/**
 * 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.drivers;

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

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.mapreduce.InputFormat;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.pig.LoadCaster;
import org.apache.pig.LoadFunc;
import org.apache.pig.LoadMetadata;
import org.apache.pig.ResourceSchema;
import org.apache.pig.ResourceSchema.ResourceFieldSchema;
import org.apache.pig.data.DataByteArray;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;

/**
 * based on {@link org.apache.pig.builtin.PigStorage}
 */
public class LoadFuncBasedInputFormat extends InputFormat<BytesWritable, Tuple> {

    private final LoadFunc loadFunc;
    private static ResourceFieldSchema[] fields;

    public LoadFuncBasedInputFormat(LoadFunc loadFunc, ResourceSchema dataSchema, String location, Configuration conf) throws IOException {

        this.loadFunc = loadFunc;
        fields = dataSchema.getFields();

        // Simulate the frontend call sequence for LoadFunc, in case LoadFunc need to store something into UDFContext (as JsonLoader does)
        if (loadFunc instanceof LoadMetadata) {
            ((LoadMetadata) loadFunc).getSchema(location, new Job(conf));
        }
    }

    @Override
    public RecordReader<BytesWritable, Tuple> createRecordReader(
        InputSplit split, TaskAttemptContext taskContext) throws IOException,
        InterruptedException {
        RecordReader<BytesWritable, Tuple> reader = loadFunc.getInputFormat().createRecordReader(split, taskContext);
        return new LoadFuncBasedRecordReader(reader, loadFunc);
    }

    @Override
    public List<InputSplit> getSplits(JobContext jobContext) throws IOException,
        InterruptedException {
        try {
            InputFormat<BytesWritable, Tuple> inpFormat = loadFunc.getInputFormat();
            return inpFormat.getSplits(jobContext);

        } catch (InterruptedException e) {
            throw new IOException(e);
        }
    }

    static class LoadFuncBasedRecordReader extends RecordReader<BytesWritable, Tuple> {

        private Tuple tupleFromDisk;
        private final RecordReader<BytesWritable, Tuple> reader;
        private final LoadFunc loadFunc;
        private final LoadCaster caster;

        /**
         * @param reader
         * @param loadFunc
         * @throws IOException
         */
        public LoadFuncBasedRecordReader(RecordReader<BytesWritable, Tuple> reader, LoadFunc loadFunc) throws IOException {
            this.reader = reader;
            this.loadFunc = loadFunc;
            this.caster = loadFunc.getLoadCaster();
        }

        @Override
        public void close() throws IOException {
            reader.close();
        }

        @Override
        public BytesWritable getCurrentKey() throws IOException,
            InterruptedException {
            return null;
        }

        @Override
        public Tuple getCurrentValue() throws IOException, InterruptedException {

            for (int i = 0; i < tupleFromDisk.size(); i++) {

                Object data = tupleFromDisk.get(i);

                // We will do conversion for bytes only for now
                if (data instanceof DataByteArray) {

                    DataByteArray dba = (DataByteArray) data;

                    if (dba == null) {
                        // PigStorage will insert nulls for empty fields.
                        tupleFromDisk.set(i, null);
                        continue;
                    }

                    switch (fields[i].getType()) {

                    case DataType.CHARARRAY:
                        tupleFromDisk.set(i, caster.bytesToCharArray(dba.get()));
                        break;

                    case DataType.INTEGER:
                        tupleFromDisk.set(i, caster.bytesToInteger(dba.get()));
                        break;

                    case DataType.FLOAT:
                        tupleFromDisk.set(i, caster.bytesToFloat(dba.get()));
                        break;

                    case DataType.LONG:
                        tupleFromDisk.set(i, caster.bytesToLong(dba.get()));
                        break;

                    case DataType.DOUBLE:
                        tupleFromDisk.set(i, caster.bytesToDouble(dba.get()));
                        break;

                    case DataType.MAP:
                        tupleFromDisk.set(i, caster.bytesToMap(dba.get()));
                        break;

                    case DataType.BAG:
                        tupleFromDisk.set(i, caster.bytesToBag(dba.get(), fields[i]));
                        break;

                    case DataType.TUPLE:
                        tupleFromDisk.set(i, caster.bytesToTuple(dba.get(), fields[i]));
                        break;

                    default:
                        throw new IOException("Unknown Pig type in data: " + fields[i].getType());
                    }
                }
            }

            return tupleFromDisk;
        }


        @Override
        public void initialize(InputSplit split, TaskAttemptContext ctx)
            throws IOException, InterruptedException {

            reader.initialize(split, ctx);
            loadFunc.prepareToRead(reader, null);
        }

        @Override
        public boolean nextKeyValue() throws IOException, InterruptedException {

            // even if we don't need any data from disk, we will need to call
            // getNext() on pigStorage() so we know how many rows to emit in our
            // final output - getNext() will eventually return null when it has
            // read all disk data and we will know to stop emitting final output
            tupleFromDisk = loadFunc.getNext();
            return tupleFromDisk != null;
        }

        @Override
        public float getProgress() throws IOException, InterruptedException {
            return 0;
        }

    }
}