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.worker.block;
  
  import alluxio.exception.ExceptionMessage;
  import alluxio.worker.block.meta.StorageTier;
  import alluxio.worker.block.meta.StorageTierView;
  
  import com.google.common.base.Preconditions;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import javax.annotation.Nullable;
  
  /**
   * This class is an abstract class for allocators and evictors to extend to provide
   * limited access to block metadata.
   */
  public abstract class BlockMetadataView {
    /** The {@link BlockMetadataManager} this view is derived from. */
    protected final BlockMetadataManager mMetadataManager;
    protected final boolean mUseReservedSpace;
  
    /**
     * A list of {@link StorageTierView}, derived from {@link StorageTier}s from the
     * {@link BlockMetadataManager}.
     */
    final List<StorageTierView> mTierViews = new ArrayList<>();
  
    /** A map from tier alias to {@link StorageTierView}. */
    Map<String, StorageTierView> mAliasToTierViews = new HashMap<>();
  
    /**
     * Creates a new instance of {@link BlockMetadataView}.
     *
     * @param manager which the view should be constructed from
     */
    public BlockMetadataView(BlockMetadataManager manager) {
      this(manager, false);
    }
  
    /**
     * Creates a new instance of {@link BlockMetadataView}.
     *
     * @param manager which the view should be constructed from
     * @param useReservedSpace whether to include reserved space in available bytes
     */
    public BlockMetadataView(BlockMetadataManager manager, boolean useReservedSpace) {
      mMetadataManager = Preconditions.checkNotNull(manager, "manager");
      mUseReservedSpace = useReservedSpace;
      initializeView();
    }
  
    /**
     * Provides {@link StorageTierView} given tierAlias. Throws an {@link IllegalArgumentException} if
     * the tierAlias is not found.
     *
     * @param tierAlias the alias of this tierView
     * @return the {@link StorageTierView} object associated with the alias
     */
    public StorageTierView getTierView(String tierAlias) {
      StorageTierView tierView = mAliasToTierViews.get(tierAlias);
      if (tierView == null) {
        throw new IllegalArgumentException(
            ExceptionMessage.TIER_VIEW_ALIAS_NOT_FOUND.getMessage(tierAlias));
      } else {
        return tierView;
      }
    }
  
    /**
     * Gets all tierViews under this storage metadata view.
     *
     * @return the list of {@link StorageTierView}s
     */
    public List<StorageTierView> getTierViews() {
      return Collections.unmodifiableList(mTierViews);
    }
  
    /**
     * Gets the next storage tier view.
     *
     * @param tierView the storage tier view
     * @return the next storage tier view, null if this is the last tier view
     */
    @Nullable
    public StorageTierView getNextTier(StorageTierView tierView) {
      int nextOrdinal = tierView.getTierViewOrdinal() + 1;
      if (nextOrdinal < mTierViews.size()) {
        return mTierViews.get(nextOrdinal);
      }
      return null;
    }
  
    /**
     * Gets all tierViews before certain tierView. Throws an {@link IllegalArgumentException} if the
     * tierAlias is not found.
     *
     * @param tierAlias the alias of a tierView
     * @return the list of {@link StorageTierView}
     */
    public List<StorageTierView> getTierViewsBelow(String tierAlias) {
      int ordinal = getTierView(tierAlias).getTierViewOrdinal();
      return mTierViews.subList(ordinal + 1, mTierViews.size());
    }
  
    /**
     * Used to initialize the view based on the current metadata status.
     */
    protected abstract void initializeView();
  
    /**
     * Used to refresh the view based on current metadata status.
     *
     * @return the refreshed view instance
     */
    public BlockMetadataView refreshView() {
      // Clear previous views.
      mTierViews.clear();
      mAliasToTierViews.clear();
      // Re-initialize the view.
      initializeView();
      return this;
    }
  }
  