/**
 * 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.sqoop.manager.oracle;

import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

import org.apache.hadoop.conf.Configuration;

import org.apache.sqoop.lib.SqoopRecord;
import org.apache.sqoop.mapreduce.db.DBConfiguration;
import org.apache.sqoop.mapreduce.db.DBInputFormat;
import org.apache.sqoop.mapreduce.db.DBInputFormat.DBInputSplit;
import org.apache.sqoop.mapreduce.db.DataDrivenDBRecordReader;

import org.apache.sqoop.SqoopOptions;
import org.apache.sqoop.manager.oracle.OraOopConstants.
           OraOopTableImportWhereClauseLocation;
import org.apache.sqoop.manager.oracle.OraOopUtilities.OraOopStatsReports;

/*
 * NOTES:
 *
 *   T is the output-type of this record reader.
 *
 *   getFieldNames() is overridden to insert an "data_chunk_id" column
 *   containing the id (integer) of the Oracle data-chunk the data
 *   was obtained from. This is used to calculate the "percentage complete"
 *   for this mapper.
 *
 *   getSelectQuery() is overridden to inject the actual data_chunk_id number
 *   into the query that is executed (for the data-chunk being processed).
 *
 *   This class extends DBRecordReader. Unfortunately, DBRecordReader does
 *   not expose its results property (of type ResultSet), so we have to
 *   override executeQuery() in order to obtain a reference to the data
 *   obtained when the SQL generated by getSelectQuery() is executed.
 */
class OraOopDBRecordReader<T extends SqoopRecord> extends
    DataDrivenDBRecordReader<T> {

  private static final OraOopLog LOG = OraOopLogFactory
      .getLog(OraOopDBRecordReader.class);

  private OraOopDBInputSplit dbInputSplit; // <- The split this record-reader is
                                           // working on.
  private int numberOfBlocksInThisSplit; // <- The number of Oracle blocks in
                                         // this Oracle data-chunk.
  private int numberOfBlocksProcessedInThisSplit; // <- How many Oracle blocks
                                                  // we've processed with this
                                                  // record-reader.
  private String currentDataChunkId; // <- The id of the current data-chunk
                                     // being processed
  private ResultSet results; // <- The ResultSet containing the data from the
                             // query returned by getSelectQuery()
  private int columnIndexDataChunkIdZeroBased = -1; // <- The zero-based column
                                                    // index of the
                                                    // data_chunk_id column.
  private boolean progressCalculationErrorLogged; // <- Whether we've logged a
                                                  // problem with the progress
                                                  // calculation during
                                                  // nextKeyValue().
  private Object oraOopOraStats; // <- A reference to the Oracle statistics
                                 // object that is being tracked for this Oracle
                                 // session.
  private boolean profilingEnabled; // <- Whether to collect profiling metrics
  private long timeSpentInNextKeyValueInNanoSeconds; // <- Total time spent in
                                                     // super.nextKeyValue()

  public OraOopDBRecordReader(DBInputFormat.DBInputSplit split,
      Class<T> inputClass, Configuration conf, Connection conn,
      DBConfiguration dbConfig, String cond, String[] fields, String table)
      throws SQLException {

    super(split, inputClass, conf, conn, dbConfig, cond, fields, table,
        "ORACLE-ORAOOP");

    OraOopUtilities.enableDebugLoggingIfRequired(conf);

    this.dbInputSplit = castSplit(split);

    String thisOracleInstanceName =
        OraOopOracleQueries.getCurrentOracleInstanceName(conn);
    LOG.info(String.format(
        "This record reader is connected to Oracle via the JDBC URL: \n"
            + "\t\"%s\"\n" + "\tto the Oracle instance: \"%s\"", conn
            .toString(), thisOracleInstanceName));

    OracleConnectionFactory.initializeOracleConnection(conn, conf);

    if (OraOopUtilities.userWantsOracleSessionStatisticsReports(conf)) {
      this.oraOopOraStats = OraOopUtilities.startSessionSnapshot(conn);
    }

    this.numberOfBlocksInThisSplit =
        this.dbInputSplit.getTotalNumberOfBlocksInThisSplit();
    this.numberOfBlocksProcessedInThisSplit = 0;

    this.profilingEnabled = conf.getBoolean("oraoop.profiling.enabled", false);
  }

  public static OraOopDBInputSplit castSplit(DBInputSplit split) {

    // Check there's a split available...
    if (split == null) {
      throw new IllegalArgumentException("The DBInputSplit cannot be null.");
    }

