Feat/proactive token validation before requests

packages/fresh_dio/example/packages/jsonplaceholder_client/lib/src/jsonplaceholder_client.dart

@@ -33,6 +33,15 @@ class JsonplaceholderClient {
       );
     },
     shouldRefresh: (_) => Random().nextInt(3) == 0,
+    shouldRefreshBeforeRequest: (token) async {
+      print('Checking token validity before request...');
+      final now = currentUnixTime();
+      final issuedAt = await fetchIssuedAt();
+      if (token?.expiresIn != null && issuedAt != null) {
+        return (issuedAt + token!.expiresIn!) < now;
+      }
+      return false;
+    },
   );
 
   final Dio _httpClient;
@@ -45,10 +54,13 @@ class JsonplaceholderClient {
     required String password,
   }) async {
     await Future<void>.delayed(const Duration(seconds: 1));
+    final issuedAt = currentUnixTime();
+    await storeIssuedAt(issuedAt);
     await _fresh.setToken(
       const OAuth2Token(
         accessToken: 'initial_access_token',
         refreshToken: 'initial_refresh_token',
+        expiresIn: 60,
       ),
     );
   }
@@ -69,4 +81,23 @@ class JsonplaceholderClient {
         .map((dynamic item) => Photo.fromJson(item as Map<String, dynamic>))
         .toList();
   }
+
+  /// Returns the current Unix time in seconds (since January 1, 1970, UTC).
+  static int currentUnixTime() {
+    return DateTime.now().millisecondsSinceEpoch ~/ 1000;
+  }
+
+  /// Simulate storing issuedAt when a token is set or refreshed.
+  static int? _storedIssuedAt;
+
+  static Future<void> storeIssuedAt(int issuedTime) async {
+    print('Storing issuedAt: $issuedTime');
+    _storedIssuedAt = issuedTime;
+  }
+
+  /// Simulate fetching issuedAt from storage.
+  static Future<int?> fetchIssuedAt() async {
+    print('Fetching issuedAt...');
+    return _storedIssuedAt;
+  }
 }

packages/fresh_dio/lib/src/fresh.dart

@@ -6,6 +6,9 @@ import 'package:fresh_dio/fresh_dio.dart';
 /// Signature for `shouldRefresh` on [Fresh].
 typedef ShouldRefresh = bool Function(Response<dynamic>? response);
 
+/// Signature for proactive token validation before a request.
+typedef ShouldRefreshBeforeRequest<T> = Future<bool> Function(T? token);
+
 /// Signature for `refreshToken` on [Fresh].
 typedef RefreshToken<T> = Future<T> Function(T? token, Dio httpClient);
 
@@ -30,10 +33,12 @@ class Fresh<T> extends QueuedInterceptor with FreshMixin<T> {
     required TokenStorage<T> tokenStorage,
     required RefreshToken<T> refreshToken,
     ShouldRefresh? shouldRefresh,
+    ShouldRefreshBeforeRequest<T>? shouldRefreshBeforeRequest,
     Dio? httpClient,
   })  : _refreshToken = refreshToken,
         _tokenHeader = tokenHeader,
         _shouldRefresh = shouldRefresh ?? _defaultShouldRefresh,
+        _shouldRefreshBeforeRequest = shouldRefreshBeforeRequest,
         _httpClient = httpClient ?? Dio() {
     this.tokenStorage = tokenStorage;
   }
@@ -53,13 +58,15 @@ class Fresh<T> extends QueuedInterceptor with FreshMixin<T> {
     required TokenStorage<OAuth2Token> tokenStorage,
     required RefreshToken<OAuth2Token> refreshToken,
     ShouldRefresh? shouldRefresh,
+    ShouldRefreshBeforeRequest<OAuth2Token>? shouldRefreshBeforeRequest,
     Dio? httpClient,
     TokenHeaderBuilder<OAuth2Token>? tokenHeader,
   }) {
     return Fresh<OAuth2Token>(
       refreshToken: refreshToken,
       tokenStorage: tokenStorage,
       shouldRefresh: shouldRefresh,
+      shouldRefreshBeforeRequest: shouldRefreshBeforeRequest,
       httpClient: httpClient,
       tokenHeader: tokenHeader ??
           (token) {
@@ -73,6 +80,7 @@ class Fresh<T> extends QueuedInterceptor with FreshMixin<T> {
   final Dio _httpClient;
   final TokenHeaderBuilder<T> _tokenHeader;
   final ShouldRefresh _shouldRefresh;
+  final ShouldRefreshBeforeRequest<T>? _shouldRefreshBeforeRequest;
   final RefreshToken<T> _refreshToken;
 
