package com.atlassian.plugin.osgi.util;
   
   import aQute.bnd.osgi.AbstractResource;
   import aQute.bnd.osgi.ClassDataCollector;
   import aQute.bnd.osgi.Clazz;
   import aQute.bnd.osgi.Descriptors;
   import com.google.common.collect.Collections2;
   import com.google.common.collect.ImmutableSet;
   import com.google.common.collect.Sets;
  import org.apache.commons.io.IOUtils;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.Set;
  
  /**
   * Contains all the utility methods and classes for scanning class file binary.
   *
   * @since 2.10
   */
  public class ClassBinaryScanner {
      /**
       * Scans class binary to extract 1) referred classes 2) imported packages 3) the class's superclass.
       *
       * @param clazz the input class binary
       * @return result, never null
       * @throws java.io.IOException if the scan dies along the way
       * @since 2.10
       */
      public static ScanResult scanClassBinary(Clazz clazz) throws IOException {
          final ImmutableSet.Builder<String> allReferredClasses = new ImmutableSet.Builder<>();
          final String[] superClassName = new String[]{null};
          try {
              // TODO: Perhaps, we should start scanning for annotations as well. This ClassDataCollector in bndlib 1.4.3 is quite powerful.
              clazz.parseClassFileWithCollector(new ClassDataCollector() {
  
                  @Override
                  public void extendsClass(Descriptors.TypeRef ref) {
                      superClassName[0] = ref.getBinary();
                      allReferredClasses.add(ref.getBinary());
                  }
  
                  @Override
                  public void implementsInterfaces(Descriptors.TypeRef[] refs) {
                      for (Descriptors.TypeRef ref : refs) {
                          allReferredClasses.add(ref.getBinary());
                      }
                  }
  
                  @Override
                  public void addReference(Descriptors.TypeRef ref) {
                      allReferredClasses.add(ref.getBinary());
                  }
              });
          } catch (Exception e) {
              throw new IOException("Error parsing class file", e);
          }
  
          Set<String> referredPackages = Sets.newHashSet(Collections2.transform(clazz.getReferred(),
                  packageRef -> {
                      if (packageRef != null) {
                          return packageRef.getFQN();
                      } else {
                          return null;
                      }
                  }));
          return new ScanResult(allReferredClasses.build(), referredPackages, superClassName[0]);
      }
  
      /**
       * Contains the result of class binary scanning.
       *
       * @since 2.10
       */
      public static class ScanResult {
          // this classes are referred to as strings since we don't want to load them all at this stage.
          private Set<String> referredClasses;
          private Set<String> referredPackages;
          private String superClass;
  
          public ScanResult(Set<String> referredClasses, Set<String> referredPackages, String superClass) {
              this.referredClasses = referredClasses;
              this.referredPackages = referredPackages;
              this.superClass = superClass;
          }
  
          public Set<String> getReferredClasses() {
              return referredClasses;
          }
  
          public Set<String> getReferredPackages() {
              return referredPackages;
          }
  
          public String getSuperClass() {
              return superClass;
          }
      }
 
     /**
      * InputStream-based resource for class scanning purpose (in the format required by bndlib).
      *
      * @since 2.10
      */
     public static class InputStreamResource extends AbstractResource implements Closeable {
         private InputStream inputStream;
 
         public InputStreamResource(InputStream inputStream) {
             super(-1);
             this.inputStream = inputStream;
         }
 
         @Override
         protected byte[] getBytes() throws Exception {
             return IOUtils.toByteArray(inputStream);
         }
 
         @Override
         public void close() throws IOException {
             inputStream.close();
         }
 
     }
 }