wehub-resource-sync
104 lines
5.3 KiB
C#
104 lines
5.3 KiB
C#
/*
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* QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
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* Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Net.Http;
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using System.Threading;
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using System.Threading.Tasks;
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using System.Net.Http.Headers;
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namespace QuantConnect.Brokerages.Authentication
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{
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/// <summary>
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/// Provides base functionality for token-based HTTP request handling.
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/// Token acquisition and retry logic are delegated entirely to <see cref="GetAccessToken"/>,
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/// implemented by derived classes (e.g., <see cref="LeanOAuthTokenHandler"/>).
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/// </summary>
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public abstract class LeanTokenHandler<T> : DelegatingHandler
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where T : LeanTokenCredentials
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{
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/// <summary>
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/// Raised when authentication fails after all retry attempts are exhausted.
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/// Subscribers can use this to trigger graceful application shutdown.
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/// </summary>
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public event EventHandler<Exception> AuthenticationFailed;
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/// <summary>
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/// A delegate used to construct an <see cref="AuthenticationHeaderValue"/> from a token type and access token string.
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/// </summary>
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private readonly Func<TokenType, string, AuthenticationHeaderValue> _createAuthHeader;
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/// <summary>
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/// Initializes a new instance of the <see cref="LeanTokenHandler{T}"/> class.
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/// </summary>
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/// <param name="createAuthHeader">
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/// An optional delegate for creating an <see cref="AuthenticationHeaderValue"/>
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/// from the token type and access token. If not provided, a default implementation is used.
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/// </param>
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/// <param name="handler">An optional inner <see cref="HttpMessageHandler"/>. If not provided, a default <see cref="HttpClientHandler"/> is used.</param>
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protected LeanTokenHandler(Func<TokenType, string, AuthenticationHeaderValue> createAuthHeader = null, HttpClientHandler handler = null)
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: base(handler ?? new HttpClientHandler())
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{
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_createAuthHeader = createAuthHeader ?? ((tokenType, accessToken) => new AuthenticationHeaderValue(tokenType.ToString(), accessToken));
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}
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/// <summary>
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/// Retrieves a valid access token for authenticating HTTP requests.
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/// Must be implemented by derived classes to provide token type and value,
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/// with optional support for caching and refresh logic.
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/// </summary>
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/// <param name="cancellationToken">A cancellation token that can be used to cancel the token retrieval operation.</param>
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/// <returns>A <see cref="LeanTokenCredentials"/> instance containing the token type and access token string.</returns>
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public abstract T GetAccessToken(CancellationToken cancellationToken);
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/// <summary>
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/// Invokes the <see cref="AuthenticationFailed"/> event.
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/// Derived classes call this when authentication fails after exhausting all retry attempts.
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/// </summary>
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/// <param name="exception">The exception that caused the authentication failure.</param>
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protected void OnAuthenticationFailed(Exception exception)
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{
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AuthenticationFailed?.Invoke(this, exception);
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}
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/// <summary>
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/// Sends an HTTP request asynchronously by internally invoking the synchronous <see cref="Send(HttpRequestMessage, CancellationToken)"/> method.
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/// This is useful for compatibility with components that require an asynchronous pipeline, even though the core logic is synchronous.
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/// </summary>
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/// <param name="request">The HTTP request message to send.</param>
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/// <param name="cancellationToken">A cancellation token to cancel the operation.</param>
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/// <returns>
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/// A task representing the asynchronous operation, containing the HTTP response message.
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/// </returns>
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protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
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{
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return Task.FromResult(Send(request, cancellationToken));
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}
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/// <summary>
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/// Sends an HTTP request synchronously, applying token-based authentication.
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/// </summary>
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/// <param name="request">The HTTP request message to send.</param>
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/// <param name="cancellationToken">A cancellation token to cancel operation.</param>
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/// <returns>The HTTP response message.</returns>
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protected override HttpResponseMessage Send(HttpRequestMessage request, CancellationToken cancellationToken)
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{
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var accessToken = GetAccessToken(cancellationToken);
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request.Headers.Authorization = _createAuthHeader(accessToken.TokenType, accessToken.AccessToken);
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return base.Send(request, cancellationToken);
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}
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}
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}
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