fix: Retry access token refresh when offline

lib/src/fetch.dart

@@ -1,4 +1,5 @@
 import 'dart:convert';
+import 'dart:io';
 
 import 'package:gotrue/src/fetch_options.dart';
 import 'package:gotrue/src/gotrue_error.dart';
@@ -25,6 +26,11 @@ class Fetch {
       } on FormatException catch (_) {
         return GotrueError(error.body);
       }
+    } else if (error is SocketException) {
+      return GotrueError(
+        error.toString(),
+        statusCode: error.runtimeType.toString(),
+      );
     } else {
       return GotrueError(error.toString());
     }
@@ -74,6 +80,8 @@ class Fetch {
       } else {
         throw response;
       }
+    } on SocketException catch (e) {
+      return GotrueResponse(error: handleError(e));
     } catch (e) {
       return GotrueResponse(error: handleError(e));
     } finally {

lib/src/gotrue_api.dart

@@ -37,14 +37,14 @@ class GoTrueApi {
         body,
         options: fetchOptions,
       );
-      final data = response.rawData as Map<String, dynamic>;
+      final data = response.rawData as Map<String, dynamic>?;
       if (response.error != null) {
         return GotrueSessionResponse(error: response.error);
-      } else if (data['access_token'] == null) {
+      } else if (data?['access_token'] == null) {
         // email validation required
         User? user;
-        if (data['id'] != null) {
-          user = User.fromJson(data);
+        if (data?['id'] != null) {
+          user = User.fromJson(data!);
         }
         return GotrueSessionResponse(user: user);
       } else {

lib/src/gotrue_client.dart

@@ -434,15 +434,19 @@ class GoTrueClient {
       final nextDuration = expiresIn - refreshDurationBeforeExpires;
       if (nextDuration > 0) {
         final timerDuration = Duration(seconds: nextDuration);
-        _refreshTokenTimer = Timer(timerDuration, () {
-          _callRefreshToken();
-        });
+        _setTokenRefreshTimer(timerDuration);
       } else {
         _callRefreshToken();
       }
     }
   }
 
+  void _setTokenRefreshTimer(Duration timerDuration) {
+    _refreshTokenTimer = Timer(timerDuration, () {
+      _callRefreshToken();
+    });
+  }
+
   void _removeSession() {
     currentSession = null;
     currentUser = null;
@@ -464,7 +468,12 @@ class GoTrueClient {
     }
 
     final response = await api.refreshAccessToken(token, jwt);
-    if (response.error != null) return response;
+    if (response.error != null) {
+      if (response.error!.statusCode == 'SocketException') {
+        _setTokenRefreshTimer(const Duration(seconds: 5));
+      }
+      return response;
+    }
     if (response.data == null) {
       final error = GotrueError('Invalid session data.');
       return GotrueSessionResponse(error: error);

lib/src/gotrue_error.dart

@@ -1,10 +1,14 @@
 class GotrueError {
   String message;
+  String? statusCode;
 
-  GotrueError(this.message);
+  GotrueError(
+    this.message, {
+    this.statusCode,
+  });
 
   @override
   String toString() {
-    return 'GotrueError(message: $message)';
+    return 'GotrueError(message: $message, statusCode: $statusCode)';
   }
 }