//
   //  ========================================================================
   //  Copyright (c) 1995-2013 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  
  package org.eclipse.jetty.util;
  
  import java.io.File;
  import java.io.FilenameFilter;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  import java.util.Set;
  import java.util.Timer;
  import java.util.TimerTask;
  
  import org.eclipse.jetty.util.component.AbstractLifeCycle;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  
  /**
   * Scanner
   * 
   * Utility for scanning a directory for added, removed and changed
   * files and reporting these events via registered Listeners.
   *
   */
  public class Scanner extends AbstractLifeCycle
  {
      private static final Logger LOG = Log.getLogger(Scanner.class);
      private static int __scannerId=0;
      private int _scanInterval;
      private int _scanCount = 0;
      private final List<Listener> _listeners = new ArrayList<Listener>();
      private final Map<String,TimeNSize> _prevScan = new HashMap<String,TimeNSize> ();
      private final Map<String,TimeNSize> _currentScan = new HashMap<String,TimeNSize> ();
      private FilenameFilter _filter;
      private final List<File> _scanDirs = new ArrayList<File>();
      private volatile boolean _running = false;
      private boolean _reportExisting = true;
      private boolean _reportDirs = true;
      private Timer _timer;
      private TimerTask _task;
      private int _scanDepth=0;
      
      public enum Notification { ADDED, CHANGED, REMOVED };
      private final Map<String,Notification> _notifications = new HashMap<String,Notification>();
  
      static class TimeNSize
      {
          final long _lastModified;
          final long _size;
          
          public TimeNSize(long lastModified, long size)
          {
              _lastModified = lastModified;
              _size = size;
          }
          
          @Override
          public int hashCode()
          {
              return (int)_lastModified^(int)_size;
          }
          
          @Override
          public boolean equals(Object o)
          {
              if (o instanceof TimeNSize)
              {
                  TimeNSize tns = (TimeNSize)o;
                  return tns._lastModified==_lastModified && tns._size==_size;
              }
              return false;
          }
          
          @Override
          public String toString()
         {
             return "[lm="+_lastModified+",s="+_size+"]";
         }
     }
     
     /**
      * Listener
      * 
      * Marker for notifications re file changes.
      */
     public interface Listener
     {
     }
 
     public interface ScanListener extends Listener
     {
         public void scan();
     }
     
     public interface DiscreteListener extends Listener
     {
         public void fileChanged (String filename) throws Exception;
         public void fileAdded (String filename) throws Exception;
         public void fileRemoved (String filename) throws Exception;
     }
     
     
     public interface BulkListener extends Listener
     {
         public void filesChanged (List<String> filenames) throws Exception;
     }
 
     /**
      * Listener that notifies when a scan has started and when it has ended.
      */
     public interface ScanCycleListener extends Listener
     {
         public void scanStarted(int cycle) throws Exception;
         public void scanEnded(int cycle) throws Exception;
     }
 
     /**
      * 
      */
     public Scanner ()
     {       
     }
 
     /**
      * Get the scan interval
      * @return interval between scans in seconds
      */
     public int getScanInterval()
     {
         return _scanInterval;
     }
 
     /**
      * Set the scan interval
      * @param scanInterval pause between scans in seconds, or 0 for no scan after the initial scan.
      */
     public synchronized void setScanInterval(int scanInterval)
     {
         _scanInterval = scanInterval;
         schedule();
     }
 
     /**
      * Set the location of the directory to scan.
      * @param dir
      * @deprecated use setScanDirs(List dirs) instead
      */
     @Deprecated
     public void setScanDir (File dir)
     {
         _scanDirs.clear(); 
         _scanDirs.add(dir);
     }
 
     /**
      * Get the location of the directory to scan
      * @return the first directory (of {@link #getScanDirs()} being scanned)
      * @deprecated use getScanDirs() instead
      */
     @Deprecated
     public File getScanDir ()
     {
         return (_scanDirs==null?null:(File)_scanDirs.get(0));
     }
 
     public void setScanDirs (List<File> dirs)
     {
         _scanDirs.clear(); 
         _scanDirs.addAll(dirs);
     }
     
     public synchronized void addScanDir( File dir )
     {
         _scanDirs.add( dir );
     }
     
     public List<File> getScanDirs ()
     {
         return Collections.unmodifiableList(_scanDirs);
     }
     
