/* ============================================================
   Festival skin gating — date-driven, URL-overridable.
   Only Christmas is implemented today; add more festivals by
   extending FESTIVAL_WINDOWS plus the matching components under
   components/festival/.
   ============================================================ */
import { useMemo } from "react";

export type FestivalId = "christmas" | "halloween" | "newyear";

/** Inclusive [month, day] windows. Christmas: Dec 20 – Dec 26; Halloween: Oct 26 – Nov 1. */
const FESTIVAL_WINDOWS: Record<
  FestivalId,
  { from: [number, number]; to: [number, number] }
> = {
  christmas: { from: [12, 20], to: [12, 26] },
  halloween: { from: [10, 26], to: [11, 1] },
  // 元旦接续圣诞节，跨年窗口包含首尾日期。
  newyear: { from: [12, 27], to: [1, 3] },
};

function inWindow(
  month: number,
  day: number,
  w: { from: [number, number]; to: [number, number] },
) {
  const cur = month * 100 + day;
  const from = w.from[0] * 100 + w.from[1];
  const to = w.to[0] * 100 + w.to[1];
  // Support windows that wrap the new year (from > to).
  return from <= to ? cur >= from && cur <= to : cur >= from || cur <= to;
}

/**
 * Resolve the active festival skin.
 * `?festival=christmas` forces it on and `?festival=off` forces it off (QA hook,
 * so the skin can be verified without waiting for the real date window).
 * Otherwise falls back to the system-date window.
 */
export function getFestival(
  now: Date = new Date(),
  search: string = typeof location !== "undefined" ? location.search : "",
): FestivalId | null {
  const override = new URLSearchParams(search).get("festival");
  if (override === "off" || override === "none") return null;
  if (override && Object.prototype.hasOwnProperty.call(FESTIVAL_WINDOWS, override)) {
    return override as FestivalId;
  }
  for (const id of Object.keys(FESTIVAL_WINDOWS) as FestivalId[]) {
    if (inWindow(now.getMonth() + 1, now.getDate(), FESTIVAL_WINDOWS[id])) return id;
  }
  return null;
}

/** Stable per-mount festival resolution (the date won't matter mid-session). */
export function useFestival(): FestivalId | null {
  return useMemo(() => getFestival(), []);
}

/** 跨年夜展示即将到来的年份，其余月份预览展示当年。 */
export function getNewYearDisplayYear(now: Date = new Date()): number {
  return now.getFullYear() + (now.getMonth() === 11 ? 1 : 0);
}

/** 首页 VU 区的节日问候语，键与 FestivalId 对应。 */
export const FESTIVAL_GREETINGS: Record<FestivalId, string> = {
  christmas: "Merry Christmas",
  halloween: "Happy Halloween",
  newyear: "Happy New Year",
};