import type { PresenceSample } from "#lib/api/types.js";
import { formatDay, formatTime } from "#lib/format/datetime.js";
import { locale, t } from "#lib/i18n/locale.svelte.js";
import type { MessageKey } from "#lib/i18n/messages.js";

const SECONDS_IN_MINUTE = 60;
const MINUTES_IN_HOUR = 60;
const SECONDS_IN_HOUR = 3600;
const MS_IN_MINUTE = 60_000;
const SECONDS_IN_DAY = 86_400;
const MS_IN_DAY = 86_400_000;
const DAYS_IN_WEEK = 7;
const MONDAY = Date.UTC(2024, 0, 1);

const FUZZY: Record<string, MessageKey> = {
  last_month: "presence.lastMonth",
  last_week: "presence.lastWeek",
  long_time_ago: "presence.longAgo",
  recently: "presence.recently",
};

export function isOnline(
  sample: PresenceSample | null,
  now = Date.now()
): boolean {
  if (sample?.status !== "online" || sample.next_offline_date === null) {
    return false;
  }
  return new Date(sample.next_offline_date).getTime() > now;
}

function lastSeen(iso: string, now: number): string {
  const date = new Date(iso);
  const minutes = Math.floor((now - date.getTime()) / MS_IN_MINUTE);
  if (minutes < 1) {
    return t("presence.justNow");
  }
  if (minutes < MINUTES_IN_HOUR) {
    return t("presence.ago", { count: minutes });
  }
  const time = formatTime(iso);
  const today = new Date(now);
  if (date.toDateString() === today.toDateString()) {
    return t("presence.todayAt", { time });
  }
  if (date.toDateString() === new Date(now - MS_IN_DAY).toDateString()) {
    return t("presence.yesterdayAt", { time });
  }
  return t("presence.on", { day: formatDay(iso), time });
}

export function formatPresence(
  sample: PresenceSample,
  now = Date.now()
): string {
  if (sample.status === "online") {
    return isOnline(sample, now)
      ? t("presence.online")
      : lastSeen(sample.next_offline_date ?? sample.ts, now);
  }
  const fuzzy = FUZZY[sample.status];
  if (fuzzy) {
    return t(fuzzy);
  }
  return sample.last_online_date
    ? lastSeen(sample.last_online_date, now)
    : t("presence.offline");
}

export function formatSpan(seconds: number): string {
  if (seconds < SECONDS_IN_MINUTE) {
    return t("presence.seconds", { seconds: Math.round(seconds) });
  }
  const minutes = Math.round(seconds / SECONDS_IN_MINUTE);
  if (minutes < MINUTES_IN_HOUR) {
    return t("presence.minutes", { minutes });
  }
  const hours = Math.floor(minutes / MINUTES_IN_HOUR);
  const rest = minutes % MINUTES_IN_HOUR;
  return rest === 0
    ? t("presence.hours", { hours })
    : t("presence.hoursMinutes", { hours, minutes: rest });
}

export function formatClock(secondsOfDay: number): string {
  const hours = Math.floor(secondsOfDay / SECONDS_IN_HOUR);
  const minutes = Math.floor(
    (secondsOfDay % SECONDS_IN_HOUR) / SECONDS_IN_MINUTE
  );
  return `${String(hours).padStart(2, "0")}:${String(minutes).padStart(2, "0")}`;
}

export function formatLongSpan(seconds: number): string {
  if (seconds < 2 * SECONDS_IN_DAY) {
    return formatSpan(seconds);
  }
  const days = Math.floor(seconds / SECONDS_IN_DAY);
  const hours = Math.round((seconds % SECONDS_IN_DAY) / SECONDS_IN_HOUR);
  const text = t("presence.days", { count: days });
  return hours === 0 ? text : `${text} ${t("presence.hours", { hours })}`;
}

function capitalize(text: string): string {
  return text.charAt(0).toUpperCase() + text.slice(1);
}

export function weekdayLabels(): string[] {
  const format = new Intl.DateTimeFormat(locale.tag, {
    timeZone: "UTC",
    weekday: "short",
  });
  return Array.from({ length: DAYS_IN_WEEK }, (_, day) =>
    capitalize(format.format(MONDAY + day * MS_IN_DAY))
  );
}