/*
 * 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.wayang.java.operators;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.apache.wayang.basic.data.Tuple2;
import org.apache.wayang.core.function.ReduceDescriptor;
import org.apache.wayang.core.types.DataSetType;
import org.apache.wayang.core.types.DataUnitType;
import org.apache.wayang.java.channels.JavaChannelInstance;
import org.junit.Assert;
import org.junit.Test;

/**
 * Test suite for {@link JavaGlobalReduceOperator}.
 */
public class JavaGlobalReduceOperatorTest extends JavaExecutionOperatorTestBase {

    @Test
    public void testExecution() {
        // Prepare test data.
        Stream<Integer> inputStream = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10).stream();

        // Build the reduce operator.
        JavaGlobalReduceOperator<Integer> globalReduce =
                new JavaGlobalReduceOperator<>(
                        DataSetType.createDefaultUnchecked(Tuple2.class),
                        new ReduceDescriptor<>(
                                (a, b) -> a + b, DataUnitType.createGrouped(Integer.class),
                                DataUnitType.createBasic(Integer.class)
                        )
                );

        // Execute.
        JavaChannelInstance[] inputs = new JavaChannelInstance[]{createStreamChannelInstance(inputStream)};
        JavaChannelInstance[] outputs = new JavaChannelInstance[]{createCollectionChannelInstance()};
        evaluate(globalReduce, inputs, outputs);

        // Verify the outcome.
        final List<Integer> result = outputs[0].<Integer>provideStream().collect(Collectors.toList());
        Assert.assertEquals(1, result.size());
        Assert.assertEquals(Integer.valueOf((10 + 1) * (10 / 2)), result.get(0)); // Props to Gauss!

    }

    @Test
    public void testExecutionWithoutData() {
        // Prepare test data.
        Stream<Integer> inputStream = Arrays.<Integer>asList().stream();

        // Build the reduce operator.
        JavaGlobalReduceOperator<Integer> globalReduce =
                new JavaGlobalReduceOperator<>(
                        DataSetType.createDefaultUnchecked(Tuple2.class),
                        new ReduceDescriptor<>(
                                (a, b) -> a + b, DataUnitType.createGrouped(Integer.class),
                                DataUnitType.createBasic(Integer.class)
                        )
                );

        // Execute the reduce operator.
        JavaChannelInstance[] inputs = new JavaChannelInstance[]{createStreamChannelInstance(inputStream)};
        JavaChannelInstance[] outputs = new JavaChannelInstance[]{createCollectionChannelInstance()};
        evaluate(globalReduce, inputs, outputs);

        // Verify the outcome.
        final List<Integer> result = outputs[0].<Integer>provideStream().collect(Collectors.toList());
        Assert.assertEquals(0, result.size());

    }
}