/// <summary>
/// return OAuth 2.0 Credentials. If the token is expired, it will first attempt to refresh the token.
/// </summary>
/// <param name="uri">Ignored.</param>
/// <param name="authType">Ignored.</param>
/// <exception cref="WebException">May occour when refreshing the token</exception>
public NetworkCredential GetCredential(Uri uri, string authType)
{
if (AccessTokenExpiration != null && RefreshToken != null && AccessTokenExpiration.Subtract(DateTime.Now).TotalSeconds < RefreshThreshold)
{
OAuthCredential newCreds = _client.RefreshAccessToken(RefreshToken);
AccessToken = newCreds.AccessToken;
// a new refresh token may be issued, per 5.2
if (newCreds.RefreshToken != null)
{
RefreshToken = newCreds.RefreshToken;
AccessTokenExpiration = newCreds.AccessTokenExpiration;
ExpiresIn = newCreds.ExpiresIn;
}
else
{
// otherwise, calculate the next refresh time
AccessTokenExpiration = DateTime.Now.AddSeconds(ExpiresIn);
}
}
return(new NetworkCredential("OAuth", AccessToken));
}
/// <summary>
/// TODO Comment
/// </summary>
/// <param name="values"></param>
/// <returns></returns>
private OAuthCredential RequestOrRefreshAuthToken(NameValueCollection values)
{
OAuthCredential credentials;
try
{
using (var client = new WebClient {
BaseAddress = _tokenUri.ToString()
})
{
// Construct the Access Token Request request, per OAuth 2.0 spec at 4.1.3, or Refresh Token request in section 6
values["scope"] = _tokenEndpointScopeEncoded;
values["client_id"] = HttpUtility.HtmlEncode(_clientId);
values["client_secret"] = HttpUtility.HtmlEncode(_clientSecret.ConvertToString());
var responseBytes = client.UploadValues(_tokenUri.AbsolutePath, "POST", values);
OAuthAccessTokenResponseJson resultJson = null;
try
{
JavaScriptSerializer ser = new JavaScriptSerializer();
resultJson = ser.Deserialize <OAuthAccessTokenResponseJson>(client.Encoding.GetString(responseBytes));
}
// catch various exceptions and filter them to a ProtocolViolationException, as if not, it is a violation of OAuth protocol.
catch (ArgumentException)
{
throw new ProtocolViolationException("Response could not be parsed");
}
catch (InvalidOperationException)
{
throw new ProtocolViolationException("Response could not be parsed");
}
if (resultJson != null)
{
if (string.IsNullOrEmpty(resultJson.refresh_token))
{
// Create a new set of credentials that doesn't expire
credentials = new OAuthCredential(resultJson.access_token);
}
else
{
try
{
// expires_in should always be with a refresh_token.
int expires_in = Int32.Parse(resultJson.expires_in);
credentials = new OAuthCredential(resultJson.access_token, resultJson.refresh_token, expires_in, this);
}
catch (FormatException)
{
throw new ProtocolViolationException("expires_in is malformed");
}
}
}
else
{
throw new ProtocolViolationException("Response wasn't in JSON format.");
}
}
}
catch (WebException ex)
{
// Error conditions are returned as 400 Bad Request, per section 5.2 of the OAuth 2.0 spec
if (ex.Response != null && ((HttpWebResponse)ex.Response).StatusCode == HttpStatusCode.BadRequest)
{
OAuthErrorException errorEx = OAuthErrorException.FromWebException(ex);
if (errorEx != null)
{
throw errorEx;
}
}
throw;
}
return(credentials);
}
