using System;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;
using FluentAssertions;
using StellaOps.Attestation;
using StellaOps.Attestor.Envelope;
using Xunit;

using StellaOps.TestKit;
public class DsseHelperTests
{
    private sealed class FakeSigner : IAuthoritySigner
    {
        public Task<string> GetKeyIdAsync(System.Threading.CancellationToken cancellationToken = default)
            => Task.FromResult("fake-key");

        public Task<byte[]> SignAsync(ReadOnlyMemory<byte> paePayload, System.Threading.CancellationToken cancellationToken = default)
            => Task.FromResult(Convert.FromHexString("deadbeef"));
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public async Task WrapAsync_ProducesDsseEnvelope()
    {
        var stmt = new InTotoStatement(
            Type: "https://in-toto.io/Statement/v1",
            Subject: new[] { new Subject("demo", new System.Collections.Generic.Dictionary<string, string> { { "sha256", "abcd" } }) },
            PredicateType: "demo/predicate",
            Predicate: new { hello = "world" });

        var envelope = await DsseHelper.WrapAsync(stmt, new FakeSigner());

        envelope.PayloadType.Should().Be("https://in-toto.io/Statement/v1");
        var roundtrip = JsonSerializer.Deserialize<InTotoStatement>(envelope.Payload.Span);
        roundtrip!.PredicateType.Should().Be("demo/predicate");
        envelope.Signatures.Should().ContainSingle();
        envelope.Signatures[0].KeyId.Should().Be("fake-key");
        envelope.Signatures[0].Signature.Should().Be(Convert.ToBase64String(Convert.FromHexString("deadbeef")));
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void PreAuthenticationEncoding_FollowsDsseSpec()
    {
        var payloadType = "example/type";
        var payload = Encoding.UTF8.GetBytes("{}");

        var pae = DsseHelper.PreAuthenticationEncoding(payloadType, payload);

        // Verify PAE contains expected components (payload type and payload)
        var paeString = Encoding.UTF8.GetString(pae);
        paeString.Should().Contain(payloadType);
        paeString.Should().Contain("{}");
    }
}