hazelcast-master/hazelcast/src/main/java/com/hazelcast/jet/pipeline/WindowGroupAggregateBuilder.java
/*
 * Copyright (c) 2008-2023, Hazelcast, Inc. All Rights Reserved.
 *
 * Licensed 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.hazelcast.jet.pipeline;

import com.hazelcast.jet.aggregate.AggregateOperation;
import com.hazelcast.jet.aggregate.AggregateOperation1;
import com.hazelcast.jet.aggregate.CoAggregateOperationBuilder;
import com.hazelcast.jet.datamodel.ItemsByTag;
import com.hazelcast.jet.datamodel.KeyedWindowResult;
import com.hazelcast.jet.datamodel.Tag;
import com.hazelcast.jet.impl.pipeline.GrAggBuilder;

import javax.annotation.Nonnull;

import static com.hazelcast.jet.aggregate.AggregateOperations.coAggregateOperationBuilder;

/**
 * Offers a step-by-step API to build a pipeline stage that performs a
 * windowed co-grouping and aggregation of the data from several input
 * stages. To obtain it, call {@link
 * StageWithKeyAndWindow#aggregateBuilder()} on one of the stages to
 * co-aggregate and refer to that method's Javadoc for further details.
 * <p>
 * <strong>Note:</strong> this is not a builder of {@code
 * AggregateOperation}. If that' s what you are looking for, go {@link
 * AggregateOperation#withCreate here}.
 *
 * @param <K> type of the key
 * @param <R0> type of the aggregation result for stream-0
 *
 * @since Jet 3.0
 */
public class WindowGroupAggregateBuilder<K, R0> {
    private final GrAggBuilder<K> grAggBuilder;
    private final CoAggregateOperationBuilder aggrOpBuilder = coAggregateOperationBuilder();

    <T0> WindowGroupAggregateBuilder(
            @Nonnull StageWithKeyAndWindow<T0, K> stage0,
            @Nonnull AggregateOperation1<? super T0, ?, ? extends R0> aggrOp0
    ) {
        grAggBuilder = new GrAggBuilder<>(stage0);
        aggrOpBuilder.add(Tag.tag0(), aggrOp0);
    }

    /**
     * Returns the tag corresponding to the pipeline stage this builder was
     * obtained from. Use this tag to refer to this stage when extracting the
     * results from the aggregated stage.
     */
    @Nonnull
    public Tag<R0> tag0() {
        return Tag.tag0();
    }

    /**
     * Adds another stage that will contribute its data to the windowed
     * group-and-aggregate stage being constructed. Returns the tag you'll use
     * to refer to this stage when building the {@code AggregateOperation} that
     * you'll pass to {@link #build build()}.
     */
    @Nonnull
    public <T, R> Tag<R> add(
            @Nonnull StreamStageWithKey<T, K> stage,
            @Nonnull AggregateOperation1<? super T, ?, ? extends R> aggrOp
    ) {
        Tag<T> tag = grAggBuilder.add(stage);
        return aggrOpBuilder.add(tag, aggrOp);
    }

    /**
     * Creates and returns a pipeline stage that performs a windowed
     * cogroup-and-aggregate operation on the stages registered with this
     * builder object. The composite aggregate operation places the results of
     * the individual aggregate operations in an {@code ItemsByTag}. Use the
     * tags you got from this builder to access the results.
     */
    @Nonnull
    public StreamStage<KeyedWindowResult<K, ItemsByTag>> build() {
        AggregateOperation<Object[], ItemsByTag> aggrOp = aggrOpBuilder.build();
        return grAggBuilder.buildStream(aggrOp);
    }
}
