import dayjs, { type Dayjs } from "dayjs";
import customParseFormat from "dayjs/plugin/customParseFormat";

dayjs.extend(customParseFormat);

const CLOCK_DATE = "2000-01-01";
const CLOCK_TIME_FORMATS = [
  "YYYY-MM-DD H:m",
  "YYYY-MM-DD H:mm",
  "YYYY-MM-DD HH:m",
  "YYYY-MM-DD HH:mm",
];

/** Parse a timetable clock value, accepting legacy and zero-padded forms. */
export const parseClockTime = (time: string): Dayjs | null => {
  const value = time?.trim();
  if (!value) return null;

  const parsed = dayjs(`${CLOCK_DATE} ${value}`, CLOCK_TIME_FORMATS, true);
  return parsed.isValid() ? parsed : null;
};

/** Normalize a timetable clock value to HH:mm, preserving invalid input. */
export const normalizeTime = (time: string) =>
  parseClockTime(time)?.format("HH:mm") ?? time;

/** Set a clock value on a base date without applying service-day rollover. */
export const setClockTime = (base: Dayjs, time: string, delayMinutes = 0) => {
  const parsed = parseClockTime(time);
  if (!parsed) return null;

  return base
    .clone()
    .hour(parsed.hour())
    .minute(parsed.minute())
    .second(0)
    .millisecond(0)
    .add(delayMinutes, "minute");
};

/** Set a timetable value on a base date, treating 00:00-03:59 as service-day late night. */
export const setServiceTime = (base: Dayjs, time: string, delayMinutes = 0) => {
  const parsed = parseClockTime(time);
  if (!parsed) return null;

  return base
    .clone()
    .hour(parsed.hour() < 4 ? parsed.hour() + 24 : parsed.hour())
    .minute(parsed.minute())
    .second(0)
    .millisecond(0)
    .add(delayMinutes, "minute");
};

export const getServiceTimeDifference = (
  base: Dayjs,
  time: string,
  delayMinutes = 0
) => {
  const parsed = parseClockTime(time);
  const target = setServiceTime(base, time, delayMinutes);
  if (!parsed || !target) return null;

  const adjustedTarget =
    base.hour() < 4 && parsed.hour() < 4
      ? target.subtract(1, "day")
      : target;
  return adjustedTarget.diff(base, "minute");
};

export const getServiceMinute = (time: string) => {
  const parsed = parseClockTime(time);
  if (!parsed) return null;

  return (parsed.hour() < 4 ? parsed.hour() + 24 : parsed.hour()) * 60 + parsed.minute();
};