Rename patterns/server-action.md to docs/patterns/server-action.md

docs/patterns/server-action.md

@@ -0,0 +1,53 @@
+# Patroon: Server Action
+
+Altijd in `actions/[domein].ts`. Nooit inline in page.tsx.
+
+```ts
+'use server'
+
+import { revalidatePath } from 'next/cache'
+import { getIronSession } from 'iron-session'
+import { cookies } from 'next/headers'
+import { z } from 'zod'
+import { prisma } from '@/lib/prisma'
+import { SessionData, sessionOptions } from '@/lib/session'
+
+const schema = z.object({
+  productId: z.string().cuid(),
+  title: z.string().min(1).max(200),
+  priority: z.number().int().min(1).max(4),
+})
+
+export async function createPbi(formData: FormData) {
+  // 1. Auth
+  const session = await getIronSession<SessionData>(await cookies(), sessionOptions)
+  if (!session.userId) return { error: 'Niet ingelogd' }
+  if (session.isDemo) return { error: 'Niet beschikbaar in demo-modus' }
+
+  // 2. Validatie
+  const parsed = schema.safeParse({
+    productId: formData.get('productId'),
+    title: formData.get('title'),
+    priority: Number(formData.get('priority')),
+  })
+  if (!parsed.success) return { error: parsed.error.flatten().fieldErrors }
+
+  // 3. Eigenaarschap controleren
+  const product = await prisma.product.findFirst({
+    where: { id: parsed.data.productId, user_id: session.userId }
+  })
+  if (!product) return { error: 'Product niet gevonden' }
+
+  // 4. Schrijven
+  const last = await prisma.pbi.findFirst({
+    where: { product_id: parsed.data.productId, priority: parsed.data.priority },
+    orderBy: { sort_order: 'desc' },
+  })
+  const pbi = await prisma.pbi.create({
+    data: { ...parsed.data, product_id: parsed.data.productId, sort_order: (last?.sort_order ?? 0) + 1.0 },
+  })
+
+  revalidatePath(`/products/${parsed.data.productId}`)
+  return { success: true, pbi }
+}
+```