Kantongku: aplikasi pencatat keuangan pribadi offline-first

src/utils/format.ts

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+export function formatRupiah(value: number): string {
+  const formatted = Math.abs(value).toLocaleString('id-ID');
+  return `${value < 0 ? '-' : ''}Rp ${formatted}`;
+}
+
+/** Format angka mentah (string digit) jadi ribuan ber-titik, misal "50000" -> "50.000" */
+export function formatRibuan(raw: string): string {
+  if (!raw) return '';
+  const n = Number(raw);
+  if (!Number.isFinite(n)) return raw;
+  return n.toLocaleString('id-ID');
+}
+
+export function formatRupiahShort(value: number): string {
+  if (Math.abs(value) >= 1_000_000) {
+    const juta = value / 1_000_000;
+    return `Rp ${juta.toLocaleString('id-ID', { maximumFractionDigits: 1 })} jt`;
+  }
+  if (Math.abs(value) >= 1_000) {
+    const ribu = value / 1_000;
+    return `Rp ${ribu.toLocaleString('id-ID', { maximumFractionDigits: 1 })} rb`;
+  }
+  return formatRupiah(value);
+}
+
+export function formatDate(iso: string): string {
+  const d = new Date(iso);
+  return d.toLocaleDateString('id-ID', {
+    day: 'numeric',
+    month: 'short',
+    year: 'numeric',
+  });
+}
+
+export function formatDateTime(iso: string): string {
+  const d = new Date(iso);
+  const date = d.toLocaleDateString('id-ID', { day: 'numeric', month: 'short' });
+  const time = d.toLocaleTimeString('id-ID', {
+    hour: '2-digit',
+    minute: '2-digit',
+  });
+  return `${date} · ${time}`;
+}
+
+export function todayLabel(): string {
+  return new Date().toLocaleDateString('id-ID', {
+    weekday: 'long',
+    day: 'numeric',
+    month: 'long',
+    year: 'numeric',
+  });
+}
+
+/** Kunci minggu ISO sederhana: tanggal Senin (YYYY-MM-DD) */
+export function isoWeekKey(d: Date): string {
+  const date = new Date(d);
+  const day = date.getDay() || 7; // Senin=1, ..., Minggu=7
+  date.setDate(date.getDate() - (day - 1));
+  date.setHours(0, 0, 0, 0);
+  return date.toISOString().slice(0, 10);
+}
+
+export function shiftWeekKey(key: string, deltaWeeks: number): string {
+  const monday = new Date(`${key}T00:00:00Z`);
+  monday.setUTCDate(monday.getUTCDate() + deltaWeeks * 7);
+  return monday.toISOString().slice(0, 10);
+}