import { getIndexSubSequences } from "./getIndexSubSequences.js"

export function combinations<T>(setOrArray: Set<T> | T[]): T[][] {
  const array = [...setOrArray]

  let indexSubSequences
  const length = array.length
  if (combinations.indexSubSequencesCache.has(length)) {
    indexSubSequences = combinations.indexSubSequencesCache.get(length)!
  } else {
    indexSubSequences = getIndexSubSequences(length)
    combinations.indexSubSequencesCache.set(length, indexSubSequences)
  }

  const subSequences = indexSubSequences.map((indexSubSequence) =>
    indexSubSequence.map((index) => array[index]),
  )

  return subSequences
}

combinations.indexSubSequencesCache = new Map<number, number[][]>()