natural-date.ts

import {
  add,
  set,
  format,
  startOfWeek,
  endOfWeek,
  eachDayOfInterval,
  isBefore,
} from "npm:date-fns";

/*
 * Explicação da regex
  (?<startDate>
      (

        define: próximo dia da semana
        (?<nextWeekDay>(pr[oó]xim[ao])? (((segunda|terça|quarta|quinta|sexta)(-| )feira)|s[aá]bado|domingo))

        define: amanhã
        |(?<tomorrow>amanh[aã])
      ) 

      define: às HH:mm
      (às ([0-9][0-9]:[0-9][0-9]|[0-9][0-9]h)?)
    )
*/

type RegexMatch = Partial<{
  startDate: string;
  nextWeekDay: string;
  tomorrow: string;
  startTime: string;
}>;

const matchTime = /(\d\d:\d\d|\d\dh)/i;

type DateOnlyOperator = {
  regex: RegExp;
  fn: (d: Date) => Date;
};

const dateOnlyOperator: DateOnlyOperator[] = [
  {
    regex: /domingo/,
    fn: (d: Date): Date => {
      const range = eachDayOfInterval({
        start: startOfWeek(d),
        end: endOfWeek(d),
      });
      const weekDay = +format(d, "i"); // 1 até 7 -> 0 até 6
      const result = range[weekDay - 1];
      if (isBefore(result, d)) {
        const nextWeek = add(d, { weeks: 1 });
        const range = eachDayOfInterval({
          start: startOfWeek(nextWeek),
          end: endOfWeek(nextWeek),
        });
        return range[weekDay - 1];
      }
      return result;
    },
  },
  {
    regex: /amanh[ãa]/,
    fn: (d: Date): Date => add(d, { days: 1 }),
  },
];

const parseStartDateOnly = (match: RegexMatch): Date => {
  const now = new Date();
  if (!match.startDate) return now;
  const find = dateOnlyOperator.find((x) =>
    x.regex.exec(match.startDate || "")
  );
  if (!find) return now;
  return find.fn(now);
};

const sanitizeTime = (t: string) => t.replace(/h$/g, "");

const setTime = (d: Date, timeString: string) => {
  const [hours, minutes = "0"] = sanitizeTime(timeString).split(":");
  console.log({ hours, minutes });
  if (hours && minutes) {
    return set(d, { hours: Number(hours), minutes: Number(minutes) });
  }
  return d;
};

export const parseStartDate = (match: RegexMatch) => {
  const time = matchTime.exec(match.startTime || "")?.[0];
  const date = parseStartDateOnly(match);
  if (time) return setTime(date, time);
  return date;
};

const regex =
  /(?<startDate>((?<nextWeekDay>(pr[oó]xim[ao])? (((segunda|terça|quarta|quinta|sexta)(-| )feira)|s[aá]bado|domingo))|(?<tomorrow>amanh[aã])) (?<startTime>às ([0-9][0-9]:[0-9][0-9]|[0-9][0-9]h)?))/i;

const sentence = "Dever de casa número 5 para domingo às 16h";

const match = regex.exec(sentence);

const result = parseStartDate(match?.groups || {});
console.log("pt-BR:", result.toLocaleString("pt-BR"));