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A library for invoking native functions from java
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/*
 * Copyright (C) 2012 Wayne Meissner
 *
 * This file is part of the JNR project.
 *
 * 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 jnr.ffi.util;

import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.SortedSet;
import java.util.TreeSet;

/**
 * Utilities for collections of annotations
 */
public final class Annotations {
    public static final Collection EMPTY_ANNOTATIONS = Collections.emptyList();

    private Annotations() {}

    public static Collection sortedAnnotationCollection(Annotation[] annotations) {
        if (annotations.length > 1) {
            return sortedAnnotationCollection(Arrays.asList(annotations));

        } else if (annotations.length > 0) {
            return Collections.singletonList(annotations[0]);

        } else {
            return Collections.emptyList();
        }
    }

    public static Collection sortedAnnotationCollection(Collection annotations) {
        // If already sorted, or empty, or only one element, no need to sort again
        if (annotations.size() < 2 || (annotations instanceof SortedSet && ((SortedSet) annotations).comparator() instanceof AnnotationNameComparator)) {
            return annotations;
        }

        SortedSet sorted = new TreeSet(AnnotationNameComparator.getInstance());
        sorted.addAll(annotations);

        return Collections.unmodifiableSortedSet(sorted);
    }

    public static final Collection mergeAnnotations(Collection a, Collection b) {
        if (a.isEmpty() && b.isEmpty()) {
            return EMPTY_ANNOTATIONS;

        } else if (!a.isEmpty() && b.isEmpty()) {
            return a;

        } else if (a.isEmpty() && !b.isEmpty()) {
            return b;

        } else {
            List all = new ArrayList(a);
            all.addAll(b);
            return sortedAnnotationCollection(all);
        }
    }

    public static final Collection mergeAnnotations(Collection... collections) {
        int totalLength = 0;
        for (Collection c : collections) {
            totalLength += c.size();
        }

        List all = new ArrayList(totalLength);
        for (Collection c : collections) {
            all.addAll(c);
        }
        
        return sortedAnnotationCollection(all);
    }
}