import { curryN } from "@unboxing/function";
import { Ord, ArrOrdFunc } from '@unboxing/core'

interface MaxBy {
  <T, R extends Ord>(fn: ArrOrdFunc<T, R>, arr: ArrayLike<T>): T;
  <T, R extends Ord>(fn: ArrOrdFunc<T, R>): (arr: ArrayLike<T>) => T;
}

/**
 * Return max value in array, depending on result of calling `fn`
 */
export const maxBy = curryN(2, <T, R extends Ord>(fn: ArrOrdFunc<T, R>, arr: ArrayLike<T> = []) => {
  let result;
  let max: Ord = -Infinity;

  for (let i = 0; i < arr.length; i++) {
      const computed = fn(arr[i], i, arr);

      if (computed > max) {
          max = computed;
          result = arr[i];
      }
  }

  return result;
}) as MaxBy