feat: add currency for articles (#834)

Co-authored-by: Jakob Wennberg <jakob.wennberg@gmail.com>

components/articles/ArticleForm.tsx

@@ -19,6 +19,13 @@ import AccountCombobox from '@/components/bookkeeping/AccountCombobox'
 import { AddAccountDialog } from '@/components/bookkeeping/AddAccountDialog'
 import type { BASAccount, CreateArticleInput } from '@/types'
 
+// A row from the currencies reference table (lib migration
+// 20260630110000_currencies_reference_table.sql).
+interface CurrencyOption {
+  code: string
+  name: string
+}
+
 // Unit list mirrors the invoice line editor (app/(dashboard)/invoices/new/page.tsx).
 const UNITS = ['st', 'tim', 'dag', 'månad', 'km', 'kg'] as const
 
@@ -52,6 +59,10 @@ export default function ArticleForm({
   // Momsregistrerad? A non-VAT-registered company never charges moms, so the
   // VAT field is hidden and the rate forced to 0: mirrors the invoice editor.
   const [vatRegistered, setVatRegistered] = useState(true)
+  // Supported currencies, fetched from the currencies reference table rather
+  // than hard-coded. Falls back to the article's own currency (or SEK) if the
+  // fetch fails so the Select is never empty.
+  const [currencies, setCurrencies] = useState<CurrencyOption[]>([])
 
   async function fetchRevenueAccounts() {
     try {
@@ -67,6 +78,24 @@ export default function ArticleForm({
     fetchRevenueAccounts()
   }, [])
 
+  // Currency options come from the currencies reference table: one source of
+  // truth, no hard-coded list.
+  useEffect(() => {
+    let cancelled = false
+    supabase
+      .from('currencies')
+      .select('code, name')
+      .eq('active', true)
+      .order('sort_order', { ascending: true })
+      .then(({ data }) => {
+        if (!cancelled && data) setCurrencies(data as CurrencyOption[])
+      })
+    return () => {
+      cancelled = true
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [])
+
   useEffect(() => {
     if (!company?.id) return
     let cancelled = false
@@ -89,7 +118,8 @@ export default function ArticleForm({
   // edit never hides a value the user previously set.
   const [advancedOpen, setAdvancedOpen] = useState(
     Boolean(
-      initialData?.revenue_account ||
+      (initialData?.currency && initialData.currency !== 'SEK') ||
+        initialData?.revenue_account ||
         initialData?.cost_price != null ||
         initialData?.ean ||
         initialData?.housework_type ||
@@ -107,6 +137,9 @@ export default function ArticleForm({
         unit: z.string().min(1),
         price_excl_vat: z.number({ message: t('price_required') }).nonnegative(t('price_required')),
         vat_rate: z.union([z.literal(25), z.literal(12), z.literal(6), z.literal(0)]),
+        // ISO 4217 alpha-3; the authoritative allow-list is the currencies
+        // table (the DB FK rejects unknown codes).
+        currency: z.string().regex(/^[A-Z]{3}$/),
         revenue_account: z.string().optional(),
         cost_price: z.number().nonnegative().optional(),
         ean: z.string().optional(),
@@ -134,6 +167,7 @@ export default function ArticleForm({
       unit: initialData?.unit || 'st',
       price_excl_vat: initialData?.price_excl_vat ?? 0,
       vat_rate: (initialData?.vat_rate as FormData['vat_rate']) ?? 25,
+      currency: initialData?.currency ?? 'SEK',
       revenue_account: initialData?.revenue_account || '',
       cost_price: initialData?.cost_price ?? undefined,
       ean: initialData?.ean || '',
@@ -152,6 +186,7 @@ export default function ArticleForm({
       unit: data.unit,
       price_excl_vat: data.price_excl_vat,
       vat_rate: vatRegistered ? data.vat_rate : 0,
+      currency: data.currency,
       revenue_account: data.revenue_account || null,
       cost_price: data.cost_price ?? null,
       ean: data.ean || null,
@@ -317,6 +352,36 @@ export default function ArticleForm({
               <p className="text-xs text-muted-foreground">{t('cost_price_hint')}</p>
             </div>
 
