enhance(rtc): add ns frontend.worker.rtc.migrate

src/main/frontend/worker/rtc/migrate.cljs

@@ -0,0 +1,39 @@
+(ns frontend.worker.rtc.migrate
+  "Fns to migrate rtc graphs when client-graph-schema and server-graph-schema not matching
+  * when to upload/download to/from remote graph?
+    suppose we have client-schema=X and server-schema=Y.
+    there're several different schema-version graphs on server at the same time.
+    - if X = Y, nothing need to do with migration
+    - if X > Y, client-graph is newer than server-graph, we need to upload this client-graph
+    - if X < Y, client-app need to upgrade, otherwise, this client will keep rtc with server-graph-X
+    - if X < Y, and client-app upgraded, now it should download the server-graph-Y"
+  (:require [logseq.db.frontend.schema :as db-schema]))
+
+(def client-app-schema db-schema/version)
+
+(defn compare-schemas
+  "Return one of [:upload :download nil].
+  when nil, nothing need to do"
+  [server-graph-state server-graph-schema app-schema client-graph-schema]
+  (cond
+    (= server-graph-schema client-graph-schema)
+    nil
+
+    (> server-graph-schema client-graph-schema)
+    (cond
+      ;; client will do some migrations on local-graph,
+      ;; so rtc-migrate do nothing for now
+      (< server-graph-schema app-schema) nil
+      ;; server-graph is newer than client-graph,
+      ;; but client-app-schema > server-graph-schema,
+      ;; so, app need to be upgraded, do nothing for now
+      (> server-graph-schema app-schema) nil
+      (= server-graph-schema app-schema) :download)
+
+    (< server-graph-schema client-graph-schema)
+    (cond
+      ;; TODO: this remote-graph is migrating now,
+      ;; disallow upload a new schema-version graph for now
+      (= :TODO-migrating server-graph-state) nil
+      :else :upload
+      )))