/// <summary>
 /// Invoked whenever Amazon successfully 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(AmazonAuthenticatedContext 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("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(properties, _logger))
                {
                    return(new AuthenticationTicket(null, properties));
                }

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

                // Build up the body for the token request
                var body = new List <KeyValuePair <string, string> >();
                body.Add(new KeyValuePair <string, string>("grant_type", "authorization_code"));
                body.Add(new KeyValuePair <string, string>("code", code));
                body.Add(new KeyValuePair <string, string>("redirect_uri", redirectUri));
                body.Add(new KeyValuePair <string, string>("client_id", Options.ClientId));
                body.Add(new KeyValuePair <string, string>("client_secret", Options.ClientSecret));

                // Request the token
                HttpResponseMessage tokenResponse =
                    await _httpClient.PostAsync(TokenEndpoint, new FormUrlEncodedContent(body));

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

                // Deserializes the token response
                JObject response     = JsonConvert.DeserializeObject <JObject>(text);
                string  accessToken  = response.Value <string>("access_token");
                string  expires      = response.Value <string>("expires_in");
                string  refreshToken = response.Value <string>("refresh_token");

                // Get the Amazon user
                HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, UserInfoEndpoint);
                request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
                HttpResponseMessage userResponse = await _httpClient.SendAsync(request, Request.CallCancelled);

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

                JObject user = JObject.Parse(text);

                var context = new AmazonAuthenticatedContext(Context, user, accessToken, expires, refreshToken);
                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.Name))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Name, context.Name, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.Email))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Email, context.Email, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.PostalCode))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.PostalCode, context.PostalCode, 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));
            }
        }