Added fail-safe

app/src/main/java/eu/faircode/email/GmailState.java

@@ -24,8 +24,10 @@ import android.accounts.AccountManager;
 import android.accounts.AuthenticatorException;
 import android.accounts.OperationCanceledException;
 import android.content.Context;
+import android.content.SharedPreferences;
 
 import androidx.annotation.NonNull;
+import androidx.preference.PreferenceManager;
 
 import org.json.JSONException;
 import org.json.JSONObject;
@@ -71,6 +73,19 @@ public class GmailState {
                 expiration - ServiceAuthenticator.MIN_FORCE_REFRESH_INTERVAL < now)
             needsRefresh = true;
 
+        if (needsRefresh) {
+            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+            String key = "token." + id + "." + user;
+            long last_refresh = prefs.getLong(key, 0);
+            long ago = now - last_refresh;
+            EntityLog.log(context, EntityLog.Type.Debug, "Token needs refresh" +
+                    " user=" + id + ":" + user + " ago=" + (ago / 60 / 1000L) + " min");
+            if (ago < ServiceAuthenticator.MIN_FORCE_REFRESH_INTERVAL) {
+                Log.e("Blocked token refresh id=" + id + " ago=" + (ago / 1000L));
+                return;
+            }
+            prefs.edit().putLong(key, now).apply();
+        }
 
         EntityLog.log(context, EntityLog.Type.Debug, "Token user=" + id + ":" + user +
                 " expiration=" + (expiration == null ? null : new Date(expiration)) +

app/src/main/java/eu/faircode/email/ServiceAuthenticator.java

@@ -24,6 +24,9 @@ import static eu.faircode.email.GmailState.TYPE_GOOGLE;
 import android.accounts.AuthenticatorException;
 import android.accounts.OperationCanceledException;
 import android.content.Context;
+import android.content.SharedPreferences;
+
+import androidx.preference.PreferenceManager;
 
 import net.openid.appauth.AuthState;
 import net.openid.appauth.AuthorizationException;
@@ -150,14 +153,29 @@ public class ServiceAuthenticator extends Authenticator {
             long now = new Date().getTime();
             Long expiration = authState.getAccessTokenExpirationTime();
             boolean needsRefresh = (expiration != null && expiration < now);
-            if (needsRefresh)
-                authState.setNeedsTokenRefresh(true);
 
             if (!needsRefresh && forceRefresh &&
                     expiration != null &&
                     expiration - ServiceAuthenticator.MIN_FORCE_REFRESH_INTERVAL < now)
+                needsRefresh = true;
+
+            if (needsRefresh)
                 authState.setNeedsTokenRefresh(true);
 
+            if (needsRefresh) {
+                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+                String key = "token." + id + "." + user;
+                long last_refresh = prefs.getLong(key, 0);
+                long ago = now - last_refresh;
+                EntityLog.log(context, EntityLog.Type.Debug, "Token needs refresh" +
+                        " user=" + id + ":" + user + " ago=" + (ago / 60 / 1000L) + " min");
+                if (ago < ServiceAuthenticator.MIN_FORCE_REFRESH_INTERVAL) {
+                    Log.e("Blocked token refresh id=" + id + " ago=" + (ago / 1000L));
+                    return;
+                }
+                prefs.edit().putLong(key, now).apply();
+            }
+
             EntityLog.log(context, EntityLog.Type.Debug, "Token user=" + id + ":" + user +
                     " expiration=" + (expiration == null ? null : new Date(expiration)) +
                     " need=" + needsRefresh + "/" + authState.getNeedsTokenRefresh() +