/**
    *
    * 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.util;
  
  import java.io.IOException;
  import java.util.NavigableSet;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.fs.PathFilter;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.wal.WALSplitter;
  
  /**
   * Utility methods for interacting with the hbase.root file system.
   */
  @InterfaceAudience.Private
  public final class FSVisitor {
    private static final Log LOG = LogFactory.getLog(FSVisitor.class);
  
    public interface RegionVisitor {
      void region(final String region) throws IOException;
    }
  
    public interface StoreFileVisitor {
      void storeFile(final String region, final String family, final String hfileName)
         throws IOException;
    }
  
    public interface RecoveredEditsVisitor {
      void recoveredEdits (final String region, final String logfile)
        throws IOException;
    }
  
    public interface LogFileVisitor {
      void logFile (final String server, final String logfile)
        throws IOException;
    }
  
    private FSVisitor() {
      // private constructor for utility class
    }
  
    /**
     * Iterate over the table store files
     *
     * @param fs {@link FileSystem}
     * @param tableDir {@link Path} to the table directory
     * @param visitor callback object to get the store files
     * @throws IOException if an error occurred while scanning the directory
     */
    public static void visitRegions(final FileSystem fs, final Path tableDir,
        final RegionVisitor visitor) throws IOException {
      FileStatus[] regions = FSUtils.listStatus(fs, tableDir, new FSUtils.RegionDirFilter(fs));
      if (regions == null) {
        if (LOG.isTraceEnabled()) {
          LOG.trace("No regions under directory:" + tableDir);
        }
        return;
      }
  
      for (FileStatus region: regions) {
        visitor.region(region.getPath().getName());
      }
    }
  
    /**
     * Iterate over the table store files
     *
     * @param fs {@link FileSystem}
     * @param tableDir {@link Path} to the table directory
     * @param visitor callback object to get the store files
     * @throws IOException if an error occurred while scanning the directory
     */
    public static void visitTableStoreFiles(final FileSystem fs, final Path tableDir,
        final StoreFileVisitor visitor) throws IOException {
      FileStatus[] regions = FSUtils.listStatus(fs, tableDir, new FSUtils.RegionDirFilter(fs));
      if (regions == null) {
        if (LOG.isTraceEnabled()) {
         LOG.trace("No regions under directory:" + tableDir);
       }
       return;
     }
 
     for (FileStatus region: regions) {
       visitRegionStoreFiles(fs, region.getPath(), visitor);
     }
   }
 
   /**
    * Iterate over the region store files
    *
    * @param fs {@link FileSystem}
    * @param regionDir {@link Path} to the region directory
    * @param visitor callback object to get the store files
    * @throws IOException if an error occurred while scanning the directory
    */
   public static void visitRegionStoreFiles(final FileSystem fs, final Path regionDir,
       final StoreFileVisitor visitor) throws IOException {
     FileStatus[] families = FSUtils.listStatus(fs, regionDir, new FSUtils.FamilyDirFilter(fs));
     if (families == null) {
       if (LOG.isTraceEnabled()) {
         LOG.trace("No families under region directory:" + regionDir);
       }
       return;
     }
 
     PathFilter fileFilter = new FSUtils.FileFilter(fs);
     for (FileStatus family: families) {
       Path familyDir = family.getPath();
       String familyName = familyDir.getName();
 
       // get all the storeFiles in the family
       FileStatus[] storeFiles = FSUtils.listStatus(fs, familyDir, fileFilter);
       if (storeFiles == null) {
         if (LOG.isTraceEnabled()) {
           LOG.trace("No hfiles found for family: " + familyDir + ", skipping.");
         }
         continue;
       }
 
       for (FileStatus hfile: storeFiles) {
         Path hfilePath = hfile.getPath();
         visitor.storeFile(regionDir.getName(), familyName, hfilePath.getName());
       }
     }
   }
 
   /**
    * Iterate over each region in the table and inform about recovered.edits
    *
    * @param fs {@link FileSystem}
    * @param tableDir {@link Path} to the table directory
    * @param visitor callback object to get the recovered.edits files
    * @throws IOException if an error occurred while scanning the directory
    */
   public static void visitTableRecoveredEdits(final FileSystem fs, final Path tableDir,
       final FSVisitor.RecoveredEditsVisitor visitor) throws IOException {
     FileStatus[] regions = FSUtils.listStatus(fs, tableDir, new FSUtils.RegionDirFilter(fs));
     if (regions == null) {
       if (LOG.isTraceEnabled()) {
         LOG.trace("No recoveredEdits regions under directory:" + tableDir);
       }
       return;
     }
 
     for (FileStatus region: regions) {
       visitRegionRecoveredEdits(fs, region.getPath(), visitor);
     }
   }
 
   /**
    * Iterate over recovered.edits of the specified region
    *
    * @param fs {@link FileSystem}
    * @param regionDir {@link Path} to the Region directory
    * @param visitor callback object to get the recovered.edits files
    * @throws IOException if an error occurred while scanning the directory
    */
   public static void visitRegionRecoveredEdits(final FileSystem fs, final Path regionDir,
       final FSVisitor.RecoveredEditsVisitor visitor) throws IOException {
     NavigableSet<Path> files = WALSplitter.getSplitEditFilesSorted(fs, regionDir);
     if (files == null || files.size() == 0) return;
 
     for (Path source: files) {
       // check to see if the file is zero length, in which case we can skip it
       FileStatus stat = fs.getFileStatus(source);
       if (stat.getLen() <= 0) continue;
 
       visitor.recoveredEdits(regionDir.getName(), source.getName());
     }
   }
 
   /**
    * Iterate over hbase log files
    *
    * @param fs {@link FileSystem}
    * @param rootDir {@link Path} to the HBase root folder
    * @param visitor callback object to get the log files
    * @throws IOException if an error occurred while scanning the directory
    */
   public static void visitLogFiles(final FileSystem fs, final Path rootDir,
       final LogFileVisitor visitor) throws IOException {
     Path logsDir = new Path(rootDir, HConstants.HREGION_LOGDIR_NAME);
     FileStatus[] logServerDirs = FSUtils.listStatus(fs, logsDir);
     if (logServerDirs == null) {
       if (LOG.isTraceEnabled()) {
         LOG.trace("No logs under directory:" + logsDir);
       }
       return;
     }
 
     for (FileStatus serverLogs: logServerDirs) {
       String serverName = serverLogs.getPath().getName();
 
       FileStatus[] wals = FSUtils.listStatus(fs, serverLogs.getPath());
       if (wals == null) {
         if (LOG.isTraceEnabled()) {
           LOG.trace("No wals found for server: " + serverName + ", skipping.");
         }
         continue;
       }
 
       for (FileStatus walRef: wals) {
         visitor.logFile(serverName, walRef.getPath().getName());
       }
     }
   }
 }