export interface DailyCount {
  day: string;
  count: number;
}

export function mergeRiskActivity<
  T extends { userId: string; observedAt: Date },
  S extends { userId: string | null },
>(latestRows: T[], summaryRows: S[]) {
  const summaries = new Map(summaryRows.flatMap((summary) => summary.userId ? [[summary.userId, summary] as const] : []));
  return latestRows
    .flatMap((activity) => {
      const summary = summaries.get(activity.userId);
      return summary ? [{ ...activity, ...summary }] : [];
    })
    .sort((left, right) => right.observedAt.getTime() - left.observedAt.getTime());
}

export function fillDailySeries(rows: DailyCount[], end: Date, days: number) {
  const counts = new Map(rows.map((row) => [row.day, Number(row.count)]));
  const endDay = new Date(Date.UTC(end.getUTCFullYear(), end.getUTCMonth(), end.getUTCDate()));
  return Array.from({ length: days }, (_, index) => {
    const date = new Date(endDay);
    date.setUTCDate(endDay.getUTCDate() - (days - index - 1));
    const day = date.toISOString().slice(0, 10);
    return { day, count: counts.get(day) ?? 0 };
  });
}