/*
 * 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.hadoop.io.BytesWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.JavaRDD;
import org.apache.wayang.basic.channels.FileChannel;
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.core.util.fs.FileSystems;
import org.apache.wayang.spark.channels.RddChannel;
import org.apache.wayang.spark.execution.SparkExecutor;
import org.apache.wayang.spark.platform.SparkPlatform;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 * {@link Operator} for the {@link SparkPlatform} that creates a sequence file.
 *
 * @see SparkObjectFileSink
 */
public class SparkObjectFileSource<T> extends ObjectFileSource<T> implements SparkExecutionOperator {

    private final Logger logger = LogManager.getLogger(this.getClass());

    public SparkObjectFileSource(ObjectFileSource that) {
        super(that);
    }

    public SparkObjectFileSource(DataSetType<T> type) {
        this(null, type);
    }

    public SparkObjectFileSource(String sourcePath, DataSetType<T> type) {
        super(sourcePath, type);
    }

    @Override
    public Tuple<Collection<ExecutionLineageNode>, Collection<ChannelInstance>> evaluate(
            ChannelInstance[] inputs,
            ChannelInstance[] outputs,
            SparkExecutor sparkExecutor,
            OptimizationContext.OperatorContext operatorContext) {
        final String sourcePath;
        if (this.getInputUrl() != null) {
            assert inputs.length == 0;
            sourcePath = this.getInputUrl();
        } else {
            FileChannel.Instance input = (FileChannel.Instance) inputs[0];
            sourcePath = input.getSinglePath();
        }
        RddChannel.Instance output = (RddChannel.Instance) outputs[0];

        final String actualInputPath = FileSystems.findActualSingleInputPath(sourcePath);
        final ObjectFileSerializationMode serializationMode = this.getSerializationMode();
        final JavaPairRDD<NullWritable, BytesWritable> rawRdd =
                sparkExecutor.sc.sequenceFile(actualInputPath, NullWritable.class, BytesWritable.class);
        final Class<T> typeClass = this.getTypeClass();
        final JavaRDD<Object> rdd = rawRdd.flatMap(tuple -> {
            byte[] payload = Arrays.copyOf(tuple._2.getBytes(), tuple._2.getLength());
            try {
                return ObjectFileSerialization.deserializeChunk(payload, serializationMode, typeClass).iterator();
            } catch (IOException | ClassNotFoundException e) {
                throw new UncheckedIOException(new IOException("Failed to deserialize Spark object file chunk.", e));
            }
        });
        this.name(rdd);
        output.accept(rdd, sparkExecutor);

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

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

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

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

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

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

}
