/**
 * Returns a function that reports whether a given rank is shared by more than
 * one team. Pass an array of all the rank values in the standings.
 *
 * @example
 * const isTied = buildTiedRankChecker(standings.map(s => s.currentRank));
 * isTied(3); // true if two or more teams share rank 3
 */
export function buildTiedRankChecker(ranks: number[]): (rank: number) => boolean {
  const counts = new Map<number, number>();
  for (const rank of ranks) counts.set(rank, (counts.get(rank) ?? 0) + 1);
  return (rank) => (counts.get(rank) ?? 1) > 1;
}

/**
 * Returns the display rank for a team on the league home standings preview.
 *
 * Rules:
 * - If the team has a standing, return its numeric rank, prefixed with "T" if
 *   the rank is shared by more than one team.
 * - If the team has no standing, it is tied at the position just after all
 *   ranked teams. For example, if 3 teams have standings the unranked teams
 *   show "T4". If no team has standings yet (scores haven't been calculated)
 *   every team is genuinely tied at zero and shows "T1".
 *
 * @param standing - The team's standing record, or undefined if none exists.
 * @param standingsCount - Total number of teams that have a standing record.
 * @param isTied - Whether this team's rank is shared with another team.
 */
export function getDisplayRank(
  standing: { currentRank: number } | undefined,
  standingsCount: number,
  isTied?: boolean
): number | string {
  if (standing) return isTied ? `T${standing.currentRank}` : standing.currentRank;
  return `T${standingsCount + 1}`;
}