|string> */ public function rules(): array { return [ 'purchase_date' => ['required', 'date'], 'note' => ['nullable', 'string', 'max:100'], 'items' => ['required', 'array', 'min:1'], 'items.*.product_id' => ['required', Rule::exists('products', 'id')], 'items.*.quantity' => ['required', 'integer', 'min:1'], 'items.*.unit_price' => ['required', 'integer', 'min:0'], ]; } }