import type { RoutineEventBlock } from "@rakazo/contracts";
import { routineScheduleShape } from "@rakazo/core";
import { dateLocaleForUi, t } from "./i18n";

/** 2024-01-07 is a Sunday, so day n of that week has weekday n. */
const weekdayName = (weekday: number, locale: string) =>
  new Intl.DateTimeFormat(locale, { weekday: "long", timeZone: "UTC" }).format(
    new Date(Date.UTC(2024, 0, 7 + weekday)),
  );

const clock = (hour: number, minute: number, locale: string) =>
  new Intl.DateTimeFormat(locale, { hour: "numeric", minute: "2-digit", timeZone: "UTC" }).format(
    new Date(Date.UTC(2024, 0, 1, hour, minute)),
  );

/** When a routine runs, in a few words of the active locale. */
export function routineLineSchedule(
  block: Pick<RoutineEventBlock, "crons" | "nextRunAt" | "timezone">,
  locale = dateLocaleForUi(),
): string {
  const shape = routineScheduleShape(block.crons);
  switch (shape.kind) {
    case "hourly":
      return t("Every hour");
    case "minutes":
      return t("Every {count} min", { count: shape.every });
    case "hours":
      return t("Every {count} h", { count: shape.every });
    case "daily":
      return t("Daily, {time}", { time: clock(shape.hour, shape.minute, locale) });
    case "weekdays":
      return t("Weekdays, {time}", { time: clock(shape.hour, shape.minute, locale) });
    case "weekly":
      return t("Every {day}, {time}", {
        day: weekdayName(shape.weekday, locale),
        time: clock(shape.hour, shape.minute, locale),
      });
    case "monthly":
      return t("Monthly on day {day}, {time}", {
        day: shape.day,
        time: clock(shape.hour, shape.minute, locale),
      });
    default: {
      if (!block.nextRunAt) return "";
      const date = new Intl.DateTimeFormat(locale, {
        weekday: "short",
        day: "numeric",
        month: "short",
        hour: "numeric",
        minute: "2-digit",
        timeZone: block.timezone,
      }).format(new Date(block.nextRunAt));
      return shape.kind === "once" ? date : t("Next {date}", { date });
    }
  }
}