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.calcite.adapter.csv;
  
  import org.apache.calcite.DataContext;
  import org.apache.calcite.adapter.file.CsvEnumerator;
  import org.apache.calcite.adapter.java.JavaTypeFactory;
  import org.apache.calcite.linq4j.AbstractEnumerable;
  import org.apache.calcite.linq4j.Enumerable;
  import org.apache.calcite.linq4j.Enumerator;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelProtoDataType;
  import org.apache.calcite.rex.RexCall;
  import org.apache.calcite.rex.RexInputRef;
  import org.apache.calcite.rex.RexLiteral;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.schema.FilterableTable;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.util.ImmutableIntList;
  import org.apache.calcite.util.Source;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * Table based on a CSV file that can implement simple filtering.
   *
   * <p>It implements the {@link FilterableTable} interface, so Calcite gets
   * data by calling the {@link #scan(DataContext, List)} method.
   */
  public class CsvFilterableTable extends CsvTable
      implements FilterableTable {
    /** Creates a CsvFilterableTable. */
    public CsvFilterableTable(Source source,
        @Nullable RelProtoDataType protoRowType) {
      super(source, protoRowType);
    }
  
    @Override public String toString() {
      return "CsvFilterableTable";
    }
  
    @Override public Enumerable<@Nullable Object[]> scan(DataContext root, List<RexNode> filters) {
      JavaTypeFactory typeFactory = root.getTypeFactory();
      final List<RelDataType> fieldTypes = getFieldTypes(typeFactory);
      final @Nullable String[] filterValues = new String[fieldTypes.size()];
      filters.removeIf(filter -> addFilter(filter, filterValues));
      final List<Integer> fields = ImmutableIntList.identity(fieldTypes.size());
      final AtomicBoolean cancelFlag = DataContext.Variable.CANCEL_FLAG.get(root);
      return new AbstractEnumerable<@Nullable Object[]>() {
        @Override public Enumerator<@Nullable Object[]> enumerator() {
          return new CsvEnumerator<>(source, cancelFlag, false, filterValues,
              CsvEnumerator.arrayConverter(fieldTypes, fields, false));
        }
      };
    }
  
    private static boolean addFilter(RexNode filter, @Nullable Object[] filterValues) {
      if (filter.isA(SqlKind.AND)) {
          // We cannot refine(remove) the operands of AND,
          // it will cause o.a.c.i.TableScanNode.createFilterable filters check failed.
        ((RexCall) filter).getOperands().forEach(subFilter -> addFilter(subFilter, filterValues));
      } else if (filter.isA(SqlKind.EQUALS)) {
        final RexCall call = (RexCall) filter;
        RexNode left = call.getOperands().get(0);
        if (left.isA(SqlKind.CAST)) {
          left = ((RexCall) left).operands.get(0);
        }
        final RexNode right = call.getOperands().get(1);
        if (left instanceof RexInputRef
            && right instanceof RexLiteral) {
          final int index = ((RexInputRef) left).getIndex();
          if (filterValues[index] == null) {
            filterValues[index] = ((RexLiteral) right).getValue2().toString();
            return true;
          }
        }
      }
      return false;
    }
  }
  