/*
    * 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.configuration2.tree;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.mockito.Mockito.mock;
  
  import java.util.LinkedList;
  import java.util.List;
  
  import org.junit.jupiter.api.Test;
  
  /**
   * Test class for {@code NodeTreeWalker}.
   */
  public class TestNodeTreeWalker {
      /**
       * A visitor implementation used for testing purposes. The visitor produces a list with the names of the nodes visited
       * in the order it was called. With this it can be tested whether the nodes were visited in the correct order.
       */
      private static final class TestVisitor implements ConfigurationNodeVisitor<ImmutableNode> {
          /** A list with the names of the visited nodes. */
          private final List<String> visitedNodes = new LinkedList<>();
  
          /** The maximum number of nodes to be visited. */
          private int maxNodeCount = Integer.MAX_VALUE;
  
          /**
           * Returns the maximum number of nodes visited by this visitor.
           *
           * @return the maximum number of nodes
           */
          public int getMaxNodeCount() {
              return maxNodeCount;
          }
  
          /**
           * Returns the list with the names of the visited nodes.
           *
           * @return the visit list
           */
          public List<String> getVisitedNodes() {
              return visitedNodes;
          }
  
          /**
           * Sets the maximum number of nodes to be visited. After this the terminate flag is set.
           *
           * @param maxNodeCount the maximum number of nodes
           */
          public void setMaxNodeCount(final int maxNodeCount) {
              this.maxNodeCount = maxNodeCount;
          }
  
          @Override
          public boolean terminate() {
              return visitedNodes.size() >= getMaxNodeCount();
          }
  
          @Override
          public void visitAfterChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) {
              visitedNodes.add(visitAfterName(handler.nodeName(node)));
          }
  
          @Override
          public void visitBeforeChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) {
              visitedNodes.add(handler.nodeName(node));
          }
      }
  
      /**
       * Creates a dummy node handler.
       *
       * @return the node handler
       */
      private static NodeHandler<ImmutableNode> createHandler() {
          return new InMemoryNodeModel().getNodeHandler();
      }
  
      /**
       * Creates a mock for a node handler.
       *
       * @return the handler mock
       */
     @SuppressWarnings("unchecked")
     private static NodeHandler<ImmutableNode> handlerMock() {
         return mock(NodeHandler.class);
     }
 
     /**
      * Generates a name which indicates that the corresponding node was visited after its children.
      *
      * @param name the node name to be decorated
      * @return the name with the after indicator
      */
     private static String visitAfterName(final String name) {
         return "->" + name;
     }
 
     /**
      * Creates a mock for a visitor.
      *
      * @return the visitor mock
      */
     @SuppressWarnings("unchecked")
     private static ConfigurationNodeVisitor<ImmutableNode> visitorMock() {
         return mock(ConfigurationNodeVisitor.class);
     }
 
     /**
      * Prepares a list with the names of nodes encountered during a BFS walk.
      *
      * @return the expected node names in BFS mode
      */
     private List<String> expectBFS() {
         final List<String> expected = new LinkedList<>();
         final List<String> works = new LinkedList<>();
         final List<String> personae = new LinkedList<>();
         expected.add(NodeStructureHelper.ROOT_AUTHORS_TREE.getNodeName());
         for (int authorIdx = 0; authorIdx < NodeStructureHelper.authorsLength(); authorIdx++) {
             expected.add(NodeStructureHelper.author(authorIdx));
             for (int workIdx = 0; workIdx < NodeStructureHelper.worksLength(authorIdx); workIdx++) {
                 works.add(NodeStructureHelper.work(authorIdx, workIdx));
                 for (int personIdx = 0; personIdx < NodeStructureHelper.personaeLength(authorIdx, workIdx); personIdx++) {
                     personae.add(NodeStructureHelper.persona(authorIdx, workIdx, personIdx));
                 }
             }
         }
         expected.addAll(works);
         expected.addAll(personae);
         return expected;
     }
 
