import type { Payload } from "payload";
import { aggregateEvents } from "@/lib/analytics/aggregate";

function dateKey(date: Date): string {
  return date.toISOString().slice(0, 10);
}

function startOfUTCDay(date: Date): Date {
  return new Date(`${dateKey(date)}T00:00:00.000Z`);
}

function addDays(date: Date, days: number): Date {
  return new Date(date.getTime() + days * 24 * 60 * 60 * 1000);
}

/**
 * Rolls up every not-yet-aggregated, fully-completed calendar day (UTC -
 * matching the UTC-day salt rotation in lib/analytics/salt.ts) from raw
 * analytics-events into analytics-daily-stats, THEN purges raw events older
 * than the configured retention, THEN purges old daily-stats rows. Order
 * matters: a day must be aggregated before its raw rows can ever be
 * deleted, or that history is gone for good.
 *
 * Only aggregates days that don't already have a daily-stats row (each day
 * is aggregated exactly once, ever) - safe to call this daily via
 * app/(payload)/api/cron/analytics-cleanup/route.ts, and safe to re-run.
 */
export async function runAnalyticsCleanup(payload: Payload) {
  const settings = await payload.findGlobal({ slug: "analytics-settings" });
  const rawRetentionDays = settings.rawRetentionDays ?? 90;
  const aggregateRetentionMonths = settings.aggregateRetentionMonths ?? 12;

  const today = startOfUTCDay(new Date());

  const { docs: earliestDocs } = await payload.find({
    collection: "analytics-events",
    sort: "createdAt",
    limit: 1,
    depth: 0,
  });
  const earliest = earliestDocs[0];

  let daysAggregated = 0;
  if (earliest) {
    let cursor = startOfUTCDay(new Date(earliest.createdAt));
    while (cursor < today) {
      const key = dateKey(cursor);
      const { totalDocs: alreadyAggregated } = await payload.count({
        collection: "analytics-daily-stats",
        where: { date: { equals: key } },
      });

      if (alreadyAggregated === 0) {
        const dayEnd = addDays(cursor, 1);
        const { docs: dayEvents } = await payload.find({
          collection: "analytics-events",
          where: {
            and: [
              { createdAt: { greater_than_equal: cursor.toISOString() } },
              { createdAt: { less_than: dayEnd.toISOString() } },
            ],
          },
          limit: 0, // no limit - pull the whole day, small-site scale
          depth: 0,
        });

        if (dayEvents.length > 0) {
          const stats = aggregateEvents(dayEvents);
          await payload.create({
            collection: "analytics-daily-stats",
            data: { date: key, ...stats },
          });
          daysAggregated += 1;
        }
      }

      cursor = addDays(cursor, 1);
    }
  }

  const rawCutoff = addDays(today, -rawRetentionDays).toISOString();
  const { docs: staleEvents } = await payload.find({
    collection: "analytics-events",
    where: { createdAt: { less_than: rawCutoff } },
    limit: 0,
    depth: 0,
  });
  for (const doc of staleEvents) {
    await payload.delete({ collection: "analytics-events", id: doc.id });
  }

  const aggregateCutoff = new Date(today);
  aggregateCutoff.setUTCMonth(aggregateCutoff.getUTCMonth() - aggregateRetentionMonths);
  const { docs: staleDailyStats } = await payload.find({
    collection: "analytics-daily-stats",
    where: { date: { less_than: dateKey(aggregateCutoff) } },
    limit: 0,
    depth: 0,
  });
  for (const doc of staleDailyStats) {
    await payload.delete({ collection: "analytics-daily-stats", id: doc.id });
  }

  return {
    daysAggregated,
    rawEventsDeleted: staleEvents.length,
    dailyStatsDeleted: staleDailyStats.length,
  };
}