     /* ------------------------------------------------------------ */
     /**
      * @param recursive True if scanning is recursive
      * @see  #setScanDepth(int)
      */
     public void setRecursive (boolean recursive)
     {
         _scanDepth=recursive?-1:0;
     }
     
     /* ------------------------------------------------------------ */
     /**
      * @return True if scanning is fully recursive (scandepth==-1)
      * @see #getScanDepth()
      */
     public boolean getRecursive ()
     {
         return _scanDepth==-1;
     }
     
     /* ------------------------------------------------------------ */
     /** Get the scanDepth.
      * @return the scanDepth
      */
     public int getScanDepth()
     {
         return _scanDepth;
     }
 
     /* ------------------------------------------------------------ */
     /** Set the scanDepth.
      * @param scanDepth the scanDepth to set
      */
     public void setScanDepth(int scanDepth)
     {
         _scanDepth = scanDepth;
     }
 
     /**
      * Apply a filter to files found in the scan directory.
      * Only files matching the filter will be reported as added/changed/removed.
      * @param filter
      */
     public void setFilenameFilter (FilenameFilter filter)
     {
         _filter = filter;
     }
 
     /**
      * Get any filter applied to files in the scan dir.
      * @return the filename filter
      */
     public FilenameFilter getFilenameFilter ()
     {
         return _filter;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Whether or not an initial scan will report all files as being
      * added.
      * @param reportExisting if true, all files found on initial scan will be 
      * reported as being added, otherwise not
      */
     public void setReportExistingFilesOnStartup (boolean reportExisting)
     {
         _reportExisting = reportExisting;
     }
 
     /* ------------------------------------------------------------ */
     public boolean getReportExistingFilesOnStartup()
     {
         return _reportExisting;
     }
     
     /* ------------------------------------------------------------ */
     /** Set if found directories should be reported.
      * @param dirs
      */
     public void setReportDirs(boolean dirs)
     {
         _reportDirs=dirs;
     }
     
     /* ------------------------------------------------------------ */
     public boolean getReportDirs()
     {
         return _reportDirs;
     }
     
     /* ------------------------------------------------------------ */
     /**
      * Add an added/removed/changed listener
      * @param listener
      */
     public synchronized void addListener (Listener listener)
     {
         if (listener == null)
             return;
         _listeners.add(listener);   
     }
 
 
 
     /**
      * Remove a registered listener
      * @param listener the Listener to be removed
      */
     public synchronized void removeListener (Listener listener)
     {
         if (listener == null)
             return;
         _listeners.remove(listener);    
     }
 
 
     /**
      * Start the scanning action.
      */
     @Override
     public synchronized void doStart()
     {
         if (_running)
             return;
 
         _running = true;
 
         if (_reportExisting)
         {
             // if files exist at startup, report them
             scan();
             scan(); // scan twice so files reported as stable
         }
         else
         {
             //just register the list of existing files and only report changes
             scanFiles();
             _prevScan.putAll(_currentScan);
         }
         schedule();
     }
 
     public TimerTask newTimerTask ()
     {
         return new TimerTask()
         {
             @Override
             public void run() { scan(); }
         };
     }
 
     public Timer newTimer ()
     {
         return new Timer("Scanner-"+__scannerId++, true);
     }
     
     public void schedule ()
     {  
         if (_running)
         {
             if (_timer!=null)
                 _timer.cancel();
             if (_task!=null)
                 _task.cancel();
             if (getScanInterval() > 0)
             {
                 _timer = newTimer();
                 _task = newTimerTask();
                 _timer.schedule(_task, 1010L*getScanInterval(),1010L*getScanInterval());
             }
         }
     }
     /**
      * Stop the scanning.
      */
     @Override
     public synchronized void doStop()
     {
         if (_running)
         {
             _running = false; 
             if (_timer!=null)
                 _timer.cancel();
             if (_task!=null)
                 _task.cancel();
             _task=null;
             _timer=null;
         }
     }
 