    // Check that the split is the correct type...
    Class<?> desiredSplitClass = OraOopDBInputSplit.class;
    if (!(split.getClass() == desiredSplitClass)) {
      String errMsg =
          String.format("The type of Split available within %s "
              + "should be an instance of class %s, "
              + "but is actually an instance of class %s", OraOopUtilities
              .getCurrentMethodName(), desiredSplitClass.getName(), split
              .getClass().getName());
      throw new RuntimeException(errMsg);
    }

    // TODO Cast this using desiredSplitClass, so we only need 1 line of code
    // that
    // identifies the type of the split class...
    // inputSplit = (desiredSplitClass)this.getSplit();
    return (OraOopDBInputSplit) split;
  }

  @Override
  protected String[] getFieldNames() {

    String[] fieldNames = super.getFieldNames();
    ArrayList<String> result = new ArrayList<String>();

    for (int idx = 0; idx < fieldNames.length; idx++) {
      result.add(fieldNames[idx]);
    }

    result.add(OraOopConstants.COLUMN_NAME_DATA_CHUNK_ID);
    this.columnIndexDataChunkIdZeroBased = result.size() - 1;

    return result.toArray(new String[result.size()]);
  }

  @Override
  protected String getSelectQuery() {

    boolean consistentRead =
        this.getDBConf().getConf().getBoolean(
            OraOopConstants.ORAOOP_IMPORT_CONSISTENT_READ, false);
    long consistentReadScn =
        this.getDBConf().getConf().getLong(
            OraOopConstants.ORAOOP_IMPORT_CONSISTENT_READ_SCN, 0L);
    if (consistentRead && consistentReadScn == 0L) {
      throw new RuntimeException("Could not get SCN for consistent read.");
    }

    StringBuilder query = new StringBuilder();

    if (this.dbInputSplit.getDataChunks() == null) {
      String errMsg =
          String.format("The %s does not contain any data-chunks, within %s.",
              this.dbInputSplit.getClass().getName(), OraOopUtilities
                  .getCurrentMethodName());
      throw new RuntimeException(errMsg);
    }

    OraOopConstants.OraOopTableImportWhereClauseLocation whereClauseLocation =
        OraOopUtilities.getOraOopTableImportWhereClauseLocation(this
            .getDBConf().getConf(),
            OraOopConstants.OraOopTableImportWhereClauseLocation.SUBSPLIT);

    OracleTable tableContext = getOracleTableContext();
    OracleTableColumns tableColumns = null;
    try {

      Configuration conf = this.getDBConf().getConf();

      tableColumns =
          OraOopOracleQueries.getTableColumns(getConnection(), tableContext,
              OraOopUtilities.omitLobAndLongColumnsDuringImport(conf),
              OraOopUtilities.recallSqoopJobType(conf)
              , true // <- onlyOraOopSupportedTypes
              , true // <- omitOraOopPseudoColumns
              , OracleUtils.isOracleEscapingDisabled(conf)
          );
    } catch (SQLException ex) {
      LOG.error(String.format(
          "Unable to obtain the data-types of the columns in table %s.\n"
              + "Error:\n%s", tableContext.toString(), ex.getMessage()));
      throw new RuntimeException(ex);
    }

    int numberOfDataChunks = this.dbInputSplit.getNumberOfDataChunks();
    for (int idx = 0; idx < numberOfDataChunks; idx++) {

      OraOopOracleDataChunk dataChunk =
          this.dbInputSplit.getDataChunks().get(idx);

      if (idx > 0) {
        query.append("UNION ALL \n");
      }

      query.append(getColumnNamesClause(tableColumns, dataChunk.getId())) // <-
                                                                     // SELECT
                                                                     // clause
          .append("\n");

      query.append(" FROM ").append(this.getTableName()).append(" ");

      if (consistentRead) {
        query.append("AS OF SCN ").append(consistentReadScn).append(" ");
      }

      query.append(getPartitionClauseForDataChunk(this.dbInputSplit, idx))
          .append(" t").append("\n");

      query.append(" WHERE (").append(
          getWhereClauseForDataChunk(this.dbInputSplit, idx)).append(")\n");

