/*
 * Copyright 2017 HugeGraph Authors
 *
 * 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 com.baidu.hugegraph.unit.iterator;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Function;

import org.junit.Test;

import com.baidu.hugegraph.iterator.FlatMapperIterator;
import com.baidu.hugegraph.testutil.Assert;
import com.baidu.hugegraph.unit.BaseUnitTest;
import com.baidu.hugegraph.unit.iterator.ExtendableIteratorTest.CloseableItor;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;

@SuppressWarnings("resource")
public class FlatMapperIteratorTest extends BaseUnitTest {

    private static final Map<String, List<Integer>> DATA = ImmutableMap.of(
            "first", ImmutableList.of(11),
            "second", ImmutableList.of(21, 22),
            "third", ImmutableList.of(31, 32, 33),
            "forth", ImmutableList.of(41, 42, 43, 44)
    );

    private static final Function<String, Iterator<Integer>> MAPPER = key -> {
        List<Integer> value = DATA.get(key);
        if (value == null) {
            return ImmutableList.<Integer>of().iterator();
        }
        return value.iterator();
    };

    @Test
    public void testFlatMapper() {

        AtomicInteger keysCount = new AtomicInteger(0);

        Iterator<String> keys = DATA.keySet().iterator();

        Function<String, Iterator<Integer>> mapper = key -> {
            keysCount.incrementAndGet();

            return DATA.get(key).iterator();
        };

        Iterator<Integer> results = new FlatMapperIterator<>(keys, mapper);

        List<Integer> actual = new ArrayList<>();
        while (results.hasNext()) {
            actual.add(results.next());
        }

        List<Integer> expected = ImmutableList.of(11,
                                                  21, 22,
                                                  31, 32, 33,
                                                  41, 42, 43, 44);
        Assert.assertEquals(4, keysCount.get());
        Assert.assertEquals(expected, actual);
    }

    @Test
    public void testHasNext() {
        Iterator<String> keys = DATA.keySet().iterator();

        Iterator<Integer> results = new FlatMapperIterator<>(keys, MAPPER);
        Assert.assertTrue(results.hasNext());
    }

    @Test
    public void testHasNextAndNextWithMultiTimes() {
        Iterator<String> keys = DATA.keySet().iterator();

        Iterator<Integer> results = new FlatMapperIterator<>(keys, MAPPER);

        for (int i = 0; i < 12; i++) {
            Assert.assertTrue(results.hasNext());
        }

        for (int i = 0; i < 10; i++) {
            results.next();
        }

        Assert.assertFalse(results.hasNext());
        Assert.assertFalse(results.hasNext());

        Assert.assertThrows(NoSuchElementException.class, () -> {
            results.next();
        });
        Assert.assertThrows(NoSuchElementException.class, () -> {
            results.next();
        });
    }

    @Test
    public void testNext() {
        Iterator<String> keys = DATA.keySet().iterator();

        Iterator<Integer> results = new FlatMapperIterator<>(keys, MAPPER);
        // Call next() without hasNext()
        results.next();
    }

    @Test
    public void testNextWithMultiTimes() {
        Iterator<String> keys = DATA.keySet().iterator();

        Iterator<Integer> results = new FlatMapperIterator<>(keys, MAPPER);
        for (int i = 0; i < 10; i++) {
            results.next();
        }
        Assert.assertThrows(NoSuchElementException.class, () -> {
            results.next();
        });
    }

    @Test
    public void testMapperReturnNullThenHasNext() {
        Iterator<String> keys = ImmutableList.of("fifth").iterator();

        Iterator<Integer> results = new FlatMapperIterator<>(keys, key -> {
            Assert.assertNull(DATA.get(key));
            return null;
        });
        Assert.assertFalse(results.hasNext());
        Assert.assertFalse(results.hasNext());
    }

    @Test
    public void testMapperReturnNullThenNext() {
        Iterator<String> keys = ImmutableList.of("fifth").iterator();

        Iterator<Integer> results = new FlatMapperIterator<>(keys, key -> {
            Assert.assertNull(DATA.get(key));
            return null;
        });
        Assert.assertThrows(NoSuchElementException.class, () -> {
            results.next();
        });
        Assert.assertThrows(NoSuchElementException.class, () -> {
            results.next();
        });
    }

    @Test
    public void testClose() throws Exception {
        CloseableItor<String> vals = new CloseableItor<>(
                                     DATA.keySet().iterator());

        FlatMapperIterator<String, Integer> results;
        results = new FlatMapperIterator<>(vals,
                                           key -> DATA.get(key).iterator());

        Assert.assertFalse(vals.closed());
        results.close();
        Assert.assertTrue(vals.closed());
    }
}