     /**
      * Perform a pass of the scanner and report changes
      */
     public synchronized void scan ()
     {
         reportScanStart(++_scanCount);
         scanFiles();
         reportDifferences(_currentScan, _prevScan);
         _prevScan.clear();
         _prevScan.putAll(_currentScan);
         reportScanEnd(_scanCount);
         
         for (Listener l : _listeners)
         {
             try
             {
                 if (l instanceof ScanListener)
                     ((ScanListener)l).scan();
             }
             catch (Exception e)
             {
                 LOG.warn(e);
             }
             catch (Error e)
             {
                 LOG.warn(e);
             }
         }
     }
 
     /**
      * Recursively scan all files in the designated directories.
      */
     public synchronized void scanFiles ()
     {
         if (_scanDirs==null)
             return;
         
         _currentScan.clear();
         Iterator<File> itor = _scanDirs.iterator();
         while (itor.hasNext())
         {
             File dir = itor.next();
             
             if ((dir != null) && (dir.exists()))
                 try
                 {
                     scanFile(dir.getCanonicalFile(), _currentScan,0);
                 }
                 catch (IOException e)
                 {
                     LOG.warn("Error scanning files.", e);
                 }
         }
     }
 
 
     /**
      * Report the adds/changes/removes to the registered listeners
      * 
      * @param currentScan the info from the most recent pass
      * @param oldScan info from the previous pass
      */
     public synchronized void reportDifferences (Map<String,TimeNSize> currentScan, Map<String,TimeNSize> oldScan) 
     {
         // scan the differences and add what was found to the map of notifications:
 
         Set<String> oldScanKeys = new HashSet<String>(oldScan.keySet());
         
         // Look for new and changed files
         for (Map.Entry<String, TimeNSize> entry: currentScan.entrySet())
         {
             String file = entry.getKey(); 
             if (!oldScanKeys.contains(file))
             {
                 Notification old=_notifications.put(file,Notification.ADDED);
                 if (old!=null)
                 { 
                     switch(old)
                     {
                         case REMOVED: 
                         case CHANGED:
                             _notifications.put(file,Notification.CHANGED);
                     }
                 }
             }
             else if (!oldScan.get(file).equals(currentScan.get(file)))
             {
                 Notification old=_notifications.put(file,Notification.CHANGED);
                 if (old!=null)
                 {
                     switch(old)
                     {
                         case ADDED:
                             _notifications.put(file,Notification.ADDED);
                     }
                 }
             }
         }
         
         // Look for deleted files
         for (String file : oldScan.keySet())
         {
             if (!currentScan.containsKey(file))
             {
                 Notification old=_notifications.put(file,Notification.REMOVED);
                 if (old!=null)
                 {
                     switch(old)
                     {
                         case ADDED:
                             _notifications.remove(file);
                     }
                 }
             }
         }
         
         if (LOG.isDebugEnabled())
             LOG.debug("scanned "+_scanDirs+": "+_notifications);
                 
         // Process notifications
         // Only process notifications that are for stable files (ie same in old and current scan).
         List<String> bulkChanges = new ArrayList<String>();
         for (Iterator<Entry<String,Notification>> iter = _notifications.entrySet().iterator();iter.hasNext();)
         {
             Entry<String,Notification> entry=iter.next();
             String file=entry.getKey();
             
             // Is the file stable?
             if (oldScan.containsKey(file))
             {
                 if (!oldScan.get(file).equals(currentScan.get(file)))
                     continue;
             }
             else if (currentScan.containsKey(file))
                 continue;
                             
             // File is stable so notify
             Notification notification=entry.getValue();
             iter.remove();
             bulkChanges.add(file);
             switch(notification)
             {
                 case ADDED:
                     reportAddition(file);
                     break;
                 case CHANGED:
                     reportChange(file);
                     break;
                 case REMOVED:
                     reportRemoval(file);
                     break;
             }
         }
         if (!bulkChanges.isEmpty())
             reportBulkChanges(bulkChanges);
     }
 
