/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.commons.jcs3.jcache.extras.loader;
  
  import javax.cache.configuration.Factory;
  import javax.cache.integration.CacheLoader;
  import javax.cache.integration.CacheLoaderException;
  
  import org.apache.commons.jcs3.jcache.extras.closeable.Closeables;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.Map;
  
  public class CompositeCacheLoader<K, V> implements CacheLoader<K, V>, Closeable, Factory<CacheLoader<K, V>>
  {
      private final CacheLoader<K, V>[] delegates;
  
      public CompositeCacheLoader(final CacheLoader<K, V>... delegates)
      {
          this.delegates = delegates;
      }
  
      @Override
      public V load(final K key) throws CacheLoaderException
      {
          for (final CacheLoader<K, V> delegate : delegates)
          {
              final V v = delegate.load(key);
              if (v != null)
              {
                  return v;
              }
          }
          return null;
      }
  
      @Override
      public Map<K, V> loadAll(final Iterable<? extends K> keys) throws CacheLoaderException
      {
          final Collection<K> list = new ArrayList<>();
          for (final K k : keys)
          {
              list.add(k);
          }
  
          final Map<K, V> result = new HashMap<>();
          for (final CacheLoader<K, V> delegate : delegates)
          {
              final Map<K, V> v = delegate.loadAll(list);
              if (v != null)
              {
                  result.putAll(v);
                  list.removeAll(v.keySet());
                  if (list.isEmpty())
                  {
                      return v;
                  }
              }
          }
  
          return result;
      }
  
      @Override
      public void close() throws IOException
      {
          Closeables.close(delegates);
      }
  
      @Override
      public CacheLoader<K, V> create()
      {
          return this;
      }
  }