// Date helpers shared by the site and the admin panel (no server-only imports).
import type { MeetingItem } from "./content";

/** Today's date in India as YYYY-MM-DD. */
export function todayIST() {
  return new Date().toLocaleDateString("en-CA", { timeZone: "Asia/Kolkata" });
}

/** The next meeting on or after today, if any. */
export function getNextMeeting(list: MeetingItem[]): MeetingItem | undefined {
  const today = todayIST();
  return [...list].filter((m) => m.date >= today).sort((a, b) => a.date.localeCompare(b.date))[0];
}

export function formatMeetingDate(date: string) {
  const [y, m, d] = date.split("-").map(Number);
  return new Date(Date.UTC(y, m - 1, d)).toLocaleDateString("en-IN", {
    weekday: "short",
    day: "numeric",
    month: "short",
    year: "numeric",
    timeZone: "UTC",
  });
}

/** Event dates are saved as YYYY-MM-DD (date picker); older free-text dates are shown as typed. */
export function formatEventDate(date: string) {
  return /^\d{4}-\d{2}-\d{2}$/.test(date) ? formatMeetingDate(date) : date;
}

/** A card in the website's "Past Events" list: a manual event or a completed meeting. */
export type PastEventCard = {
  id: string;
  href: string;
  image: string;
  date: string;
  title: string;
  text: string;
  kind: "event" | "meeting";
};

/** Best-effort sortable timestamp from free-text dates like "12 Aug 2026" or "Aug 2026". */
function toTime(date: string): number | null {
  if (!date) return null;
  const t = Date.parse(/^\d{4}-\d{2}-\d{2}$/.test(date) ? `${date}T00:00:00Z` : date);
  return Number.isNaN(t) ? null : t;
}

/**
 * Website "Past Events" = events added by the admin + meetings whose date has passed.
 * Newest first. Admin events without a readable date keep their admin order at the top.
 */
export function buildPastEvents(
  events: { id: string; image: string; date: string; title: string; text: string }[],
  meetings: (MeetingItem & { details?: string })[],
): PastEventCard[] {
  const today = todayIST();
  const cards: (PastEventCard & { t: number | null; i: number })[] = [
    ...events.map((e, i) => ({
      id: e.id,
      href: `/events/${e.id}`,
      image: e.image,
      date: formatEventDate(e.date),
      title: e.title,
      text: e.text,
      kind: "event" as const,
      t: toTime(e.date),
      i,
    })),
    ...meetings
      .filter((m) => m.date < today)
      .map((m, i) => ({
        id: `m-${m.id}`,
        href: `/meetings/${m.id}`,
        image: m.poster,
        date: formatMeetingDate(m.date),
        title: m.topic || "Club meeting",
        text:
          (m.details ?? "").replace(/\s+/g, " ").trim().slice(0, 160) ||
          [m.venue && `Club meeting at ${m.venue}`, m.time].filter(Boolean).join(" · "),
        kind: "meeting" as const,
        t: toTime(m.date),
        i: events.length + i,
      })),
  ];
  cards.sort((a, b) => {
    if (a.t === null && b.t === null) return a.i - b.i;
    if (a.t === null) return -1;
    if (b.t === null) return 1;
    return b.t - a.t || a.i - b.i;
  });
  return cards.map((c) => ({
    id: c.id,
    href: c.href,
    image: c.image,
    date: c.date,
    title: c.title,
    text: c.text,
    kind: c.kind,
  }));
}