/// <summary>
 /// Invoked whenever Purecloud succesfully authenticates a user
 /// </summary>
 /// <param name="context">Contains information about the login session as well as the user <see cref="System.Security.Claims.ClaimsIdentity"/>.</param>
 /// <returns>A <see cref="Task"/> representing the completed operation.</returns>
 public virtual Task Authenticated(PurecloudAuthenticatedContext context)
 {
     return(OnAuthenticated(context));
 }
        protected override async Task <AuthenticationTicket> AuthenticateCoreAsync()
        {
            AuthenticationProperties properties = null;

            try
            {
                string code  = null;
                string state = null;

                IReadableStringCollection query = Request.Query;

                IList <string> values = query.GetValues("error");
                if (values != null && values.Count >= 1)
                {
                    _logger.WriteVerbose("Remote server returned an error: " + Request.QueryString);
                }

                values = query.GetValues("code");
                if (values != null && values.Count == 1)
                {
                    code = values[0];
                }

                values = query.GetValues("state");
                if (values != null && values.Count == 1)
                {
                    state = values[0];
                }

                properties = Options.StateDataFormat.Unprotect(state);
                if (properties == null)
                {
                    return(null);
                }

                // OAuth2 10.12 CSRF
                if (!ValidateCorrelationId(Options.CookieManager, properties, _logger))
                {
                    return(new AuthenticationTicket(null, properties));
                }

                if (code == null)
                {
                    // Null if the remote server returns an error.
                    return(new AuthenticationTicket(null, properties));
                }

                string requestPrefix = Request.Scheme + "://" + Request.Host;
                string redirectUri   = requestPrefix + Request.PathBase + Options.CallbackPath;

                var content = new FormUrlEncodedContent(new[]
                {
                    new KeyValuePair <string, string>("grant_type", "authorization_code"),
                    new KeyValuePair <string, string>("code", code),
                    new KeyValuePair <string, string>("redirect_uri", redirectUri)
                });

                var basicAuth = Convert.ToBase64String(Encoding.GetEncoding("ISO-8859-1")
                                                       .GetBytes($"{Options.AppId}:{Options.AppSecret}"));

                string tokenRequest = "grant_type=authorization_code" +
                                      "&code=" + Uri.EscapeDataString(code) +
                                      "&redirect_uri=" + Uri.EscapeDataString(redirectUri) +
                                      "&client_id=" + Uri.EscapeDataString(Options.AppId) +
                                      "&client_secret=" + Uri.EscapeDataString(Options.AppSecret);
                var client = new HttpClient();
                client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", basicAuth);

                HttpResponseMessage tokenResponse = await client.PostAsync(Options.TokenEndpoint, content, Request.CallCancelled);

                tokenResponse.EnsureSuccessStatusCode();
                string text = await tokenResponse.Content.ReadAsStringAsync();

                JObject response = JObject.Parse(text);

                string accessToken = response.Value <string>("access_token");

                if (string.IsNullOrWhiteSpace(accessToken))
                {
                    _logger.WriteWarning("Access token was not found");
                    return(new AuthenticationTicket(null, properties));
                }

                string expires = response.Value <string>("expires_in");

                var clientGetUser = new HttpClient();
                clientGetUser.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
                var userResponse = await clientGetUser.GetAsync(Options.UserInformationEndpoint, Request.CallCancelled);

                userResponse.EnsureSuccessStatusCode();
                text = await userResponse.Content.ReadAsStringAsync();

                JObject user = JObject.Parse(text);

                var context = new PurecloudAuthenticatedContext(Context, user, accessToken, expires);
                context.Identity = new ClaimsIdentity(
                    Options.AuthenticationType,
                    ClaimsIdentity.DefaultNameClaimType,
                    ClaimsIdentity.DefaultRoleClaimType);
                if (!string.IsNullOrEmpty(context.Id))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.NameIdentifier, context.Id, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.UserName))
                {
                    context.Identity.AddClaim(new Claim(ClaimsIdentity.DefaultNameClaimType, context.UserName, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.Email))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Email, context.Email, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.Name))
                {
                    context.Identity.AddClaim(new Claim("urn:Purecloud:name", context.Name, XmlSchemaString, Options.AuthenticationType));

                    // Many Purecloud accounts do not set the UserName field.  Fall back to the Name field instead.
                    if (string.IsNullOrEmpty(context.UserName))
                    {
                        context.Identity.AddClaim(new Claim(ClaimsIdentity.DefaultNameClaimType, context.Name, XmlSchemaString, Options.AuthenticationType));
                    }
                }
                if (!string.IsNullOrEmpty(context.Link))
                {
                    context.Identity.AddClaim(new Claim("urn:Purecloud:link", context.Link, XmlSchemaString, Options.AuthenticationType));
                }
                context.Properties = properties;

                await Options.Provider.Authenticated(context);

                return(new AuthenticationTicket(context.Identity, context.Properties));
            }
            catch (Exception ex)
            {
                _logger.WriteError("Authentication failed", ex);
                return(new AuthenticationTicket(null, properties));
            }
        }