/*
    * 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.tools.plugin.generator;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.io.StringWriter;
  import java.io.Writer;
  
  import org.apache.maven.project.MavenProject;
  import org.apache.velocity.VelocityContext;
  import org.codehaus.plexus.util.io.CachingOutputStream;
  import org.codehaus.plexus.velocity.VelocityComponent;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  /**
   * Generates an <code>HelpMojo</code> class from <code>help-class-source.vm</code> template.
   * The generated mojo reads help content from <code>META-INF/maven/${groupId}/${artifactId}/plugin-help.xml</code>
   * resource, which is generated by this {@link PluginDescriptorFilesGenerator}.
   *
   * @author <a href="mailto:vincent.siveton@gmail.com">Vincent Siveton</a>
   * @since 2.4
   */
  public class PluginHelpGenerator {
      /**
       * Default generated class name
       */
      private static final String HELP_MOJO_CLASS_NAME = "HelpMojo";
  
      private String helpPackageName;
      private String goalPrefix;
      private MavenProject mavenProject;
      private boolean useMaven4Api;
      private VelocityComponent velocityComponent;
  
      /**
       * Default constructor
       */
      public PluginHelpGenerator() {
          // nop
      }
  
      // ----------------------------------------------------------------------
      // Public methods
      // ----------------------------------------------------------------------
  
      public void execute(File destinationDirectory) throws GeneratorException {
          String helpImplementation = getImplementation();
  
          useMaven4Api = mavenProject.getDependencies().stream()
                  .anyMatch(dep ->
                          "org.apache.maven".equals(dep.getGroupId()) && "maven-api-core".equals(dep.getArtifactId()));
  
          try {
              String sourcePath = helpImplementation.replace('.', File.separatorChar) + ".java";
  
              File helpClass = new File(destinationDirectory, sourcePath);
              helpClass.getParentFile().mkdirs();
  
              String helpClassSources = getHelpClassSources(getPluginHelpPath(mavenProject));
  
              try (Writer w = new OutputStreamWriter(new CachingOutputStream(helpClass), UTF_8)) {
                  w.write(helpClassSources);
              }
          } catch (IOException e) {
              throw new GeneratorException(e.getMessage(), e);
          }
      }
  
      public PluginHelpGenerator setHelpPackageName(String helpPackageName) {
          this.helpPackageName = helpPackageName;
          return this;
      }
  
      public PluginHelpGenerator setVelocityComponent(VelocityComponent velocityComponent) {
          this.velocityComponent = velocityComponent;
          return this;
      }
  
     public PluginHelpGenerator setGoalPrefix(String goalPrefix) {
         this.goalPrefix = goalPrefix;
         return this;
     }
 
     public PluginHelpGenerator setMavenProject(MavenProject mavenProject) {
         this.mavenProject = mavenProject;
         return this;
     }
 
     // ----------------------------------------------------------------------
     // Private methods
     // ----------------------------------------------------------------------
 
     private String getHelpClassSources(String pluginHelpPath) throws IOException {
         VelocityContext context = new VelocityContext();
         boolean useAnnotations =
                 mavenProject.getArtifactMap().containsKey("org.apache.maven.plugin-tools:maven-plugin-annotations");
 
         context.put("helpPackageName", helpPackageName);
         context.put("pluginHelpPath", pluginHelpPath);
         context.put("artifactId", mavenProject.getArtifactId());
         // TODO: evaluate prefix from deserialized plugin
         context.put("goalPrefix", goalPrefix);
         context.put("useAnnotations", useAnnotations);
 
         StringWriter stringWriter = new StringWriter();
 
         // plugin-tools sources are UTF-8 (and even ASCII in this case))
         try (InputStream is = Thread.currentThread()
                         .getContextClassLoader()
                         .getResourceAsStream(useMaven4Api ? "help-class-source-v4.vm" : "help-class-source.vm"); //
                 InputStreamReader isReader = new InputStreamReader(is, UTF_8)) {
             // isReader =
             velocityComponent.getEngine().evaluate(context, stringWriter, "", isReader);
         }
         // Apply OS lineSeparator instead of template's lineSeparator to have consistent separators for
         // all source files.
         return stringWriter.toString().replaceAll("(\r\n|\n|\r)", System.lineSeparator());
     }
 
     /**
      * @return The implementation.
      */
     private String getImplementation() {
         return (helpPackageName == null || helpPackageName.isEmpty())
                 ? HELP_MOJO_CLASS_NAME
                 : helpPackageName + '.' + HELP_MOJO_CLASS_NAME;
     }
 
     static String getPluginHelpPath(MavenProject mavenProject) {
         return mavenProject.getGroupId() + "/" + mavenProject.getArtifactId() + "/plugin-help.xml";
     }
 }