Issue 463: Provide a signout\logout method

Src/GoogleApis.Auth/OAuth2/UserCredential.cs

Index: Src/GoogleApis.Auth/OAuth2/UserCredential.cs
===================================================================
--- a/Src/GoogleApis.Auth/OAuth2/UserCredential.cs
 b/Src/GoogleApis.Auth/OAuth2/UserCredential.cs
@@ -34,12 34,12 @@
 public class UserCredential : IHttpExecuteInterceptor, IHttpUnsuccessfulResponseHandler,
 IConfigurableHttpClientInitializer
 {
- private static readonly ILogger Logger = ApplicationContext.Logger.ForType<UserCredential>();
 protected static readonly ILogger Logger = ApplicationContext.Logger.ForType<UserCredential>();
 private TokenResponse token;
 private object lockObject = new object();
- /// <summary>Gets the token response which contains the access token.</summary>
 /// <summary>Gets or sets the token response which contains the access token.</summary>
 public TokenResponse Token
 {
 get
@@ -49,7 49,7 @@
 return token;
 }
 }
- private set
 set
 {
 lock (lockObject)
 {
@@ -58,6 58,18 @@
 }
 }
 /// <summary>Gets the authorization code flow.</summary>
 public IAuthorizationCodeFlow Flow
 {
 get { return flow; }
 }
 /// <summary>Gets the user identity.</summary>
 public string UderId
 {
 get { return userId; }
 }
 private readonly IAuthorizationCodeFlow flow;
 private readonly string userId;
@@ -72,6 84,8 @@
 this.token = token;
 }
 #region IHttpExecuteInterceptor
 /// <summary>
 /// Default implementation is to try to refresh the access token if there is no access token or if we are 1
 /// minute away from expiration. If token server is unavailable, it will try to use the access token even if
@@ -91,6 105,34 @@
 flow.AccessMethod.Intercept(request, Token.AccessToken);
 }
 #endregion
 #region IHttpUnsuccessfulResponseHandler
 public async Task<bool> HandleResponseAsync(HandleUnsuccessfulResponseArgs args)
 {
 // TODO(peleyal): check WWW-Authenticate header.
 if (args.Response.StatusCode == HttpStatusCode.Unauthorized)
 {
 return !Object.Equals(Token.AccessToken, flow.AccessMethod.GetAccessToken(args.Request))
 || await RefreshTokenAsync(args.CancellationToken).ConfigureAwait(false);
 }
 return false;
 }
 #endregion
 #region IConfigurableHttpClientInitializer
 public void Initialize(ConfigurableHttpClient httpClient)
 {
 httpClient.MessageHandler.ExecuteInterceptors.Add(this);
 httpClient.MessageHandler.UnsuccessfulResponseHandlers.Add(this);
 }
 #endregion
 /// <summary>
 /// Refreshes the token by calling to <seealso cref="IAuthorizationCodeFlow.RefreshTokenAsync"/>. Then it
 /// updates the <see cref="TokenResponse"/> with the new token instance.
@@ -121,22 163,24 @@
 return true;
 }
- public async Task<bool> HandleResponseAsync(HandleUnsuccessfulResponseArgs args)
 /// <summary>
 /// Asynchronously revokes the token by calling
 /// <see cref="Google.Apis.Auth.OAuth2.Flows.IAuthorizationCodeFlow.RevokeTokenAsync"/>.
 /// </summary>
 /// <param name="taskCancellationToken">Cancellation token to cancel an operation.</param>
 /// <returns><c>true</c> if the token was revoked successfully.</returns>
 public async Task<bool> RevokeTokenAsync(CancellationToken taskCancellationToken)
 {
- // TODO(peleyal): check WWW-Authenticate header.
- if (args.Response.StatusCode == HttpStatusCode.Unauthorized)
 if (Token == null)
 {
- return !Object.Equals(Token.AccessToken, flow.AccessMethod.GetAccessToken(args.Request))
- || await RefreshTokenAsync(args.CancellationToken).ConfigureAwait(false);
 Logger.Warning("Token is already null, no need to revoke it.");
 return false;
 }
- return false;
- }
-
- public void Initialize(ConfigurableHttpClient httpClient)
- {
- httpClient.MessageHandler.ExecuteInterceptors.Add(this);
- httpClient.MessageHandler.UnsuccessfulResponseHandlers.Add(this);
 await flow.RevokeTokenAsync(userId, Token.AccessToken, taskCancellationToken).ConfigureAwait(false);
 Logger.Info("Access token was revoked successfully");
 // We don't set the token to null, cause we want that the next request (without reauthorizing) will fail).
 return true;
 }
 }
 }