/*
 * 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 org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.hadoop.mapred.HadoopInputFormat;
import org.apache.flink.hadoopcompatibility.HadoopInputs;
import org.apache.flink.util.Collector;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.wayang.basic.channels.FileChannel;
import org.apache.wayang.basic.data.Tuple2;
import org.apache.wayang.basic.operators.ObjectFileSerialization;
import org.apache.wayang.basic.operators.ObjectFileSerializationMode;
import org.apache.wayang.basic.operators.ObjectFileSource;
import org.apache.wayang.core.optimizer.OptimizationContext;
import org.apache.wayang.core.plan.wayangplan.ExecutionOperator;
import org.apache.wayang.core.plan.wayangplan.Operator;
import org.apache.wayang.core.plan.wayangplan.UnarySource;
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.execution.FlinkExecutor;
import org.apache.wayang.flink.platform.FlinkPlatform;

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


/**
 * {@link Operator} for the {@link FlinkPlatform} that creates a sequence file.
 *
 * @see FlinkObjectFileSource
 */
public class FlinkObjectFileSource<Type> extends ObjectFileSource<Type> implements FlinkExecutionOperator {

    public FlinkObjectFileSource(ObjectFileSource<Type> that) {
        super(that);
    }

    public FlinkObjectFileSource(DataSetType<Type> type) {
        this(null, type);
    }

    public FlinkObjectFileSource(String sourcePath, DataSetType<Type> type) {
        super(sourcePath, type);
    }

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

        final String path;
        if (this.getInputUrl() == null) {
            final FileChannel.Instance input = (FileChannel.Instance) inputs[0];
            path = input.getSinglePath();
        } else {
            assert inputs.length == 0;
            path = this.getInputUrl();
        }
        DataSetChannel.Instance output = (DataSetChannel.Instance) outputs[0];
        ObjectFileSerializationMode serializationMode = this.getSerializationMode();
        final Class<Type> typeClass = this.getTypeClass();

        HadoopInputFormat<NullWritable, BytesWritable> _file = HadoopInputs.readSequenceFile(NullWritable.class, BytesWritable.class, path);
        final DataSet<Tuple2> dataSet =
                flinkExecutor
                        .fee.createInput(_file)
                        .setParallelism(flinkExecutor.fee.getParallelism())
                        .flatMap(new FlatMapFunction<org.apache.flink.api.java.tuple.Tuple2<NullWritable,BytesWritable>, Tuple2>() {
                            @Override
                            public void flatMap(org.apache.flink.api.java.tuple.Tuple2<NullWritable, BytesWritable> value, Collector<Tuple2> out) throws Exception {
                                byte[] payload = value.f1.copyBytes();
                                List<Object> chunk = ObjectFileSerialization.deserializeChunk(payload, serializationMode, typeClass);
                                for (Object element : chunk) {
                                    out.collect((Tuple2) element);
                                }
                            }

                        });

        output.accept(dataSet, flinkExecutor);

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

    @Override
    protected ExecutionOperator createCopy() {
        return new FlinkObjectFileSource<Type>(this.getInputUrl(), this.getType());
    }

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

    @Override
    public List<ChannelDescriptor> getSupportedInputChannels(int index) {
        assert index <= this.getNumInputs() || (index == 0 && this.getNumInputs() == 0);
        return Collections.singletonList(FileChannel.HDFS_OBJECT_FILE_DESCRIPTOR);
    }

    @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 true;
    }

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