/*

  * Copyright 2009, Josh Devins, Jitr.org.

  *

  * 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.jitr;

 import java.io.IOException;

 import java.lang.annotation.Annotation;

 import java.lang.reflect.Field;

 import java.net.ServerSocket;

 import java.util.Collection;

 import java.util.LinkedList;

 import org.apache.commons.lang.Validate;

 import org.jitr.core.JitrException;

 /**

  * Provides various simple utility methods.

  * 

  * @author Josh Devins (info@joshdevins.net)

  */

 public final class JitrUtils {

     private JitrUtils() {

         // non-instantiable class

     }

     /**

      * Finds any declared fields in the given class with the given annotation.

      */

     public static Collection<Field> getAnnotatedDeclaredFields(final Class<?> clazz,

             final Class<? extends Annotation> annotationClass) {

         validateClassesNotNull(clazz, annotationClass);

         final Field[] fields = clazz.getDeclaredFields();

         final Collection<Field> foundFields = new LinkedList<Field>();

         for (Field field : fields) {

             if (field.getAnnotation(annotationClass) != null) {

                 foundFields.add(field);

             }

         }

         return foundFields;

     }

     /**

      * Finds an annotated field amongst a hierarchy of classes. Should multiple classes in the

      * hierarchy have a field with the same annotation, the field from the most specific or lowest

      * subclass is used.

      * 

      * @throws JitrException

      *             When multiple annotated fields are found in any one class.

      */

     public static Field getMostSpecificAnnotatedDeclaredField(final Class<?> clazz,

             final Class<? extends Annotation> annotationClass) {

         validateClassesNotNull(clazz, annotationClass);

         // if this is the top of the hierarchy, end here

         if (Object.class.equals(clazz)) {

             return null;

         }

         // first look in this class

         final Collection<Field> fields = getAnnotatedDeclaredFields(clazz, annotationClass);

         if (fields.size() > 1) {

             throw new JitrException("One field was expected, but multiple fields in "

                     + clazz.getSimpleName() + " were annotated with "

                     + annotationClass.getSimpleName());

         }

         // nothing found, recurse and try the next class

         if (fields.isEmpty()) {

             return getMostSpecificAnnotatedDeclaredField(clazz.getSuperclass(), annotationClass);

         }

         // only found one, continue with that

         return fields.iterator().next();

     }

     /**

      * Provides a quick way to get a random, unused port by opening a {@link ServerSocket} and

      * getting the locally assigned port for the server socket.

      * 

      * @return A random, unused port.

      * 

      * @throws JitrException

      *             Thrown if any {@link IOException}s are thrown by the underlying calls to

      *             {@link ServerSocket}.

      */

     public static int getRandomUnusedPort() throws JitrException {

         final int port;

         ServerSocket socket = null;

         try {

             socket = new ServerSocket(0);

             port = socket.getLocalPort();

         } catch (final Exception e) {

             throw new JitrException("Failure picking a random, unused port.", e);

         } finally {

             if (socket != null) {

                 try {

                     socket.close();

                 } catch (final IOException ioe) {

                     throw new JitrException("Failure closing temporary socket.", ioe);

                 }

             }

         }

         return port;

     }

     private static void validateClassesNotNull(final Class<?> clazz,

             final Class<? extends Annotation> annotationClass) {

         Validate.notNull(clazz, "Class is required.");

         Validate.notNull(annotationClass, "Annotation class is required.");

     }

 }