import { DateTime } from "luxon";
import { DEFAULT_TIMEZONE } from "@cmbot/shared";

export type Quick = "now" | "tomorrow_9am" | "next_mon_9am";

export function quickToDate(quick: Quick, timezone: string = DEFAULT_TIMEZONE): Date {
  const now = DateTime.now().setZone(timezone);
  switch (quick) {
    case "now":
      // Add 30s so pg-boss has time to schedule + the system has time to dispatch
      return now.plus({ seconds: 30 }).toJSDate();
    case "tomorrow_9am":
      return now.plus({ days: 1 }).set({ hour: 9, minute: 0, second: 0, millisecond: 0 }).toJSDate();
    case "next_mon_9am": {
      const dow = now.weekday; // 1 = Mon
      const daysUntilMon = ((1 - dow + 7) % 7) || 7;
      return now.plus({ days: daysUntilMon }).set({ hour: 9, minute: 0, second: 0, millisecond: 0 }).toJSDate();
    }
  }
}

/**
 * Build a Date from a day-offset (days from today, in the operator's timezone),
 * an hour (0-23) and a minute (0-59). Returns the JS Date or null if the
 * resulting time is in the past.
 */
export function buildCustomDate(
  dayOffset: number,
  hour: number,
  minute: number,
  timezone: string = DEFAULT_TIMEZONE,
): { ok: true; date: Date } | { ok: false; reason: string } {
  const target = DateTime.now()
    .setZone(timezone)
    .plus({ days: dayOffset })
    .set({ hour, minute, second: 0, millisecond: 0 });
  if (!target.isValid) {
    return { ok: false, reason: "Invalid date" };
  }
  const jsDate = target.toJSDate();
  if (jsDate.getTime() <= Date.now()) {
    return { ok: false, reason: "Time is in the past" };
  }
  return { ok: true, date: jsDate };
}

export function formatCustomDay(dayOffset: number, timezone: string = DEFAULT_TIMEZONE): string {
  const dt = DateTime.now().setZone(timezone).plus({ days: dayOffset });
  if (dayOffset === 0) return `Today (${dt.toFormat("EEE dd MMM")})`;
  if (dayOffset === 1) return `Tomorrow (${dt.toFormat("EEE dd MMM")})`;
  return dt.toFormat("EEE dd MMM");
}

export type ParseResult = { ok: true; date: Date } | { ok: false; reason: string };

const FORMATS = [
  "yyyy-MM-dd HH:mm",
  "yyyy-MM-dd HH:mm:ss",
  "yyyy/MM/dd HH:mm",
  "dd/MM/yyyy HH:mm",
  "dd-MM-yyyy HH:mm",
];

export function parseFreeText(input: string, timezone: string = DEFAULT_TIMEZONE): ParseResult {
  const trimmed = input.trim();
  for (const fmt of FORMATS) {
    const dt = DateTime.fromFormat(trimmed, fmt, { zone: timezone });
    if (dt.isValid) {
      const jsDate = dt.toJSDate();
      if (jsDate.getTime() <= Date.now()) {
        return { ok: false, reason: "Time is in the past" };
      }
      return { ok: true, date: jsDate };
    }
  }
  return { ok: false, reason: "Couldn't parse — try YYYY-MM-DD HH:MM (e.g. 2026-05-15 09:00)" };
}