import { DEFAULT_DASHBOARD_RANGE } from "@/domain/dashboard/types/dashboard-range";
import type {
  DashboardRangeKey,
  DashboardRangeParams,
} from "@/domain/dashboard/types/dashboard-range";

export const BUSINESS_TIME_ZONE = "America/New_York";

const ISO_DATE_PATTERN = /^\d{4}-\d{2}-\d{2}$/;

export function businessTodayIso(now: Date = new Date()): string {
  return new Intl.DateTimeFormat("en-CA", {
    timeZone: BUSINESS_TIME_ZONE,
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
  }).format(now);
}

export function isIsoDate(value: string): boolean {
  return ISO_DATE_PATTERN.test(value);
}

export function addDaysIso(isoDate: string, days: number): string {
  const [year, month, day] = isoDate.split("-").map(Number);
  const shifted = new Date(Date.UTC(year, month - 1, day + days));
  return shifted.toISOString().slice(0, 10);
}

export function mondayOf(isoDate: string): string {
  const [year, month, day] = isoDate.split("-").map(Number);
  const weekday = new Date(Date.UTC(year, month - 1, day)).getUTCDay();
  return addDaysIso(isoDate, -((weekday + 6) % 7));
}

export function monthStartIso(isoDate: string): string {
  return `${isoDate.slice(0, 7)}-01`;
}

export function monthEndIso(isoDate: string): string {
  const year = Number(isoDate.slice(0, 4));
  const month = Number(isoDate.slice(5, 7));
  const lastDay = new Date(Date.UTC(year, month, 0)).getUTCDate();
  return `${isoDate.slice(0, 7)}-${String(lastDay).padStart(2, "0")}`;
}

function shiftMonthsIso(isoDate: string, months: number): string {
  const year = Number(isoDate.slice(0, 4));
  const month = Number(isoDate.slice(5, 7));
  const shifted = new Date(Date.UTC(year, month - 1 + months, 1));
  return `${shifted.getUTCFullYear()}-${String(shifted.getUTCMonth() + 1).padStart(2, "0")}-01`;
}

export function dashboardRangeParams(
  range: DashboardRangeKey = DEFAULT_DASHBOARD_RANGE,
  today: string = businessTodayIso(),
): DashboardRangeParams {
  switch (range) {
    case "today":
      return { dateFrom: today, dateTo: today };
    case "this-week": {
      const monday = mondayOf(today);
      return { dateFrom: monday, dateTo: addDaysIso(monday, 4) };
    }
    case "last-3-months":
      return {
        dateFrom: monthStartIso(shiftMonthsIso(today, -2)),
        dateTo: monthEndIso(today),
      };
    case "all-time":
      return {};
  }
}