   @override
@@ -103,7 +111,20 @@ Example:
 ''',
     );
 
-    final currentToken = await token;
+    var currentToken = await token;
+
+    if (_shouldRefreshBeforeRequest != null &&
+        currentToken != null &&
+        await _shouldRefreshBeforeRequest!(currentToken)) {
+      try {
+        final refreshedToken = await _refreshToken(currentToken, _httpClient);
+        await setToken(refreshedToken);
+        currentToken = await token;
+      } on RevokeTokenException catch (_) {
+        unawaited(revokeToken());
+      }
+    }
+
     final headers = currentToken != null
         ? _tokenHeader(currentToken)
         : const <String, String>{};

packages/fresh_graphql/example/main.dart

@@ -14,21 +14,61 @@ const getJobsQuery = '''
   }
 ''';
 
+// Mock storage for issuedAt
+int? issuedAt;
+
+// Simulate storing issuedAt when the token is set
+Future<void> storeIssuedAt(int issuedTime) async {
+  print('Storing issuedAt: $issuedTime');
+  issuedAt = issuedTime;
+}
+
+// Simulate fetching issuedAt from storage
+Future<int?> fetchIssuedAt() async {
+  print('Fetching issuedAt...');
+  return issuedAt;
+}
+
+/// Returns the current Unix time in seconds (since January 1, 1970, UTC).
+int currentUnixTime() => DateTime.now().millisecondsSinceEpoch ~/ 1000;
+
 void main() async {
   final freshLink = FreshLink.oAuth2(
     tokenStorage: InMemoryTokenStorage(),
     refreshToken: (token, client) async {
       // Perform refresh and return new token
       print('refreshing token!');
       await Future<void>.delayed(const Duration(seconds: 1));
-      if (Random().nextInt(1) == 0) {
+      if (Random().nextInt(2) == 0) {
         throw RevokeTokenException();
       }
-      return const OAuth2Token(accessToken: 't0ps3cret_r3fresh3d!');
+      final newIssuedAt = currentUnixTime();
+      await storeIssuedAt(newIssuedAt);
+      return const OAuth2Token(accessToken: 'refreshed_token!', expiresIn: 30);
     },
     shouldRefresh: (_) => Random().nextInt(2) == 0,
+    shouldRefreshBeforeRequest: (token) async {
+      print('Checking token validity before request...');
+      final now = currentUnixTime();
+      final storedIssuedAt = await fetchIssuedAt();
+      if (token?.expiresIn != null && storedIssuedAt != null) {
+        return (storedIssuedAt + token!.expiresIn!) < now;
+      }
+      return false;
+    },
   )..authenticationStatus.listen(print);
-  await freshLink.setToken(const OAuth2Token(accessToken: 't0ps3cret!'));
+
+  // Set the initial token and store issuedAt
+  final initialIssuedAt = currentUnixTime();
+  await storeIssuedAt(initialIssuedAt);
+
+  await freshLink.setToken(
+    const OAuth2Token(
+      accessToken: 't0ps3cret!',
+      expiresIn: 30,
+    ),
+  );
+
   final graphQLClient = GraphQLClient(
     cache: GraphQLCache(),
     link: Link.from([freshLink, HttpLink('https://api.graphql.jobs')]),

packages/fresh_graphql/lib/src/fresh_link.dart

@@ -8,14 +8,17 @@ import 'package:http/http.dart' as http;
 /// Signature for `shouldRefresh` on [FreshLink].
 typedef ShouldRefresh = bool Function(Response);
 
