feat: versionedLocalStorage

core/static/bundled/core/cache.ts

@@ -1,13 +1,21 @@
+/**
+ * For more detailed infos on how to use this file,
+ * check /docs/tutorial/front/localstorage.md,
+ * or https://ae-utbm.github.io/sith/tutorial/front/localstorage/
+ */
+
 // increment this number when a breaking change is made with localStorage
 const CURRENT_CACHE_VERSION = 1;
 
+/**
+ * Remove keys that are no longer used from localStorage
+ */
 export function cacheBuster() {
   const version = Number.parseInt(localStorage.getItem("version") ?? "0", 10);
   if (version === CURRENT_CACHE_VERSION) {
     // The cache schema is up-to-date. Nothing to do.
     return;
   }
-  localStorage.removeItem("basket");
   localStorage.removeItem("basket1");
   // remove all storage items which key is in the form
   // `userXXXPictures` or `userXXXPicturesNumber`
@@ -22,3 +30,43 @@ export function cacheBuster() {
     });
   localStorage.setItem("version", CURRENT_CACHE_VERSION.toString());
 }
+
+interface VersionedStorageItem<T> {
+  version?: number;
+  val: T | undefined;
+}
+
+export const versionedLocalStorage = {
+  ...localStorage,
+  /**
+   * set this item in localStorage, alongside its version.
+   *
+   * Note: this expects an object, not a JSON string, because the parsing
+   * into JSON needs to be done inside the function.
+   */
+  setItem<T>(key: string, value: T, { version }: { version: number }) {
+    localStorage.setItem(key, JSON.stringify({ version: version, val: value }));
+  },
+  /**
+   * Get the item linked with the given key and version from localStorage.
+   *
+   * Note: if the given key exists in localStorage but doesn't satisfy
+   * the given version, it will be cleared from cache.
+   *
+   * @return the object if found and with the good version, else null;
+   */
+  getItem<T>(key: string, { version }: { version: number }): T | null {
+    const stored = localStorage.getItem(key);
+    if (!stored) {
+      // this key doesn't exist, return null;
+      return null;
+    }
+    const obj: VersionedStorageItem<T> = JSON.parse(stored);
+    if (obj.version !== version || obj.val === undefined) {
+      // The version is wrong, return null and remove this item from cache
+      localStorage.removeItem(key);
+      return null;
+    }
+    return obj.val;
+  },
+};