interface StandingsEntry {
  teamId: string;
  teamName: string;
  totalPoints: number;
  rank: number | null;
}

interface SendStandingsUpdateOptions {
  webhookUrl: string;
  seasonName: string;
  standings: StandingsEntry[];
  previousStandings: Map<string, number> | Record<string, number>;
  eventName?: string;
}

export async function sendStandingsUpdateNotification({
  webhookUrl,
  seasonName,
  standings,
  previousStandings,
  eventName,
}: SendStandingsUpdateOptions): Promise<void> {
  const title = eventName
    ? `📊 ${seasonName} — Standings after ${eventName}`
    : `📊 ${seasonName} — Standings Update`;

  const getPrev = (teamId: string) =>
    previousStandings instanceof Map
      ? previousStandings.get(teamId)
      : previousStandings[teamId];

  const lines = standings
    .sort((a, b) => (a.rank ?? 999) - (b.rank ?? 999))
    .map((s) => {
      const prev = getPrev(s.teamId);
      const diff =
        prev !== undefined ? s.totalPoints - prev : null;
      const diffStr =
        diff !== null && diff !== 0
          ? diff > 0
            ? ` (+${diff.toFixed(1)})`
            : ` (${diff.toFixed(1)})`
          : "";
      const rankStr = s.rank != null ? `${s.rank}.` : "-";
      return `${rankStr} **${s.teamName}** — ${s.totalPoints.toFixed(1)} pts${diffStr}`;
    });

  const content = [`**${title}**`, "", ...lines].join("\n");

  const response = await fetch(webhookUrl, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ content }),
  });

  if (!response.ok) {
    throw new Error(
      `Discord webhook returned ${response.status}: ${await response.text()}`
    );
  }
}