export type RangePreset = 'today' | 'yesterday' | 'thisWeek' | 'thisMonth' | 'last7' | 'last15';

function formatLocalDate(date: Date): string {
  return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}-${String(date.getDate()).padStart(2, '0')}`;
}

/**
 * The monitoring day rolls over at 05:00 local time. Before then the dashboard
 * continues to use the previous calendar day, matching the existing UI rule.
 */
export function defaultMileageDate(now = new Date()): string {
  const date = new Date(now);
  if (date.getHours() < 5) date.setDate(date.getDate() - 1);
  return formatLocalDate(date);
}

export function normalizeRangeLabel(start: string, end: string): string {
  if (!start && !end) return '最新数据';
  if (start && end && start === end) return start;
  return `${start || end} 至 ${end || start}`;
}

export function getRangePreset(
  preset: RangePreset,
  now = new Date(),
): { start: string; end: string } {
  const end = new Date(`${defaultMileageDate(now)}T00:00:00`);
  const start = new Date(end);

  if (preset === 'yesterday') {
    start.setDate(start.getDate() - 1);
    end.setDate(end.getDate() - 1);
  } else if (preset === 'thisWeek') {
    const day = start.getDay() || 7;
    start.setDate(start.getDate() - day + 1);
  } else if (preset === 'thisMonth') {
    start.setDate(1);
  } else if (preset === 'last7') {
    start.setDate(start.getDate() - 6);
  } else if (preset === 'last15') {
    start.setDate(start.getDate() - 14);
  }

  return { start: formatLocalDate(start), end: formatLocalDate(end) };
}