using System.Security.Cryptography;
using System.Xml.Linq;

namespace Distribution.Infra.Authorization;

/// <summary>
/// Parses an XML-format RSA public key (`&lt;RSAKeyValue&gt;...&lt;/RSAKeyValue&gt;`, as issued by
/// AuthHex) into an <see cref="RSA"/> instance. Written by hand instead of relying on
/// RSA.FromXmlString, which is Windows-only in .NET (throws PlatformNotSupportedException on
/// Linux/macOS) — this keeps token validation portable across hosts.
/// </summary>
public static class RsaXmlKeyReader
{
    public static RSA ReadPublicKey(string xml)
    {
        var root = XElement.Parse(xml);
        var modulus = root.Element("Modulus")?.Value
            ?? throw new InvalidOperationException("RSA XML key is missing <Modulus>.");
        var exponent = root.Element("Exponent")?.Value
            ?? throw new InvalidOperationException("RSA XML key is missing <Exponent>.");

        var parameters = new RSAParameters
        {
            Modulus = Convert.FromBase64String(modulus),
            Exponent = Convert.FromBase64String(exponent)
        };

        var rsa = RSA.Create();
        rsa.ImportParameters(parameters);
        return rsa;
    }
}