/*

 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.reflect.annotation;

import java.lang.annotation.*;

import java.lang.reflect.*;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

import java.util.Map;

public final class AnnotationSupport {

    /**

     * Finds and returns all annotation of the type indicated by

     * {@code annotationClass} from the {@code Map} {@code

     * annotationMap}. Looks into containers of the {@code

     * annotationClass} (as specified by an the {@code

     * annotationClass} type being meta-annotated with an {@code

     * Repeatable} annotation).

     *

     * @param annotationMap the {@code Map} used to store annotations indexed by their type

     * @param annotationClass the type of annotation to search for

     *

     * @return an array of instances of {@code annotationClass} or an empty array if none were found

     */

    public static  <A extends Annotation> A[] getMultipleAnnotations(

            final Map<Class<? extends Annotation>, Annotation> annotationMap,

            final Class<A> annotationClass) {

        final List<A> res = new ArrayList<A>();

        @SuppressWarnings("unchecked")

        final A candidate = (A)annotationMap.get(annotationClass);

        if (candidate != null) {

            res.add(candidate);

        }

        final Class<? extends Annotation> containerClass = getContainer(annotationClass);

        if (containerClass != null) {

            res.addAll(unpackAll(annotationMap.get(containerClass), annotationClass));

        }

        @SuppressWarnings("unchecked") // should be safe annotationClass is a token for A

        final A[] emptyTemplateArray = (A[])Array.newInstance(annotationClass, 0);

        return res.isEmpty() ? emptyTemplateArray : res.toArray(emptyTemplateArray);

    }

    /** Helper to get the container, or null if none, of an annotation. */

    private static <A extends Annotation> Class<? extends Annotation> getContainer(Class<A> annotationClass) {

        Repeatable containingAnnotation = annotationClass.getDeclaredAnnotation(Repeatable.class);

        return (containingAnnotation == null) ? null : containingAnnotation.value();

    }

    /** Reflectively look up and get the returned array from the the

     * invocation of the value() element on an instance of an

     * Annotation.

     */

    private static  <A extends Annotation> A[] getValueArray(Annotation containerInstance) {

        try {

            // the spec tells us the container must have an array-valued

            // value element. Get the AnnotationType, get the "value" element

            // and invoke it to get the contents.

            Class<? extends Annotation> containerClass = containerInstance.annotationType();

            AnnotationType annoType = AnnotationType.getInstance(containerClass);

            if (annoType == null)

            Method m = annoType.members().get("value");

            if (m == null)

                                                          " is an invalid container for repeating annotations");

            m.setAccessible(true);

            @SuppressWarnings("unchecked") // not provably safe, but we catch the ClassCastException

            A[] a = (A[])m.invoke(containerInstance); // this will erase to (Annotation[]) but we

                                                      // do a runtime cast on the return-value

                                                      // in the methods that call this method

            return a;

        } catch (IllegalAccessException | // couldnt loosen security

                 IllegalArgumentException | // parameters doesn't match

                 InvocationTargetException | // the value method threw an exception

                 ClassCastException e) { // well, a cast failed ...

                    containerInstance + " is an invalid container for repeating annotations",

        }

    }

    /* Sanity check type of and return a list of all the annotation

     * instances of type {@code annotationClass} from {@code

     * containerInstance}.

     */

    private static <A extends Annotation> List<A> unpackAll(Annotation containerInstance,

                                                            Class<A> annotationClass) {

        if (containerInstance == null) {

            return Collections.emptyList(); // container not present

        }

        try {

            A[] a = getValueArray(containerInstance);

            List<A> l = new ArrayList<>(a.length);

            for (int i  = 0; i < a.length; i++)

                l.add(annotationClass.cast(a[i]));

            return l;

        } catch (ClassCastException |

                 NullPointerException e) {

                    String.format("%s is an invalid container for repeating annotations of type: %s",

                        containerInstance, annotationClass),

        }

    }

}