/*
 * 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.phoenix.hive.mapreduce;

import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.InputSplit;
import org.apache.hadoop.mapred.RecordReader;
import org.apache.hadoop.mapreduce.lib.db.DBWritable;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.phoenix.compile.QueryPlan;
import org.apache.phoenix.compile.StatementContext;
import org.apache.phoenix.coprocessor.BaseScannerRegionObserver;
import org.apache.phoenix.hive.PhoenixRowKey;
import org.apache.phoenix.hive.util.PhoenixStorageHandlerUtil;
import org.apache.phoenix.iterate.ConcatResultIterator;
import org.apache.phoenix.iterate.LookAheadResultIterator;
import org.apache.phoenix.iterate.MapReduceParallelScanGrouper;
import org.apache.phoenix.iterate.PeekingResultIterator;
import org.apache.phoenix.iterate.ResultIterator;
import org.apache.phoenix.iterate.RoundRobinResultIterator;
import org.apache.phoenix.iterate.SequenceResultIterator;
import org.apache.phoenix.iterate.TableResultIterator;
import org.apache.phoenix.jdbc.PhoenixResultSet;
import org.apache.phoenix.monitoring.ReadMetricQueue;
import org.apache.phoenix.monitoring.ScanMetricsHolder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.phoenix.thirdparty.com.google.common.base.Throwables;

/**
 * RecordReader implementation that iterates over the the records.
 */
@SuppressWarnings("rawtypes")
public class PhoenixRecordReader<T extends DBWritable> implements
        RecordReader<WritableComparable, T> {

    private static final Logger LOG = LoggerFactory.getLogger(PhoenixRecordReader.class);

    private final Configuration configuration;
    private final QueryPlan queryPlan;
    private WritableComparable key;
    private T value = null;
    private Class<T> inputClass;
    private ResultIterator resultIterator = null;
    private PhoenixResultSet resultSet;
    private long readCount;


    private boolean isTransactional;

    public PhoenixRecordReader(Class<T> inputClass, final Configuration configuration, final
    QueryPlan queryPlan) throws IOException {
        this.inputClass = inputClass;
        this.configuration = configuration;
        this.queryPlan = queryPlan;

        isTransactional = PhoenixStorageHandlerUtil.isTransactionalTable(configuration);
    }

    public void initialize(InputSplit split) throws IOException {
        final PhoenixInputSplit pSplit = (PhoenixInputSplit) split;
        final List<Scan> scans = pSplit.getScans();

        if (LOG.isInfoEnabled()) {
            LOG.info("Target table : " + queryPlan.getTableRef().getTable().getPhysicalName());
        }

        if (LOG.isDebugEnabled()) {
            LOG.debug("Scan count[" + scans.size() + "] : " + Bytes.toStringBinary(scans.get(0)
                    .getStartRow()) + " ~ " + Bytes.toStringBinary(scans.get(scans.size() - 1)
                    .getStopRow()));
            LOG.debug("First scan : " + scans.get(0) + " scanAttribute : " + scans.get(0)
                    .getAttributesMap());

            for (int i = 0, limit = scans.size(); i < limit; i++) {
                LOG.debug("EXPECTED_UPPER_REGION_KEY[" + i + "] : " +
                        Bytes.toStringBinary(scans.get(i).getAttribute(BaseScannerRegionObserver
                                .EXPECTED_UPPER_REGION_KEY)));
            }
        }

        try {
            List<PeekingResultIterator> iterators = new ArrayList<>(scans.size
                    ());
            StatementContext ctx = queryPlan.getContext();
            ReadMetricQueue readMetrics = ctx.getReadMetricsQueue();
            String tableName = queryPlan.getTableRef().getTable().getPhysicalName().getString();
            long renewScannerLeaseThreshold = queryPlan.getContext().getConnection()
                    .getQueryServices().getRenewLeaseThresholdMilliSeconds();
            for (Scan scan : scans) {
                scan.setAttribute(BaseScannerRegionObserver.SKIP_REGION_BOUNDARY_CHECK, Bytes
                        .toBytes(true));
                ScanMetricsHolder scanMetricsHolder = ScanMetricsHolder.getInstance(readMetrics, tableName, scan, ctx.getConnection().getLogLevel());
                final TableResultIterator tableResultIterator = new TableResultIterator(
                        queryPlan.getContext().getConnection().getMutationState(), scan, scanMetricsHolder,
                        renewScannerLeaseThreshold, queryPlan, MapReduceParallelScanGrouper.getInstance());

                PeekingResultIterator peekingResultIterator = LookAheadResultIterator.wrap
                        (tableResultIterator);
                iterators.add(peekingResultIterator);
            }
            ResultIterator iterator = queryPlan.useRoundRobinIterator()
                    ? RoundRobinResultIterator.newIterator(iterators, queryPlan)
                    : ConcatResultIterator.newIterator(iterators);
            if (queryPlan.getContext().getSequenceManager().getSequenceCount() > 0) {
                iterator = new SequenceResultIterator(iterator, queryPlan.getContext()
                        .getSequenceManager());
            }
            this.resultIterator = iterator;
            // Clone the row projector as it's not thread safe and would be used
            // simultaneously by multiple threads otherwise.
            this.resultSet = new PhoenixResultSet(this.resultIterator, queryPlan.getProjector()
                    .cloneIfNecessary(),
                    queryPlan.getContext());
        } catch (SQLException e) {
            LOG.error(String.format(" Error [%s] initializing PhoenixRecordReader. ", e
                    .getMessage()));
            Throwables.propagate(e);
        }
    }

    @Override
    public boolean next(WritableComparable key, T value) throws IOException {
        try {
            if (!resultSet.next()) {
                return false;
            }
            value.readFields(resultSet);

            if (isTransactional) {
                ((PhoenixResultWritable) value).readPrimaryKey((PhoenixRowKey) key);
            }

            ++readCount;

            if (LOG.isTraceEnabled()) {
                LOG.trace("Result[" + readCount + "] : " + ((PhoenixResultWritable) value)
                        .getResultMap());
            }

            return true;
        } catch (SQLException e) {
            LOG.error(String.format(" Error [%s] occurred while iterating over the resultset. ",
                    e.getMessage()));
            throw new RuntimeException(e);
        }
    }

    @Override
    public WritableComparable createKey() {
        if (isTransactional) {
            key = new PhoenixRowKey();
        } else {
            key = NullWritable.get();
        }

        return key;
    }

    @Override
    public T createValue() {
        value = ReflectionUtils.newInstance(inputClass, this.configuration);
        return value;
    }

    @Override
    public long getPos() throws IOException {
        return 0;
    }

    @Override
    public void close() throws IOException {
        if (LOG.isInfoEnabled()) {
            LOG.info("Read Count : " + readCount);
        }

        if (resultIterator != null) {
            try {
                resultIterator.close();
            } catch (SQLException e) {
                LOG.error(" Error closing resultset.");
                throw new RuntimeException(e);
            }
        }

    }

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