import { curryN } from "@unboxing/function";
import { isArray } from "@unboxing/is";

interface Join {
  (x: string, xs: ArrayLike<any>): string;
  (x: string): (xs: ArrayLike<any>) => string;
}

/**
 * Returns a string made by inserting the `separator` between each element and
 * concatenating all the elements into a single string.
 */
export const joinArray = curryN(2, <T>(separator = '', arr: ArrayLike<T> = []) => {
  let resultArr: T[];

  if (isArray(arr)) {
      resultArr = arr;
  } else {
      resultArr = Array.prototype.slice.call(arr);
  }

  return resultArr.join(separator);
}) as Join