JsonToXmlTransformProvider.cs

using Yarp.ReverseProxy.Transforms;
using Yarp.ReverseProxy.Transforms.Builder;

namespace XmlDataSourceProxy;

/// <summary>
/// Registers the JSON-to-XML response transform on every route, picking up
/// an optional <c>RowPath</c> from the route's <c>Metadata</c> dictionary.
/// All authentication (API keys, bearer tokens, basic auth) is configured
/// declaratively in <c>appsettings.json</c> using YARP's built-in
/// <c>RequestHeader</c> and <c>QueryValueParameter</c> transforms.
/// </summary>
public class JsonToXmlTransformProvider : ITransformProvider
{
    public const string RowPathMetadataKey = "RowPath";

    public void ValidateRoute(TransformRouteValidationContext context) { }
    public void ValidateCluster(TransformClusterValidationContext context) { }

    public void Apply(TransformBuilderContext context)
    {
        string? rowPath = null;
        if (context.Route.Metadata != null &&
            context.Route.Metadata.TryGetValue(RowPathMetadataKey, out var value))
        {
            rowPath = value;
        }

        // Ask upstream for uncompressed JSON. SSRS doesn't send Accept-Encoding
        // itself, but other test clients (browsers, curl, Invoke-WebRequest) do,
        // and YARP forwards it; clearing it keeps the response body uncompressed
        // so the JSON->XML transform can parse it directly.
        context.AddRequestTransform(t =>
        {
            t.ProxyRequest.Headers.Accept.Clear();
            t.ProxyRequest.Headers.TryAddWithoutValidation("Accept", "application/json");
            t.ProxyRequest.Headers.AcceptEncoding.Clear();
            return ValueTask.CompletedTask;
        });

        context.AddResponseTransform(ctx => JsonToXmlResponseTransform.TransformAsync(ctx, rowPath));
    }
}