content: /*
   * 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.kafka.common.config.provider;
  
  import org.apache.kafka.common.config.ConfigData;
  import org.apache.kafka.common.config.ConfigException;
  import org.apache.kafka.common.config.internals.AllowedPaths;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.Map;
  import java.util.Set;
  import java.util.function.Predicate;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import static java.util.Collections.emptyMap;
  
  /**
   * An implementation of {@link ConfigProvider} based on a directory of files.
   * Property keys correspond to the names of the regular (i.e. non-directory)
   * files in a directory given by the path parameter.
   * Property values are taken from the file contents corresponding to each key.
   */
  public class DirectoryConfigProvider implements ConfigProvider {
  
      private static final Logger log = LoggerFactory.getLogger(DirectoryConfigProvider.class);
  
      public static final String ALLOWED_PATHS_CONFIG = "allowed.paths";
      public static final String ALLOWED_PATHS_DOC = "A comma separated list of paths that this config provider is " +
              "allowed to access. If not set, all paths are allowed.";
      private volatile AllowedPaths allowedPaths;
  
      @Override
      public void configure(Map<String, ?> configs) {
          allowedPaths = new AllowedPaths((String) configs.getOrDefault(ALLOWED_PATHS_CONFIG, null));
      }
  
      @Override
      public void close() throws IOException { }
  
      /**
       * Retrieves the data contained in regular files in the directory given by {@code path}.
       * Non-regular files (such as directories) in the given directory are silently ignored.
       * @param path the directory where data files reside.
       * @return the configuration data.
       */
      @Override
      public ConfigData get(String path) {
          return get(path, Files::isRegularFile);
      }
  
      /**
       * Retrieves the data contained in the regular files named by {@code keys} in the directory given by {@code path}.
       * Non-regular files (such as directories) in the given directory are silently ignored.
       * @param path the directory where data files reside.
       * @param keys the keys whose values will be retrieved.
       * @return the configuration data.
       */
      @Override
      public ConfigData get(String path, Set<String> keys) {
          return get(path, pathname ->
                  Files.isRegularFile(pathname)
                          && keys.contains(pathname.getFileName().toString()));
      }
  
      private ConfigData get(String path, Predicate<Path> fileFilter) {
          if (allowedPaths == null) {
              throw new IllegalStateException("The provider has not been configured yet.");
          }
  
          Map<String, String> map = emptyMap();
  
          if (path != null && !path.isEmpty()) {
              Path dir = allowedPaths.parseUntrustedPath(path);
              if (dir == null) {
                  log.warn("The path {} is not allowed to be accessed", path);
                  return new ConfigData(map);
              }
  
              if (!Files.isDirectory(dir)) {
                  log.warn("The path {} is not a directory", path);
              } else {
                  try (Stream<Path> stream = Files.list(dir)) {
                      map = stream
                          .filter(fileFilter)
                          .collect(Collectors.toMap(
                              p -> p.getFileName().toString(),
                              p -> read(p)));
                  } catch (IOException e) {
                      log.error("Could not list directory {}", dir, e);
                      throw new ConfigException("Could not list directory " + dir);
                  }
              }
          }
          return new ConfigData(map);
      }
  
      private static String read(Path path) {
          try {
              return Files.readString(path);
          } catch (IOException e) {
              log.error("Could not read file {} for property {}", path, path.getFileName(), e);
              throw new ConfigException("Could not read file " + path + " for property " + path.getFileName());
          }
      }
  
  }
  