export function toGroups<TItem = unknown>(
  groupByFn: (item: TItem) => PropertyKey,
) {
  type GroupKey = ReturnType<typeof groupByFn>
  type GroupResult = Record<GroupKey, TItem[]>

  const reducer = (
    groups: Record<PropertyKey, TItem[]>,
    current: TItem,
    index: number,
    arr: TItem[],
  ): GroupResult => {
    const key = groupByFn(current)
    const group = groups[key] ?? []

    groups[key] = [...group, current]

    return groups
  }

  return [reducer, {} as GroupResult] as const
}