import type { FieldValues, Path, UseFormSetValue } from 'react-hook-form';

type Groups = Record<string, Record<string, unknown>>;

/** The dotted paths of a section's fields: in the form, with a default, and placed there by `belongs`. */
export const sectionFields = (
  formValues: object,
  formDefaults: object,
  belongs: (path: string) => boolean
): { path: string; value: unknown }[] => {
  const values = formValues as Groups;
  const defaults = formDefaults as Groups;
  const fields: { path: string; value: unknown }[] = [];
  for (const [group, entries] of Object.entries(defaults)) {
    for (const [key, value] of Object.entries(entries)) {
      const path = `${group}.${key}`;
      if (belongs(path) && values[group] && key in values[group]) {
        fields.push({ path, value });
      }
    }
  }
  return fields;
};

/**
 * Puts the defaults back into the fields of one section. The form turns
 * dirty, nothing is saved: the merchant still decides with Save changes.
 */
export const resetSectionFields = <T extends FieldValues>(
  setValue: UseFormSetValue<T>,
  values: object,
  defaults: object,
  belongs: (path: string) => boolean
): void => {
  for (const { path, value } of sectionFields(values, defaults, belongs)) {
    setValue(path as Path<T>, value as never, {
      shouldDirty: true,
      shouldValidate: true,
    });
  }
};