/**
    * 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.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.snapshot.SnapshotDescriptionUtils;
  
  /**
   * A class to migrate table descriptor files to a dedicated subdir.
   * Invoked by HMaster.finishInitialization before accessing table descriptors.
   * Migrates snapshots, user tables, and system tables.
   * 
   * @deprecated will be removed for the major release after 0.96.
   */
  @Deprecated
  public class FSTableDescriptorMigrationToSubdir {
    
    private static final Log LOG = LogFactory.getLog(FSTableDescriptorMigrationToSubdir.class);
  
    public static void migrateFSTableDescriptorsIfNecessary(FileSystem fs, Path rootDir)
    throws IOException {
      if (needsMigration(fs, rootDir)) {
        migrateFsTableDescriptors(fs, rootDir);
        LOG.info("Migration complete.");
      }
    }
  
    /**
     * Determines if migration is required by checking to see whether the hbase:meta table has been
     * migrated.
     */
    private static boolean needsMigration(FileSystem fs, Path rootDir) throws IOException {
      Path metaTableDir = FSUtils.getTableDir(rootDir,
        TableName.META_TABLE_NAME);
      FileStatus metaTableInfoStatus =
        FSTableDescriptors.getTableInfoPath(fs, metaTableDir);
      return metaTableInfoStatus == null;
    }
    
    /**
     * Migrates all snapshots, user tables and system tables that require migration.
     * First migrates snapshots.
     * Then migrates each user table in order,
     * then attempts ROOT (should be gone)
     * Migrates hbase:meta last to indicate migration is complete.
     */
    private static void migrateFsTableDescriptors(FileSystem fs, Path rootDir) throws IOException {
      // First migrate snapshots - will migrate any snapshot dir that contains a table info file
      Path snapshotsDir = SnapshotDescriptionUtils.getSnapshotsDir(rootDir);
      if (fs.exists(snapshotsDir)) {
        LOG.info("Migrating snapshots");
        FileStatus[] snapshots = fs.listStatus(snapshotsDir,
            new SnapshotDescriptionUtils.CompletedSnaphotDirectoriesFilter(fs));
        for (FileStatus snapshot : snapshots) {
          migrateTable(fs, snapshot.getPath());
        }
      }
      
      LOG.info("Migrating user tables");
      List<Path> userTableDirs = FSUtils.getTableDirs(fs, rootDir);
      for (Path userTableDir : userTableDirs) {
        migrateTable(fs, userTableDir);
      }
      
      LOG.info("Migrating system tables");
      // migrate meta last because that's what we check to see if migration is complete
      migrateTableIfExists(fs, rootDir, TableName.META_TABLE_NAME);
    }
  
    private static void migrateTableIfExists(FileSystem fs, Path rootDir, TableName tableName)
    throws IOException {
      Path tableDir = FSUtils.getTableDir(rootDir, tableName);
      if (fs.exists(tableDir)) {
        migrateTable(fs, tableDir);
      }
    }
 
   /**
    * Migrates table info files.
    * Moves the latest table info file (is present) from the table dir to the table info subdir.
    * Removes any older table info files from the table dir and any existing table info subdir.
    */
   private static void migrateTable(FileSystem fs, Path tableDir) throws IOException {
     FileStatus oldTableStatus = FSTableDescriptors.getCurrentTableInfoStatus(fs,  tableDir, true);
     if (oldTableStatus == null) {
       LOG.debug("No table info file to migrate for " + tableDir);
       return;
     }
     
     Path tableInfoDir = new Path(tableDir, FSTableDescriptors.TABLEINFO_DIR);
     // remove table info subdir if it already exists
     boolean removedExistingSubdir = FSUtils.deleteDirectory(fs, tableInfoDir);
     if (removedExistingSubdir) {
       LOG.info("Removed existing subdir at: " + tableInfoDir);
     }
     boolean createdSubdir = fs.mkdirs(tableInfoDir);
     if (!createdSubdir) {
       throw new IOException("Unable to create new table info directory: " + tableInfoDir);
     }
     
     Path oldTableInfoPath = oldTableStatus.getPath();
     Path newTableInfoPath = new Path(tableInfoDir, oldTableInfoPath.getName());
     boolean renamedInfoFile = fs.rename(oldTableInfoPath, newTableInfoPath);
     if (!renamedInfoFile) {
       throw new IOException("Failed to move table info file from old location: "
         + oldTableInfoPath + " to new location: " + newTableInfoPath);
     }
    
     LOG.info("Migrated table info from: " + oldTableInfoPath
       + " to new location: " + newTableInfoPath);
   }
 
 }