/**
    * Licensed to jclouds, Inc. (jclouds) under one or more
    * contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  jclouds 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.jclouds.ec2.compute.strategy;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Predicates.and;
  import static com.google.common.base.Predicates.notNull;
  import static com.google.common.collect.Iterables.concat;
  import static com.google.common.collect.Iterables.filter;
  import static com.google.common.collect.Iterables.transform;
  import static org.jclouds.concurrent.FutureIterables.transformParallel;
  
  import java.util.Set;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Future;
  
  import javax.annotation.Resource;
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import org.jclouds.Constants;
  import org.jclouds.compute.domain.ComputeMetadata;
  import org.jclouds.compute.domain.NodeMetadata;
  import org.jclouds.compute.predicates.NodePredicates;
  import org.jclouds.compute.reference.ComputeServiceConstants;
  import org.jclouds.compute.strategy.ListNodesStrategy;
  import org.jclouds.ec2.EC2AsyncClient;
  import org.jclouds.ec2.domain.Reservation;
  import org.jclouds.ec2.domain.RunningInstance;
  import org.jclouds.location.Region;
  import org.jclouds.logging.Logger;
  
  import com.google.common.base.Function;
  import com.google.common.base.Predicate;
  import com.google.common.collect.ImmutableSet;
  
  /**
   * 
   * @author Adrian Cole
   */
  @Singleton
  public class EC2ListNodesStrategy implements ListNodesStrategy {
     @Resource
     @Named(ComputeServiceConstants.COMPUTE_LOGGER)
     protected Logger logger = Logger.NULL;
  
     protected final EC2AsyncClient client;
     protected final Set<String> regions;
     protected final Function<RunningInstance, NodeMetadata> runningInstanceToNodeMetadata;
     protected final ExecutorService executor;
  
     @Inject
     protected EC2ListNodesStrategy(EC2AsyncClient client, @Region Set<String> regions,
              Function<RunningInstance, NodeMetadata> runningInstanceToNodeMetadata,
              @Named(Constants.PROPERTY_USER_THREADS) ExecutorService executor) {
        this.client =  checkNotNull(client, "client");
        this.regions =  checkNotNull(regions, "regions");
        this.runningInstanceToNodeMetadata = checkNotNull(runningInstanceToNodeMetadata, "runningInstanceToNodeMetadata");
        this.executor =  checkNotNull(executor, "executor");
     }
  
     @Override
     public Set<? extends ComputeMetadata> listNodes() {
        return listDetailsOnNodesMatching(NodePredicates.all());
     }
  
     @Override
     public Set<? extends NodeMetadata> listDetailsOnNodesMatching(Predicate<ComputeMetadata> filter) {
        Iterable<? extends RunningInstance> instances = pollRunningInstances();
        Iterable<? extends NodeMetadata> nodes = filter(transform(filter(instances, notNull()),
                 runningInstanceToNodeMetadata), and(notNull(), filter));
        return ImmutableSet.copyOf(nodes);
     }
  
     protected Iterable<? extends RunningInstance> pollRunningInstances() {
        Iterable<? extends Set<? extends Reservation<? extends RunningInstance>>> reservations = transformParallel(
                 regions, new Function<String, Future<Set<? extends Reservation<? extends RunningInstance>>>>() {
  
                    @SuppressWarnings("unchecked")
                    @Override
                    public Future<Set<? extends Reservation<? extends RunningInstance>>> apply(String from) {
                       return (Future<Set<? extends Reservation<? extends RunningInstance>>>) client
                               .getInstanceServices().describeInstancesInRegion(from);
                   }
 
                }, executor, null, logger, "reservations");
 
       return concat(concat(reservations));
    }
 }