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/*
 * Copyright (C) 2009 The Guava Authors
 *
 * 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.glassfish.jersey.internal.guava;

import java.util.ListIterator;
import java.util.NoSuchElementException;

import static org.glassfish.jersey.internal.guava.Preconditions.checkPositionIndex;

/**
 * This class provides a skeletal implementation of the {@link ListIterator}
 * interface across a fixed number of elements that may be retrieved by
 * position. It does not support {@link #remove}, {@link #set}, or {@link #add}.
 *
 * @author Jared Levy
 */
abstract class AbstractIndexedListIterator
        extends UnmodifiableListIterator {
    private final int size;
    private int position;

    /**
     * Constructs an iterator across a sequence of the given size with the given
     * initial position. That is, the first call to {@link #nextIndex()} will
     * return {@code position}, and the first call to {@link #next()} will return
     * the element at that index, if available. Calls to {@link #previous()} can
     * retrieve the preceding {@code position} elements.
     *
     * @throws IndexOutOfBoundsException if {@code position} is negative or is
     *                                   greater than {@code size}
     * @throws IllegalArgumentException  if {@code size} is negative
     */
    AbstractIndexedListIterator(int size, int position) {
        checkPositionIndex(position, size);
        this.size = size;
        this.position = position;
    }

    /**
     * Returns the element with the specified index. This method is called by
     * {@link #next()}.
     */
    protected abstract E get(int index);

    @Override
    public final boolean hasNext() {
        return position < size;
    }

    @Override
    public final E next() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        return get(position++);
    }

    @Override
    public final int nextIndex() {
        return position;
    }

    @Override
    public final boolean hasPrevious() {
        return position > 0;
    }

    @Override
    public final E previous() {
        if (!hasPrevious()) {
            throw new NoSuchElementException();
        }
        return get(--position);
    }

    @Override
    public final int previousIndex() {
        return position - 1;
    }
}