import type { Locale } from "./i18n";

function intlLocale(locale: Locale): string {
  if (locale === "zh-Hant") return "zh-TW";
  if (locale === "zh-Hans") return "zh-CN";
  if (locale === "ja") return "ja-JP";
  return "en";
}

export function formatClock(iso: string, locale: Locale): string {
  const date = new Date(iso);
  if (Number.isNaN(date.getTime())) return "";
  return new Intl.DateTimeFormat(intlLocale(locale), {
    hour: "numeric",
    minute: "2-digit",
  }).format(date);
}

export function formatDay(iso: string, locale: Locale): string {
  const date = new Date(iso);
  if (Number.isNaN(date.getTime())) return "";
  const now = new Date();
  const start = (d: Date) => Date.UTC(d.getFullYear(), d.getMonth(), d.getDate());
  const diff = Math.round((start(now) - start(date)) / 86400000);
  if (diff === 0) {
    if (locale === "en") return "Today";
    if (locale === "ja") return "今日";
    if (locale === "zh-Hans") return "今天";
    return "今天";
  }
  if (diff === 1) {
    if (locale === "en") return "Yesterday";
    if (locale === "ja") return "昨日";
    if (locale === "zh-Hans") return "昨天";
    return "昨天";
  }
  return new Intl.DateTimeFormat(intlLocale(locale), { dateStyle: "medium" }).format(date);
}

export function sameLocalDay(a?: string, b?: string): boolean {
  if (!a || !b) return false;
  const left = new Date(a);
  const right = new Date(b);
  if (Number.isNaN(left.getTime()) || Number.isNaN(right.getTime())) return false;
  return (
    left.getFullYear() === right.getFullYear() &&
    left.getMonth() === right.getMonth() &&
    left.getDate() === right.getDate()
  );
}