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/*
 * Copyright 2011-2016 the original author or 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 com.lambdaworks.redis.cluster;

import java.util.Collection;

/**
 * Circular element provider. This class allows infinite scrolling over a collection with the possibility to provide an initial
 * offset.
 * 
 * @author Mark Paluch
 */
class RoundRobin {

    protected final Collection collection;

    protected V offset;

    public RoundRobin(Collection collection) {
        this(collection, null);
    }

    public RoundRobin(Collection collection, V offset) {
        this.collection = collection;
        this.offset = offset;
    }

    /**
     * Returns the next item.
     * 
     * @return the next item
     */
    public V next() {
        if (offset != null) {
            boolean accept = false;
            for (V element : collection) {
                if (element == offset) {
                    accept = true;
                    continue;
                }

                if (accept) {
                    return offset = element;
                }
            }
        }

        return offset = collection.iterator().next();
    }
}