Fix format for integer amounts (#231)

* support both fractions and integer values

* test fractions

* prettier

src/app/groups/[groupId]/expenses/create-from-receipt-button.tsx

@@ -206,6 +206,7 @@ export function CreateFromReceiptButton({
                         groupCurrency,
                         receiptInfo.amount,
                         locale,
+                        true,
                       )}
                     </>
                   ) : (

src/lib/utils.test.ts

@@ -57,10 +57,15 @@ describe('formatCurrency', () => {
   ]
 
   for (const variation of variations) {
-    it(`formats ${variation.amount} in ${variation.locale}`, () => {
-      expect(formatCurrency(currency, variation.amount, variation.locale)).toBe(
-        variation.result,
-      )
+    it(`formats ${variation.amount} in ${variation.locale} without fractions`, () => {
+      expect(
+        formatCurrency(currency, variation.amount * 100, variation.locale),
+      ).toBe(variation.result)
+    })
+    it(`formats ${variation.amount} in ${variation.locale} with fractions`, () => {
+      expect(
+        formatCurrency(currency, variation.amount, variation.locale, true),
+      ).toBe(variation.result)
     })
   }
 })

src/lib/utils.ts

@@ -28,10 +28,16 @@ export function formatCategoryForAIPrompt(category: Category) {
   return `"${category.grouping}/${category.name}" (ID: ${category.id})`
 }
 
+/**
+ * @param fractions Financial values in this app are generally processed in cents (or equivalent).
+ * They are are therefore integer representations of the amount (e.g. 100 for USD 1.00).
+ * Set this to `true` if you need to pass a value with decimal fractions instead (e.g. 1.00 for USD 1.00).
+ */
 export function formatCurrency(
   currency: string,
   amount: number,
   locale: string,
+  fractions?: boolean,
 ) {
   const format = new Intl.NumberFormat(locale, {
     minimumFractionDigits: 2,
@@ -40,7 +46,7 @@ export function formatCurrency(
     // '€' will be placed in correct position
     currency: 'EUR',
   })
-  const formattedAmount = format.format(amount)
+  const formattedAmount = format.format(fractions ? amount : amount / 100)
   return formattedAmount.replace('€', currency)
 }