/**
    * 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.snapshot;
  
  import java.io.IOException;
  import java.util.Collections;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FSDataInputStream;
  import org.apache.hadoop.fs.FSDataOutputStream;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.fs.permission.FsPermission;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.exceptions.CorruptedSnapshotException;
  import org.apache.hadoop.hbase.exceptions.SnapshotCreationException;
  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.FSUtils;
  
  /**
   * Utility class to help manage {@link SnapshotDescription SnapshotDesriptions}.
   * <p>
   * Snapshots are laid out on disk like this:
   *
   * <pre>
   * /hbase/.snapshots
   *          /.tmp                <---- working directory
   *          /[snapshot name]     <----- completed snapshot
   * </pre>
   *
   * A completed snapshot named 'completed' then looks like (multiple regions, servers, files, etc.
   * signified by '...' on the same directory depth).
   *
   * <pre>
   * /hbase/.snapshots/completed
   *                   .snapshotinfo          <--- Description of the snapshot
   *                   .tableinfo             <--- Copy of the tableinfo
   *                    /.logs
   *                        /[server_name]
   *                            /... [log files]
   *                         ...
   *                   /[region name]           <---- All the region's information
   *                   .regioninfo              <---- Copy of the HRegionInfo
   *                      /[column family name]
   *                          /[hfile name]     <--- name of the hfile in the real region
   *                          ...
   *                      ...
   *                    ...
   * </pre>
   *
   * Utility methods in this class are useful for getting the correct locations for different parts of
   * the snapshot, as well as moving completed snapshots into place (see
   * {@link #completeSnapshot}, and writing the
   * {@link SnapshotDescription} to the working snapshot directory.
   */
  public class SnapshotDescriptionUtils {
  
    /**
     * Filter that only accepts completed snapshot directories
     */
    public static class CompletedSnaphotDirectoriesFilter extends FSUtils.BlackListDirFilter {
  
      /**
       * @param fs
       */
      public CompletedSnaphotDirectoriesFilter(FileSystem fs) {
        super(fs, Collections.singletonList(SNAPSHOT_TMP_DIR_NAME));
      }
    }
  
    private static final Log LOG = LogFactory.getLog(SnapshotDescriptionUtils.class);
    /**
     * Version of the fs layout for a snapshot. Future snapshots may have different file layouts,
     * which we may need to read in differently.
     */
    public static final int SNAPSHOT_LAYOUT_VERSION = 0;
  
    // snapshot directory constants
    /**
     * The file contains the snapshot basic information and it is under the directory of a snapshot.
     */
   public static final String SNAPSHOTINFO_FILE = ".snapshotinfo";
 
   /** Temporary directory under the snapshot directory to store in-progress snapshots */
   public static final String SNAPSHOT_TMP_DIR_NAME = ".tmp";
   // snapshot operation values
   /** Default value if no start time is specified */
   public static final long NO_SNAPSHOT_START_TIME_SPECIFIED = 0;
 
   public static final String MASTER_SNAPSHOT_TIMEOUT_MILLIS = "hbase.snapshot.master.timeout.millis";
 
   /** By default, wait 60 seconds for a snapshot to complete */
   public static final long DEFAULT_MAX_WAIT_TIME = 60000;
 
   private SnapshotDescriptionUtils() {
     // private constructor for utility class
   }
 
   /**
    * @param conf {@link Configuration} from which to check for the timeout
    * @param type type of snapshot being taken
    * @param defaultMaxWaitTime Default amount of time to wait, if none is in the configuration
    * @return the max amount of time the master should wait for a snapshot to complete
    */
   public static long getMaxMasterTimeout(Configuration conf, SnapshotDescription.Type type,
       long defaultMaxWaitTime) {
     String confKey;
     switch (type) {
     case DISABLED:
     default:
       confKey = MASTER_SNAPSHOT_TIMEOUT_MILLIS;
     }
     return conf.getLong(confKey, defaultMaxWaitTime);
   }
 
