/**
    * 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.hadoop.hbase.mapreduce;
  
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HRegionLocation;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.Connection;
  import org.apache.hadoop.hbase.client.ConnectionFactory;
  import org.apache.hadoop.hbase.client.RegionLocator;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.client.Table;
  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.Pair;
  import org.apache.hadoop.hbase.util.RegionSizeCalculator;
  import org.apache.hadoop.mapreduce.InputFormat;
  import org.apache.hadoop.mapreduce.InputSplit;
  import org.apache.hadoop.mapreduce.JobContext;
  import org.apache.hadoop.mapreduce.RecordReader;
  import org.apache.hadoop.mapreduce.TaskAttemptContext;
  
  import java.util.Map;
  import java.util.HashMap;
  import java.util.Iterator;
  /**
   * A base for {@link MultiTableInputFormat}s. Receives a list of
   * {@link Scan} instances that define the input tables and
   * filters etc. Subclasses may use other TableRecordReader implementations.
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public abstract class MultiTableInputFormatBase extends
      InputFormat<ImmutableBytesWritable, Result> {
  
    private static final Log LOG = LogFactory.getLog(MultiTableInputFormatBase.class);
  
    /** Holds the set of scans used to define the input. */
    private List<Scan> scans;
  
    /** The reader scanning the table, can be a custom one. */
    private TableRecordReader tableRecordReader = null;
  
    /**
     * Builds a TableRecordReader. If no TableRecordReader was provided, uses the
     * default.
     *
     * @param split The split to work with.
     * @param context The current context.
     * @return The newly created record reader.
     * @throws IOException When creating the reader fails.
     * @throws InterruptedException when record reader initialization fails
     * @see org.apache.hadoop.mapreduce.InputFormat#createRecordReader(
     *      org.apache.hadoop.mapreduce.InputSplit,
     *      org.apache.hadoop.mapreduce.TaskAttemptContext)
     */
    @Override
    public RecordReader<ImmutableBytesWritable, Result> createRecordReader(
        InputSplit split, TaskAttemptContext context)
        throws IOException, InterruptedException {
      TableSplit tSplit = (TableSplit) split;
      LOG.info(MessageFormat.format("Input split length: {0} bytes.", tSplit.getLength()));
  
      if (tSplit.getTable() == null) {
        throw new IOException("Cannot create a record reader because of a"
            + " previous error. Please look at the previous logs lines from"
            + " the task's full log for more details.");
      }
      final Connection connection = ConnectionFactory.createConnection(context.getConfiguration());
      Table table = connection.getTable(tSplit.getTable());
  
      if (this.tableRecordReader == null) {
        this.tableRecordReader = new TableRecordReader();
      }
     final TableRecordReader trr = this.tableRecordReader;
 
     try {
       Scan sc = tSplit.getScan();
       sc.setStartRow(tSplit.getStartRow());
       sc.setStopRow(tSplit.getEndRow());
       trr.setScan(sc);
       trr.setTable(table);
       return new RecordReader<ImmutableBytesWritable, Result>() {
 
         @Override
         public void close() throws IOException {
           trr.close();
           connection.close();
         }
 
         @Override
         public ImmutableBytesWritable getCurrentKey() throws IOException, InterruptedException {
           return trr.getCurrentKey();
         }
 
         @Override
         public Result getCurrentValue() throws IOException, InterruptedException {
           return trr.getCurrentValue();
         }
 
         @Override
         public float getProgress() throws IOException, InterruptedException {
           return trr.getProgress();
         }
 
         @Override
         public void initialize(InputSplit inputsplit, TaskAttemptContext context)
             throws IOException, InterruptedException {
           trr.initialize(inputsplit, context);
         }
 
         @Override
         public boolean nextKeyValue() throws IOException, InterruptedException {
           return trr.nextKeyValue();
         }
       };
     } catch (IOException ioe) {
       // If there is an exception make sure that all
       // resources are closed and released.
       trr.close();
       connection.close();
       throw ioe;
     }
   }
 
   /**
    * Calculates the splits that will serve as input for the map tasks. The
    * number of splits matches the number of regions in a table.
    *
    * @param context The current job context.
    * @return The list of input splits.
    * @throws IOException When creating the list of splits fails.
    * @see org.apache.hadoop.mapreduce.InputFormat#getSplits(org.apache.hadoop.mapreduce.JobContext)
    */
   @Override
   public List<InputSplit> getSplits(JobContext context) throws IOException {
     if (scans.isEmpty()) {
       throw new IOException("No scans were provided.");
     }
 
     Map<TableName, List<Scan>> tableMaps = new HashMap<TableName, List<Scan>>();
     for (Scan scan : scans) {
       byte[] tableNameBytes = scan.getAttribute(Scan.SCAN_ATTRIBUTES_TABLE_NAME);
       if (tableNameBytes == null)
         throw new IOException("A scan object did not have a table name");
 
