private async Task <bool> InvokeReplyPathAsync()
        {
            if (Options.CallbackPath.HasValue && Options.CallbackPath == Request.Path)
            {
                // TODO: error responses

                AuthenticationTicket ticket = await AuthenticateAsync();

                if (ticket == null)
                {
                    _logger.WriteWarning("Invalid return state, unable to redirect.");
                    Response.StatusCode = 500;
                    return(true);
                }

                var context = new OrcidReturnEndpointContext(Context, ticket)
                {
                    SignInAsAuthenticationType = Options.SignInAsAuthenticationType,
                    RedirectUri = ticket.Properties.RedirectUri
                };

                await Options.Provider.ReturnEndpoint(context);

                if (context.SignInAsAuthenticationType != null &&
                    context.Identity != null)
                {
                    ClaimsIdentity grantIdentity = context.Identity;
                    if (!string.Equals(grantIdentity.AuthenticationType, context.SignInAsAuthenticationType, StringComparison.Ordinal))
                    {
                        grantIdentity = new ClaimsIdentity(grantIdentity.Claims, context.SignInAsAuthenticationType, grantIdentity.NameClaimType, grantIdentity.RoleClaimType);
                    }
                    Context.Authentication.SignIn(context.Properties, grantIdentity);
                }

                if (!context.IsRequestCompleted && context.RedirectUri != null)
                {
                    string redirectUri = context.RedirectUri;
                    if (context.Identity == null)
                    {
                        // add a redirect hint that sign-in failed in some way
                        redirectUri = WebUtilities.AddQueryString(redirectUri, "error", "access_denied");
                    }
                    Response.Redirect(redirectUri);
                    context.RequestCompleted();
                }

                return(context.IsRequestCompleted);
            }
            return(false);
        }
 /// <summary>
 /// Invoked prior to the <see cref="System.Security.Claims.ClaimsIdentity"/> being saved in a local cookie and the browser being redirected to the originally requested URL.
 /// </summary>
 /// <param name="context"></param>
 /// <returns>A <see cref="Task"/> representing the completed operation.</returns>
 public virtual Task ReturnEndpoint(OrcidReturnEndpointContext context)
 {
     return OnReturnEndpoint(context);
 }
 /// <summary>
 /// Invoked prior to the <see cref="System.Security.Claims.ClaimsIdentity"/> being saved in a local cookie and the browser being redirected to the originally requested URL.
 /// </summary>
 /// <param name="context"></param>
 /// <returns>A <see cref="Task"/> representing the completed operation.</returns>
 public virtual Task ReturnEndpoint(OrcidReturnEndpointContext context)
 {
     return(OnReturnEndpoint(context));
 }