/**
    * 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.hadoop.hbase.master.cleaner;
  
  import java.io.IOException;
  import java.util.LinkedList;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.RemoteExceptionHandler;
  import org.apache.hadoop.hbase.ScheduledChore;
  import org.apache.hadoop.hbase.Stoppable;
  import org.apache.hadoop.hbase.util.FSUtils;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.collect.ImmutableSet;
  import com.google.common.collect.Iterables;
  import com.google.common.collect.Lists;
  
  /**
   * Abstract Cleaner that uses a chain of delegates to clean a directory of files
   * @param <T> Cleaner delegate class that is dynamically loaded from configuration
   */
  public abstract class CleanerChore<T extends FileCleanerDelegate> extends ScheduledChore {
  
    private static final Log LOG = LogFactory.getLog(CleanerChore.class.getName());
  
    private final FileSystem fs;
    private final Path oldFileDir;
    private final Configuration conf;
    protected List<T> cleanersChain;
  
    /**
     * @param name name of the chore being run
     * @param sleepPeriod the period of time to sleep between each run
     * @param s the stopper
     * @param conf configuration to use
     * @param fs handle to the FS
     * @param oldFileDir the path to the archived files
     * @param confKey configuration key for the classes to instantiate
     */
    public CleanerChore(String name, final int sleepPeriod, final Stoppable s, Configuration conf,
        FileSystem fs, Path oldFileDir, String confKey) {
      super(name, s, sleepPeriod);
      this.fs = fs;
      this.oldFileDir = oldFileDir;
      this.conf = conf;
  
      initCleanerChain(confKey);
    }
  
    /**
     * Validate the file to see if it even belongs in the directory. If it is valid, then the file
     * will go through the cleaner delegates, but otherwise the file is just deleted.
     * @param file full {@link Path} of the file to be checked
     * @return <tt>true</tt> if the file is valid, <tt>false</tt> otherwise
     */
    protected abstract boolean validate(Path file);
  
    /**
     * Instantiate and initialize all the file cleaners set in the configuration
     * @param confKey key to get the file cleaner classes from the configuration
     */
    private void initCleanerChain(String confKey) {
      this.cleanersChain = new LinkedList<T>();
      String[] logCleaners = conf.getStrings(confKey);
      if (logCleaners != null) {
        for (String className : logCleaners) {
          T logCleaner = newFileCleaner(className, conf);
          if (logCleaner != null) {
            LOG.debug("initialize cleaner=" + className);
            this.cleanersChain.add(logCleaner);
          }
        }
      }
    }
  
    /**
     * A utility method to create new instances of LogCleanerDelegate based on the class name of the
    * LogCleanerDelegate.
    * @param className fully qualified class name of the LogCleanerDelegate
    * @param conf
    * @return the new instance
    */
   private T newFileCleaner(String className, Configuration conf) {
     try {
       Class<? extends FileCleanerDelegate> c = Class.forName(className).asSubclass(
         FileCleanerDelegate.class);
       @SuppressWarnings("unchecked")
       T cleaner = (T) c.newInstance();
       cleaner.setConf(conf);
       return cleaner;
     } catch (Exception e) {
       LOG.warn("Can NOT create CleanerDelegate: " + className, e);
       // skipping if can't instantiate
       return null;
     }
   }
 
   @Override
   protected void chore() {
     try {
       FileStatus[] files = FSUtils.listStatus(this.fs, this.oldFileDir);
       checkAndDeleteEntries(files);
     } catch (IOException e) {
       e = RemoteExceptionHandler.checkIOException(e);
       LOG.warn("Error while cleaning the logs", e);
     }
   }
 
   /**
    * Loop over the given directory entries, and check whether they can be deleted.
    * If an entry is itself a directory it will be recursively checked and deleted itself iff
    * all subentries are deleted (and no new subentries are added in the mean time)
    *
    * @param entries directory entries to check
    * @return true if all entries were successfully deleted
    */
   private boolean checkAndDeleteEntries(FileStatus[] entries) {
     if (entries == null) {
       return true;
     }
     boolean allEntriesDeleted = true;
     List<FileStatus> files = Lists.newArrayListWithCapacity(entries.length);
     for (FileStatus child : entries) {
       Path path = child.getPath();
       if (child.isDirectory()) {
         // for each subdirectory delete it and all entries if possible
         if (!checkAndDeleteDirectory(path)) {
           allEntriesDeleted = false;
         }
       } else {
         // collect all files to attempt to delete in one batch
         files.add(child);
       }
     }
     if (!checkAndDeleteFiles(files)) {
       allEntriesDeleted = false;
     }
     return allEntriesDeleted;
   }
   
