/**
 * Remove duplicate values from an array.
 *
 * @param getId callback used to calculate a unique value for an element of the array.
 *
 * @example
 * dedupe([1,1,2,3]) // [1,2,3]
 *
 * dedupe(
 *   [
 *     { a: 1, b: 2 },
 *     { a: 1, b: 2 },
 *     { a: 2, b: 2 },
 *   ],
 *   (e) => `${e.a}_${e.b}`,
 * ) // [{a: 1, b: 2}, {a: 2, b: 2}]
 *
 */
export function dedupe<item, id>(
  arr: item[] | readonly item[],
  getId?: (x: item) => id,
): item[] {
  const seen = new Set<id | item>();

  return arr.filter((x) => {
    const id = getId ? getId(x) : x;
    if (seen.has(id)) return false;

    seen.add(id);
    return true;
  });
}