Initial work, copied from the Shopify provider

framework/saleor/customer/get-customer-id.ts

@@ -0,0 +1,24 @@
+import { getConfig, SaleorConfig } from '../api'
+import getCustomerIdQuery from '../utils/queries/get-customer-id-query'
+import Cookies from 'js-cookie'
+
+async function getCustomerId({
+  customerToken: customerAccesToken,
+  config,
+}: {
+  customerToken: string
+  config?: SaleorConfig
+}): Promise<number | undefined> {
+  config = getConfig(config)
+
+  const { data } = await config.fetch(getCustomerIdQuery, {
+    variables: {
+      customerAccesToken:
+        customerAccesToken || Cookies.get(config.customerCookie),
+    },
+  })
+
+  return data.customer?.id
+}
+
+export default getCustomerId