/**
 * 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.hcatalog.pig;

import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.Properties;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hcatalog.data.HCatRecord;
import org.apache.hcatalog.data.schema.HCatSchema;
import org.apache.hcatalog.mapreduce.InputJobInfo;
import org.apache.hcatalog.mapreduce.PartInfo;
import org.apache.pig.LoadFunc;
import org.apache.pig.LoadMetadata;
import org.apache.pig.LoadPushDown;
import org.apache.pig.PigException;
import org.apache.pig.ResourceStatistics;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigSplit;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.impl.util.UDFContext;

/**
 * Base class for HCatLoader and HCatEximLoader
 */

public abstract class HCatBaseLoader extends LoadFunc implements LoadMetadata, LoadPushDown {

    protected static final String PRUNE_PROJECTION_INFO = "prune.projection.info";

    private RecordReader<?, ?> reader;
    protected String signature;

    HCatSchema outputSchema = null;


    @Override
    public Tuple getNext() throws IOException {
        try {
            HCatRecord hr = (HCatRecord) (reader.nextKeyValue() ? reader.getCurrentValue() : null);
            Tuple t = PigHCatUtil.transformToTuple(hr, outputSchema);
            // TODO : we were discussing an iter interface, and also a LazyTuple
            // change this when plans for that solidifies.
            return t;
        } catch (ExecException e) {
            int errCode = 6018;
            String errMsg = "Error while reading input";
            throw new ExecException(errMsg, errCode,
                PigException.REMOTE_ENVIRONMENT, e);
        } catch (Exception eOther) {
            int errCode = 6018;
            String errMsg = "Error converting read value to tuple";
            throw new ExecException(errMsg, errCode,
                PigException.REMOTE_ENVIRONMENT, eOther);
        }

    }

    @Override
    public void prepareToRead(RecordReader reader, PigSplit arg1) throws IOException {
        this.reader = reader;
    }

    @Override
    public ResourceStatistics getStatistics(String location, Job job) throws IOException {
        // statistics not implemented currently
        return null;
    }

    @Override
    public List<OperatorSet> getFeatures() {
        return Arrays.asList(LoadPushDown.OperatorSet.PROJECTION);
    }

    @Override
    public RequiredFieldResponse pushProjection(RequiredFieldList requiredFieldsInfo) throws FrontendException {
        // Store the required fields information in the UDFContext so that we
        // can retrieve it later.
        storeInUDFContext(signature, PRUNE_PROJECTION_INFO, requiredFieldsInfo);

        // HCat will always prune columns based on what we ask of it - so the
        // response is true
        return new RequiredFieldResponse(true);
    }

    @Override
    public void setUDFContextSignature(String signature) {
        this.signature = signature;
    }


    // helper methods
    protected void storeInUDFContext(String signature, String key, Object value) {
        UDFContext udfContext = UDFContext.getUDFContext();
        Properties props = udfContext.getUDFProperties(
            this.getClass(), new String[]{signature});
        props.put(key, value);
    }

    /**
     * A utility method to get the size of inputs. This is accomplished by summing the
     * size of all input paths on supported FileSystems. Locations whose size cannot be
     * determined are ignored. Note non-FileSystem and unpartitioned locations will not
     * report their input size by default.
     */
    protected static long getSizeInBytes(InputJobInfo inputJobInfo) throws IOException {
        Configuration conf = new Configuration();
        long sizeInBytes = 0;

        for (PartInfo partInfo : inputJobInfo.getPartitions()) {
            try {
                Path p = new Path(partInfo.getLocation());
                if (p.getFileSystem(conf).isFile(p)) {
                    sizeInBytes += p.getFileSystem(conf).getFileStatus(p).getLen();
                } else {
                    for (FileStatus child : p.getFileSystem(conf).listStatus(p)) {
                        sizeInBytes += child.getLen();
                    }
                }
            } catch (IOException e) {
                // Report size to the extent possible.
            }
        }

        return sizeInBytes;
    }
}