 
     /**
      * Get last modified time on a single file or recurse if
      * the file is a directory. 
      * @param f file or directory
      * @param scanInfoMap map of filenames to last modified times
      */
     private void scanFile (File f, Map<String,TimeNSize> scanInfoMap, int depth)
     {
         try
         {
             if (!f.exists())
                 return;
 
             if (f.isFile() || depth>0&& _reportDirs && f.isDirectory())
             {
                 if ((_filter == null) || ((_filter != null) && _filter.accept(f.getParentFile(), f.getName())))
                 {
                     String name = f.getCanonicalPath();
                     scanInfoMap.put(name, new TimeNSize(f.lastModified(),f.length()));
                 }
             }
             
             // If it is a directory, scan if it is a known directory or the depth is OK.
             if (f.isDirectory() && (depth<_scanDepth || _scanDepth==-1 || _scanDirs.contains(f)))
             {
                 File[] files = f.listFiles();
                 if (files != null)
                 {
                     for (int i=0;i<files.length;i++)
                         scanFile(files[i], scanInfoMap,depth+1);
                 }
                 else
                     LOG.warn("Error listing files in directory {}", f);
                     
             }
         }
         catch (IOException e)
         {
             LOG.warn("Error scanning watched files", e);
         }
     }
 
     private void warn(Object listener,String filename,Throwable th)
     {
         LOG.warn(listener+" failed on '"+filename, th);
     }
 
     /**
      * Report a file addition to the registered FileAddedListeners
      * @param filename
      */
     private void reportAddition (String filename)
     {
         Iterator<Listener> itor = _listeners.iterator();
         while (itor.hasNext())
         {
             Listener l = itor.next();
             try
             {
                 if (l instanceof DiscreteListener)
                     ((DiscreteListener)l).fileAdded(filename);
             }
             catch (Exception e)
             {
                 warn(l,filename,e);
             }
             catch (Error e)
             {
                 warn(l,filename,e);
             }
         }
     }
 
 
     /**
      * Report a file removal to the FileRemovedListeners
      * @param filename
      */
     private void reportRemoval (String filename)
     {
         Iterator<Listener> itor = _listeners.iterator();
         while (itor.hasNext())
         {
             Object l = itor.next();
             try
             {
                 if (l instanceof DiscreteListener)
                     ((DiscreteListener)l).fileRemoved(filename);
             }
             catch (Exception e)
             {
                 warn(l,filename,e);
             }
             catch (Error e)
             {
                 warn(l,filename,e);
             }
         }
     }
 
 
     /**
      * Report a file change to the FileChangedListeners
      * @param filename
      */
     private void reportChange (String filename)
     {
         Iterator<Listener> itor = _listeners.iterator();
         while (itor.hasNext())
         {
             Listener l = itor.next();
             try
             {
                 if (l instanceof DiscreteListener)
                     ((DiscreteListener)l).fileChanged(filename);
             }
             catch (Exception e)
             {
                 warn(l,filename,e);
             }
             catch (Error e)
             {
                 warn(l,filename,e);
             }
         }
     }
     
     private void reportBulkChanges (List<String> filenames)
     {
         Iterator<Listener> itor = _listeners.iterator();
         while (itor.hasNext())
         {
             Listener l = itor.next();
             try
             {
                 if (l instanceof BulkListener)
                     ((BulkListener)l).filesChanged(filenames);
             }
             catch (Exception e)
             {
                 warn(l,filenames.toString(),e);
             }
             catch (Error e)
             {
                 warn(l,filenames.toString(),e);
             }
         }
     }
     
     /**
      * signal any scan cycle listeners that a scan has started
      */
     private void reportScanStart(int cycle)
     {
         for (Listener listener : _listeners)
         {
             try
             {
                 if (listener instanceof ScanCycleListener)
                 {
                     ((ScanCycleListener)listener).scanStarted(cycle);
                 }
             }
             catch (Exception e)
             {
                 LOG.warn(listener + " failed on scan start for cycle " + cycle, e);
             }
         }
     }
 
     /**
      * sign
      */
     private void reportScanEnd(int cycle)
     {
         for (Listener listener : _listeners)
         {
             try
             {
                 if (listener instanceof ScanCycleListener)
                 {
                     ((ScanCycleListener)listener).scanEnded(cycle);
                 }
             }
             catch (Exception e)
             {
                 LOG.warn(listener + " failed on scan end for cycle " + cycle, e);
             }
         }
     }
 
 }