   /**
    * Get the snapshot root directory. All the snapshots are kept under this directory, i.e.
    * ${hbase.rootdir}/.snapshot
    * @param rootDir hbase root directory
    * @return the base directory in which all snapshots are kept
    */
   public static Path getSnapshotRootDir(final Path rootDir) {
     return new Path(rootDir, HConstants.SNAPSHOT_DIR_NAME);
   }
 
   /**
    * Get the directory for a specified snapshot. This directory is a sub-directory of snapshot root
    * directory and all the data files for a snapshot are kept under this directory.
    * @param snapshot snapshot being taken
    * @param rootDir hbase root directory
    * @return the final directory for the completed snapshot
    */
   public static Path getCompletedSnapshotDir(final SnapshotDescription snapshot, final Path rootDir) {
     return getCompletedSnapshotDir(snapshot.getName(), rootDir);
   }
 
   /**
    * Get the directory for a completed snapshot. This directory is a sub-directory of snapshot root
    * directory and all the data files for a snapshot are kept under this directory.
    * @param snapshotName name of the snapshot being taken
    * @param rootDir hbase root directory
    * @return the final directory for the completed snapshot
    */
   public static Path getCompletedSnapshotDir(final String snapshotName, final Path rootDir) {
     return getCompletedSnapshotDir(getSnapshotsDir(rootDir), snapshotName);
   }
 
   /**
    * Get the general working directory for snapshots - where they are built, where they are
    * temporarily copied on export, etc.
    * @param rootDir root directory of the HBase installation
    * @return Path to the snapshot tmp directory, relative to the passed root directory
    */
   public static Path getWorkingSnapshotDir(final Path rootDir) {
     return new Path(getSnapshotsDir(rootDir), SNAPSHOT_TMP_DIR_NAME);
   }
 
   /**
    * Get the directory to build a snapshot, before it is finalized
    * @param snapshot snapshot that will be built
    * @param rootDir root directory of the hbase installation
    * @return {@link Path} where one can build a snapshot
    */
   public static Path getWorkingSnapshotDir(SnapshotDescription snapshot, final Path rootDir) {
     return getCompletedSnapshotDir(getWorkingSnapshotDir(rootDir), snapshot.getName());
   }
 
   /**
    * Get the directory to build a snapshot, before it is finalized
    * @param snapshotName name of the snapshot
    * @param rootDir root directory of the hbase installation
    * @return {@link Path} where one can build a snapshot
    */
   public static Path getWorkingSnapshotDir(String snapshotName, final Path rootDir) {
     return getCompletedSnapshotDir(getWorkingSnapshotDir(rootDir), snapshotName);
   }
 
   /**
    * Get the directory to store the snapshot instance
    * @param snapshotsDir hbase-global directory for storing all snapshots
    * @param snapshotName name of the snapshot to take
    * @return the final directory for the completed snapshot
    */
   private static final Path getCompletedSnapshotDir(final Path snapshotsDir, String snapshotName) {
     return new Path(snapshotsDir, snapshotName);
   }
 
   /**
    * @param rootDir hbase root directory
    * @return the directory for all completed snapshots;
    */
   public static final Path getSnapshotsDir(Path rootDir) {
     return new Path(rootDir, HConstants.SNAPSHOT_DIR_NAME);
   }
 
   /**
    * Convert the passed snapshot description into a 'full' snapshot description based on default
    * parameters, if none have been supplied. This resolves any 'optional' parameters that aren't
    * supplied to their default values.
    * @param snapshot general snapshot descriptor
    * @param conf Configuration to read configured snapshot defaults if snapshot is not complete
    * @return a valid snapshot description
    * @throws IllegalArgumentException if the {@link SnapshotDescription} is not a complete
    *           {@link SnapshotDescription}.
    */
   public static SnapshotDescription validate(SnapshotDescription snapshot, Configuration conf)
       throws IllegalArgumentException {
     if (!snapshot.hasTable()) {
       throw new IllegalArgumentException(
         "Descriptor doesn't apply to a table, so we can't build it.");
     }
 
