/*
    * Copyright (C) 2007 the original author or authors.
    *
    * 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 org.codehaus.plexus.metadata;
  
  import java.io.File;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.net.URLClassLoader;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.maven.plugin.MojoExecutionException;
  import org.codehaus.plexus.component.annotations.Component;
  import org.codehaus.plexus.component.repository.ComponentDescriptor;
  import org.codehaus.plexus.metadata.gleaner.AnnotationComponentGleaner;
  import org.codehaus.plexus.metadata.gleaner.ClassComponentGleaner;
  import org.codehaus.plexus.util.DirectoryScanner;
  
  /**
   * Extracts {@link ComponentDescriptor} from class files.
   *
   */
  @Component(role = ComponentDescriptorExtractor.class, hint = "class")
  public class ClassComponentDescriptorExtractor extends ComponentDescriptorExtractorSupport {
      private ClassComponentGleaner gleaner;
  
      public ClassComponentDescriptorExtractor(final ClassComponentGleaner gleaner) {
          this.gleaner = gleaner;
      }
  
      public ClassComponentDescriptorExtractor() {
          this.gleaner = new AnnotationComponentGleaner();
      }
  
      public List<ComponentDescriptor<?>> extract(
              MetadataGenerationRequest configuration, final ComponentDescriptor<?>[] roleDefaults) throws Exception {
          // We don't have a reasonable default to use, so just puke up
          if (gleaner == null) {
              throw new IllegalStateException("Gleaner is not bound");
          }
  
          if (!configuration.classesDirectory.exists()) {
              return Collections.emptyList();
          }
  
          if (configuration.useContextClassLoader) {
              return extract(
                      configuration.classesDirectory,
                      Thread.currentThread().getContextClassLoader(),
                      getDefaultsByRole(roleDefaults));
          } else {
              ClassLoader prev = Thread.currentThread().getContextClassLoader();
              ClassLoader cl = createClassLoader(configuration.classpath);
  
              Thread.currentThread().setContextClassLoader(cl);
  
              try {
                  return extract(configuration.classesDirectory, cl, getDefaultsByRole(roleDefaults));
              } finally {
                  Thread.currentThread().setContextClassLoader(prev);
              }
          }
      }
  
      private ClassLoader createClassLoader(final List<String> elements) throws Exception {
          List<URL> list = new ArrayList<URL>();
  
          // Add the projects dependencies
          for (String filename : elements) {
              try {
                  list.add(new File(filename).toURI().toURL());
              } catch (MalformedURLException e) {
                  throw new MojoExecutionException("Invalid classpath entry: " + filename, e);
              }
          }
  
          URL[] urls = list.toArray(new URL[list.size()]);
  
          // getLogger().debug( "Classpath:" );
          for (URL url : urls) {
              // getLogger().debug( "    " + urls[i] );
          }
  
          return new URLClassLoader(urls, null);
      }
 
     private List<ComponentDescriptor<?>> extract(
             File classesDir, ClassLoader cl, Map<String, ComponentDescriptor<?>> defaultsByRole) throws Exception {
         assert classesDir != null;
         assert cl != null;
         assert defaultsByRole != null;
 
         List<ComponentDescriptor<?>> descriptors = new ArrayList<ComponentDescriptor<?>>();
 
         DirectoryScanner scanner = new DirectoryScanner();
         scanner.setBasedir(classesDir);
         scanner.addDefaultExcludes();
         scanner.setIncludes(new String[] {"**/*.class"});
         // exclude special classes like module-info.class
         scanner.setExcludes(new String[] {"**/*-*.class"});
 
         // getLogger().debug( "Scanning for classes in: " + classesDir );
 
         scanner.scan();
 
         String[] includes = scanner.getIncludedFiles();
 
         for (String include : includes) {
             String className = include.substring(0, include.lastIndexOf(".class"))
                     .replace('\\', '.')
                     .replace('/', '.');
 
             try {
                 // Class type = cl.loadClass( className );
 
                 ComponentDescriptor<?> descriptor = gleaner.glean(className, cl);
 
                 if (descriptor != null) {
                     applyDefaults(descriptor, defaultsByRole);
 
                     descriptors.add(descriptor);
                 }
             } catch (VerifyError e) {
                 // getLogger().error( "Failed to load class: " + className + "; cause: " + e );
             }
         }
 
         return descriptors;
     }
 }