FetchWriter.java

/*
 * Copyright (C) 2023 DANS - Data Archiving and Networked Services (info@dans.knaw.nl)
 *
 * Licensed 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 nl.knaw.dans.bagit.writer;

import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.List;
import java.util.ResourceBundle;

import nl.knaw.dans.bagit.domain.FetchItem;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.BufferedWriter;

/**
 * Responsible for writing out the list of {@link FetchItem} to the fetch.txt file on the filesystem
 */
public final class FetchWriter {
  private static final Logger logger = LoggerFactory.getLogger(FetchWriter.class);
  private static final ResourceBundle messages = ResourceBundle.getBundle("MessageBundle");
  
  private FetchWriter(){
    //intentionally left empty
  }
  
  /**
   * Write the fetch.txt file to the outputDir with the specified encoding (charsetName)
   * 
   * @param itemsToFetch the list of {@link FetchItem}s to write into the fetch.txt
   * @param outputDir the root of the bag
   * @param bagitRootDir the path to the root of the bag
   * @param charsetName the name of the encoding for the file
   * 
   * @throws IOException if there was a problem writing a file
   */
  public static void writeFetchFile(final List<FetchItem> itemsToFetch, final Path outputDir, final Path bagitRootDir, final Charset charsetName) throws IOException{
    logger.debug(messages.getString("writing_fetch_file_to_path"), outputDir);
    final Path fetchFilePath = outputDir.resolve("fetch.txt");

    try (BufferedWriter writer = Files.newBufferedWriter(fetchFilePath, charsetName,
            StandardOpenOption.APPEND, StandardOpenOption.CREATE)) {
      for (final FetchItem item : itemsToFetch) {
        final String line = formatFetchLine(item, bagitRootDir);
        logger.debug(messages.getString("writing_line_to_file"), line, fetchFilePath);
        writer.append(line);
      }
    }
  }
  
  private static String formatFetchLine(final FetchItem fetchItem, final Path bagitRootDir){
    final StringBuilder sb = new StringBuilder();
    sb.append(fetchItem.getUrl()).append(' ');
    
    if(fetchItem.getLength() == null || fetchItem.getLength() < 0){
      sb.append("- ");
    }
    else{
      sb.append(fetchItem.getLength()).append(' ');
    }
    
    sb.append(RelativePathWriter.formatRelativePathString(bagitRootDir, fetchItem.getPath()));
      
    return sb.toString();
  }
}