/// <summary>
/// Gets a token for the specified subscription.
/// </summary>
/// <returns>The encoded JWT token prefixed with the string "Bearer ".</returns>
/// <remarks>
/// This method uses a cache to limit the number of request to the token service.
/// A fresh token can be re-used during its lifetime of 10 minutes. After a successful
/// request to the token service, this method caches the access token. Subsequent
/// invocations of the method return the cached token for the next 5 minutes. After
/// 5 minutes, a new token is fetched from the token service and the cache is updated.
/// </remarks>
public async Task <string> GetAccessTokenAsync()
{
if (string.IsNullOrEmpty(SubscriptionKey))
{
throw new ArgumentNullException(nameof(SubscriptionKey), "A subscription key is required");
}
// Re-use the cached token if there is one.
if ((DateTime.Now - _storedTokenTime) < TokenCacheDuration && !string.IsNullOrWhiteSpace(_storedTokenValue))
{
return(_storedTokenValue);
}
using (var request = new HttpHelperRequest(ServiceUrl, HttpMethod.Post))
{
request.Headers.Add(OcpApimSubscriptionKeyHeader, SubscriptionKey);
var response = await HttpHelper.Instance.SendRequestAsync(request).ConfigureAwait(false);
var token = await response.GetTextResultAsync().ConfigureAwait(false);
_storedTokenTime = DateTime.Now;
_storedTokenValue = $"Bearer {token}";
return(_storedTokenValue);
}
}
/// <summary>
/// Process Http Request using instance of HttpClient.
/// </summary>
/// <param name="request">instance of <see cref="HttpHelperRequest"/></param>
/// <param name="cancellationToken">instance of <see cref="CancellationToken"/></param>
/// <returns>Instane of <see cref="HttpHelperResponse"/></returns>
public async Task <HttpHelperResponse> SendRequestAsync(HttpHelperRequest request, CancellationToken cancellationToken = default(CancellationToken))
{
await _semaphore.WaitAsync().ConfigureAwait(false);
HttpClient client = null;
try
{
var httpRequestMessage = request.ToHttpRequestMessage();
client = GetHttpClientInstance();
var response = await client.SendRequestAsync(httpRequestMessage).AsTask(cancellationToken).ConfigureAwait(false);
FixInvalidCharset(response);
return(new HttpHelperResponse(response));
}
finally
{
// Add the HttpClient instance back to the queue.
if (client != null)
{
_httpClientQueue.Enqueue(client);
}
_semaphore.Release();
}
}
private HttpHelperRequest CreateHttpRequest(string uriString)
{
var request = new HttpHelperRequest(new Uri(uriString));
request.Headers.Add(AuthorizationUri, _authorizationHeaderValue);
return(request);
}