/*
    * 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.maven.internal.impl;
  
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import java.io.IOException;
  import java.nio.file.Path;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  import java.util.function.Predicate;
  import java.util.stream.Collectors;
  
  import org.apache.maven.api.*;
  import org.apache.maven.api.Artifact;
  import org.apache.maven.api.ArtifactCoordinate;
  import org.apache.maven.api.Dependency;
  import org.apache.maven.api.Node;
  import org.apache.maven.api.PathType;
  import org.apache.maven.api.Session;
  import org.apache.maven.api.services.*;
  import org.eclipse.aether.graph.DependencyFilter;
  import org.eclipse.aether.graph.DependencyNode;
  
  import static org.apache.maven.internal.impl.Utils.cast;
  import static org.apache.maven.internal.impl.Utils.map;
  import static org.apache.maven.internal.impl.Utils.nonNull;
  
  @Named
  @Singleton
  public class DefaultDependencyResolver implements DependencyResolver {
  
      @Override
      public List<Node> flatten(Session s, Node node, PathScope scope) throws DependencyResolverException {
          InternalSession session = InternalSession.from(s);
          DependencyNode root = cast(AbstractNode.class, node, "node").getDependencyNode();
          List<DependencyNode> dependencies = session.getRepositorySystem()
                  .flattenDependencyNodes(session.getSession(), root, getScopeDependencyFilter(scope));
          dependencies.remove(root);
          return map(dependencies, session::getNode);
      }
  
      private static DependencyFilter getScopeDependencyFilter(PathScope scope) {
          Set<String> scopes =
                  scope.dependencyScopes().stream().map(DependencyScope::id).collect(Collectors.toSet());
          return (n, p) -> {
              org.eclipse.aether.graph.Dependency d = n.getDependency();
              return d == null || scopes.contains(d.getScope());
          };
      }
  
      /**
       * Collects, flattens and resolves the dependencies.
       *
       * @param request the request to resolve
       * @return the result of the resolution
       */
      @Override
      public DependencyResolverResult resolve(DependencyResolverRequest request)
              throws DependencyCollectorException, DependencyResolverException, ArtifactResolverException {
          InternalSession session =
                  InternalSession.from(nonNull(request, "request").getSession());
          Predicate<PathType> filter = request.getPathTypeFilter();
          PathModularizationCache cache = new PathModularizationCache(); // TODO: should be project-wide cache.
          DependencyCollectorResult collectorResult =
                  session.getService(DependencyCollector.class).collect(request);
          List<Node> nodes = flatten(session, collectorResult.getRoot(), request.getPathScope());
          List<ArtifactCoordinate> coordinates = nodes.stream()
                  .map(Node::getDependency)
                  .filter(Objects::nonNull)
                  .map(Artifact::toCoordinate)
                  .collect(Collectors.toList());
          Map<Artifact, Path> artifacts = session.resolveArtifacts(coordinates);
          DefaultDependencyResolverResult result = new DefaultDependencyResolverResult(
                  cache, collectorResult.getExceptions(), collectorResult.getRoot(), nodes.size());
          for (Node node : nodes) {
              Dependency d = node.getDependency();
              Path path = (d != null) ? artifacts.get(d) : null;
              try {
                  result.addDependency(node, d, filter, path);
             } catch (IOException e) {
                 throw cannotReadModuleInfo(path, e);
             }
         }
         return result;
     }
 
     private static DependencyResolverException cannotReadModuleInfo(final Path path, final IOException cause) {
         return new DependencyResolverException("Cannot read module information of " + path, cause);
     }
 }