function parseField(source, min, max) {
  const values = new Set();
  for (const part of source.split(",")) {
    const match = /^(\*|\d+(?:-\d+)?)(?:\/(\d+))?$/.exec(part);
    if (!match) throw new Error("Campo cron inválido.");
    const step = Number(match[2] || 1);
    if (step < 1) throw new Error("Passo cron inválido.");
    const base = match[1],
      range =
        base === "*"
          ? [min, max]
          : base.includes("-")
            ? base.split("-").map(Number)
            : [Number(base), match[2] ? max : Number(base)];
    if (range[0] < min || range[1] > max || range[0] > range[1])
      throw new Error("Valor cron fora do intervalo.");
    for (let i = range[0]; i <= range[1]; i += step) values.add(i);
  }
  return values;
}
export function compileCron(expression, timezone = "Europe/Lisbon") {
  const fields = String(expression).trim().split(/\s+/);
  if (fields.length === 5) fields.unshift("0");
  if (fields.length !== 6) throw new Error("O cron precisa de 5 ou 6 campos.");
  const limits = [
      [0, 59],
      [0, 59],
      [0, 23],
      [1, 31],
      [1, 12],
      [0, 7],
    ],
    sets = fields.map((v, i) => parseField(v, ...limits[i]));
  if (sets[5].has(7)) sets[5].add(0);
  const formatter = new Intl.DateTimeFormat("en-GB", {
    timeZone: timezone,
    second: "2-digit",
    minute: "2-digit",
    hour: "2-digit",
    day: "2-digit",
    month: "2-digit",
    weekday: "short",
    hourCycle: "h23",
  });
  return (date) => {
    const p = Object.fromEntries(
        formatter.formatToParts(date).map((p) => [p.type, p.value]),
      ),
      values = [
        +p.second,
        +p.minute,
        +p.hour,
        +p.day,
        +p.month,
        ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"].indexOf(p.weekday),
      ];
    const day = sets[3].has(values[3]),
      week = sets[5].has(values[5]);
    return (
      [0, 1, 2, 4].every((i) => sets[i].has(values[i])) &&
      (fields[3] !== "*" && fields[5] !== "*" ? day || week : day && week)
    );
  };
}