       TableName tableName = TableName.valueOf(tableNameBytes);
 
       List<Scan> scanList = tableMaps.get(tableName);
       if (scanList == null) {
         scanList = new ArrayList<Scan>();
         tableMaps.put(tableName, scanList);
       }
       scanList.add(scan);
     }
 
     List<InputSplit> splits = new ArrayList<InputSplit>();
     Iterator iter = tableMaps.entrySet().iterator();
     // Make a single Connection to the Cluster and use it across all tables.
     try (Connection conn = ConnectionFactory.createConnection(context.getConfiguration())) {
       while (iter.hasNext()) {
         Map.Entry<TableName, List<Scan>> entry = (Map.Entry<TableName, List<Scan>>) iter.next();
         TableName tableName = entry.getKey();
         List<Scan> scanList = entry.getValue();
 
         try (Table table = conn.getTable(tableName);
              RegionLocator regionLocator = conn.getRegionLocator(tableName)) {
           RegionSizeCalculator sizeCalculator = new RegionSizeCalculator(
                   regionLocator, conn.getAdmin());
           Pair<byte[][], byte[][]> keys = regionLocator.getStartEndKeys();
           for (Scan scan : scanList) {
             if (keys == null || keys.getFirst() == null || keys.getFirst().length == 0) {
               throw new IOException("Expecting at least one region for table : "
                       + tableName.getNameAsString());
             }
             int count = 0;
 
             byte[] startRow = scan.getStartRow();
             byte[] stopRow = scan.getStopRow();
 
             for (int i = 0; i < keys.getFirst().length; i++) {
               if (!includeRegionInSplit(keys.getFirst()[i], keys.getSecond()[i])) {
                 continue;
               }
 
               if ((startRow.length == 0 || keys.getSecond()[i].length == 0 ||
                       Bytes.compareTo(startRow, keys.getSecond()[i]) < 0) &&
                       (stopRow.length == 0 || Bytes.compareTo(stopRow,
                               keys.getFirst()[i]) > 0)) {
                 byte[] splitStart = startRow.length == 0 ||
                         Bytes.compareTo(keys.getFirst()[i], startRow) >= 0 ?
                         keys.getFirst()[i] : startRow;
                 byte[] splitStop = (stopRow.length == 0 ||
                         Bytes.compareTo(keys.getSecond()[i], stopRow) <= 0) &&
                         keys.getSecond()[i].length > 0 ?
                         keys.getSecond()[i] : stopRow;
 
                 HRegionLocation hregionLocation = regionLocator.getRegionLocation(
                         keys.getFirst()[i], false);
                 String regionHostname = hregionLocation.getHostname();
                 HRegionInfo regionInfo = hregionLocation.getRegionInfo();
                 long regionSize = sizeCalculator.getRegionSize(
                         regionInfo.getRegionName());
 
                 TableSplit split = new TableSplit(table.getName(),
                         scan, splitStart, splitStop, regionHostname, regionSize);
 
                 splits.add(split);
 
                 if (LOG.isDebugEnabled()) {
                   LOG.debug("getSplits: split -> " + (count++) + " -> " + split);
                 }
               }
             }
           }
         }
       }
     }
 
     return splits;
   }
 
   /**
    * Test if the given region is to be included in the InputSplit while
    * splitting the regions of a table.
    * <p>
    * This optimization is effective when there is a specific reasoning to
    * exclude an entire region from the M-R job, (and hence, not contributing to
    * the InputSplit), given the start and end keys of the same. <br>
    * Useful when we need to remember the last-processed top record and revisit
    * the [last, current) interval for M-R processing, continuously. In addition
    * to reducing InputSplits, reduces the load on the region server as well, due
    * to the ordering of the keys. <br>
    * <br>
    * Note: It is possible that <code>endKey.length() == 0 </code> , for the last
    * (recent) region. <br>
    * Override this method, if you want to bulk exclude regions altogether from
    * M-R. By default, no region is excluded( i.e. all regions are included).
    *
    * @param startKey Start key of the region
    * @param endKey End key of the region
    * @return true, if this region needs to be included as part of the input
    *         (default).
    */
   protected boolean includeRegionInSplit(final byte[] startKey,
       final byte[] endKey) {
     return true;
   }
 
   /**
    * Allows subclasses to get the list of {@link Scan} objects.
    */
   protected List<Scan> getScans() {
     return this.scans;
   }
 
   /**
    * Allows subclasses to set the list of {@link Scan} objects.
    *
    * @param scans The list of {@link Scan} used to define the input
    */
   protected void setScans(List<Scan> scans) {
     this.scans = scans;
   }
 
   /**
    * Allows subclasses to set the {@link TableRecordReader}.
    *
    * @param tableRecordReader A different {@link TableRecordReader}
    *          implementation.
    */
   protected void setTableRecordReader(TableRecordReader tableRecordReader) {
     this.tableRecordReader = tableRecordReader;
   }
 }