     // set the creation time, if one hasn't been set
     long time = snapshot.getCreationTime();
     if (time == SnapshotDescriptionUtils.NO_SNAPSHOT_START_TIME_SPECIFIED) {
       time = EnvironmentEdgeManager.currentTimeMillis();
       LOG.debug("Creation time not specified, setting to:" + time + " (current time:"
           + EnvironmentEdgeManager.currentTimeMillis() + ").");
       SnapshotDescription.Builder builder = snapshot.toBuilder();
       builder.setCreationTime(time);
       snapshot = builder.build();
     }
     return snapshot;
   }
 
   /**
    * Write the snapshot description into the working directory of a snapshot
    * @param snapshot description of the snapshot being taken
    * @param workingDir working directory of the snapshot
    * @param fs {@link FileSystem} on which the snapshot should be taken
    * @throws IOException if we can't reach the filesystem and the file cannot be cleaned up on
    *           failure
    */
   public static void writeSnapshotInfo(SnapshotDescription snapshot, Path workingDir, FileSystem fs)
       throws IOException {
     FsPermission perms = FSUtils.getFilePermissions(fs, fs.getConf(),
       HConstants.DATA_FILE_UMASK_KEY);
     Path snapshotInfo = new Path(workingDir, SnapshotDescriptionUtils.SNAPSHOTINFO_FILE);
     try {
       FSDataOutputStream out = FSUtils.create(fs, snapshotInfo, perms, true);
       try {
         snapshot.writeTo(out);
       } finally {
         out.close();
       }
     } catch (IOException e) {
       // if we get an exception, try to remove the snapshot info
       if (!fs.delete(snapshotInfo, false)) {
         String msg = "Couldn't delete snapshot info file: " + snapshotInfo;
         LOG.error(msg);
         throw new IOException(msg);
       }
     }
   }
 
   /**
    * Read in the {@link SnapshotDescription} stored for the snapshot in the passed directory
    * @param fs filesystem where the snapshot was taken
    * @param snapshotDir directory where the snapshot was stored
    * @return the stored snapshot description
    * @throws org.apache.hadoop.hbase.exceptions.CorruptedSnapshotException if the snapshot cannot be read
    */
   public static SnapshotDescription readSnapshotInfo(FileSystem fs, Path snapshotDir)
       throws CorruptedSnapshotException {
     Path snapshotInfo = new Path(snapshotDir, SNAPSHOTINFO_FILE);
     try {
       FSDataInputStream in = null;
       try {
         in = fs.open(snapshotInfo);
         return SnapshotDescription.parseFrom(in);
       } finally {
         if (in != null) in.close();
       }
     } catch (IOException e) {
       throw new CorruptedSnapshotException("Couldn't read snapshot info from:" + snapshotInfo, e);
     }
   }
 
   /**
    * Move the finished snapshot to its final, publicly visible directory - this marks the snapshot
    * as 'complete'.
    * @param snapshot description of the snapshot being tabken
    * @param rootdir root directory of the hbase installation
    * @param workingDir directory where the in progress snapshot was built
    * @param fs {@link FileSystem} where the snapshot was built
    * @throws org.apache.hadoop.hbase.exceptions.SnapshotCreationException if the snapshot could not be moved
    * @throws IOException the filesystem could not be reached
    */
   public static void completeSnapshot(SnapshotDescription snapshot, Path rootdir, Path workingDir,
       FileSystem fs) throws SnapshotCreationException, IOException {
     Path finishedDir = getCompletedSnapshotDir(snapshot, rootdir);
     LOG.debug("Snapshot is done, just moving the snapshot from " + workingDir + " to "
         + finishedDir);
     if (!fs.rename(workingDir, finishedDir)) {
       throw new SnapshotCreationException("Failed to move working directory(" + workingDir
           + ") to completed directory(" + finishedDir + ").", snapshot);
     }
   }
 
 }