/*
    * 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.project;
  
  import java.io.BufferedInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.jar.JarFile;
  import java.util.zip.ZipEntry;
  import org.apache.maven.api.xml.Dom;
  import org.apache.maven.internal.xml.Xpp3DomBuilder;
  import org.codehaus.plexus.util.ReaderFactory;
  import org.codehaus.plexus.util.xml.pull.XmlPullParserException;
  
  /**
   * Creates an extension descriptor from some XML stream.
   *
   * @author Benjamin Bentmann
   */
  public class ExtensionDescriptorBuilder {
  
      /**
       * @since 3.3.0
       */
      public String getExtensionDescriptorLocation() {
          return "META-INF/maven/extension.xml";
      }
  
      /**
       * Extracts the extension descriptor (if any) from the specified JAR file.
       *
       * @param extensionJar The JAR file or directory to extract the descriptor from, must not be {@code null}.
       * @return The extracted descriptor or {@code null} if no descriptor was found.
       * @throws IOException If the descriptor is present but could not be parsed.
       */
      public ExtensionDescriptor build(File extensionJar) throws IOException {
          ExtensionDescriptor extensionDescriptor = null;
  
          if (extensionJar.isFile()) {
              try (JarFile pluginJar = new JarFile(extensionJar, false)) {
                  ZipEntry pluginDescriptorEntry = pluginJar.getEntry(getExtensionDescriptorLocation());
  
                  if (pluginDescriptorEntry != null) {
                      try (InputStream is = pluginJar.getInputStream(pluginDescriptorEntry)) {
                          extensionDescriptor = build(is);
                      }
                  }
              }
          } else {
              File pluginXml = new File(extensionJar, getExtensionDescriptorLocation());
  
              if (pluginXml.canRead()) {
                  try (InputStream is = new BufferedInputStream(new FileInputStream(pluginXml))) {
                      extensionDescriptor = build(is);
                  }
              }
          }
  
          return extensionDescriptor;
      }
  
      /**
       * @since 3.3.0
       */
      public ExtensionDescriptor build(InputStream is) throws IOException {
          ExtensionDescriptor extensionDescriptor = new ExtensionDescriptor();
  
          Dom dom;
          try {
              dom = Xpp3DomBuilder.build(ReaderFactory.newXmlReader(is));
          } catch (XmlPullParserException e) {
              throw new IOException(e.getMessage(), e);
          }
  
          if (!"extension".equals(dom.getName())) {
              throw new IOException("Unexpected root element \"" + dom.getName() + "\", expected \"extension\"");
          }
  
          extensionDescriptor.setExportedPackages(parseStrings(dom.getChild("exportedPackages")));
 
         extensionDescriptor.setExportedArtifacts(parseStrings(dom.getChild("exportedArtifacts")));
 
         return extensionDescriptor;
     }
 
     private List<String> parseStrings(Dom dom) {
         List<String> strings = null;
 
         if (dom != null) {
             strings = new ArrayList<>();
 
             for (Dom child : dom.getChildren()) {
                 String string = child.getValue();
                 if (string != null) {
                     string = string.trim();
                     if (string.length() > 0) {
                         strings.add(string);
                     }
                 }
             }
         }
 
         return strings;
     }
 }