+/// Signature for proactive token validation before a request.
+typedef ShouldRefreshBeforeRequest<T> = Future<bool> Function(T? token);
+
 /// Signature for `refreshToken` on [FreshLink].
 typedef RefreshToken<T> = Future<T> Function(T, http.Client);
 
 /// {@template fresh_link}
-/// A GraphQL Link which handles manages an authentication token automatically.
+/// A GraphQL Link which manages an authentication token automatically.
 ///
 /// A constructor that returns a Fresh interceptor that uses the
-/// [OAuth2Token] token, the standard token class and define the`
+/// [OAuth2Token] token, the standard token class and defines the
 /// tokenHeader as 'authorization': '${token.tokenType} ${token.accessToken}'
 ///
 /// ```dart
@@ -37,15 +40,17 @@ class FreshLink<T> extends Link with FreshMixin<T> {
     required TokenStorage<T> tokenStorage,
     required RefreshToken<T?> refreshToken,
     required ShouldRefresh shouldRefresh,
+    ShouldRefreshBeforeRequest<T>? shouldRefreshBeforeRequest,
     TokenHeaderBuilder<T?>? tokenHeader,
   })  : _refreshToken = refreshToken,
         _tokenHeader = (tokenHeader ?? (_) => <String, String>{}),
-        _shouldRefresh = shouldRefresh {
+        _shouldRefresh = shouldRefresh,
+        _shouldRefreshBeforeRequest = shouldRefreshBeforeRequest {
     this.tokenStorage = tokenStorage;
   }
 
   ///{@template fresh_link}
-  ///A GraphQL Link which handles manages an authentication token automatically.
+  ///A GraphQL Link which manages an authentication token automatically.
   ///
   /// ```dart
   /// final freshLink = FreshLink.oAuth2(
@@ -64,12 +69,14 @@ class FreshLink<T> extends Link with FreshMixin<T> {
     required TokenStorage<OAuth2Token> tokenStorage,
     required RefreshToken<OAuth2Token?> refreshToken,
     required ShouldRefresh shouldRefresh,
+    ShouldRefreshBeforeRequest<OAuth2Token>? shouldRefreshBeforeRequest,
     TokenHeaderBuilder<OAuth2Token?>? tokenHeader,
   }) {
     return FreshLink<OAuth2Token>(
       refreshToken: refreshToken,
       tokenStorage: tokenStorage,
       shouldRefresh: shouldRefresh,
+      shouldRefreshBeforeRequest: shouldRefreshBeforeRequest,
       tokenHeader: tokenHeader ??
           (token) {
             return {
@@ -82,10 +89,24 @@ class FreshLink<T> extends Link with FreshMixin<T> {
   final RefreshToken<T?> _refreshToken;
   final TokenHeaderBuilder<T?> _tokenHeader;
   final ShouldRefresh _shouldRefresh;
+  final ShouldRefreshBeforeRequest<T>? _shouldRefreshBeforeRequest;
 
   @override
   Stream<Response> request(Request request, [NextLink? forward]) async* {
-    final currentToken = await token;
+    var currentToken = await token;
+
+    if (_shouldRefreshBeforeRequest != null &&
+        currentToken != null &&
+        await _shouldRefreshBeforeRequest!(currentToken)) {
+      try {
+        final refreshedToken = await _refreshToken(currentToken, http.Client());
+        await setToken(refreshedToken);
+        currentToken = await token;
+      } on RevokeTokenException catch (_) {
+        unawaited(revokeToken());
+      }
+    }
+
     final tokenHeaders = currentToken != null
         ? _tokenHeader(currentToken)
         : const <String, String>{};