package com.atlassian.vcache.internal.core.service;
   
   import java.util.Map;
   import java.util.Optional;
   import java.util.stream.Collectors;
   import java.util.stream.StreamSupport;
   import javax.annotation.Nonnull;
   
   import com.atlassian.vcache.StableReadExternalCache;
  
  /**
   * Provides operations common to {@link com.atlassian.vcache.StableReadExternalCache} instances.
   *
   * @param <V> the value type
   */
  public abstract class AbstractStableReadExternalCache<V>
          extends AbstractNonDirectExternalCache<V>
          implements StableReadExternalCache<V>
  {
      protected AbstractStableReadExternalCache(String name)
      {
          super(name);
      }
  
      @Nonnull
      protected final Optional<Optional<V>> checkValueRecorded(String internalKey)
      {
          return ensureCacheContext().getValueRecorded(internalKey);
      }
  
      @Nonnull
      protected final Map<String, Optional<V>> checkValuesRecorded(Iterable<String> internalKeys)
      {
          final AbstractExternalCacheRequestContext<V> cacheContext = ensureCacheContext();
          return StreamSupport.stream(internalKeys.spliterator(), false)
                  .filter(k -> cacheContext.getValueRecorded(k).isPresent())
                  .distinct()
                  .collect(Collectors.toMap(
                                  k -> k,
                                  k -> cacheContext.getValueRecorded(k).get())
                  );
      }
  }