Add function to check if a token can be placed under a name path

frontend/src/app/main/ui/workspace/tokens/token.cljs

@@ -18,3 +18,31 @@
        (let [path (token-name->path name)]
          (assoc-in acc path token))))
    {} tokens))
+
+(defn token-name-path-exists?
+  "Traverses the path from `token-name` down a `token-tree` and checks if a token at that path exists.
+
+  It's not allowed to create a token inside a token. E.g.:
+  Creating a token with
+
+    {:name \"foo.bar\"}
+
+  in the tokens tree:
+
+    {\"foo\" {:name \"other\"}}"
+  [token-name token-names-tree]
+  (let [name-path (token-name->path token-name)
+        result (reduce
+                (fn [acc cur]
+                  (let [target (get acc cur)]
+                    (cond
+                      ;; Path segment doesn't exist yet
+                      (nil? target) (reduced false)
+                      ;; A token exists at this path
+                      (:name target) (reduced true)
+                      ;; Continue traversing the true
+                      :else target)))
+                token-names-tree name-path)]
+    (if (map? result)
+      (some? (:name result))
+      result)))