very basics of auth state - not actually authenticating anything right now....

app/useStorageState.tsx

@@ -0,0 +1,65 @@
+import * as SecureStore from 'expo-secure-store'
+import { useCallback, useEffect, useReducer } from 'react'
+import { Platform } from 'react-native'
+
+type UseStateHook<T> = [[boolean, T | null], (value: T | null) => void]
+
+function useAsyncState<T>(initialValue: [boolean, T | null] = [true, null]): UseStateHook<T> {
+    return useReducer(
+        (state: [boolean, T | null], action: T | null = null): [boolean, T | null] => [false, action],
+        initialValue
+    ) as UseStateHook<T>
+}
+
+export async function setStorageItemAsync(key: string, value: string | null) {
+    if (Platform.OS === 'web') {
+        try {
+            if (value === null) {
+                localStorage.removeItem(key)
+            } else {
+                localStorage.setItem(key, value)
+            }
+        } catch (e) {
+            console.error('Local storage is unavailable:', e)
+        }
+    } else {
+        if (value == null) {
+            await SecureStore.deleteItemAsync(key)
+        } else {
+            await SecureStore.setItemAsync(key, value)
+        }
+    }
+}
+
+export function useStorageState(key: string): UseStateHook<string> {
+    // Public
+    const [state, setState] = useAsyncState<string>()
+
+    // Get
+    useEffect(() => {
+        if (Platform.OS === 'web') {
+            try {
+                if (typeof localStorage !== 'undefined') {
+                    setState(localStorage.getItem(key))
+                }
+            } catch (e) {
+                console.error('Local storage is unavailable:', e)
+            }
+        } else {
+            SecureStore.getItemAsync(key).then((value) => {
+                setState(value)
+            })
+        }
+    }, [key, setState])
+
+    // Set
+    const setValue = useCallback(
+        (value: string | null) => {
+            setState(value)
+            setStorageItemAsync(key, value)
+        },
+        [key, setState]
+    )
+
+    return [state, setValue]
+}