Added fake storage shim for local and session storage

src/contexts/AuthContext.js

@@ -4,18 +4,27 @@ import shortid from "shortid";
 import DatabaseContext from "./DatabaseContext";
 
 import { getRandomMonster } from "../helpers/monsters";
+import FakeStorage from "../helpers/FakeStorage";
 
 const AuthContext = React.createContext();
 
+let storage;
+try {
+  sessionStorage.setItem("__test", "__test");
+  sessionStorage.removeItem("__test");
+  storage = sessionStorage;
+} catch (e) {
+  console.warn("Session storage is disabled, no authentication will be saved");
+  storage = new FakeStorage();
+}
+
 export function AuthProvider({ children }) {
   const { database } = useContext(DatabaseContext);
 
-  const [password, setPassword] = useState(
-    sessionStorage.getItem("auth") || ""
-  );
+  const [password, setPassword] = useState(storage.getItem("auth") || "");
 
   useEffect(() => {
-    sessionStorage.setItem("auth", password);
+    storage.setItem("auth", password);
   }, [password]);
 
   const [authenticationStatus, setAuthenticationStatus] = useState("unknown");

src/helpers/FakeStorage.js

@@ -0,0 +1,23 @@
+/**
+ * A faked local or session storage used when the user has disabled storage
+ */
+class FakeStorage {
+  data = {};
+  key(index) {
+    return Object.keys(this.data)[index] || null;
+  }
+  getItem(keyName) {
+    return this.data[keyName] || null;
+  }
+  setItem(keyName, keyValue) {
+    this.data[keyName] = keyValue;
+  }
+  removeItem(keyName) {
+    delete this.data[keyName];
+  }
+  clear() {
+    this.data = {};
+  }
+}
+
+export default FakeStorage;

src/helpers/Settings.js

@@ -1,12 +1,24 @@
+import FakeStorage from "./FakeStorage";
+
 /**
  * An interface to a local storage back settings store with a versioning mechanism
  */
 class Settings {
   name;
   currentVersion;
+  storage;
 
   constructor(name) {
     this.name = name;
+    // Try and use local storage if it is available, if not mock it with an in memory storage
+    try {
+      localStorage.setItem("__test", "__test");
+      localStorage.removeItem("__test");
+      this.storage = localStorage;
+    } catch (e) {
+      console.warn("Local storage is disabled, no settings will be saved");
+      this.storage = new FakeStorage();
+    }
     this.currentVersion = this.get("__version");
   }
 
@@ -18,7 +30,7 @@ class Settings {
   }
 
   getAll() {
-    return JSON.parse(localStorage.getItem(this.name));
+    return JSON.parse(this.storage.getItem(this.name));
   }
 
   get(key) {
@@ -27,7 +39,7 @@ class Settings {
   }
 
   setAll(newSettings) {
-    localStorage.setItem(
+    this.storage.setItem(
       this.name,
       JSON.stringify({ ...newSettings, __version: this.currentVersion })
     );