ArcGIS token challenge

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// Copyright 2017 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
// language governing permissions and limitations under the License.

using Esri.ArcGISRuntime.Security;
using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Threading.Tasks;
using System.Windows;

namespace ArcGIS.WPF.Samples.TokenSecuredChallenge
{
    [ArcGIS.Samples.Shared.Attributes.Sample(
        name: "ArcGIS token challenge",
        category: "Security",
        description: "This sample demonstrates how to prompt the user for a username and password to authenticate with ArcGIS Server to access an ArcGIS token-secured service. Accessing secured services requires a login that's been defined on the server.",
        instructions: "When you run the sample, the app will load a map that contains a layer from a secured service. Then, you will be challenged for a user name and password to view that layer. Enter the correct user name (user1) and password (user1). If you authenticate successfully, the secured layer will display, otherwise the map will contain only the public layers.",
        tags: new[] { "authentication", "cloud", "portal", "remember", "security" })]
    public partial class TokenSecuredChallenge
    {
        // Task completion source to track a login attempt.
        private TaskCompletionSource<Credential> _loginTaskCompletionSource;

        public TokenSecuredChallenge()
        {
            InitializeComponent();

            // Define a method to challenge the user for credentials when a secured resource is encountered.
            AuthenticationManager.Current.ChallengeHandler = new ChallengeHandler(Challenge);
        }

        // Function that's called when authentication is needed for a secure resource.
        private async Task<Credential> Challenge(CredentialRequestInfo info)
        {
            // Make sure to run on the UI thread.
            if (this.Dispatcher == null)
            {
                // No current dispatcher, code is already running on the UI thread.
                return await GetUserCredentialsFromUI(info);
            }
            else
            {
                // Use the dispatcher to invoke the challenge UI.
                return await this.Dispatcher.Invoke(() => GetUserCredentialsFromUI(info));
            }
        }

        private async Task<Credential> GetUserCredentialsFromUI(CredentialRequestInfo info)
        {
            // Show the login UI (text boxes for username and password).
            try
            {
                // Create an instance of the custom LoginInfo class to store the entered username and password.
                // Pass the CredentialRequestInfo object so the resource URI can be stored.
                LoginInfo loginInputInfo = new LoginInfo(info);

                // Set the login UI data context with the LoginInfo.
                loginPanel.DataContext = loginInputInfo;

                // Show the login UI.
                loginPanel.Visibility = Visibility.Visible;

                // Create a new task completion source to return the user's login when complete.
                // Set the login UI data context (LoginInfo object) as the AsyncState so it can be retrieved later.
                _loginTaskCompletionSource = new TaskCompletionSource<Credential>(loginPanel.DataContext);

                // Return the task from the completion source.
                // When the login button on the UI is clicked, the info will be returned for creating the credential.
                return await _loginTaskCompletionSource.Task;
            }
            finally
            {
                // Hide the login UI when done.
                loginPanel.Visibility = Visibility.Collapsed;
            }
        }

        // Handle the click event for the login button on the login UI.
        private async void LoginButtonClick(object sender, RoutedEventArgs e)
        {
            // Make sure there's a task completion source for the login operation.
            if (_loginTaskCompletionSource == null || _loginTaskCompletionSource.Task == null || _loginTaskCompletionSource.Task.AsyncState == null)
            {
                return;
            }

            // Get the login info from the task completion source.
            LoginInfo loginEntry = (LoginInfo)_loginTaskCompletionSource.Task.AsyncState;

            try
            {
                // Create a token credential using the provided username and password.
                AccessTokenCredential userCredentials = await AccessTokenCredential.CreateAsync
                                            (new Uri(loginEntry.ServiceUrl),
                                             loginEntry.UserName,
                                             loginEntry.Password);

                // Set the result on the task completion source.
                _loginTaskCompletionSource.TrySetResult(userCredentials);
            }
            catch (Exception ex)
            {
                // Show exceptions on the login UI.
                loginEntry.ErrorMessage = ex.Message;

                // Increment the login attempt count.
                loginEntry.AttemptCount++;

                // Set an exception on the login task completion source after three login attempts.
                if (loginEntry.AttemptCount >= 3)
                {
                    // This causes the login attempt to fail.
                    _loginTaskCompletionSource.TrySetException(ex);
                }
            }
        }
    }

    // Helper class to contain login information.
    internal class LoginInfo : INotifyPropertyChanged
    {
        // Information about the current request for credentials.
        private CredentialRequestInfo _requestInfo;

        public CredentialRequestInfo RequestInfo
        {
            get { return _requestInfo; }
            set
            {
                _requestInfo = value;
                OnPropertyChanged();
            }
        }

        // URI for the service that is requesting credentials.
        private string _serviceUrl;

        public string ServiceUrl
        {
            get { return _serviceUrl; }
            set
            {
                _serviceUrl = value;
                OnPropertyChanged();
            }
        }

        // Username entered by the user.
        private string _userName;

        public string UserName
        {
            get { return _userName; }
            set
            {
                _userName = value;
                OnPropertyChanged();
            }
        }

        // Password entered by the user.
        private string _password;

        public string Password
        {
            get { return _password; }
            set
            {
                _password = value;
                OnPropertyChanged();
            }
        }

        // Last error message encountered while creating credentials.
        private string _errorMessage;

        public string ErrorMessage
        {
            get { return _errorMessage; }
            set
            {
                _errorMessage = value;
                OnPropertyChanged();
            }
        }

        // Number of login attempts.
        private int _attemptCount;

        public int AttemptCount
        {
            get { return _attemptCount; }
            set
            {
                _attemptCount = value;
                OnPropertyChanged();
            }
        }

        // Store the credential request information when the class is constructed.
        public LoginInfo(CredentialRequestInfo info)
        {
            RequestInfo = info;
            ServiceUrl = info.ServiceUri.GetLeftPart(UriPartial.Path);
            ErrorMessage = string.Empty;
            AttemptCount = 0;
        }

        // Raise a property changed event so bound controls can update.
        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}