/*
    * 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.plugins.shade.resource;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.charset.StandardCharsets;
  import java.util.HashMap;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Scanner;
  import java.util.Set;
  import java.util.jar.JarEntry;
  import java.util.jar.JarOutputStream;
  
  import org.apache.commons.io.IOUtils;
  import org.apache.maven.plugins.shade.relocation.Relocator;
  
  /**
   * Resources transformer that relocates classes in META-INF/services and appends entries in META-INF/services resources
   * into a single resource. For example, if there are several META-INF/services/org.apache.maven.project.ProjectBuilder
   * resources spread across many JARs the individual entries will all be concatenated into a single
   * META-INF/services/org.apache.maven.project.ProjectBuilder resource packaged into the resultant JAR produced by the
   * shading process.
   */
  public class ServicesResourceTransformer extends AbstractCompatibilityTransformer {
      private static final String SERVICES_PATH = "META-INF/services";
  
      private final Map<String, Set<String>> serviceEntries = new HashMap<>();
  
      private long time = Long.MIN_VALUE;
  
      @Override
      public boolean canTransformResource(String resource) {
          return resource.startsWith(SERVICES_PATH);
      }
  
      @Override
      public void processResource(String resource, InputStream is, final List<Relocator> relocators, long time)
              throws IOException {
          resource = resource.substring(SERVICES_PATH.length() + 1);
          for (Relocator relocator : relocators) {
              if (relocator.canRelocateClass(resource)) {
                  resource = relocator.relocateClass(resource);
                  break;
              }
          }
          resource = SERVICES_PATH + '/' + resource;
  
          Set<String> out = serviceEntries.computeIfAbsent(resource, k -> new LinkedHashSet<>());
  
          Scanner scanner = new Scanner(is, StandardCharsets.UTF_8.name());
          while (scanner.hasNextLine()) {
              String relContent = scanner.nextLine();
              for (Relocator relocator : relocators) {
                  if (relocator.canRelocateClass(relContent)) {
                      relContent = relocator.applyToSourceContent(relContent);
                  }
              }
              out.add(relContent);
          }
  
          if (time > this.time) {
              this.time = time;
          }
      }
  
      @Override
      public boolean hasTransformedResource() {
          return !serviceEntries.isEmpty();
      }
  
      @Override
      public void modifyOutputStream(JarOutputStream jos) throws IOException {
          for (Map.Entry<String, Set<String>> entry : serviceEntries.entrySet()) {
              String key = entry.getKey();
              Set<String> data = entry.getValue();
  
              JarEntry jarEntry = new JarEntry(key);
              jarEntry.setTime(time);
              jos.putNextEntry(jarEntry);
  
             IOUtils.writeLines(data, "\n", jos, StandardCharsets.UTF_8);
             jos.flush();
             data.clear();
         }
     }
 }