/*
    * 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.maven.plugin;
  
  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.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.maven.plugin.MojoExecutionException;
  import org.apache.maven.project.MavenProject;
  import org.codehaus.plexus.cdc.gleaner.ClassComponentGleaner;
  import org.codehaus.plexus.component.repository.cdc.ComponentDescriptor;
  import org.codehaus.plexus.util.DirectoryScanner;
  
  /**
   * Extracts {@link ComponentDescriptor} from class files.
   *
   * @version $Id$
   */
  public class ClassComponentDescriptorExtractor
      extends ComponentDescriptorExtractorSupport
  {
      private ClassComponentGleaner gleaner;
  
      public ClassComponentDescriptorExtractor(final ClassComponentGleaner gleaner) {
          this.gleaner = gleaner;
      }
  
      public ClassComponentDescriptorExtractor() {}
  
      public List extract(final MavenProject project, final String scope, final ComponentDescriptor[] roleDefaults) throws Exception {
          assert project != null;
          assert scope != null;
          assert roleDefaults != null;
  
          // We don't have a reasonable default to use, so just puke up
          if (gleaner == null) {
              throw new IllegalStateException("Gleaner is not bound");
          }
  
          log.debug("Gleaner: " + gleaner + ", scope: " + scope);
  
          List classpath;
          File classesDir;
  
          if (COMPILE_SCOPE.equals(scope)) {
              classpath =  project.getCompileClasspathElements();
              classesDir = new File(project.getBuild().getOutputDirectory());
          }
          else if (TEST_SCOPE.equals(scope)) {
              classpath = project.getTestClasspathElements();
              classesDir = new File(project.getBuild().getTestOutputDirectory());
          }
          else {
              throw new IllegalArgumentException("Invalid scope: " + scope);
          }
  
          if (!classesDir.exists()) {
              log.warn("Missing classes directory: {}", classesDir);
              return Collections.EMPTY_LIST;
          }
  
          final ClassLoader prev = Thread.currentThread().getContextClassLoader();
          final ClassLoader cl = createClassLoader(classpath);
  
          Thread.currentThread().setContextClassLoader(cl);
  
          try {
              return extract(classesDir, cl, getDefaultsByRole(roleDefaults));
          }
          finally {
              Thread.currentThread().setContextClassLoader(prev);
          }
      }
      
      private ClassLoader createClassLoader(final List elements) throws Exception {
          List list = new ArrayList();
  
          // Add the projects dependencies
         for (Iterator iter = elements.iterator(); iter.hasNext();) {
             String filename = (String) iter.next();
 
             try {
                 list.add(new File(filename).toURI().toURL());
             }
             catch (MalformedURLException e) {
                 throw new MojoExecutionException("Invalid classpath entry: " + filename, e);
             }
         }
 
         URL[] urls = (URL[]) list.toArray(new URL[list.size()]);
 
         log.debug("Classpath:");
         for (int i=0; i<urls.length; i++) {
             log.debug("    " + urls[i]);
         }
 
         return new URLClassLoader(urls, getClass().getClassLoader());
     }
 
     private List extract(final File classesDir, final ClassLoader cl, final Map defaultsByRole) throws Exception {
         assert classesDir != null;
         assert cl != null;
         assert defaultsByRole != null;
 
         List descriptors = new ArrayList();
 
         DirectoryScanner scanner = new DirectoryScanner();
         scanner.setBasedir(classesDir);
         scanner.addDefaultExcludes();
         scanner.setIncludes(new String[]{ "**/*.class" });
 
         log.debug("Scanning for classes in: " + classesDir);
 
         scanner.scan();
 
         String[] includes = scanner.getIncludedFiles();
 
         for (int i=0; i<includes.length; i++) {
             String className = includes[i].substring(0, includes[i].lastIndexOf(".class")).replace('\\', '.').replace('/', '.');
 
             log.debug("Loading class: " + className);
 
             try {
                 Class type = cl.loadClass(className);
 
                 log.debug("Gleaning from: " + type);
 
                 ComponentDescriptor descriptor = gleaner.glean(type);
 
                 if (descriptor != null) {
                     applyDefaults(descriptor, defaultsByRole);
 
                     descriptors.add(descriptor);
                 }
             }
             catch (VerifyError e) {
                 log.error("Failed to load class: " + className + "; cause: " + e);
             }
         }
 
         log.debug("Extracted " + descriptors.size() + " descriptor(s)");
 
         return descriptors;
     }
 }