/*
 * 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.flink.streaming.runtime.translators;

import org.apache.flink.annotation.Internal;
import org.apache.flink.api.dag.Transformation;
import org.apache.flink.streaming.api.graph.SimpleTransformationTranslator;
import org.apache.flink.streaming.api.graph.TransformationTranslator;
import org.apache.flink.streaming.api.transformations.UnionTransformation;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * A {@link TransformationTranslator} for the {@link UnionTransformation}.
 *
 * @param <OUT> The type of the elements that result from the {@link UnionTransformation} being
 *     translated.
 */
@Internal
public class UnionTransformationTranslator<OUT>
        extends SimpleTransformationTranslator<OUT, UnionTransformation<OUT>> {

    @Override
    protected Collection<Integer> translateForBatchInternal(
            final UnionTransformation<OUT> transformation, final Context context) {
        return translateInternal(transformation, context);
    }

    @Override
    protected Collection<Integer> translateForStreamingInternal(
            final UnionTransformation<OUT> transformation, final Context context) {
        return translateInternal(transformation, context);
    }

    private Collection<Integer> translateInternal(
            final UnionTransformation<OUT> transformation, final Context context) {
        checkNotNull(transformation);
        checkNotNull(context);

        final List<Integer> resultIds = new ArrayList<>();
        for (Transformation<?> input : transformation.getInputs()) {
            resultIds.addAll(context.getStreamNodeIds(input));
        }
        return resultIds;
    }
}
