/*
    * 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.util.graph.visitor;
  
  import java.util.IdentityHashMap;
  import java.util.Map;
  import java.util.function.Consumer;
  
  import org.eclipse.aether.graph.DependencyFilter;
  import org.eclipse.aether.graph.DependencyNode;
  import org.eclipse.aether.graph.DependencyVisitor;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Abstract base class for dependency tree traverses that feed {@link Consumer<DependencyNode>}.
   * <p>
   * <strong>Implementations derived from this class cannot be embedded into {@link FilteringDependencyVisitor}</strong>,
   * this is why these classes accept {@link DependencyFilter} in constructor instead.
   *
   * @since 2.0.0
   */
  abstract class AbstractDependencyNodeConsumerVisitor implements DependencyVisitor {
      private static final DependencyFilter ACCEPT_ALL = (d, p) -> true;
  
      private final Consumer<DependencyNode> nodeConsumer;
  
      private final DependencyFilter filter;
  
      private final Stack<DependencyNode> path;
  
      private final Map<DependencyNode, Object> visitedNodes;
  
      protected AbstractDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer, DependencyFilter filter) {
          this.nodeConsumer = requireNonNull(nodeConsumer);
          this.filter = filter == null ? ACCEPT_ALL : filter;
          this.path = new Stack<>();
          this.visitedNodes = new IdentityHashMap<>(512);
      }
  
      /**
       * Marks the specified node as being visited and determines whether the node has been visited before.
       *
       * @param node the node being visited, must not be {@code null}
       * @return {@code true} if the node has not been visited before, {@code false} if the node was already visited
       */
      protected boolean setVisited(DependencyNode node) {
          return visitedNodes.put(node, Boolean.TRUE) == null;
      }
  
      @Override
      public final boolean visitEnter(DependencyNode node) {
          path.push(node);
          return doVisitEnter(node);
      }
  
      protected abstract boolean doVisitEnter(DependencyNode node);
  
      @Override
      public final boolean visitLeave(DependencyNode node) {
          path.pop();
          return doVisitLeave(node);
      }
  
      protected abstract boolean doVisitLeave(DependencyNode node);
  
      protected boolean acceptNode(DependencyNode node) {
          return filter.accept(node, path);
      }
  
      protected void consumeNode(DependencyNode node) {
          nodeConsumer.accept(node);
      }
  }