content: /*
   * 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.arrow.driver.jdbc;
  
  import java.util.ArrayList;
  import java.util.Calendar;
  import java.util.List;
  import java.util.stream.Collectors;
  import java.util.stream.IntStream;
  import org.apache.arrow.driver.jdbc.accessor.ArrowFlightJdbcAccessorFactory;
  import org.apache.arrow.util.AutoCloseables;
  import org.apache.arrow.vector.FieldVector;
  import org.apache.arrow.vector.VectorSchemaRoot;
  import org.apache.calcite.avatica.ColumnMetaData;
  import org.apache.calcite.avatica.util.AbstractCursor;
  import org.apache.calcite.avatica.util.ArrayImpl;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /** Arrow Flight Jdbc's Cursor class. */
  public class ArrowFlightJdbcCursor extends AbstractCursor {
  
    private static final Logger LOGGER;
    private final VectorSchemaRoot root;
    private final int rowCount;
    private int currentRow = -1;
  
    static {
      LOGGER = LoggerFactory.getLogger(ArrowFlightJdbcCursor.class);
    }
  
    public ArrowFlightJdbcCursor(VectorSchemaRoot root) {
      this.root = root;
      rowCount = root.getRowCount();
    }
  
    @Override
    public List<Accessor> createAccessors(
        List<ColumnMetaData> columns, Calendar localCalendar, ArrayImpl.Factory factory) {
      final List<FieldVector> fieldVectors = root.getFieldVectors();
  
      return IntStream.range(0, fieldVectors.size())
          .mapToObj(root::getVector)
          .map(this::createAccessor)
          .collect(Collectors.toCollection(() -> new ArrayList<>(fieldVectors.size())));
    }
  
    private Accessor createAccessor(FieldVector vector) {
      return ArrowFlightJdbcAccessorFactory.createAccessor(
          vector,
          this::getCurrentRow,
          (boolean wasNull) -> {
            // AbstractCursor creates a boolean array of length 1 to hold the wasNull value
            this.wasNull[0] = wasNull;
          });
    }
  
    /**
     * ArrowFlightJdbcAccessors do not use {@link AbstractCursor.Getter}, as it would box primitive
     * types and cause performance issues. Each Accessor implementation works directly on Arrow
     * Vectors.
     */
    @Override
    protected Getter createGetter(int column) {
      throw new UnsupportedOperationException("Not allowed.");
    }
  
    @Override
    public boolean next() {
      currentRow++;
      return currentRow < rowCount;
    }
  
    @Override
    public void close() {
      try {
        AutoCloseables.close(root);
      } catch (Exception e) {
        LOGGER.error(e.getMessage(), e);
      }
    }
  
    private int getCurrentRow() {
      return currentRow;
    }
  }
  