     /**
      * Prepares a list with the names of nodes encountered during a DFS walk.
      *
      * @return the expected node names in DFS mode
      */
     private List<String> expectDFS() {
         final List<String> expected = new LinkedList<>();
         expected.add(NodeStructureHelper.ROOT_AUTHORS_TREE.getNodeName());
         for (int authorIdx = 0; authorIdx < NodeStructureHelper.authorsLength(); authorIdx++) {
             expected.add(NodeStructureHelper.author(authorIdx));
             for (int workIdx = 0; workIdx < NodeStructureHelper.worksLength(authorIdx); workIdx++) {
                 expected.add(NodeStructureHelper.work(authorIdx, workIdx));
                 for (int personaIdx = 0; personaIdx < NodeStructureHelper.personaeLength(authorIdx, workIdx); personaIdx++) {
                     final String persona = NodeStructureHelper.persona(authorIdx, workIdx, personaIdx);
                     expected.add(persona);
                     expected.add(visitAfterName(persona));
                 }
                 expected.add(visitAfterName(NodeStructureHelper.work(authorIdx, workIdx)));
             }
             expected.add(visitAfterName(NodeStructureHelper.author(authorIdx)));
         }
         expected.add(visitAfterName(NodeStructureHelper.ROOT_AUTHORS_TREE.getNodeName()));
         return expected;
     }
 
     /**
      * Tests a traversal in BFS mode.
      */
     @Test
     public void testWalkBFS() {
         final List<String> expected = expectBFS();
         final TestVisitor visitor = new TestVisitor();
         NodeTreeWalker.INSTANCE.walkBFS(NodeStructureHelper.ROOT_AUTHORS_TREE, visitor, createHandler());
         assertEquals(expected, visitor.getVisitedNodes());
     }
 
     /**
      * Tests a BFS walk if node is passed in.
      */
     @Test
     public void testWalkBFSNoNode() {
         final ConfigurationNodeVisitor<ImmutableNode> visitor = visitorMock();
         final NodeHandler<ImmutableNode> handler = handlerMock();
         NodeTreeWalker.INSTANCE.walkBFS(null, visitor, handler);
     }
 
     /**
      * Tests whether the terminate flag is evaluated in BFS mode.
      */
     @Test
     public void testWalkBFSTerminate() {
         final TestVisitor visitor = new TestVisitor();
         final int nodeCount = 9;
         visitor.setMaxNodeCount(nodeCount);
         NodeTreeWalker.INSTANCE.walkBFS(NodeStructureHelper.ROOT_AUTHORS_TREE, visitor, createHandler());
         assertEquals(nodeCount, visitor.getVisitedNodes().size());
     }
 
     /**
      * Tests a DFS traversal.
      */
     @Test
     public void testWalkDFS() {
         final List<String> expected = expectDFS();
         final TestVisitor visitor = new TestVisitor();
         NodeTreeWalker.INSTANCE.walkDFS(NodeStructureHelper.ROOT_AUTHORS_TREE, visitor, createHandler());
         assertEquals(expected, visitor.getVisitedNodes());
     }
 
     /**
      * Tests whether walkDFS() can handle a null node.
      */
     @Test
     public void testWalkDFSNoNode() {
         final ConfigurationNodeVisitor<ImmutableNode> visitor = visitorMock();
         final NodeHandler<ImmutableNode> handler = handlerMock();
         NodeTreeWalker.INSTANCE.walkDFS(null, visitor, handler);
     }
 
     /**
      * Tests whether the terminate flag is taken into account during a DFS walk.
      */
     @Test
     public void testWalkDFSTerminate() {
         final TestVisitor visitor = new TestVisitor();
         final int nodeCount = 5;
         visitor.setMaxNodeCount(nodeCount);
         NodeTreeWalker.INSTANCE.walkDFS(NodeStructureHelper.ROOT_AUTHORS_TREE, visitor, createHandler());
         assertEquals(nodeCount, visitor.getVisitedNodes().size());
     }
 
     /**
      * Tries a walk() operation without a node handler.
      */
     @Test
     public void testWalkNoNodeHandler() {
         final TestVisitor visitor = new TestVisitor();
         assertThrows(IllegalArgumentException.class, () -> NodeTreeWalker.INSTANCE.walkDFS(NodeStructureHelper.ROOT_AUTHORS_TREE, visitor, null));
     }
 
     /**
      * Tries a walk operation without a visitor.
      */
     @Test
     public void testWalkNoVisitor() {
         final NodeHandler<ImmutableNode> handler = createHandler();
         assertThrows(IllegalArgumentException.class, () -> NodeTreeWalker.INSTANCE.walkDFS(NodeStructureHelper.ROOT_AUTHORS_TREE, null, handler));
     }
 }