/*
 * 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.core.optimizer.cardinality;

import org.apache.wayang.core.api.Configuration;
import org.apache.wayang.core.optimizer.OptimizationContext;
import org.apache.wayang.core.plan.wayangplan.InputSlot;
import org.apache.wayang.core.plan.wayangplan.LoopHeadAlternative;
import org.apache.wayang.core.plan.wayangplan.LoopHeadOperator;
import org.apache.wayang.core.plan.wayangplan.OperatorAlternative;
import org.apache.wayang.core.plan.wayangplan.OutputSlot;
import org.apache.wayang.core.plan.wayangplan.Slot;
import org.apache.wayang.core.util.Tuple;

import java.util.Collection;
import java.util.function.BiFunction;
import java.util.stream.Collectors;

/**
 * {@link CardinalityPusher} implementation for {@link LoopHeadAlternative}s.
 */
public class LoopHeadAlternativeCardinalityPusher extends AbstractAlternativeCardinalityPusher {

    Collection<Tuple<OperatorAlternative.Alternative, CardinalityPusher>> alternativePushers;

    public LoopHeadAlternativeCardinalityPusher(
            final LoopHeadAlternative loopHeadAlternative,
            Collection<InputSlot<?>> relevantInputSlots,
            Collection<OutputSlot<?>> relevantOutputSlots,
            BiFunction<OperatorAlternative.Alternative, Configuration, CardinalityPusher> pusherRetriever,
            final Configuration configuration
    ) {
        super(Slot.toIndices(relevantInputSlots), Slot.toIndices(relevantOutputSlots));
        this.alternativePushers = loopHeadAlternative.getAlternatives().stream()
                .map(alternative -> {
                    final CardinalityPusher alternativePusher = pusherRetriever.apply(alternative, configuration);
                    return new Tuple<>(alternative, alternativePusher);
                })
                .collect(Collectors.toList());
    }


    @Override
    public void pushThroughAlternatives(OptimizationContext.OperatorContext opCtx, Configuration configuration) {
        final OptimizationContext optCtx = opCtx.getOptimizationContext();
        for (Tuple<OperatorAlternative.Alternative, CardinalityPusher> alternativePusher : this.alternativePushers) {
            LoopHeadOperator loopHeadOperator = (LoopHeadOperator) alternativePusher.field0.getContainedOperator();
            final OptimizationContext.OperatorContext lhoCtx = optCtx.getOperatorContext(loopHeadOperator);
            alternativePusher.field1.push(lhoCtx, configuration);
        }
    }

}