   /**
    * Attempt to delete a directory and all files under that directory. Each child file is passed
    * through the delegates to see if it can be deleted. If the directory has no children when the
    * cleaners have finished it is deleted.
    * <p>
    * If new children files are added between checks of the directory, the directory will <b>not</b>
    * be deleted.
    * @param dir directory to check
    * @return <tt>true</tt> if the directory was deleted, <tt>false</tt> otherwise.
    */
   @VisibleForTesting boolean checkAndDeleteDirectory(Path dir) {
     if (LOG.isTraceEnabled()) {
       LOG.trace("Checking directory: " + dir);
     }
 
     try {
       FileStatus[] children = FSUtils.listStatus(fs, dir);
       boolean allChildrenDeleted = checkAndDeleteEntries(children);
   
       // if the directory still has children, we can't delete it, so we are done
       if (!allChildrenDeleted) return false;
     } catch (IOException e) {
       e = RemoteExceptionHandler.checkIOException(e);
       LOG.warn("Error while listing directory: " + dir, e);
       // couldn't list directory, so don't try to delete, and don't return success
       return false;
     }
 
     // otherwise, all the children (that we know about) have been deleted, so we should try to
     // delete this directory. However, don't do so recursively so we don't delete files that have
     // been added since we last checked.
     try {
       return fs.delete(dir, false);
     } catch (IOException e) {
       if (LOG.isTraceEnabled()) {
         LOG.trace("Couldn't delete directory: " + dir, e);
       }
       // couldn't delete w/o exception, so we can't return success.
       return false;
     }
   }
 
   /**
    * Run the given files through each of the cleaners to see if it should be deleted, deleting it if
    * necessary.
    * @param files List of FileStatus for the files to check (and possibly delete)
    * @return true iff successfully deleted all files
    */
   private boolean checkAndDeleteFiles(List<FileStatus> files) {
     // first check to see if the path is valid
     List<FileStatus> validFiles = Lists.newArrayListWithCapacity(files.size());
     List<FileStatus> invalidFiles = Lists.newArrayList();
     for (FileStatus file : files) {
       if (validate(file.getPath())) {
         validFiles.add(file);
       } else {
         LOG.warn("Found a wrongly formatted file: " + file.getPath() + " - will delete it.");
         invalidFiles.add(file);
       }
     }
 
     Iterable<FileStatus> deletableValidFiles = validFiles;
     // check each of the cleaners for the valid files
     for (T cleaner : cleanersChain) {
       if (cleaner.isStopped() || getStopper().isStopped()) {
         LOG.warn("A file cleaner" + this.getName() + " is stopped, won't delete any more files in:"
             + this.oldFileDir);
         return false;
       }
 
       Iterable<FileStatus> filteredFiles = cleaner.getDeletableFiles(deletableValidFiles);
       
       // trace which cleaner is holding on to each file
       if (LOG.isTraceEnabled()) {
         ImmutableSet<FileStatus> filteredFileSet = ImmutableSet.copyOf(filteredFiles);
         for (FileStatus file : deletableValidFiles) {
           if (!filteredFileSet.contains(file)) {
             LOG.trace(file.getPath() + " is not deletable according to:" + cleaner);
           }
         }
       }
       
       deletableValidFiles = filteredFiles;
     }
     
     Iterable<FileStatus> filesToDelete = Iterables.concat(invalidFiles, deletableValidFiles);
     int deletedFileCount = 0;
     for (FileStatus file : filesToDelete) {
       Path filePath = file.getPath();
       if (LOG.isDebugEnabled()) {
         LOG.debug("Removing: " + filePath + " from archive");
       }
       try {
         boolean success = this.fs.delete(filePath, false);
         if (success) {
           deletedFileCount++;
         } else {
           LOG.warn("Attempted to delete:" + filePath
               + ", but couldn't. Run cleaner chain and attempt to delete on next pass.");
         }
       } catch (IOException e) {
         e = RemoteExceptionHandler.checkIOException(e);
         LOG.warn("Error while deleting: " + filePath, e);
       }
     }
 
     return deletedFileCount == files.size();
   }
 
   @Override
   public void cleanup() {
     for (T lc : this.cleanersChain) {
       try {
         lc.stop("Exiting");
       } catch (Throwable t) {
         LOG.warn("Stopping", t);
       }
     }
   }
 }