Chapter 14 - Improve validation

app/lib/actions.ts

@@ -7,9 +7,11 @@ import {redirect} from "next/navigation";
 
 const FormSchema = z.object({
     id: z.string(),
-    customerId: z.string(),
-    amount: z.coerce.number(),
-    status: z.enum(['pending', 'paid']),
+    customerId: z.string({
+        invalid_type_error: 'Please select a customer.',
+    }),
+    amount: z.coerce.number().gt(0, { message: 'Please enter an amount greater than $0.' }),
+    status: z.enum(['pending', 'paid'], { invalid_type_error: 'Please select an invoice status'}),
     date: z.string(),
 });
 
@@ -17,14 +19,33 @@ const UpdateInvoice = FormSchema.omit({ id: true, date: true });
 
 const CreateInvoice = FormSchema.omit({ id: true, date: true });
 
-export async function createInvoice(formData: FormData) {
+export type State = {
+    errors?: {
+        customerId?: string[];
+        amount?: string[];
+        status?: string[];
+    };
+    message?: string | null;
+};
 
-    const { customerId, amount, status } = CreateInvoice.parse({
+export async function createInvoice(prevState: State, formData: FormData) {
+
+    const validatedFields = CreateInvoice.safeParse({
         customerId: formData.get('customerId'),
         amount: formData.get('amount'),
         status: formData.get('status'),
     });
 
+    // If form validation fails, return errors early. Otherwise, continue.
+    if (!validatedFields.success) {
+        return {
+            errors: validatedFields.error.flatten().fieldErrors,
+            message: 'Missing Fields. Failed to Create Invoice.',
+        };
+    }
+
+    const { customerId, amount, status } = validatedFields.data;
+
     const amountInCents = amount * 100;
     const date = new Date().toISOString().split('T')[0];