/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.common.util;

import org.opensearch.common.lease.Releasables;
import org.opensearch.common.settings.Settings;
import org.opensearch.core.indices.breaker.NoneCircuitBreakerService;
import org.opensearch.test.OpenSearchTestCase;
import org.junit.Before;

import java.util.Arrays;

public class BinarySearcherTests extends OpenSearchTestCase {

    private BigArrays randombigArrays() {
        return new MockBigArrays(new MockPageCacheRecycler(Settings.EMPTY), new NoneCircuitBreakerService());
    }

    private BigArrays bigArrays;

    @Before
    public void init() {
        bigArrays = randombigArrays();
    }

    public void testDoubleBinarySearch() throws Exception {
        final int size = randomIntBetween(50, 10000);
        DoubleArray bigArray = new BigDoubleArray(size, bigArrays, false);
        double[] array = new double[size];

        // Fill array with sorted values
        double currentValue = randomDoubleBetween(-100, 100, true);
        for (int i = 0; i < size; ++i) {
            bigArray.set(i, currentValue);
            array[i] = currentValue;
            currentValue += randomDoubleBetween(0, 30, false);
        }

        // Pick a number to search for
        int index = randomIntBetween(0, size - 1);
        double searchFor = bigArray.get(index);
        if (randomBoolean()) {
            // Pick a number where there is no exact match, but that is closest to array.get(index)
            if (randomBoolean()) {
                // Pick a number above array.get(index)
                if (index < size - 1) {
                    // Divide by 3 so that it's closer to array.get(index) than to array.get(index + 1)
                    searchFor += (bigArray.get(index + 1) - bigArray.get(index)) / 3;
                } else {
                    // There is nothing about index
                    searchFor += 0.1;
                }
            } else {
                // Pick one below array.get(index)
                if (index > 0) {
                    searchFor -= (bigArray.get(index) - bigArray.get(index - 1)) / 3;
                } else {
                    // There is nothing below index
                    searchFor -= 0.1;
                }
            }
        }

        BigArrays.DoubleBinarySearcher searcher = new BigArrays.DoubleBinarySearcher(bigArray);
        assertEquals(index, searcher.search(0, size - 1, searchFor));

        // Sanity check: confirm that ArrayUtils.binarySearch() returns the same index
        int arraysIndex = Arrays.binarySearch(array, searchFor);
        if (arraysIndex < 0) {
            // Arrays.binarySearch didn't find an exact match
            arraysIndex = -(arraysIndex + 1);
        }

        // Arrays.binarySearch always rounds down whereas BinarySearcher rounds to the closest index
        // So sometimes they will be off by 1
        assertEquals(Math.abs(index - arraysIndex) <= 1, true);

        Releasables.close(bigArray);
    }

    class IntBinarySearcher extends BinarySearcher {

        int[] array;
        int searchFor;

        IntBinarySearcher(int[] array, int searchFor) {
            this.array = array;
            this.searchFor = searchFor;
        }

        @Override
        protected int compare(int index) {
            return Integer.compare(array[index], searchFor);
        }

        @Override
        protected double distance(int index) {
            return Math.abs(array[index] - searchFor);
        }
    }

    public void testCompareWithArraysBinarySearch() throws Exception {
        int size = randomIntBetween(30, 10000);
        int[] array = new int[size];
        for (int i = 0; i < size; i++) {
            array[i] = randomInt();
        }
        Arrays.sort(array);
        int searchFor = randomInt();
        BinarySearcher searcher = new IntBinarySearcher(array, searchFor);

        int searcherIndex = searcher.search(0, size - 1);
        int arraysIndex = Arrays.binarySearch(array, searchFor);

        if (arraysIndex < 0) {
            // Arrays.binarySearch didn't find an exact match
            arraysIndex = -(arraysIndex + 1);
        }

        // Arrays.binarySearch always rounds down whereas BinarySearcher rounds to the closest index
        // So sometimes they will be off by 1
        assertEquals(Math.abs(searcherIndex - arraysIndex) <= 1, true);
    }
}
