Paramutations - parameter permutation utility

paramutations.ts

type VariadicTupleOfVariadicTuples = readonly [...(readonly [...(readonly unknown[])])];

type ProductResult<T extends VariadicTupleOfVariadicTuples> = {
  // @ts-expect-error should be good
  [K in keyof T]: T[K][number];
};

function product<T extends VariadicTupleOfVariadicTuples>(arrays: T): ProductResult<T> {
  return arrays.reduce(
    (prevAccumulator: any[][], currentArray: any[]) => {
      const newAccumulator: any[][] = [];
      prevAccumulator.forEach(prevAccumulatorArray => {
        currentArray.forEach(currentValue => {
          newAccumulator.push(prevAccumulatorArray.concat(currentValue));
        });
      });
      return newAccumulator;
    },
    [[]],
  ) as ProductResult<T>;
}

export type ParamValues<T extends Record<string, unknown>> = {
  [K in keyof T]: T[K][];
};

export const paramutations = <T extends Record<string, unknown>>(matrix: ParamValues<T>): T[] => {
  const inputToProduct = Object.values(matrix);
  const keys = Object.keys(matrix);
  const permutations = product(inputToProduct);

  return permutations.map(permutations => {
    return Object.fromEntries(keys.map((k, i) => [k, permutations[i]])) as T;
  });
};