/*
 * Copyright 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.
 */

import type { RepeatGroupSingleModel } from '../interfaces/repeatGroup.interface';

/**
 * Get the QuestionnaireResponse index of every rendered repeating group instance, in rendered order.
 * An instance with no QuestionnaireResponse counterpart gets `null`.
 *
 * Instances that are still empty (added via "Add Item" but never filled in) hold a null `qrItem` and
 * are dropped when RepeatGroup builds its QuestionnaireResponse items, so an instance's rendered
 * index is not its index in the QuestionnaireResponse. Validation walks the QuestionnaireResponse, so
 * instance-scoped error keys must use these indices instead.
 *
 * Computed for the whole list in a single pass, so callers rendering n instances stay linear rather
 * than re-scanning the preceding instances once per instance.
 *
 * Keep this in sync with how RepeatGroup projects `repeatGroups` into `onQrRepeatGroupChange`.
 *
 * @author Clinton Gillespie
 */
export function getQrRepeatGroupInstanceIndexes(
  repeatGroups: RepeatGroupSingleModel[]
): (number | null)[] {
  let qrIndex = 0;

  return repeatGroups.map((repeatGroup) => (repeatGroup.qrItem ? qrIndex++ : null));
}