CODEBASE: Refactor and fix issues in db.ts (#2623)

src/utils/SaveDataMigrationUtils.ts

@@ -537,8 +537,12 @@ Error: ${e}`,
        * Backup pre-v3 save data. We must use the data in IndexedDB instead of calling saveObject.getSaveData().
        * getSaveData() returns data in v3 format, so the exported data will not be importable in pre-v3.
        */
-      const saveData = await load();
-      downloadContentAsFile(saveData, `bitburnerSave_backup_2.8.1_${Math.round(Player.lastUpdate / 1000)}.json.gz`);
+      const saveData = await load(true);
+      if (saveData !== undefined) {
+        downloadContentAsFile(saveData, `bitburnerSave_backup_2.8.1_${Math.round(Player.lastUpdate / 1000)}.json.gz`);
+      } else {
+        console.error("Cannot back up save data before migrating to v3. The save data is somehow undefined.");
+      }
     } catch (error) {
       console.error("Cannot export pre-v3 save data", error);
     }

src/utils/TypeAssertion.ts

@@ -90,6 +90,14 @@ export function assertNumberArray(unknownData: unknown, assertFinite = false): a
   }
 }
 
+export function isSaveData(unknownData: unknown): unknownData is SaveData {
+  if (typeof unknownData === "string") {
+    return true;
+  }
+
+  return unknownData instanceof Uint8Array && unknownData.buffer instanceof ArrayBuffer;
+}
+
 export function assertSaveData(unknownData: unknown): asserts unknownData is SaveData {
   if (typeof unknownData !== "string" && !(unknownData instanceof Uint8Array)) {
     console.error(unknownData);