content: /*
   * 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;
  
  import alluxio.annotation.SuppressFBWarnings;
  import alluxio.collections.Pair;
  import alluxio.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.worker.block.BlockStoreLocation;
  
  import com.google.common.collect.ImmutableBiMap;
  
  import java.util.ArrayList;
  import java.util.List;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Creates a two-way mapping between storage tier aliases and ordinal numbers from the given
   * {@link Configuration}.
   */
  @ThreadSafe
  public final class DefaultStorageTierAssoc
      implements StorageTierAssoc {
    /**
     * An immutable bi-directional mapping between storage level aliases and their ordinals. Immutable
     * maps are thread safe.
     */
    private final ImmutableBiMap<String, Integer> mAliasToOrdinal;
  
    /**
     * Interprets a tier ordinal given the number of tiers.
     *
     * Non-negative values identify tiers starting from top going down (0 identifies the first tier,
     * 1 identifies the second tier, and so on). If the provided value is greater than the number
     * of tiers, it identifies the last tier. Negative values identify tiers starting from the bottom
     * going up (-1 identifies the last tier, -2 identifies the second to last tier, and so on). If
     * the absolute value of the provided value is greater than the number of tiers, it identifies
     * the first tier.
     *
     * @param ordinal the storage tier ordinal to interpret
     * @param numTiers the number of storage tiers
     * @return a valid tier ordinal
     */
    static int interpretOrdinal(int ordinal, int numTiers) {
      if (ordinal >= 0) {
        return Math.min(ordinal, numTiers - 1);
      }
      return Math.max(numTiers + ordinal, 0);
    }
  
    /**
     * Constructs a new instance using the given {@link Configuration} object. The mapping
     * cannot be modified after creation.
     *
     * @param levelsProperty the property in the conf that specifies how many levels there are
     * @param template the format for the conf that identifies the alias for each level
     */
    public DefaultStorageTierAssoc(PropertyKey levelsProperty, PropertyKey.Template template) {
      int levels = Configuration.getInt(levelsProperty);
      ImmutableBiMap.Builder<String, Integer> builder = new ImmutableBiMap.Builder<>();
      for (int i = 0; i < levels; i++) {
        String alias = Configuration.getString(template.format(i));
        builder.put(alias, i);
      }
      mAliasToOrdinal = builder.build();
    }
  
    /**
     * Constructs a new instance using the given list of storage tier aliases in order of their
     * position in the hierarchy.
     *
     * @param storageTierAliases the list of aliases
     */
    public DefaultStorageTierAssoc(List<String> storageTierAliases) {
      ImmutableBiMap.Builder<String, Integer> builder = new ImmutableBiMap.Builder<>();
      for (int ordinal = 0; ordinal < storageTierAliases.size(); ordinal++) {
        builder.put(storageTierAliases.get(ordinal), ordinal);
      }
      mAliasToOrdinal = builder.build();
    }
  
    @Override
    public String getAlias(int ordinal) {
      return mAliasToOrdinal.inverse().get(interpretOrdinal(ordinal, mAliasToOrdinal.size()));
    }
  
    @Override
    @SuppressFBWarnings("NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE")
    public int getOrdinal(String alias) {
      return mAliasToOrdinal.get(alias);
    }
  
    @Override
    public int size() {
      return mAliasToOrdinal.size();
    }
  
    @Override
    public List<String> getOrderedStorageAliases() {
      int size = size();
      List<String> ret = new ArrayList<>(size);
      for (int i = 0; i < size; i++) {
        ret.add(getAlias(i));
      }
      return ret;
    }
  
    @Override
    public List<Pair<BlockStoreLocation, BlockStoreLocation>> intersectionList() {
      List<Pair<BlockStoreLocation, BlockStoreLocation>> intersectionLocations =
          new ArrayList<>(size() - 1);
      for (int tierUp = 0, tierDown = tierUp + 1; tierDown < size(); tierUp++, tierDown++) {
        intersectionLocations.add(new Pair<>(BlockStoreLocation.anyDirInTier(getAlias(tierUp)),
            BlockStoreLocation.anyDirInTier(getAlias(tierDown))));
      }
      return intersectionLocations;
    }
  }
  