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.client.file;
  
  import alluxio.AlluxioURI;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.cache.Cache;
  import com.google.common.cache.CacheBuilder;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.List;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.TimeUnit;
  import javax.annotation.Nullable;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Cache for metadata of paths.
   */
  @ThreadSafe
  public final class MetadataCache {
    private static final Logger LOG = LoggerFactory.getLogger(MetadataCache.class);
  
    private class CachedItem {
      private URIStatus mStatus = null;
      private List<URIStatus> mDirStatuses = null;
  
      /**
       * @return the metadata of the path
       */
      @Nullable
      public URIStatus getStatus() {
        return mStatus;
      }
  
      /**
       * @return the metadata list of paths directly under a directory
       */
      @Nullable
      public List<URIStatus> getDirStatuses() {
        return mDirStatuses;
      }
  
      /**
       *  Puts the status into cache.
       *
       *  @param status the metadata of the path
       */
      public void setStatus(URIStatus status) {
        mStatus = status;
      }
  
      /**
       *  Puts the directory status into cache.
       *
       *  @param statuses the metadata list
       */
      public void setDirStatuses(List<URIStatus> statuses) {
        mDirStatuses = statuses;
      }
    }
  
    private final Cache<String, CachedItem> mCache;
  
    /**
     * @param maxSize the max size of the cache
     * @param expirationTimeMs the expiration time (in milliseconds) of the cached item
     */
    public MetadataCache(int maxSize, long expirationTimeMs) {
      mCache = CacheBuilder.newBuilder()
          .maximumSize(maxSize)
          .expireAfterWrite(expirationTimeMs, TimeUnit.MILLISECONDS)
          .build();
    }
  
    /**
     * @param path the Alluxio path
     * @return the cached status or null
     */
    @Nullable
    public URIStatus get(AlluxioURI path) {
      CachedItem item = mCache.getIfPresent(path.getPath());
      if (item != null && item.getStatus() != null) {
        return item.getStatus();
      }
      return null;
    }
  
    /**
     * @param path the Alluxio path
     * @param status the status to be cached
     */
    public void put(AlluxioURI path, URIStatus status) {
      put(path.getPath(), status);
    }
  
    /**
     * @param path the Alluxio path
     * @param status the status to be cached
     */
    public void put(String path, URIStatus status) {
      try {
        CachedItem item = mCache.get(path, () -> new CachedItem());
        item.setStatus(status);
      } catch (ExecutionException e) {
        LOG.warn("Failed to cache meta data for path {}", path);
      }
    }
  
    /**
     * Caches list status results of a directory.
     *
     * @param dir the directory
     * @param statuses the list status results
     */
    public void put(AlluxioURI dir, List<URIStatus> statuses) {
      try {
        CachedItem item = mCache.get(dir.getPath(), () -> new CachedItem());
        item.setDirStatuses(statuses);
        for (URIStatus status : statuses) {
          put(status.getPath(), status);
        }
      } catch (ExecutionException e) {
        LOG.warn("Failed to cache metadata for dir {}", dir.getPath());
      }
    }
  
    /**
     * @param dir the directory
     * @return the cached list status results or null
     */
    @Nullable
    public List<URIStatus> listStatus(AlluxioURI dir) {
      return listStatus(dir.getPath());
    }
  
    /**
     * @param dir the directory
     * @return the cached list status results or null
     */
    @Nullable
    public List<URIStatus> listStatus(String dir) {
      CachedItem item = mCache.getIfPresent(dir);
      if (item != null && item.getDirStatuses() != null) {
        return item.getDirStatuses();
      }
      return null;
    }
  
    /**
     * Invalidates the cache of path.
     *
     * @param path the path
     */
    public void invalidate(AlluxioURI path) {
      invalidate(path.getPath());
    }
  
    /**
     * Invalidates the cache of path.
     *
     * @param path the path
     */
    public void invalidate(String path) {
      mCache.invalidate(path);
    }
  
    /**
     * Invalidates all the cache.
     */
    public void invalidateAll() {
      mCache.invalidateAll();
    }
  
    /**
     * @return the cache size
     */
    @VisibleForTesting
    public long size() {
      return mCache.size();
    }
  }
  