      // If the user wants the WHERE clause applied to each data-chunk...
      if (whereClauseLocation
              == OraOopTableImportWhereClauseLocation.SUBSPLIT) {
        String conditions = this.getConditions();
        if (conditions != null && conditions.length() > 0) {
          query.append(" AND (").append(conditions).append(")\n");
        }
      }

    }

    // If the user wants the WHERE clause applied to the whole split...
    if (whereClauseLocation == OraOopTableImportWhereClauseLocation.SPLIT) {
      String conditions = this.getConditions();
      if (conditions != null && conditions.length() > 0) {

        // Insert a "select everything" line at the start of the SQL query...
        query.insert(0, getColumnNamesClause(tableColumns, null) + " FROM (\n");

        // ...and then apply the WHERE clause to all the UNIONed sub-queries...
        query.append(")\n").append("WHERE\n").append(conditions).append("\n");
      }
    }

    LOG.info("SELECT QUERY = \n" + query.toString());

    return query.toString();
  }

  private String getColumnNamesClause(OracleTableColumns tableColumns,
      String dataChunkId) {

    StringBuilder result = new StringBuilder();

    result.append("SELECT ");
    result.append(OraOopUtilities.getImportHint(this.getDBConf().getConf()));

    String[] fieldNames = this.getFieldNames();

    int firstFieldIndex = 0;
    int lastFieldIndex = fieldNames.length - 1;
    for (int i = firstFieldIndex; i <= lastFieldIndex; i++) {
      if (i > firstFieldIndex) {
        result.append(",");
      }
      String fieldName = fieldNames[i];

      String unescapedFieldName = fieldName;
      if (fieldName.charAt(0) == '"' && fieldName.charAt(fieldName.length() - 1) == '"') {
        unescapedFieldName = fieldName.substring(1, fieldName.length() - 1);
      }

      OracleTableColumn oracleTableColumn =
          tableColumns.findColumnByName(unescapedFieldName);
      if (oracleTableColumn != null) {
        if (oracleTableColumn.getDataType().equals(
            OraOopConstants.Oracle.URITYPE)) {
          fieldName = String.format("uritype.geturl(%s)", fieldName);
        }
      }

      // If this field is the "data_chunk_id" that we inserted during
      // getFields()
      // then we need to insert the value of that data_chunk_id now...
      if (i == this.columnIndexDataChunkIdZeroBased
          && fieldName == OraOopConstants.COLUMN_NAME_DATA_CHUNK_ID) {
        if (dataChunkId != null && !dataChunkId.isEmpty()) {
          fieldName =
              String.format("'%s' %s", dataChunkId,
                  OraOopConstants.COLUMN_NAME_DATA_CHUNK_ID);
        }
      }

      result.append(fieldName);
    }
    return result.toString();
  }

  private String getPartitionClauseForDataChunk(OraOopDBInputSplit split,
      int dataChunkIndex) {
    OraOopOracleDataChunk dataChunk = split.getDataChunks().get(dataChunkIndex);
    return dataChunk.getPartitionClause();
  }

  private String getWhereClauseForDataChunk(OraOopDBInputSplit split,
      int dataChunkIndex) {

    OraOopOracleDataChunk dataChunk = split.getDataChunks().get(dataChunkIndex);
    return dataChunk.getWhereClause();
  }

  /** {@inheritDoc} */
  @Override
  public long getPos() throws IOException {

    // This split contains multiple data-chunks.
    // Each data-chunk contains multiple blocks.
    // Return the number of blocks that have been processed by this split...
    return numberOfBlocksProcessedInThisSplit;
  }

  /** {@inheritDoc} */
  @Override
  public float getProgress() throws IOException {

    return numberOfBlocksProcessedInThisSplit
        / (float) numberOfBlocksInThisSplit;
  }

