/*
    * 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.eclipse.aether.internal.impl;
  
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Files;
  import java.nio.file.Path;
  
  import org.eclipse.aether.spi.io.ChecksumProcessor;
  import org.eclipse.aether.spi.io.PathProcessor;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A utility class helping with file-based operations.
   */
  @Singleton
  @Named
  public class DefaultChecksumProcessor implements ChecksumProcessor {
      private final PathProcessor pathProcessor;
  
      @Inject
      public DefaultChecksumProcessor(PathProcessor pathProcessor) {
          this.pathProcessor = requireNonNull(pathProcessor);
      }
  
      @Override
      public String readChecksum(final Path checksumPath) throws IOException {
          // for now do exactly same as happened before, but FileProcessor is a component and can be replaced
          String checksum = "";
          try (BufferedReader br = Files.newBufferedReader(checksumPath, StandardCharsets.UTF_8)) {
              while (true) {
                  String line = br.readLine();
                  if (line == null) {
                      break;
                  }
                  line = line.trim();
                  if (!line.isEmpty()) {
                      checksum = line;
                      break;
                  }
              }
          }
  
          if (checksum.matches(".+= [0-9A-Fa-f]+")) {
              int lastSpacePos = checksum.lastIndexOf(' ');
              checksum = checksum.substring(lastSpacePos + 1);
          } else {
              int spacePos = checksum.indexOf(' ');
  
              if (spacePos != -1) {
                  checksum = checksum.substring(0, spacePos);
              }
          }
  
          return checksum;
      }
  
      @Override
      public void writeChecksum(Path target, String checksum) throws IOException {
          // for now do exactly same as happened before, but FileProcessor is a component and can be replaced
          pathProcessor.write(target, checksum);
      }
  }