/*
 * 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.iterable;

import org.opensearch.test.OpenSearchTestCase;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

import static org.hamcrest.object.HasToString.hasToString;

public class IterablesTests extends OpenSearchTestCase {
    public void testGetOverList() {
        test(Arrays.asList("a", "b", "c"));
    }

    public void testGetOverIterable() {
        Iterable<String> iterable = () -> new Iterator<String>() {
            private int position = 0;

            @Override
            public boolean hasNext() {
                return position < 3;
            }

            @Override
            public String next() {
                if (position < 3) {
                    String s = position == 0 ? "a" : position == 1 ? "b" : "c";
                    position++;
                    return s;
                } else {
                    throw new NoSuchElementException();
                }
            }
        };
        test(iterable);
    }

    public void testFlatten() {
        List<List<Integer>> list = new ArrayList<>();
        list.add(new ArrayList<>());

        Iterable<Integer> allInts = Iterables.flatten(list);
        int count = 0;
        for (@SuppressWarnings("unused")
        int x : allInts) {
            count++;
        }
        assertEquals(0, count);
        list.add(new ArrayList<>());
        list.get(1).add(0);

        // changes to the outer list are not seen since flatten pre-caches outer list on init:
        count = 0;
        for (@SuppressWarnings("unused")
        int x : allInts) {
            count++;
        }
        assertEquals(0, count);

        // but changes to the original inner lists are seen:
        list.get(0).add(0);
        for (@SuppressWarnings("unused")
        int x : allInts) {
            count++;
        }
        assertEquals(1, count);
    }

    private void test(Iterable<String> iterable) {
        try {
            Iterables.get(iterable, -1);
            fail("expected IllegalArgumentException");
        } catch (IllegalArgumentException e) {
            assertThat(e, hasToString("java.lang.IllegalArgumentException: position >= 0"));
        }
        assertEquals("a", Iterables.get(iterable, 0));
        assertEquals("b", Iterables.get(iterable, 1));
        assertEquals("c", Iterables.get(iterable, 2));
        try {
            Iterables.get(iterable, 3);
            fail("expected IndexOutOfBoundsException");
        } catch (IndexOutOfBoundsException e) {
            assertThat(e, hasToString("java.lang.IndexOutOfBoundsException: 3"));
        }
    }
}
