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StructuredTransformer.cs
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StructuredTransformer.cs
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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Features;
using Yarp.ReverseProxy.Forwarder;
namespace Yarp.ReverseProxy.Transforms.Builder;
/// <summary>
/// Transforms for a given route.
/// </summary>
internal sealed class StructuredTransformer : HttpTransformer
{
/// <summary>
/// Creates a new <see cref="StructuredTransformer"/> instance.
/// </summary>
internal StructuredTransformer(bool? copyRequestHeaders, bool? copyResponseHeaders, bool? copyResponseTrailers,
IList<RequestTransform> requestTransforms,
IList<ResponseTransform> responseTransforms,
IList<ResponseTrailersTransform> responseTrailerTransforms)
{
ShouldCopyRequestHeaders = copyRequestHeaders;
ShouldCopyResponseHeaders = copyResponseHeaders;
ShouldCopyResponseTrailers = copyResponseTrailers;
RequestTransforms = requestTransforms?.ToArray() ?? throw new ArgumentNullException(nameof(requestTransforms));
ResponseTransforms = responseTransforms?.ToArray() ?? throw new ArgumentNullException(nameof(responseTransforms));
ResponseTrailerTransforms = responseTrailerTransforms?.ToArray() ?? throw new ArgumentNullException(nameof(responseTrailerTransforms));
}
/// <summary>
/// Indicates if all request headers should be copied to the proxy request before applying transforms.
/// </summary>
internal bool? ShouldCopyRequestHeaders { get; }
/// <summary>
/// Indicates if all response headers should be copied to the client response before applying transforms.
/// </summary>
internal bool? ShouldCopyResponseHeaders { get; }
/// <summary>
/// Indicates if all response trailers should be copied to the client response before applying transforms.
/// </summary>
internal bool? ShouldCopyResponseTrailers { get; }
/// <summary>
/// Request transforms.
/// </summary>
internal RequestTransform[] RequestTransforms { get; }
/// <summary>
/// Response header transforms.
/// </summary>
internal ResponseTransform[] ResponseTransforms { get; }
/// <summary>
/// Response trailer transforms.
/// </summary>
internal ResponseTrailersTransform[] ResponseTrailerTransforms { get; }
public override async ValueTask TransformRequestAsync(HttpContext httpContext, HttpRequestMessage proxyRequest, string destinationPrefix)
{
if (ShouldCopyRequestHeaders.GetValueOrDefault(true))
{
await base.TransformRequestAsync(httpContext, proxyRequest, destinationPrefix);
}
if (RequestTransforms.Length == 0)
{
return;
}
var transformContext = new RequestTransformContext()
{
DestinationPrefix = destinationPrefix,
HttpContext = httpContext,
ProxyRequest = proxyRequest,
Path = httpContext.Request.Path,
Query = new QueryTransformContext(httpContext.Request),
HeadersCopied = ShouldCopyRequestHeaders.GetValueOrDefault(true),
};
foreach (var requestTransform in RequestTransforms)
{
await requestTransform.ApplyAsync(transformContext);
}
// Allow a transform to directly set a custom RequestUri.
proxyRequest.RequestUri ??= RequestUtilities.MakeDestinationAddress(
transformContext.DestinationPrefix, transformContext.Path, transformContext.Query.QueryString);
}
public override async ValueTask<bool> TransformResponseAsync(HttpContext httpContext, HttpResponseMessage? proxyResponse)
{
if (ShouldCopyResponseHeaders.GetValueOrDefault(true))
{
await base.TransformResponseAsync(httpContext, proxyResponse);
}
if (ResponseTransforms.Length == 0)
{
return true;
}
var transformContext = new ResponseTransformContext()
{
HttpContext = httpContext,
ProxyResponse = proxyResponse,
HeadersCopied = ShouldCopyResponseHeaders.GetValueOrDefault(true),
};
foreach (var responseTransform in ResponseTransforms)
{
await responseTransform.ApplyAsync(transformContext);
}
return !transformContext.SuppressResponseBody;
}
public override async ValueTask TransformResponseTrailersAsync(HttpContext httpContext, HttpResponseMessage proxyResponse)
{
if (ShouldCopyResponseTrailers.GetValueOrDefault(true))
{
await base.TransformResponseTrailersAsync(httpContext, proxyResponse);
}
if (ResponseTrailerTransforms.Length == 0)
{
return;
}
// Only run the transforms if trailers are actually supported by the client response.
var responseTrailersFeature = httpContext.Features.Get<IHttpResponseTrailersFeature>();
var outgoingTrailers = responseTrailersFeature?.Trailers;
if (outgoingTrailers is not null && !outgoingTrailers.IsReadOnly)
{
var transformContext = new ResponseTrailersTransformContext()
{
HttpContext = httpContext,
ProxyResponse = proxyResponse,
HeadersCopied = ShouldCopyResponseTrailers.GetValueOrDefault(true),
};
foreach (var responseTrailerTransform in ResponseTrailerTransforms)
{
await responseTrailerTransform.ApplyAsync(transformContext);
}
}
}
}