/*
    * 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.eclipse.aether.internal.impl.filter;
  
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.stream.Collectors;
  
  import org.eclipse.aether.RepositorySystemSession;
  import org.eclipse.aether.artifact.Artifact;
  import org.eclipse.aether.impl.RemoteRepositoryFilterManager;
  import org.eclipse.aether.metadata.Metadata;
  import org.eclipse.aether.repository.RemoteRepository;
  import org.eclipse.aether.spi.connector.filter.RemoteRepositoryFilter;
  import org.eclipse.aether.spi.connector.filter.RemoteRepositoryFilterSource;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Default implementation of {@link RemoteRepositoryFilterManager}, it always returns a {@link RemoteRepositoryFilter}
   * instance, even if no filter sources enabled/registered (then "always allow" instance).
   * <p>
   * The created {@link RemoteRepositoryFilter} instance is created once per session and cached.
   *
   * @since 1.9.0
   */
  @Singleton
  @Named
  public final class DefaultRemoteRepositoryFilterManager implements RemoteRepositoryFilterManager {
      private static final String INSTANCE_KEY = DefaultRemoteRepositoryFilterManager.class.getName() + ".instance";
  
      private final Map<String, RemoteRepositoryFilterSource> sources;
  
      @Inject
      public DefaultRemoteRepositoryFilterManager(Map<String, RemoteRepositoryFilterSource> sources) {
          this.sources = requireNonNull(sources);
      }
  
      @Override
      public RemoteRepositoryFilter getRemoteRepositoryFilter(RepositorySystemSession session) {
          // use session specific key to distinguish between "derived" sessions
          String instanceSpecificKey = INSTANCE_KEY + "." + session.hashCode();
          return (RemoteRepositoryFilter) session.getData().computeIfAbsent(instanceSpecificKey, () -> {
              HashMap<String, RemoteRepositoryFilter> filters = new HashMap<>();
              for (Map.Entry<String, RemoteRepositoryFilterSource> entry : sources.entrySet()) {
                  RemoteRepositoryFilter filter = entry.getValue().getRemoteRepositoryFilter(session);
                  if (filter != null) {
                      filters.put(entry.getKey(), filter);
                  }
              }
              if (!filters.isEmpty()) {
                  return new Participants(filters);
              } else {
                  return null;
              }
          });
      }
  
      /**
       * {@link RemoteRepositoryFilter} instance when there are participant filters present. It evaluates into result
       * using {@link Consensus}.
       */
      private static class Participants implements RemoteRepositoryFilter {
          private final Map<String, RemoteRepositoryFilter> participants;
  
          private Participants(Map<String, RemoteRepositoryFilter> participants) {
              this.participants = Collections.unmodifiableMap(participants);
          }
  
          @Override
          public RemoteRepositoryFilter.Result acceptArtifact(RemoteRepository remoteRepository, Artifact artifact) {
              return new Consensus(
                      participants.entrySet().stream().collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue()
                              .acceptArtifact(remoteRepository, artifact))));
          }
  
          @Override
          public RemoteRepositoryFilter.Result acceptMetadata(RemoteRepository remoteRepository, Metadata metadata) {
             return new Consensus(
                     participants.entrySet().stream().collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue()
                             .acceptMetadata(remoteRepository, metadata))));
         }
     }
 
     /**
      * {@link RemoteRepositoryFilter.Result} based on "consensus". All participant have to "accept" to make this
      * instance "accept".
      */
     private static class Consensus implements RemoteRepositoryFilter.Result {
         private final boolean accepted;
 
         private final String reasoning;
 
         Consensus(Map<String, RemoteRepositoryFilter.Result> results) {
             this.accepted = results.values().stream().allMatch(RemoteRepositoryFilter.Result::isAccepted);
             this.reasoning = results.values().stream()
                     .filter(r -> !r.isAccepted())
                     .map(RemoteRepositoryFilter.Result::reasoning)
                     .collect(Collectors.joining("; "));
         }
 
         @Override
         public boolean isAccepted() {
             return accepted;
         }
 
         @Override
         public String reasoning() {
             return reasoning;
         }
     }
 }