/*
 * 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.flink.operators;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import org.apache.flink.api.common.functions.JoinFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.functions.KeySelector;
import org.apache.wayang.basic.data.Tuple2;
import org.apache.wayang.basic.operators.JoinOperator;
import org.apache.wayang.core.api.Configuration;
import org.apache.wayang.core.function.TransformationDescriptor;
import org.apache.wayang.core.optimizer.OptimizationContext;
import org.apache.wayang.core.optimizer.costs.LoadProfileEstimator;
import org.apache.wayang.core.optimizer.costs.LoadProfileEstimators;
import org.apache.wayang.core.plan.wayangplan.ExecutionOperator;
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.flink.channels.DataSetChannel;
import org.apache.wayang.flink.compiler.FunctionCompiler;
import org.apache.wayang.flink.execution.FlinkExecutor;

/**
 * Flink implementation of the {@link JoinOperator}.
 */
public class FlinkJoinOperator<InputType0, InputType1, KeyType>
        extends JoinOperator<InputType0, InputType1, KeyType>
        implements FlinkExecutionOperator {

    /**
     * Creates a new instance.
     */
    public FlinkJoinOperator(DataSetType<InputType0> inputType0,
                             DataSetType<InputType1> inputType1,
                             TransformationDescriptor<InputType0, KeyType> keyDescriptor0,
                             TransformationDescriptor<InputType1, KeyType> keyDescriptor1) {

        super(keyDescriptor0, keyDescriptor1, inputType0, inputType1);
    }

    /**
     * Copies an instance (exclusive of broadcasts).
     *
     * @param that that should be copied
     */
    public FlinkJoinOperator(JoinOperator<InputType0, InputType1, KeyType> that) {
        super(that);
    }

    @Override
    public Tuple<Collection<ExecutionLineageNode>, Collection<ChannelInstance>> evaluate(
            ChannelInstance[] inputs,
            ChannelInstance[] outputs,
            FlinkExecutor flinkExecutor,
            OptimizationContext.OperatorContext operatorContext) {
        assert inputs.length == this.getNumInputs();
        assert outputs.length == this.getNumOutputs();

        final DataSetChannel.Instance input0 = (DataSetChannel.Instance) inputs[0];
        final DataSetChannel.Instance input1 = (DataSetChannel.Instance) inputs[1];
        final DataSetChannel.Instance output = (DataSetChannel.Instance) outputs[0];

        final DataSet<InputType0> dataSetInput0 = input0.provideDataSet();
        final DataSet<InputType1> dataSetInput1 = input1.provideDataSet();

        FunctionCompiler compiler = flinkExecutor.getCompiler();

        KeySelector<InputType0, KeyType> fun0 = compiler.compileKeySelector(this.keyDescriptor0);
        KeySelector<InputType1, KeyType> fun1 = compiler.compileKeySelector(this.keyDescriptor1);


        DataSet<Tuple2<InputType0, InputType1>> dataSetOutput =
            dataSetInput0.join(dataSetInput1)
            .where(
                fun0
            ).equalTo(
                fun1
            ).with(
                new JoinFunction<InputType0, InputType1, Tuple2<InputType0, InputType1>>() {
                    @Override
                    public Tuple2<InputType0, InputType1> join(InputType0 inputType0, InputType1 inputType1) throws Exception {
                        return new Tuple2<>(inputType0, inputType1);
                    }
                }
            ).setParallelism(flinkExecutor.getNumDefaultPartitions());


        output.accept(dataSetOutput, flinkExecutor);

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

    @Override
    protected ExecutionOperator createCopy() {
        return new FlinkJoinOperator<>(this.getInputType0(), this.getInputType1(),
                this.getKeyDescriptor0(), this.getKeyDescriptor1());
    }


    @Override
    public String getLoadProfileEstimatorConfigurationKey() {
        return "wayang.flink.join.load";
    }

    @Override
    public Optional<LoadProfileEstimator> createLoadProfileEstimator(Configuration configuration) {
        final Optional<LoadProfileEstimator> optEstimator =
                FlinkExecutionOperator.super.createLoadProfileEstimator(configuration);
        LoadProfileEstimators.nestUdfEstimator(optEstimator, this.keyDescriptor0, configuration);
        LoadProfileEstimators.nestUdfEstimator(optEstimator, this.keyDescriptor1, configuration);
        return optEstimator;
    }

    @Override
    public List<ChannelDescriptor> getSupportedInputChannels(int index) {
        assert index <= this.getNumInputs() || (index == 0 && this.getNumInputs() == 0);
        return Arrays.asList(DataSetChannel.DESCRIPTOR, DataSetChannel.DESCRIPTOR_MANY);
    }

    @Override
    public List<ChannelDescriptor> getSupportedOutputChannels(int index) {
        assert index <= this.getNumOutputs() || (index == 0 && this.getNumOutputs() == 0);
        return Collections.singletonList(DataSetChannel.DESCRIPTOR);
    }

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