func updateInventoryItem()

in inventory-service/spanner/main.go [110:167]
54 lines of code
8 McCabe index (conditional complexity)

func updateInventoryItem(w http.ResponseWriter, r *http.Request) {
	enableCors(&w)
	if r.URL.Path != "/updateInventoryItem" {
		http.NotFound(w, r)
		return
	}
	switch r.Method {
	case "GET":
		w.Write([]byte("Please POST the following format for data:  [{'itemID': int,'inventoryChange': int}]"))
		return
	case "OPTIONS":
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, Authorization")
		w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS")
		w.WriteHeader((http.StatusOK))
		return
	case "POST":
		(w).Header().Set("content-type", "application/json")
		d := json.NewDecoder(r.Body)
		d.DisallowUnknownFields()
		il := []struct {
			ItemID          int `json:"itemID"`
			InventoryChange int `json:"inventoryChange"`
		}{}
		err := d.Decode(&il)
		if err != nil {
			log.Print(err)
			return
		}
		// In production code you should check and sanatize data. This is a demo however

		log.Print(il)
		// This should be a global variable since it's used more than once
		inventoryHistoryColumns := []string{
			"ItemRowID",
			"ItemID",
			"inventoryChange",
			"timeStamp"}
		m := []*spanner.Mutation{}
		for _, element := range il {
			m = append(m, spanner.Insert(
				"inventoryHistory",
				inventoryHistoryColumns,
				[]interface{}{uuid.New().String(), element.ItemID, element.InventoryChange, time.Now()}))
		}
		_, err = dataClient.Apply(context.Background(), m)
		if err != nil {
			log.Print(err)
			return
		}
		log.Print("Data added to database")
		w.Write([]byte(http.StatusText(http.StatusOK)))

	default:
		w.WriteHeader(http.StatusNotImplemented)
		w.Write([]byte(http.StatusText(http.StatusNotImplemented)))
	}
}