1 files changed, 39 insertions, 0 deletions
diff --git a/excalidraw-app/data/tabSync.ts b/excalidraw-app/data/tabSync.ts
new file mode 100644
index 0000000..0617a55
--- /dev/null
+++ b/excalidraw-app/data/tabSync.ts
@@ -0,0 +1,39 @@
+import { STORAGE_KEYS } from "../app_constants";
+
+// in-memory state (this tab's current state) versions. Currently just
+// timestamps of the last time the state was saved to browser storage.
+const LOCAL_STATE_VERSIONS = {
+  [STORAGE_KEYS.VERSION_DATA_STATE]: -1,
+  [STORAGE_KEYS.VERSION_FILES]: -1,
+};
+
+type BrowserStateTypes = keyof typeof LOCAL_STATE_VERSIONS;
+
+export const isBrowserStorageStateNewer = (type: BrowserStateTypes) => {
+  const storageTimestamp = JSON.parse(localStorage.getItem(type) || "-1");
+  return storageTimestamp > LOCAL_STATE_VERSIONS[type];
+};
+
+export const updateBrowserStateVersion = (type: BrowserStateTypes) => {
+  const timestamp = Date.now();
+  try {
+    localStorage.setItem(type, JSON.stringify(timestamp));
+    LOCAL_STATE_VERSIONS[type] = timestamp;
+  } catch (error) {
+    console.error("error while updating browser state verison", error);
+  }
+};
+
+export const resetBrowserStateVersions = () => {
+  try {
+    for (const key of Object.keys(
+      LOCAL_STATE_VERSIONS,
+    ) as BrowserStateTypes[]) {
+      const timestamp = -1;
+      localStorage.setItem(key, JSON.stringify(timestamp));
+      LOCAL_STATE_VERSIONS[key] = timestamp;
+    }
+  } catch (error) {
+    console.error("error while resetting browser state verison", error);
+  }
+};