getParent() );
         } catch (IOException e) {
             throw new FileLockException("Could not create directory "+file.getParent(), e);
         }
 
         StopWatch stopWatch = new StopWatch();
         boolean acquired = false;
 
         Lock lock = null;
 
         stopWatch.start();
 
         while ( !acquired )
         {
             // Make sure that not a bad lock is returned, if a exception was thrown.
             lock = null;
             if ( timeout > 0 )
             {
                 long delta = stopWatch.getTime();
                 log.debug( "delta {}, timeout {}", delta, timeout );
                 if ( delta > timeout )
                 {
                     log.warn( "Cannot acquire read lock within {} millis. Will skip the file: {}", timeout, file );
                     // we could not get the lock within the timeout period, so throw FileLockTimeoutException
                     throw new FileLockTimeoutException();
                 }
             }
 
             Lock current = lockFiles.get( file );
 
             try
             {
 
                 if ( current != null )
                 {
                     log.trace( "write lock file exist continue wait" );
 
                     continue;
                 }
                 lock = new Lock( file, true );
                 createNewFileQuietly( file );
                 lock.openLock( true, timeout > 0 );
                 // We are not returning an existing lock. If the lock is not
                 // exclusive, another thread may release the lock and the client
                 // knows nothing about it.
                 // The only atomic operation is the putIfAbsent operation, so if
                 // this returns null everything is OK, otherwise we should start at
                 // the beginning.
                 current = lockFiles.putIfAbsent( file, lock );
                 if ( current == null )
                 {
                     // Success
                     acquired = true;
                 } else {
                     // We try again
                     lock.close();
                     lock=null;
                 }
             }
             catch ( FileNotFoundException | NoSuchFileException e )
             {
 
                 log.debug( "write Lock skip: {} try to create file", e.getMessage() );
                 createNewFileQuietly( file );
             }
             catch ( IOException e )
             {
                 throw new FileLockException( e.getMessage(), e );
             }
             catch ( IllegalStateException e )
             {
                 log.trace( "openLock {}:{}", e.getClass(), e.getMessage() );
             }
         }
 
         return lock;
 
 
     }
 
      private void createNewFileQuietly( Path file )
     {
         try
         {
             Files.createFile(file);
         }
         catch ( IOException e )
         {
             // skip that
         }
     }
 
     @Override
     public void release( Lock lock )
         throws FileLockException
     {
         if ( lock == null )
         {
             log.debug( "skip releasing null" );
             return;
         }
         if ( skipLocking )
         {
             return;
         }
         try
         {
             lockFiles.remove( lock.getFile() );
             lock.close();
         }
         catch ( ClosedChannelException e )
         {
             // skip this one
             log.debug( "ignore ClosedChannelException: {}", e.getMessage() );
         }
         catch ( IOException e )
         {
             throw new FileLockException( e.getMessage(), e );
         }
     }
 
     @Override
     public void clearLockFiles()
     {
         lockFiles.clear();
     }
 
     private Path mkdirs( Path directory ) throws IOException {
         return Files.createDirectories(directory);
     }
 
     @Override
     public int getTimeout()
     {
         return timeout;
     }
 
     @Override
     public void setTimeout( int timeout )
     {
         this.timeout = timeout;
     }
 
     @Override
     public boolean isSkipLocking()
     {
         return skipLocking;
     }
 
     @Override
     public void setSkipLocking( boolean skipLocking )
     {
         this.skipLocking = skipLocking;
     }
 }