feat: Sync local storage state across tabs when out of sync (#4545)

Co-authored-by: dwelle <luzar.david@gmail.com>

src/excalidraw-app/data/localStorage.ts

@@ -5,14 +5,8 @@ import {
   getDefaultAppState,
 } from "../../appState";
 import { clearElementsForLocalStorage } from "../../element";
-
-export const STORAGE_KEYS = {
-  LOCAL_STORAGE_ELEMENTS: "excalidraw",
-  LOCAL_STORAGE_APP_STATE: "excalidraw-state",
-  LOCAL_STORAGE_COLLAB: "excalidraw-collab",
-  LOCAL_STORAGE_KEY_COLLAB_FORCE_FLAG: "collabLinkForceLoadFlag",
-  LOCAL_STORAGE_LIBRARY: "excalidraw-library",
-};
+import { updateBrowserStateVersion } from "./tabSync";
+import { STORAGE_KEYS } from "../app_constants";
 
 export const saveUsernameToLocalStorage = (username: string) => {
   try {
@@ -53,6 +47,7 @@ export const saveToLocalStorage = (
       STORAGE_KEYS.LOCAL_STORAGE_APP_STATE,
       JSON.stringify(clearAppStateForLocalStorage(appState)),
     );
+    updateBrowserStateVersion(STORAGE_KEYS.VERSION_DATA_STATE);
   } catch (error: any) {
     // Unable to access window.localStorage
     console.error(error);
@@ -125,3 +120,17 @@ export const getTotalStorageSize = () => {
     return 0;
   }
 };
+
+export const getLibraryItemsFromStorage = () => {
+  try {
+    const libraryItems =
+      JSON.parse(
+        localStorage.getItem(STORAGE_KEYS.LOCAL_STORAGE_LIBRARY) as string,
+      ) || [];
+
+    return libraryItems;
+  } catch (e) {
+    console.error(e);
+    return [];
+  }
+};

src/excalidraw-app/data/tabSync.ts

@@ -0,0 +1,29 @@
+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();
+  localStorage.setItem(type, JSON.stringify(timestamp));
+  LOCAL_STATE_VERSIONS[type] = timestamp;
+};
+
+export const resetBrowserStateVersions = () => {
+  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;
+  }
+};