content: /*
   * Copyright © 2018-2025 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.fhirpath.function.provider;
  
  import au.csiro.pathling.fhirpath.annotations.SqlOnFhirConformance;
  import au.csiro.pathling.fhirpath.annotations.SqlOnFhirConformance.Profile;
  import au.csiro.pathling.fhirpath.collection.Collection;
  import au.csiro.pathling.fhirpath.function.FhirPathFunction;
  import jakarta.annotation.Nonnull;
  
  /**
   * Contains functions for subsetting collections.
   *
   * @author Piotr Szul
   * @author John Grimes
   * @see <a href="https://build.fhir.org/ig/HL7/FHIRPath/#subsetting">FHIRPath Specification -
   * Subsetting</a>
   */
  public class SubsettingFunctions {
  
    private SubsettingFunctions() {
    }
  
    /**
     * Returns a collection containing only the first item in the input collection. This function is
     * equivalent to {@code item[0]}, so it will return an empty collection if the input collection
     * has no items.
     *
     * @param input The input collection
     * @return A collection containing only the first item in the input collection
     * @see <a href="https://build.fhir.org/ig/HL7/FHIRPath/#first--collection">FHIRPath Specification
     * - first</a>
     */
    @FhirPathFunction
    @SqlOnFhirConformance(Profile.SHARABLE)
    @Nonnull
    public static Collection first(@Nonnull final Collection input) {
      return input.copyWith(input.getColumn().first());
    }
  
  }
  