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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.camel.resume;

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.function.Predicate;

/**
 * An interface that represents a set of resumables (i.e.: files in a directory, rows in a database, etc)
 *
 * @param  the indivudal type of each member of the set
 */
public interface ResumableSet {

    /**
     * Iterates over the set of input checking if they should be resumed or not.
     *
     * @param  input          the input array to check for resumables
     * @param  resumableCheck a checker method that returns true if a single entry of the input should be resumed or
     *                        false otherwise. For instance: given a set A, B and C, where B has already been processed,
     *                        then a test for A and C returns true, whereas a test for B returns false.
     * @return                a new array containing the elements that still need to be processed
     */
    default T[] resumeEach(T[] input, Predicate resumableCheck) {
        @SuppressWarnings("unchecked")
        T[] tmp = (T[]) Array.newInstance(input.getClass().getComponentType(), input.length);
        int count = 0;

        for (T entry : input) {
            if (resumableCheck.test(entry)) {
                tmp[count] = entry;
                count++;
            }
        }

        if (count != input.length) {
            return Arrays.copyOf(tmp, count);
        }

        return input;
    }

    /**
     * Iterates over the set of input checking if they should be resumed or not
     *
     * @param resumableCheck a checker method that returns true if a single entry of the input should be resumed or
     *                       false otherwise. For instance: given a set A, B and C, where B has already been processed,
     *                       then a test for A and C returns true, whereas a test for B returns false.
     */
    void resumeEach(Predicate resumableCheck);

    /**
     * Gets the input that should be resumed
     *
     * @return an array with the input that should be resumed
     */
    T[] resumed();

    /**
     * Whether there are resumable entries to process
     *
     * @return true if there are resumable entries or false otherwise
     */
    boolean hasResumables();
}