  @Override
  public boolean nextKeyValue() throws IOException {

    boolean result = false;
    try {

      long startTime = 0;
      if (this.profilingEnabled) {
        startTime = System.nanoTime();
      }

      result = super.nextKeyValue();

      if (this.profilingEnabled) {
        this.timeSpentInNextKeyValueInNanoSeconds +=
            System.nanoTime() - startTime;
      }

      // Keep track of which data-chunk we're processing, and therefore how many
      // Oracle blocks we've processed. This can be used to calculate our
      // "percentage complete"...
      if (result && this.results != null) {

        String thisDataChunkId = null;
        try {
          // ColumnIndexes are 1-based in jdbc...
          thisDataChunkId =
              this.results.getString(this.columnIndexDataChunkIdZeroBased + 1);
        } catch (SQLException ex) {
          if (!progressCalculationErrorLogged) {
            // This prevents us from flooding the log with the same message
            // thousands of times...
            progressCalculationErrorLogged = true;

            LOG.warn(String
                .format(
                  "Unable to obtain the value of the %s column in method %s.\n"
                      + "\tthis.columnIndexDataChunkIdZeroBased = %d (NB: "
                      + "jdbc field indexes are 1-based)\n\tAs a consequence, "
                      + "progress for the record-reader cannot be calculated.\n"
                      + "\tError=\n%s",
                  OraOopConstants.COLUMN_NAME_DATA_CHUNK_ID, OraOopUtilities
                      .getCurrentMethodName(),
                  this.columnIndexDataChunkIdZeroBased, ex.getMessage()));
          }
        }

        if (thisDataChunkId != null
            && !thisDataChunkId.equals(this.currentDataChunkId)) {
          if (this.currentDataChunkId != null
              && !this.currentDataChunkId.isEmpty()) {
            OraOopOracleDataChunk dataChunk =
                this.dbInputSplit.findDataChunkById(thisDataChunkId);
            if (dataChunk != null) {
              this.numberOfBlocksProcessedInThisSplit +=
                  dataChunk.getNumberOfBlocks();
            }
          }
          this.currentDataChunkId = thisDataChunkId;
        }
      }
    } catch (IOException ex) {
      if (OraOopUtilities.oracleSessionHasBeenKilled(ex)) {
        LOG.info("\n*********************************************************"
            + "\nThe Oracle session in use has been killed by a 3rd party."
            + "\n*********************************************************");
      }
      throw ex;
    }

    return result;
  }

  @Override
  protected ResultSet executeQuery(String query) throws SQLException {

    try {
      this.results = super.executeQuery(query);
      return this.results;
    } catch (SQLException ex) {
      LOG.error(String.format("Error in %s while executing the SQL query:\n"
          + "%s\n\n" + "%s", OraOopUtilities.getCurrentMethodName(), query, ex
          .getMessage()));
      throw ex;
    }
  }

  @Override
  public void close() throws IOException {

    if (this.profilingEnabled) {
      LOG.info(String.format(
          "Time spent in super.nextKeyValue() = %s seconds.",
          this.timeSpentInNextKeyValueInNanoSeconds / Math.pow(10, 9)));
    }

    if (OraOopUtilities.userWantsOracleSessionStatisticsReports(getDBConf()
        .getConf())) {
      OraOopStatsReports reports =
          OraOopUtilities.stopSessionSnapshot(this.oraOopOraStats);
      this.oraOopOraStats = null;

      LOG.info(String.format("Oracle Statistics Report for OraOop:\n\n%s",
          reports.getPerformanceReport()));

      String fileName =
          String.format("oracle-stats-csv-%d", this.dbInputSplit.getSplitId());
      OraOopUtilities.writeOutputFile(this.getDBConf().getConf(), fileName,
          reports.getCsvReport());

      fileName =
          String.format("oracle-stats-%d", this.dbInputSplit.getSplitId());
      OraOopUtilities.writeOutputFile(this.getDBConf().getConf(), fileName,
          reports.getPerformanceReport());
    }

    super.close();
  }

  public OracleTable getOracleTableContext() {

    Configuration conf = this.getDBConf().getConf();
    OracleTable result =
        new OracleTable(conf.get(OraOopConstants.ORAOOP_TABLE_OWNER), conf
            .get(OraOopConstants.ORAOOP_TABLE_NAME));
    return result;
  }

}