/**
    *
    * 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.wal;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.util.FSUtils;
  import org.apache.hadoop.hbase.wal.WAL.Entry;
  
  import static org.apache.hadoop.hbase.wal.DefaultWALProvider.DEFAULT_PROVIDER_ID;
  import static org.apache.hadoop.hbase.wal.DefaultWALProvider.META_WAL_PROVIDER_ID;
  import static org.apache.hadoop.hbase.wal.DefaultWALProvider.WAL_FILE_NAME_DELIMITER;
  
  
  // imports for things that haven't moved from regionserver.wal yet.
  import org.apache.hadoop.hbase.regionserver.wal.FSHLog;
  import org.apache.hadoop.hbase.regionserver.wal.ProtobufLogWriter;
  import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener;
  
  /**
   * A WAL Provider that returns a single thread safe WAL that optionally can skip parts of our
   * normal interactions with HDFS.
   *
   * This implementation picks a directory in HDFS based on the same mechanisms as the 
   * {@link DefaultWALProvider}. Users can configure how much interaction
   * we have with HDFS with the configuration property "hbase.wal.iotestprovider.operations".
   * The value should be a comma separated list of allowed operations:
   * <ul>
   *   <li><em>append</em>   : edits will be written to the underlying filesystem
   *   <li><em>sync</em>     : wal syncs will result in hflush calls
   *   <li><em>fileroll</em> : roll requests will result in creating a new file on the underlying
   *                           filesystem.
   * </ul>
   * Additionally, the special cases "all" and "none" are recognized.
   * If ommited, the value defaults to "all."
   * Behavior is undefined if "all" or "none" are paired with additional values. Behavior is also
   * undefined if values not listed above are included.
   *
   * Only those operations listed will occur between the returned WAL and HDFS. All others
   * will be no-ops.
   *
   * Note that in the case of allowing "append" operations but not allowing "fileroll", the returned
   * WAL will just keep writing to the same file. This won't avoid all costs associated with file
   * management over time, becaue the data set size may result in additional HDFS block allocations.
   *
   */
  @InterfaceAudience.Private
  public class IOTestProvider implements WALProvider {
    private static final Log LOG = LogFactory.getLog(IOTestProvider.class);
  
    private static final String ALLOWED_OPERATIONS = "hbase.wal.iotestprovider.operations";
    private enum AllowedOperations {
      all,
      append,
      sync,
      fileroll,
      none;
    }
  
    private FSHLog log = null;
  
    /**
     * @param factory factory that made us, identity used for FS layout. may not be null
     * @param conf may not be null
     * @param listeners may be null
     * @param providerId differentiate between providers from one facotry, used for FS layout. may be
     *                   null
     */
    @Override
    public void init(final WALFactory factory, final Configuration conf,
        final List<WALActionsListener> listeners, String providerId) throws IOException {
      if (null != log) {
        throw new IllegalStateException("WALProvider.init should only be called once.");
     }
     if (null == providerId) {
       providerId = DEFAULT_PROVIDER_ID;
     }
     final String logPrefix = factory.factoryId + WAL_FILE_NAME_DELIMITER + providerId;
     log = new IOTestWAL(FSUtils.getWALFileSystem(conf), FSUtils.getWALRootDir(conf),
         DefaultWALProvider.getWALDirectoryName(factory.factoryId),
         HConstants.HREGION_OLDLOGDIR_NAME, conf, listeners,
         true, logPrefix, META_WAL_PROVIDER_ID.equals(providerId) ? META_WAL_PROVIDER_ID : null);
   }
 
   @Override
   public List<WAL> getWALs() throws IOException {
     List<WAL> wals = new ArrayList<WAL>();
     wals.add(log);
     return wals;
   }
 
   @Override
   public WAL getWAL(final byte[] identifier, byte[] namespace) throws IOException {
    return log;
   }
 
   @Override
   public void close() throws IOException {
     log.close();
   }
 
   @Override
   public void shutdown() throws IOException {
     log.shutdown();
   }
 
   private static class IOTestWAL extends FSHLog {
 
     private final boolean doFileRolls;
 
     // Used to differntiate between roll calls before and after we finish construction.
     private final boolean initialized;
 
