/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.master.block.meta;

import alluxio.Constants;

import com.google.common.base.Objects;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.annotation.concurrent.NotThreadSafe;

/**
 * The metadata for an Alluxio block, managed by the block master. This class is not thread safe,
 * so external locking is required.
 */
@NotThreadSafe
public final class MasterBlockInfo {
  private static final Logger LOG = LoggerFactory.getLogger(MasterBlockInfo.class);

  /** The id of the block. */
  private final long mBlockId;
  /**
   * The length of the block in bytes. This can be updated if it was previously unknown,
   * {@link Constants#UNKNOWN_SIZE}
   */
  private long mLength;

  /** Maps from the worker id to the tier alias the block is on. */
  private final Map<Long, String> mWorkerIdToAlias;

  /**
   * Creates a new instance of {@link MasterBlockInfo}.
   *
   * @param blockId the block id to use
   * @param length the block length in bytes to use
   */
  public MasterBlockInfo(long blockId, long length) {
    // TODO(gene): Check valid length?
    mBlockId = blockId;
    mLength = length;

    mWorkerIdToAlias = new HashMap<>();
  }

  /**
   * @return the length of the block
   */
  public long getLength() {
    return mLength;
  }

  /**
   * Updates the length, if and only if the length was previously unknown.
   *
   * @param length the updated length
   */
  public synchronized void updateLength(long length) {
    if (mLength == Constants.UNKNOWN_SIZE) {
      mLength = length;
    } else if (mLength != length) {
      LOG.warn("Attempting to update block length ({}) to a different length ({}).", mLength,
          length);
    }
  }

  /**
   * @return the block id
   */
  public long getBlockId() {
    return mBlockId;
  }

  /**
   * Adds a location of the block. It means that the worker has the block in one of its tiers.
   *
   * @param workerId the id of the worker
   * @param tierAlias the alias of the storage tier that this block is on
   */
  public void addWorker(long workerId, String tierAlias) {
    mWorkerIdToAlias.put(workerId, tierAlias);
  }

  /**
   * Removes the worker from the locations of this block.
   *
   * @param workerId the worker id to remove
   */
  public void removeWorker(long workerId) {
    mWorkerIdToAlias.remove(workerId);
  }

  /**
   * @return all the worker ids that this block is on
   */
  public Set<Long> getWorkers() {
    return Collections.unmodifiableSet(mWorkerIdToAlias.keySet());
  }

  /**
   * @return the number of workers this block is on
   */
  public int getNumLocations() {
    return mWorkerIdToAlias.size();
  }

  /**
   * Gets the net addresses for all workers which have the block's data in their tiered storage.
   *
   * @return the net addresses of the workers
   */
  public List<MasterBlockLocation> getBlockLocations() {
    List<MasterBlockLocation> ret = new ArrayList<>(mWorkerIdToAlias.size());
    for (Map.Entry<Long, String> entry : mWorkerIdToAlias.entrySet()) {
      ret.add(new MasterBlockLocation(entry.getKey(), entry.getValue()));
    }
    return ret;
  }

  /**
   * @param targetTierAlias the tier alias to target
   * @return true if the block is in the given tier
   */
  public boolean isInTier(String targetTierAlias) {
    for (String tierAlias : mWorkerIdToAlias.values()) {
      if (tierAlias.equals(targetTierAlias)) {
        return true;
      }
    }
    return false;
  }

  @Override
  public String toString() {
    return Objects.toStringHelper(this).add("blockId", mBlockId).add("length", mLength).toString();
  }
}