Simpl-Resultat/src/utils/dateRange.ts

import type { DashboardPeriod } from "../shared/types";

/**
 * Compute a date range (dateFrom / dateTo) based on the selected period.
 * Shared between useDashboard, useReports, DashboardPage and ReportsPage.
 */
export function computeDateRange(
  period: DashboardPeriod,
  customDateFrom?: string,
  customDateTo?: string,
): { dateFrom?: string; dateTo?: string } {
  if (period === "all") return {};
  if (period === "custom" && customDateFrom && customDateTo) {
    return { dateFrom: customDateFrom, dateTo: customDateTo };
  }

  const now = new Date();
  const year = now.getFullYear();
  const month = now.getMonth();
  const day = now.getDate();

  const dateTo = `${year}-${String(month + 1).padStart(2, "0")}-${String(day).padStart(2, "0")}`;

  let from: Date;
  switch (period) {
    case "month":
      from = new Date(year, month, 1);
      break;
    case "3months":
      from = new Date(year, month - 2, 1);
      break;
    case "6months":
      from = new Date(year, month - 5, 1);
      break;
    case "year":
      from = new Date(year, 0, 1);
      break;
    case "12months":
      from = new Date(year, month - 11, 1);
      break;
    default:
      from = new Date(year, month, 1);
      break;
  }

  const dateFrom = `${from.getFullYear()}-${String(from.getMonth() + 1).padStart(2, "0")}-${String(from.getDate()).padStart(2, "0")}`;

  return { dateFrom, dateTo };
}

/**
 * Build an array of month options for the budget month dropdown.
 * Returns the last 24 months with localized labels.
 */
export function buildMonthOptions(language: string): Array<{ key: string; value: string; label: string }> {
  const now = new Date();
  const currentMonth = now.getMonth();
  const currentYear = now.getFullYear();
  return Array.from({ length: 24 }, (_, i) => {
    const d = new Date(currentYear, currentMonth - i, 1);
    const y = d.getFullYear();
    const m = d.getMonth() + 1;
    const label = new Intl.DateTimeFormat(language, { month: "long", year: "numeric" }).format(d);
    return { key: `${y}-${m}`, value: `${y}-${m}`, label: label.charAt(0).toUpperCase() + label.slice(1) };
  });
}