mobile: An ugly yet functional signin workflow

1 files changed, 50 insertions, 0 deletions

diff --git a/packages/mobile/lib/storage-state.ts b/packages/mobile/lib/storage-state.ts
new file mode 100644
index 00000000..09917c79
--- /dev/null
+++ b/packages/mobile/lib/storage-state.ts
@@ -0,0 +1,50 @@
+import * as SecureStore from "expo-secure-store";
+import * as React from "react";
+
+type UseStateHook<T> = [[boolean, T | null], (value: T | null) => void];
+
+function useAsyncState<T>(
+  initialValue: [boolean, T | null] = [true, null],
+): UseStateHook<T> {
+  return React.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 (value == null) {
+    await SecureStore.deleteItemAsync(key);
+  } else {
+    await SecureStore.setItemAsync(key, value);
+  }
+}
+
+export function useStorageState<T>(key: string): UseStateHook<T> {
+  // Public
+  const [state, setState] = useAsyncState<T>();
+
+  // Get
+  React.useEffect(() => {
+    SecureStore.getItemAsync(key).then((value) => {
+      if (!value) {
+        return null;
+      }
+      setState(JSON.parse(value));
+    });
+  }, [key]);
+
+  // Set
+  const setValue = React.useCallback(
+    (value: T | null) => {
+      setState(value);
+      setStorageItemAsync(key, JSON.stringify(value));
+    },
+    [key],
+  );
+
+  return [state, setValue];
+}