/*
    * 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.index.reader;
  
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.file.Files;
  import java.nio.file.NoSuchFileException;
  import java.nio.file.Path;
  
  /**
   * A trivial {@link Path} directory handler that does not perform any locking or extra bits, and just serves up files
   * by name from specified existing directory.
   */
  public class DirectoryResourceHandler implements WritableResourceHandler {
      private final Path rootDirectory;
  
      public DirectoryResourceHandler(final Path rootDirectory) {
          if (rootDirectory == null) {
              throw new NullPointerException("null rootDirectory");
          }
          if (!Files.isDirectory(rootDirectory)) {
              throw new IllegalArgumentException("rootDirectory exists and is not a directory");
          }
          this.rootDirectory = rootDirectory;
      }
  
      public Path getRootDirectory() {
          return rootDirectory;
      }
  
      @Override
      public WritableResource locate(final String name) {
          return new PathResource(rootDirectory.resolve(name));
      }
  
      private static class PathResource implements WritableResource {
          private final Path file;
  
          private PathResource(final Path file) {
              this.file = file;
          }
  
          @Override
          public InputStream read() throws IOException {
              try {
                  return new BufferedInputStream(Files.newInputStream(file));
              } catch (NoSuchFileException e) {
                  return null;
              }
          }
  
          @Override
          public OutputStream write() throws IOException {
              return new BufferedOutputStream(Files.newOutputStream(file));
          }
      }
  }