diff --git a/src/app/coffee-abonnements/lib/orderRules.ts b/src/app/coffee-abonnements/lib/orderRules.ts
new file mode 100644
index 0000000..affc874
--- /dev/null
+++ b/src/app/coffee-abonnements/lib/orderRules.ts
@@ -0,0 +1,52 @@
+export const CAPSULES_PER_PACK = 10;
+export const MIN_ABO_PACKS = 6;
+export const MAX_ABO_PACKS = 10000;
+export const COFFEE_SELECTIONS_STORAGE_KEY = 'coffeeSelections';
+export const COFFEE_SELECTIONS_UNIT_STORAGE_KEY = 'coffeeSelectionsUnit';
+export const COFFEE_SELECTIONS_UNIT = 'packs-v1';
+
+export function packsToCapsules(packs: number) {
+  return Math.max(0, Math.floor(Number(packs) || 0)) * CAPSULES_PER_PACK;
+}
+
+export function normalizePackCount(value: unknown) {
+  const parsed = Number(value);
+  if (!Number.isFinite(parsed)) return 0;
+  return Math.max(0, Math.floor(parsed));
+}
+
+export function getOrderPackError(totalPacks: number) {
+  if (totalPacks < MIN_ABO_PACKS) {
+    return `Order must contain at least ${MIN_ABO_PACKS} packs (${packsToCapsules(MIN_ABO_PACKS)} capsules).`;
+  }
+
+  if (totalPacks > MAX_ABO_PACKS) {
+    return `Order cannot contain more than ${MAX_ABO_PACKS.toLocaleString('en-US')} packs (${packsToCapsules(MAX_ABO_PACKS).toLocaleString('en-US')} capsules).`;
+  }
+
+  return null;
+}
+
+export function getRemainingMinPacks(totalPacks: number) {
+  return Math.max(0, MIN_ABO_PACKS - totalPacks);
+}
+
+export function normalizeStoredSelections(
+  rawSelections: Record<string, unknown>,
+  unit: string | null,
+) {
+  const entries = Object.entries(rawSelections || {});
+
+  return entries.reduce<Record<string, number>>((acc, [coffeeId, value]) => {
+    const normalizedValue = normalizePackCount(value);
+    if (normalizedValue <= 0) return acc;
+
+    const packCount = unit === COFFEE_SELECTIONS_UNIT
+      ? normalizedValue
+      : (normalizedValue % CAPSULES_PER_PACK === 0 ? normalizedValue / CAPSULES_PER_PACK : normalizedValue);
+
+    if (packCount <= 0) return acc;
+    acc[coffeeId] = Math.min(packCount, MAX_ABO_PACKS);
+    return acc;
+  }, {});
+}
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