Creating an FBSession from handleOpenUrl. Workaround for an SDK bug.

handleOpenUrl workaround

- (BOOL)application:(UIApplication *)application
            openURL:(NSURL *)url
  sourceApplication:(NSString *)sourceApplication
         annotation:(id)annotation {
    
    // Save the incoming URL to test deep links later.
    self.openedURL = url;
    
    // Work around for app link from FB with valid info. If the session is closed, set the valid info (if any) in the cache
    if (FBSession.activeSession.state == FBSessionStateCreated || FBSession.activeSession.state == FBSessionStateClosed){
        [self handleOpenURLPre:url];
    }

    // We need to handle URLs by passing them to FBSession in order for SSO authentication to work.
    return [FBSession.activeSession handleOpenURL:url];
}


- (void) handleOpenURLPre:(NSURL *) url {

    // Parse the URL
    NSString *query = [url fragment];
    if (!query) {
        query = [self.openedURL query];
    }

    NSDictionary *params = [self parseURLParams:query];

    // Look for a valid access token
    if ([params objectForKey:@"access_token"]) {
        NSString *accessToken = [params objectForKey:@"access_token"];
        NSString *expires_in = [params objectForKey:@"expires_in"];

        // Determine the expiration date
        NSDate *expirationDate = nil;
        if (expires_in != nil) {
            int expValue = [expires_in intValue];
            if (expValue != 0) {
                expirationDate = [NSDate dateWithTimeIntervalSinceNow:expValue];
            }
        }

        if (!expirationDate) {
            expirationDate = [NSDate distantFuture];
        }

        NSDate *nowDate = [NSDate date];

        // Check expiration date is in the future
        if (NSOrderedDescending == [expirationDate compare:nowDate]) {

            // Cache the token
            NSDictionary *tokenInfo = [NSDictionary dictionaryWithObjectsAndKeys:
                                       accessToken, FBTokenInformationTokenKey,
                                       expirationDate, FBTokenInformationExpirationDateKey,
                                       nowDate, FBTokenInformationRefreshDateKey,
                                       nil];
            
            FBSessionTokenCachingStrategy *tokenCachingStrategy = [FBSessionTokenCachingStrategy defaultInstance];
            [tokenCachingStrategy cacheTokenInformation:tokenInfo];

            // Now open the session and the cached token should
            // be picked up, open with nil permissions because
            // what you send is checked against any cached permissions
            // to determine token validity.
            [FBSession openActiveSessionWithReadPermissions:nil
                                               allowLoginUI:NO
                                          completionHandler:^(FBSession *session, FBSessionState state, NSError *error) {
                                              [self sessionStateChanged:session
                                                                  state:state
                                                                  error:error];
                                          }];
        }
    }
}