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/**
 * Copyright (C) 2015 Greg Brandt ([email protected])
 *
 * Licensed 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 com.github.brandtg.switchboard;

import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.protocol.HdfsConstants;
import org.apache.hadoop.hdfs.protocol.LayoutFlags;
import org.apache.hadoop.hdfs.protocol.LayoutVersion;
import org.apache.hadoop.hdfs.server.namenode.EditLogInputStream;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes;
import org.apache.hadoop.hdfs.server.namenode.NameNodeLayoutVersion;
import org.apache.log4j.Logger;

import java.io.DataInputStream;
import java.io.InputStream;
import java.io.IOException;

public class HdfsLogParser extends EditLogInputStream {
  private static final Logger LOG = Logger.getLogger(HdfsLogParser.class);

  static {
    System.setProperty("hadoop.home.dir", "/tmp");
  }

  private enum State {
    UNINIT,
    OPEN,
    CLOSED
  }

  private final InputStream inputStream;

  private State state = State.UNINIT;
  private FSEditLogOp.Reader reader = null;
  private FSEditLogLoader.PositionTrackingInputStream tracker = null;
  private DataInputStream dataInputStream = null;
  private int logVersion;
  private int maxOpSize = DFSConfigKeys.DFS_NAMENODE_MAX_OP_SIZE_DEFAULT;

  public HdfsLogParser(InputStream inputStream) {
    this.inputStream = inputStream;
  }

  public void resetReader() {
    reader = new FSEditLogOp.Reader(dataInputStream, tracker, logVersion);
    reader.setMaxOpSize(maxOpSize);
  }

  @Override
  public String getName() {
    return getClass().getSimpleName();
  }

  @Override
  public long getFirstTxId() {
    return HdfsConstants.INVALID_TXID;
  }

  @Override
  public long getLastTxId() {
    return HdfsConstants.INVALID_TXID;
  }

  @Override
  public void close() throws IOException {
    inputStream.close();
  }

  @Override
  protected FSEditLogOp nextOp() throws IOException {
    switch (state) {
      case UNINIT:
        try {
          tracker = new FSEditLogLoader.PositionTrackingInputStream(inputStream);
          dataInputStream = new DataInputStream(tracker);
          logVersion = dataInputStream.readInt();
          if (NameNodeLayoutVersion.supports(LayoutVersion.Feature.ADD_LAYOUT_FLAGS, logVersion)
              || logVersion < NameNodeLayoutVersion.CURRENT_LAYOUT_VERSION) {
            LayoutFlags.read(dataInputStream);
          }
          reader = new FSEditLogOp.Reader(dataInputStream, tracker, logVersion);
          reader.setMaxOpSize(maxOpSize);
          state = State.OPEN;
        } finally {
          if (reader == null) {
            dataInputStream.close();
            tracker.close();
            state = State.CLOSED;
          }
        }
        return nextOp();
      case OPEN:
        FSEditLogOp op = reader.readOp(false);
        if (op.opCode == FSEditLogOpCodes.OP_END_LOG_SEGMENT) {
          state = State.UNINIT;
        }
        return op;
      case CLOSED:
      default:
        return null;
    }
  }

  @Override
  public int getVersion(boolean verifyVersion) throws IOException {
    return logVersion;
  }

  @Override
  public long getPosition() {
    if (state == State.OPEN) {
      return tracker.getPos();
    } else {
      return 0;
    }
  }

  @Override
  public long length() throws IOException {
    return -1;
  }

  @Override
  public boolean isInProgress() {
    return true;
  }

  @Override
  public void setMaxOpSize(int maxOpSize) {
    this.maxOpSize = maxOpSize;
    if (reader != null) {
      reader.setMaxOpSize(maxOpSize);
    }
  }

  @Override
  public boolean isLocalLog() {
    return false;
  }
}