/*
    * 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.vfs2;
  
  import java.util.ArrayList;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  import org.apache.commons.vfs2.provider.AbstractFileObject;
  import org.apache.commons.vfs2.util.FileObjectUtils;
  import org.junit.jupiter.api.Assertions;
  
  /**
   * A file selector that asserts that all files are visited, in the correct order.
   */
  public class VerifyingFileSelector extends Assertions implements FileSelector {
  
      private final FileInfo rootFile;
      private final List<FileObject> files = new ArrayList<>();
  
      private FileInfo currentFolderInfo;
      private FileObject currentFolder;
      private Set<String> children;
      private final List<Set<String>> stack = new ArrayList<>();
  
      public VerifyingFileSelector(final FileInfo fileInfo) {
          rootFile = fileInfo;
          children = new HashSet<>();
          children.add(rootFile.baseName);
      }
  
      /**
       * Asserts that the selector has seen all the files.
       *
       * @return The files in the order they were visited.
       */
      public List<FileObject> finish() {
          assertEquals(0, children.size());
          return files;
      }
  
      /**
       * Finds a child of the current folder.
       */
      private FileInfo getChild(final String baseName) {
          if (currentFolderInfo == null) {
              assertEquals(rootFile.baseName, baseName);
              return rootFile;
          }
          final FileInfo child = currentFolderInfo.children.get(baseName);
          assertNotNull(child, "Could not locate child " + baseName);
          return child;
      }
  
      /**
       * Determines if a file or folder should be selected.
       */
      @Override
      public boolean includeFile(final FileSelectInfo fileInfo) throws FileSystemException {
          final FileObject file = fileInfo.getFile();
          if (file == currentFolder) {
              // Pop current folder
              assertEquals(0, children.size());
              currentFolder = currentFolder.getParent();
              currentFolderInfo = currentFolderInfo.getParent();
              children = stack.remove(0);
          }
  
          final String baseName = file.getName().getBaseName();
  
          final FileInfo childInfo = getChild(baseName);
          assertSame(childInfo.type, file.getType());
  
          final boolean isChild = children.remove(baseName);
          assertTrue(isChild);
  
          files.add(file);
          return true;
      }
  
      /**
       * Determines whether a folder should be traversed.
       */
      @Override
     public boolean traverseDescendents(final FileSelectInfo fileInfo) throws FileSystemException {
         // Check that the given file is a folder
         final FileObject folder = FileObjectUtils.getAbstractFileObject(fileInfo.getFile());
         assertSame(FileType.FOLDER, folder.getType());
         assertTrue(folder.isFolder());
 
         // Locate the info for the folder
         final String baseName = folder.getName().getBaseName();
         if (currentFolder == null) {
             assertEquals(rootFile.baseName, baseName);
             currentFolderInfo = rootFile;
         } else {
             final AbstractFileObject parent = FileObjectUtils.getAbstractFileObject(folder.getParent());
             assertSame(currentFolder, parent);
 
             // Locate the info for the child, and make sure it is folder
             currentFolderInfo = getChild(baseName);
             assertSame(FileType.FOLDER, currentFolderInfo.type);
         }
 
         // Push the folder
         stack.add(0, children);
         children = new HashSet<>(currentFolderInfo.children.keySet());
         currentFolder = folder;
 
         return true;
     }
 
 }