/*
 * 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.spark.operators;

import org.apache.commons.lang3.Validate;
import org.apache.spark.api.java.JavaRDD;
import org.apache.wayang.core.api.Configuration;
import org.apache.wayang.core.optimizer.OptimizationContext;
import org.apache.wayang.core.optimizer.cardinality.CardinalityEstimator;
import org.apache.wayang.core.optimizer.cardinality.DefaultCardinalityEstimator;
import org.apache.wayang.core.plan.wayangplan.ExecutionOperator;
import org.apache.wayang.core.plan.wayangplan.UnaryToUnaryOperator;
import org.apache.wayang.core.platform.ChannelDescriptor;
import org.apache.wayang.core.platform.ChannelInstance;
import org.apache.wayang.core.platform.lineage.ExecutionLineageNode;
import org.apache.wayang.core.types.DataSetType;
import org.apache.wayang.core.util.Tuple;
import org.apache.wayang.spark.channels.RddChannel;
import org.apache.wayang.spark.execution.SparkExecutor;

import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Optional;

/**
 * Converts an uncached {@link RddChannel} into a cached {@link RddChannel}.
 */
public class SparkCacheOperator<Type>
        extends UnaryToUnaryOperator<Type, Type>
        implements SparkExecutionOperator {

    public SparkCacheOperator(DataSetType<Type> type) {
        super(type, type, false);
    }

    @Override
    public Tuple<Collection<ExecutionLineageNode>, Collection<ChannelInstance>> evaluate(
            ChannelInstance[] inputs,
            ChannelInstance[] outputs,
            SparkExecutor sparkExecutor,
            OptimizationContext.OperatorContext operatorContext) {
        RddChannel.Instance input = (RddChannel.Instance) inputs[0];
        final JavaRDD<Object> rdd = input.provideRdd();
        final JavaRDD<Object> cachedRdd = rdd.cache();
        cachedRdd.foreachPartition(iterator -> {
        });

        RddChannel.Instance output = (RddChannel.Instance) outputs[0];
        output.accept(cachedRdd, sparkExecutor);

        return ExecutionOperator.modelQuasiEagerExecution(inputs, outputs, operatorContext);
    }

    @Override
    public List<ChannelDescriptor> getSupportedInputChannels(int index) {
        return Collections.singletonList(RddChannel.UNCACHED_DESCRIPTOR);
    }

    @Override
    public List<ChannelDescriptor> getSupportedOutputChannels(int index) {
        return Collections.singletonList(RddChannel.CACHED_DESCRIPTOR);
    }

    @Override
    public boolean containsAction() {
        return true;
    }

    @Override
    public Optional<CardinalityEstimator> createCardinalityEstimator(
            final int outputIndex,
            final Configuration configuration) {
        Validate.inclusiveBetween(0, 0, outputIndex);
        return Optional.of(new DefaultCardinalityEstimator(1d, 1, this.isSupportingBroadcastInputs(),
                inputCards -> inputCards[0]));
    }

    @Override
    public String getLoadProfileEstimatorConfigurationKey() {
        return "wayang.spark.cache.load";
    }

}