Issue 351: Reimplement OAuth2 (Step 3 - Tests, Flows and Credential)

Src/GoogleApis.Auth/OAuth2/Credential.cs

Index: Src/GoogleApis.Auth/OAuth2/Credential.cs
===================================================================
--- a/Src/GoogleApis.Auth/OAuth2/Credential.cs
 b/Src/GoogleApis.Auth/OAuth2/Credential.cs
@@ -15,13 15,125 @@
 */
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 using System.Net;
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
 using Google.Apis.Auth.OAuth2.Responses;
 using Google.Apis.Http;
 using Google.Apis.Logging;
 namespace Google.Apis.Auth.OAuth2
 {
- public class Credential
 /// <summary>
 /// OAuth 2.0 credential for accessing protected resources using an access token, as well as optionally refreshing
 /// the access token when it expires using a refresh token.
 /// </summary>
 public class Credential : IHttpExecuteInterceptor, IHttpUnsuccessfulResponseHandler,
 IConfigurableHttpClientInitializer
 {
 private static readonly ILogger Logger = ApplicationContext.Logger.ForType<Credential>();
 private TokenResponse token;
 private object lockObject = new object();
 public TokenResponse Token
 {
 get
 {
 lock (lockObject)
 {
 return token;
 }
 }
 private set
 {
 lock (lockObject)
 {
 token = value;
 }
 }
 }
 private readonly IAuthorizationCodeFlow flow;
 private readonly string userId;
 /// <summary>Constructs a new credential instance.</summary>
 /// <param name="flow">Authorization code flow</param>
 /// <param name="userId">User identifier</param>
 /// <param name="token">An initial token for the user</param>
 public Credential(IAuthorizationCodeFlow flow, string userId, TokenResponse token)
 {
 this.flow = flow;
 this.userId = userId;
 this.token = token;
 }
 /// <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
 /// has expired. If successful, it will call <seealso cref="IAccessMethod.Intercept"/>.
 /// </summary>
 public async Task InterceptAsync(HttpRequestMessage request, CancellationToken taskCancellationToken)
 {
 if (Token.IsExpired(flow.Clock))
 {
 if (!await RefreshTokenAsync(taskCancellationToken).ConfigureAwait(false))
 {
 throw new InvalidOperationException("The access token is expired but we can't refresh it");
 }
 }
 flow.AccessMethod.Intercept(request, Token.AccessToken);
 }
 /// <summary>
 /// Refreshes the token by calling to <seealso cref="IAuthorizationCodeFlow.RefreshTokenAsync"/>. Then it
 /// updates the <see cref="TokenResponse"/> with the new token instance.
 /// </summary>
 /// <param name="taskCancellationToken">Cancellation token to cancel an operation</param>
 /// <returns><c>true</c> if the token was refreshed</returns>
 private async Task<bool> RefreshTokenAsync(CancellationToken taskCancellationToken)
 {
 if (Token.RefreshToken == null)
 {
 Logger.Warning("Refresh token is null, can't refresh the token!");
 return false;
 }
 // It's possible that two concurrent calls will be made to refresh the token, in that case the last one
 // will win.
 var newToken = await flow.RefreshTokenAsync(userId, Token.RefreshToken, taskCancellationToken)
 .ConfigureAwait(false);
 Logger.Info("Access token was refreshed");
 if (newToken.RefreshToken == null)
 {
 newToken.RefreshToken = Token.RefreshToken;
 }
 Token = newToken;
 return true;
 }
 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;
 }
 public void Initialize(ConfigurableHttpClient httpClient)
 {
 httpClient.MessageHandler.ExecuteInterceptors.Add(this);
 httpClient.MessageHandler.UnsuccessfulResponseHandlers.Add(this);
 }
 }
 }