/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.gecko.annotationProcessors.classloader;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Iterator;

/**
 * Class for iterating over an IterableJarLoadingURLClassLoader's classes.
 *
 * <p>This class is not thread safe: use it only from a single thread.
 */
public class JarClassIterator implements Iterator<ClassWithOptions> {
  private IterableJarLoadingURLClassLoader mTarget;
  private Iterator<String> mTargetClassListIterator;

  private ClassWithOptions lookAhead;

  /**
   * Constructor for JarClassIterator.
   *
   * @param aTarget The jar class loader to iterate over
   */
  public JarClassIterator(IterableJarLoadingURLClassLoader aTarget) {
    mTarget = aTarget;
    mTargetClassListIterator = aTarget.classNames.iterator();
  }

  @Override
  public boolean hasNext() {
    return fillLookAheadIfPossible();
  }

  @Override
  public ClassWithOptions next() {
    if (!fillLookAheadIfPossible()) {
      throw new IllegalStateException("Failed to look ahead in next()!");
    }
    ClassWithOptions next = lookAhead;
    lookAhead = null;
    return next;
  }

  private boolean fillLookAheadIfPossible() {
    if (lookAhead != null) {
      return true;
    }

    if (!mTargetClassListIterator.hasNext()) {
      return false;
    }

    String className = mTargetClassListIterator.next();
    try {
      Class<?> ret = mTarget.loadClass(className);

      // Incremental builds can leave stale classfiles in the jar. Such classfiles will cause
      // an exception at this point. We can safely ignore these classes - they cannot possibly
      // ever be loaded as they conflict with their parent class and will be killed by
      // Proguard later on anyway.
      final Class<?> enclosingClass;
      try {
        enclosingClass = ret.getEnclosingClass();
      } catch (IncompatibleClassChangeError e) {
        return fillLookAheadIfPossible();
      }

      if (enclosingClass != null) {
        // Anonymous inner class - unsupported.
        // Or named inner class, which will be processed when we process the outer class.
        return fillLookAheadIfPossible();
      }

      String ifdef = "";
      for (final Annotation annotation : ret.getDeclaredAnnotations()) {
        Class<? extends Annotation> annotationType = annotation.annotationType();
        if (!annotationType.getName().equals("org.mozilla.gecko.annotation.BuildFlag")) {
          continue;
        }

        try {
          final Method valueMethod = annotationType.getDeclaredMethod("value");
          valueMethod.setAccessible(true);
          ifdef = (String) valueMethod.invoke(annotation);
          break;
        } catch (final Exception e) {
          System.err.println("Unable to read BuildFlag annotation.");
          e.printStackTrace(System.err);
          System.exit(1);
        }
      }

      lookAhead = new ClassWithOptions(ret, ret.getSimpleName(), ifdef);
      return true;
    } catch (ClassNotFoundException e) {
      System.err.println("Unable to enumerate class: " + className + ". Corrupted jar file?");
      e.printStackTrace();
      System.exit(2);
    }
    return false;
  }

  @Override
  public void remove() {
    throw new UnsupportedOperationException("Removal of classes from iterator not supported.");
  }
}
