refactor(app): extract refcount utility and clean up server sdk context (#29155)

packages/app/src/utils/refcount.ts

@@ -0,0 +1,26 @@
+import { onCleanup } from "solid-js"
+
+export function createRefCountMap<T>(create: (key: string) => T) {
+  const items = new Map<string, T>()
+  const refCounts = new Map<string, number>()
+
+  return (key: string) => {
+    onCleanup(() => {
+      refCounts.set(key, (refCounts.get(key) ?? 0) - 1)
+      if (refCounts.get(key) === 0) {
+        items.delete(key)
+        refCounts.delete(key)
+      }
+    })
+
+    const cached = items.get(key)
+    if (cached) {
+      refCounts.set(key, (refCounts.get(key) ?? 0) + 1)
+      return cached
+    }
+    const item = create(key)
+    items.set(key, item)
+    refCounts.set(key, 1)
+    return item
+  }
+}