com.googlecode.concurrentlinkedhashmap.IsValidLinkedDeque.java Source code

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Here is the source code for com.googlecode.concurrentlinkedhashmap.IsValidLinkedDeque.java

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/*
 * Copyright 2011 Google Inc. All Rights Reserved.
 *
 * 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 com.googlecode.concurrentlinkedhashmap;

import java.util.Deque;
import java.util.Iterator;
import java.util.Set;

import com.google.common.collect.Sets;
import org.hamcrest.Description;
import org.hamcrest.Factory;
import org.hamcrest.TypeSafeDiagnosingMatcher;

import static com.googlecode.concurrentlinkedhashmap.IsEmptyCollection.emptyCollection;
import static org.hamcrest.Matchers.hasSize;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.not;
import static org.hamcrest.Matchers.nullValue;

/**
 * A matcher that evaluates a {@link LinkedDeque} to determine if it is in a
 * valid state.
 *
 * @author ben.manes@gmail.com (Ben Manes)
 */
public final class IsValidLinkedDeque<E> extends TypeSafeDiagnosingMatcher<LinkedDeque<? extends E>> {

    @Override
    public void describeTo(Description description) {
        description.appendText("valid");
    }

    @Override
    protected boolean matchesSafely(LinkedDeque<? extends E> deque, Description description) {
        DescriptionBuilder builder = new DescriptionBuilder(description);

        if (deque.isEmpty()) {
            checkEmpty(deque, builder);
        }
        checkIterator(deque, deque.iterator(), builder);
        checkIterator(deque, deque.descendingIterator(), builder);

        return builder.matches();
    }

    void checkEmpty(Deque<? extends Linked<? extends E>> deque, DescriptionBuilder builder) {
        builder.expectThat(deque, emptyCollection());
        builder.expectThat(deque.pollFirst(), is(nullValue()));
        builder.expectThat(deque.pollLast(), is(nullValue()));
        builder.expectThat(deque.poll(), is(nullValue()));
    }

    void checkIterator(Deque<? extends Linked<? extends E>> deque, Iterator<? extends Linked<? extends E>> iterator,
            DescriptionBuilder builder) {
        Set<Linked<?>> seen = Sets.newIdentityHashSet();
        while (iterator.hasNext()) {
            Linked<?> element = iterator.next();
            checkElement(deque, element, builder);
            String errorMsg = String.format("Loop detected: %s in %s", element, seen);
            builder.expectThat(errorMsg, seen.add(element), is(true));
        }
        builder.expectThat(deque, hasSize(seen.size()));
    }

    void checkElement(Deque<? extends Linked<? extends E>> deque, Linked<?> element, DescriptionBuilder builder) {
        Linked<?> first = deque.peekFirst();
        Linked<?> last = deque.peekLast();
        if (element == first) {
            builder.expectThat("not null prev", element.getPrevious(), is(nullValue()));
        }
        if (element == last) {
            builder.expectThat("not null next", element.getNext(), is(nullValue()));
        }
        if ((element != first) && (element != last)) {
            builder.expectThat(element.getPrevious(), is(not(nullValue())));
            builder.expectThat(element.getNext(), is(not(nullValue())));
        }
    }

    @Factory
    public static <E> IsValidLinkedDeque<E> validLinkedDeque() {
        return new IsValidLinkedDeque<E>();
    }
}