import { getPayload } from "payload";
import config from "@payload-config";
import { combineDateAndTime } from "./status";
import { sendReminderEmail } from "@/lib/email/sendReminderEmail";

const REMINDER_TOLERANCE_MS = 10 * 60 * 1000; // cron may run every few minutes

function isDue(reminderAt: number, now: number): boolean {
  return now >= reminderAt && now < reminderAt + REMINDER_TOLERANCE_MS;
}

function formatDate(date: Date): string {
  return date.toLocaleDateString("de-DE", { day: "2-digit", month: "long", year: "numeric" });
}

function formatTime(date: Date): string {
  return date.toLocaleTimeString("de-DE", { hour: "2-digit", minute: "2-digit" });
}

/**
 * Checks all upcoming online events for due 60/30-minute reminders and sends
 * them — to registered, non-cancelled participants and (optionally) to the
 * admin host. Idempotent: every send is guarded by a "...Sent" flag so a
 * cron job that runs every few minutes never double-sends.
 */
export async function runEventReminders() {
  const payload = await getPayload({ config });
  const now = new Date();
  const serverUrl = process.env.NEXT_PUBLIC_SERVER_URL || "http://localhost:3000";

  const windowStart = new Date(now.getTime() - 24 * 60 * 60 * 1000).toISOString();
  const windowEnd = new Date(now.getTime() + 2 * 24 * 60 * 60 * 1000).toISOString();

  const { docs: events } = await payload.find({
    collection: "events",
    where: {
      and: [
        { isOnline: { equals: true } },
        { date: { greater_than_equal: windowStart } },
        { date: { less_than_equal: windowEnd } },
      ],
    },
    limit: 200,
  });

  const results = { emailsSent: 0, eventsChecked: events.length };

  for (const event of events) {
    if (!event.slug) continue;
    const start = combineDateAndTime(event.date, event.startTime);
    const dateLabel = formatDate(start);
    const timeLabel = formatTime(start);
    const joinUrl = `${serverUrl}/termine/${event.slug}/beitreten`;

    const thresholds: { minutes: 60 | 30; enabled: boolean; participantField: "reminder60Sent" | "reminder30Sent"; hostField: "hostReminder60Sent" | "hostReminder30Sent" }[] = [
      { minutes: 60, enabled: Boolean(event.reminder60Enabled), participantField: "reminder60Sent", hostField: "hostReminder60Sent" },
      { minutes: 30, enabled: Boolean(event.reminder30Enabled), participantField: "reminder30Sent", hostField: "hostReminder30Sent" },
    ];

    for (const threshold of thresholds) {
      if (!threshold.enabled) continue;
      const reminderAt = start.getTime() - threshold.minutes * 60_000;
      if (!isDue(reminderAt, now.getTime())) continue;

      // Host reminder (per event, not per registration).
      if (event.hostReminderEnabled && !event[threshold.hostField]) {
        const { docs: admins } = await payload.find({ collection: "users", limit: 50 });
        for (const admin of admins) {
          if (!admin.email) continue;
          await sendReminderEmail(admin.email, {
            recipientName: admin.name || "Team ANOUMA",
            eventTitle: event.title,
            dateLabel,
            timeLabel,
            joinUrl,
            meetingPassword: event.meetingPassword || "—",
            minutesBefore: threshold.minutes,
          });
          results.emailsSent++;
        }
        await payload.update({ collection: "events", id: event.id, data: { [threshold.hostField]: true } });
      }

      // Participant reminders — only registered (not cancelled), not yet sent.
      const { docs: registrations } = await payload.find({
        collection: "event-registrations",
        where: {
          and: [
            { event: { equals: event.id } },
            { status: { equals: "registered" } },
            { [threshold.participantField]: { equals: false } },
          ],
        },
        limit: 500,
      });

      for (const registration of registrations) {
        await sendReminderEmail(registration.email, {
          recipientName: registration.name,
          eventTitle: event.title,
          dateLabel,
          timeLabel,
          joinUrl,
          meetingPassword: event.meetingPassword || "—",
          minutesBefore: threshold.minutes,
        });
        results.emailsSent++;
        await payload.update({
          collection: "event-registrations",
          id: registration.id,
          data: { [threshold.participantField]: true },
        });
      }
    }
  }

  return results;
}