sendou.ink/app/features/plus-voting/core/voting-time.ts

import type { MonthYear } from "./types";
import { type RankingSeason, SEASONS } from "~/features/mmr/season";

export function lastCompletedVoting(now: Date): MonthYear {
  let match: { startDate: Date; endDate: Date } | null = null;
  for (const season of SEASONS) {
    const range = seasonToVotingRange(season);

    if (now.getTime() > range.endDate.getTime()) {
      match = range;
    } else if (now.getTime() < range.endDate.getTime()) {
      break;
    }
  }

  if (!match) {
    throw new Error("No previous voting found.");
  }

  return rangeToMonthYear(match);
}

export function nextNonCompletedVoting(now: Date) {
  for (const season of SEASONS) {
    const range = seasonToVotingRange(season);

    if (now.getTime() < range.endDate.getTime()) {
      return range;
    }
  }

  throw new Error("No next voting found.");
}

export function rangeToMonthYear(range: { startDate: Date; endDate: Date }) {
  return {
    month: range.startDate.getMonth(),
    year: range.startDate.getFullYear(),
  };
}

export function seasonToVotingRange(season: RankingSeason) {
  const { ends: date } = season;

  if (date.getUTCDay() !== 0) {
    throw new Error("End date is not a Sunday.");
  }

  const endDate = new Date(date);
  endDate.setUTCDate(endDate.getUTCDate() - 7);
  endDate.setUTCHours(18, 0, 0, 0);

  const startDate = new Date(endDate);
  startDate.setUTCDate(startDate.getUTCDate() - 2);

  return { startDate, endDate };
}

export function isVotingActive() {
  const now = new Date();

  for (const season of SEASONS) {
    const { startDate, endDate } = seasonToVotingRange(season);

    if (
      now.getTime() > startDate.getTime() &&
      now.getTime() < endDate.getTime()
    ) {
      return true;
    }
  }

  return false;
}