Function nearestLevelUp

packages/webapp/components/world/ladder.ts:215–240

(
  rows: readonly LadderRow[] | undefined,
)

 * from a rung, the one further along is the one they are actually reading.
 */
export const nearestLevelUp = (
  rows: readonly LadderRow[] | undefined,
): NearestLevelUp | null => {
  if (!rows?.length) {
    return null;
  }

  let best: NearestLevelUp | null = null;
  rows.forEach((row) => {
    const progress = levelProgress(row.reads);
    // Topped out: there is no next rung to walk towards.
    if (!progress.next) {
      return;
    }
    if (
      best &&
      (progress.toNext > best.toNext ||
        (progress.toNext === best.toNext && row.reads <= best.reads))
    ) {
      return;
    }
    best = { ...row, ...progress, next: progress.next };
  });

  return best;
};