combineSort.ts

type ComparatorFn<T> = (a: T, b: T) => number;
type CasterFn<T> = (value: T) => number;

export const reverse = <T>(compare: ComparatorFn<T>): ComparatorFn<T> => (a: T, b: T) => -compare(a, b);

const combineComparators = <T>(compareA: ComparatorFn<T>, compareB: ComparatorFn<T>): ComparatorFn<T> =>
   (a: T, b: T) => compareA(a, b) || compareB(a, b);

const voidComparator = <T>(a: T, b: T): number => 0;

export const combinedComparator = <T>(...comparators: ComparatorFn<T>[]): ComparatorFn<T> =>
  comparators.length > 0
    ? comparators.reduce(combineComparators)
    : voidComparator;

const sortBy = <T>(caster: CasterFn<T>): ComparatorFn<T> => (a: T, b: T) => caster(a) - caster(b);