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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.fhirpath.CalendarDurationUtils;
import au.csiro.pathling.fhirpath.encoding.QuantityEncoding;
import au.csiro.pathling.sql.udf.SqlFunction2;
import jakarta.annotation.Nonnull;
import jakarta.annotation.Nullable;
import java.math.RoundingMode;
import java.util.function.BiFunction;
import java.util.function.Function;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.types.DataType;
import org.apache.spark.sql.types.DataTypes;
import org.hl7.fhir.r4.model.BaseDateTimeType;
import org.hl7.fhir.r4.model.Quantity;

/**
 * Base class for functions that perform arithmetic on temporal values.
 *
 * @author John Grimes
 */
public abstract class TemporalArithmeticFunction implements
    SqlFunction2 {

  private static final long serialVersionUID = -5016153440496309996L;

  @Nonnull
  protected IntermediateType performAddition(@Nonnull final IntermediateType temporal,
      @Nonnull final Quantity calendarDuration) {
    return performArithmetic(temporal, calendarDuration, false);
  }

  @Nonnull
  protected IntermediateType performSubtraction(@Nonnull final IntermediateType temporal,
      @Nonnull final Quantity calendarDuration) {
    return performArithmetic(temporal, calendarDuration, true);
  }

  @Nonnull
  private IntermediateType performArithmetic(final @Nonnull IntermediateType temporal,
      final @Nonnull Quantity calendarDuration,
      final boolean subtract) {
    final int amountToAdd = calendarDuration.getValue().setScale(0, RoundingMode.HALF_UP)
        .intValue();
    final int temporalUnit = CalendarDurationUtils.getTemporalUnit(calendarDuration);

    @SuppressWarnings("unchecked")
    final IntermediateType result = (IntermediateType) temporal.copy();
    result.add(temporalUnit, subtract
                             ? -amountToAdd
                             : amountToAdd);
    return result;
  }

  protected abstract Function parseEncodedValue();

  protected abstract BiFunction getOperationFunction();

  protected abstract Function encodeResult();

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

  @Nullable
  @Override
  public String call(@Nullable final StoredType temporalValue,
      @Nullable final Row calendarDurationRow)
      throws Exception {
    if (temporalValue == null || calendarDurationRow == null) {
      return null;
    }
    final IntermediateType temporal = parseEncodedValue().apply(temporalValue);
    final Quantity calendarDuration = QuantityEncoding.decode(calendarDurationRow);
    final IntermediateType result = getOperationFunction().apply(temporal, calendarDuration);
    return encodeResult().apply(result);
  }

}