feat(auth): add useAuthIdToken (#156)

README.md

@@ -39,6 +39,7 @@ If you previously used [`react-firebase-hooks`](https://www.npmjs.com/package/re
 This library consists of 4 modules with many hooks:
 
 -   [`auth`](#Auth)
+    -   [`useAuthIdToken`](#useAuthIdToken)
     -   [`useAuthState`](#useAuthState)
 -   [`database`](#Database)
     -   [`useObject`](#useObject)
@@ -71,6 +72,24 @@ All hooks can be imported from `react-firehooks` directly or via `react-firehook
 import { ... } from 'react-firehooks/auth';
 ```
 
+#### useAuthIdToken
+
+Returns and updates the JWT of the currently authenticated user
+
+```javascript
+const [idToken, loading, error] = useAuthIdToken(auth);
+```
+
+Params:
+
+-   `auth`: Firebase Auth instance
+
+Returns:
+
+-   `value`: JWT; `undefined` if the JWT is currently being fetched, or an error occurred
+-   `loading`: `true` while fetching the JWT; `false` if the JWT was fetched successfully or an error occurred
+-   `error`: `undefined` if no error occurred
+
 #### useAuthState
 
 Returns and updates the currently authenticated user
@@ -83,7 +102,7 @@ Params:
 
 -   `auth`: Firebase Auth instance
 
-Params:
+Returns:
 
 -   `value`: User; `undefined` if user is currently being fetched, or an error occurred
 -   `loading`: `true` while fetching the user; `false` if the user was fetched successfully or an error occurred

src/auth/index.ts

@@ -1 +1,2 @@
+export * from "./useAuthIdToken.js";
 export * from "./useAuthState.js";

src/auth/useAuthIdToken.ts

@@ -0,0 +1,38 @@
+import { Auth, AuthError, getIdToken, onIdTokenChanged } from "firebase/auth";
+import { useCallback } from "react";
+import { ValueHookResult } from "../common/index.js";
+import { useListen, UseListenOnChange } from "../internal/useListen.js";
+import { LoadingState } from "../internal/useLoadingValue.js";
+
+export type UseAuthIdTokenResult = ValueHookResult<string | null, AuthError>;
+
+/**
+ * Returns and updates the JWT of the currently authenticated user
+ *
+ * @param {Auth} auth Firebase Auth instance
+ * @returns {UseAuthIdTokenResult} JWT, loading state, and error
+ * * value: JWT; `undefined` if the JWT is currently being fetched, or an error occurred
+ * * loading: `true` while fetching the JWT; `false` if the JWT was fetched successfully or an error occurred
+ * * error: `undefined` if no error occurred
+ */
+export function useAuthIdToken(auth: Auth): UseAuthIdTokenResult {
+    const onChange: UseListenOnChange<string | null, AuthError, Auth> = useCallback(
+        (stableAuth, next, error) =>
+            onIdTokenChanged(stableAuth, async (user) => {
+                if (user) {
+                    try {
+                        // Can also be accessed via `user.accessToken`, but that's not officially documented
+                        const idToken = await getIdToken(user);
+                        next(idToken);
+                    } catch (e) {
+                        error(e as AuthError);
+                    }
+                } else {
+                    next(null);
+                }
+            }),
+        []
+    );
+
+    return useListen(auth, onChange, () => true, LoadingState);
+}