public void ResponseSignIn(FormsResponseSignInContext context)
        {
            var authResult = new AuthenticationResult
            {
                Success = true
            };

            ChatUser loggedInUser = GetLoggedInUser(context);

            var principal = new ClaimsPrincipal(context.Identity);

            // Do nothing if it's authenticated
            if (principal.IsAuthenticated())
            {
                EnsurePersistentCookie(context);
                return;
            }

            ChatUser user = _repository.GetUser(principal);
            authResult.ProviderName = principal.GetIdentityProvider();

            // The user exists so add the claim
            if (user != null)
            {
                if (loggedInUser != null && user != loggedInUser)
                {
                    // Set an error message
                    authResult.Message = String.Format("This {0} account has already been linked to another user.", authResult.ProviderName);
                    authResult.Success = false;

                    // Keep the old user logged in
                    context.Identity.AddClaim(new Claim(JabbRClaimTypes.Identifier, loggedInUser.Id));
                }
                else
                {
                    // Login this user
                    AddClaim(context, user);
                }

            }
            else if (principal.HasRequiredClaims())
            {
                ChatUser targetUser = null;

                // The user doesn't exist but the claims to create the user do exist
                if (loggedInUser == null)
                {
                    // New user so add them
                    user = _membershipService.AddUser(principal);

                    targetUser = user;
                }
                else
                {
                    // If the user is logged in then link
                    _membershipService.LinkIdentity(loggedInUser, principal);

                    _repository.CommitChanges();

                    authResult.Message = String.Format("Successfully linked {0} account.", authResult.ProviderName);

                    targetUser = loggedInUser;
                }

                AddClaim(context, targetUser);
            }
            else if(!principal.HasPartialIdentity())
            {
                // A partial identity means the user needs to add more claims to login
                context.Identity.AddClaim(new Claim(JabbRClaimTypes.PartialIdentity, "true"));
            }

            var cookieOptions = new CookieOptions
            {
                HttpOnly = true
            };

            context.Response.Cookies.Append(Constants.AuthResultCookie,
                                       JsonConvert.SerializeObject(authResult),
                                       cookieOptions);
        }