+            {/* Currency */}
+            <div className="space-y-2">
+              <Label>{t('currency_label')}</Label>
+              <Controller
+                name="currency"
+                control={control}
+                render={({ field }) => {
+                  // Always keep the current value selectable, even before the
+                  // fetch resolves or if it's since been deactivated.
+                  const codes = currencies.map((c) => c.code)
+                  const options = codes.includes(field.value)
+                    ? codes
+                    : [field.value, ...codes]
+                  return (
+                    <Select value={field.value} onValueChange={(v) => { if (v) field.onChange(v) }}>
+                      <SelectTrigger>
+                        <SelectValue />
+                      </SelectTrigger>
+                      <SelectContent>
+                        {options.map((c) => (
+                          <SelectItem key={c} value={c}>{c}</SelectItem>
+                        ))}
+                      </SelectContent>
+                    </Select>
+                  )
+                }}
+              />
+              <p className="text-xs text-muted-foreground">{t('currency_hint')}</p>
+            </div>
+
             {/* EAN */}
             <div className="space-y-2">
               <Label htmlFor="ean">{t('ean_label')}</Label>

components/invoices/InvoiceEditor.tsx

@@ -84,7 +84,7 @@ export type InvoiceEditorProps = (
 // Subset of Article fields the line picker needs to pre-fill a row.
 type ArticleOption = Pick<
   Article,
-  'id' | 'article_number' | 'name' | 'unit' | 'price_excl_vat' | 'vat_rate' | 'revenue_account'
+  'id' | 'article_number' | 'name' | 'unit' | 'price_excl_vat' | 'vat_rate' | 'revenue_account' | 'currency'
 >
 
 function RequiredMark() {
@@ -321,7 +321,8 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
     watch,
     setValue,
     setError,
-    formState: { errors, isDirty },
+    getValues,
+    formState: { errors, isDirty, dirtyFields },
   } = useForm<FormData>({
     resolver: zodResolver(schema),
     // Edit mode pre-fills from the existing draft (header + every line incl.
@@ -475,7 +476,7 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
     if (!company?.id) return
     const { data } = await supabase
       .from('articles')
-      .select('id, article_number, name, unit, price_excl_vat, vat_rate, revenue_account')
+      .select('id, article_number, name, unit, price_excl_vat, vat_rate, revenue_account, currency')
       .eq('company_id', company.id)
       .eq('active', true)
       .order('name')
@@ -517,6 +518,27 @@ export default function InvoiceEditor(props: InvoiceEditorProps = { mode: 'creat
     // The account override rides along regardless of rate; the engine ignores it
     // for reverse-charge/export and validates it against the chart of accounts.
     setValue(`items.${index}.revenue_account`, a.revenue_account ?? null, { shouldDirty: true })
+    // Pre-fill the invoice's (single) currency from the article ONLY on the
+    // first priced line, and only while the user hasn't chosen a currency
+    // themselves. Never flip an in-progress invoice's currency on a later pick:
+    // an invoice carries one currency for all its lines, so overwriting it would
+    // relabel existing line amounts (or the user's explicit choice) as another
+    // currency with no FX conversion, producing a legally wrong faktura and
+    // wrong VAT (ML 17 kap). The article's currency comes from the currencies
+    // reference table.
+    const currencyUserSet = Boolean(dirtyFields.currency)
+    const invoiceHasOtherContent = (watchItems ?? []).some(
+      (it, i) => i !== index && (Boolean(it?.article_id) || Number(it?.unit_price) > 0)
+    )
+    if (
+      a.currency &&
+      currencies.includes(a.currency as Currency) &&
+      a.currency !== getValues('currency') &&
+      !currencyUserSet &&
+      !invoiceHasOtherContent
+    ) {
+      setValue('currency', a.currency as Currency, { shouldDirty: true })
+    }
   }
 
   // "Spara som artikel": persist the current free-text line into the register and