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A library that can translate FHIRPath expressions into Spark queries.

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/*
 * Copyright 2023 Commonwealth Scientific and Industrial Research
 * Organisation (CSIRO) ABN 41 687 119 230.
 *
 * Licensed 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 au.csiro.pathling.sql.dates;

import au.csiro.pathling.sql.udf.SqlFunction2;
import jakarta.annotation.Nonnull;
import jakarta.annotation.Nullable;
import org.apache.spark.sql.types.DataType;
import org.apache.spark.sql.types.DataTypes;

/**
 * Base class for functions that compare temporal values.
 *
 * @author John Grimes
 */
public abstract class TemporalComparisonFunction implements
    SqlFunction2 {

  private static final long serialVersionUID = 492467651418666881L;

  @Nullable
  protected abstract IntermediateType parseEncodedValue(StoredType value);

  @Nullable
  protected abstract Boolean compare(@Nonnull IntermediateType left,
      @Nonnull IntermediateType right);

  @Override
  public DataType getReturnType() {
    return DataTypes.BooleanType;
  }

  @Nullable
  @Override
  public Boolean call(@Nullable final StoredType left, @Nullable final StoredType right)
      throws Exception {
    if (left == null || right == null) {
      return null;
    }
    final IntermediateType parsedLeft = parseEncodedValue(left);
    final IntermediateType parsedRight = parseEncodedValue(right);

    if (parsedLeft == null || parsedRight == null) {
      // If the result of parsing either argument is null, then the result is null.
      return null;
    }

    return compare(parsedLeft, parsedRight);
  }

}