     /**
      * Create an edit log at the given <code>dir</code> location.
      *
      * You should never have to load an existing log. If there is a log at
      * startup, it should have already been processed and deleted by the time the
      * WAL object is started up.
      *
      * @param fs filesystem handle
      * @param rootDir path to where logs and oldlogs
      * @param logDir dir where wals are stored
      * @param archiveDir dir where wals are archived
      * @param conf configuration to use
      * @param listeners Listeners on WAL events. Listeners passed here will
      * be registered before we do anything else; e.g. the
      * Constructor {@link #rollWriter()}.
      * @param failIfWALExists If true IOException will be thrown if files related to this wal
      *        already exist.
      * @param prefix should always be hostname and port in distributed env and
      *        it will be URL encoded before being used.
      *        If prefix is null, "wal" will be used
      * @param suffix will be url encoded. null is treated as empty. non-empty must start with
      *        {@link DefaultWALProvider#WAL_FILE_NAME_DELIMITER}
      * @throws IOException
      */
     public IOTestWAL(final FileSystem fs, final Path rootDir, final String logDir,
         final String archiveDir, final Configuration conf,
         final List<WALActionsListener> listeners,
         final boolean failIfWALExists, final String prefix, final String suffix)
         throws IOException {
       super(fs, rootDir, logDir, archiveDir, conf, listeners, failIfWALExists, prefix, suffix);
       Collection<String> operations = conf.getStringCollection(ALLOWED_OPERATIONS);
       doFileRolls = operations.isEmpty() || operations.contains(AllowedOperations.all.name()) ||
           operations.contains(AllowedOperations.fileroll.name());
       initialized = true;
       LOG.info("Initialized with file rolling " + (doFileRolls ? "enabled" : "disabled"));
     }
 
     private Writer noRollsWriter;
 
     // creatWriterInstance is where the new pipeline is set up for doing file rolls
     // if we are skipping it, just keep returning the same writer.
     @Override
     protected Writer createWriterInstance(final Path path) throws IOException {
       // we get called from the FSHLog constructor (!); always roll in this case since
       // we don't know yet if we're supposed to generally roll and
       // we need an initial file in the case of doing appends but no rolls.
       if (!initialized || doFileRolls) {
         LOG.info("creating new writer instance.");
         final ProtobufLogWriter writer = new IOTestWriter();
         writer.init(fs, path, conf, false);
         if (!initialized) {
           LOG.info("storing initial writer instance in case file rolling isn't allowed.");
           noRollsWriter = writer;
         }
         return writer;
       } else {
         LOG.info("WAL rolling disabled, returning the first writer.");
         // Initial assignment happens during the constructor call, so there ought not be
         // a race for first assignment.
         return noRollsWriter;
       }
     }
   }
 
   /**
    * Presumes init will be called by a single thread prior to any access of other methods.
    */
   private static class IOTestWriter extends ProtobufLogWriter {
     private boolean doAppends;
     private boolean doSyncs;
 
     @Override
     public void init(FileSystem fs, Path path, Configuration conf, boolean overwritable) throws IOException {
       Collection<String> operations = conf.getStringCollection(ALLOWED_OPERATIONS);
       if (operations.isEmpty() || operations.contains(AllowedOperations.all.name())) {
         doAppends = doSyncs = true;
       } else if (operations.contains(AllowedOperations.none.name())) {
         doAppends = doSyncs = false;
       } else {
         doAppends = operations.contains(AllowedOperations.append.name());
         doSyncs = operations.contains(AllowedOperations.sync.name());
       }
       LOG.info("IOTestWriter initialized with appends " + (doAppends ? "enabled" : "disabled") +
           " and syncs " + (doSyncs ? "enabled" : "disabled"));
       super.init(fs, path, conf, overwritable);
     }
 
     @Override
     public void append(Entry entry) throws IOException {
       if (doAppends) {
         super.append(entry);
       }
     }
 
     @Override
     public void sync() throws IOException {
       if (doSyncs) {
         super.sync();
       }
     }
   }
 
   @Override
   public long getNumLogFiles() {
     return this.log.getNumLogFiles();
   }
 
   @Override
   public long getLogFileSize() {
     return this.log.getLogFileSize();
   }
 }