ersatztv/ErsatzTV.Infrastructure.Tests/Streaming/HttpRemoteStreamProberTests.cs

using System.Net;
using ErsatzTV.Infrastructure.Streaming;
using Microsoft.Extensions.Logging;
using NSubstitute;
using NUnit.Framework;
using Shouldly;

namespace ErsatzTV.Infrastructure.Tests.Streaming;

[TestFixture]
public class HttpRemoteStreamProberTests
{
    private const string Url = "http://localhost:8409/media/jellyfin/abc123";

    [Test]
    public async Task Should_Report_Unavailable_On_404()
    {
        HttpRemoteStreamProber prober = ProberReturning(HttpStatusCode.NotFound);

        bool result = await prober.IsAvailable(Url, CancellationToken.None);

        result.ShouldBeFalse();
    }

    [TestCase(HttpStatusCode.OK)]
    [TestCase(HttpStatusCode.PartialContent)]
    [TestCase(HttpStatusCode.NoContent)]
    public async Task Should_Report_Available_On_Success(HttpStatusCode statusCode)
    {
        HttpRemoteStreamProber prober = ProberReturning(statusCode);

        bool result = await prober.IsAvailable(Url, CancellationToken.None);

        result.ShouldBeTrue();
    }

    // the fail-open contract: a probe that cannot answer must never block a tune that would
    // otherwise have worked. these cases exist so a future refactor can't silently invert it.
    [TestCase(HttpStatusCode.InternalServerError)]
    [TestCase(HttpStatusCode.BadGateway)]
    [TestCase(HttpStatusCode.Unauthorized)]
    [TestCase(HttpStatusCode.Forbidden)]
    public async Task Should_Fail_Open_On_Other_Status_Codes(HttpStatusCode statusCode)
    {
        HttpRemoteStreamProber prober = ProberReturning(statusCode);

        bool result = await prober.IsAvailable(Url, CancellationToken.None);

        result.ShouldBeTrue();
    }

    [Test]
    public async Task Should_Fail_Open_On_Transport_Failure()
    {
        var prober = new HttpRemoteStreamProber(
            new StubHttpClientFactory(new ThrowingHttpMessageHandler(new HttpRequestException("no route to host"))),
            Substitute.For<ILogger<HttpRemoteStreamProber>>());

        bool result = await prober.IsAvailable(Url, CancellationToken.None);

        result.ShouldBeTrue();
    }

    [Test]
    public async Task Should_Fail_Open_On_Timeout()
    {
        var prober = new HttpRemoteStreamProber(
            new StubHttpClientFactory(new ThrowingHttpMessageHandler(new TaskCanceledException("timed out"))),
            Substitute.For<ILogger<HttpRemoteStreamProber>>());

        bool result = await prober.IsAvailable(Url, CancellationToken.None);

        result.ShouldBeTrue();
    }

    [Test]
    public async Task Should_Fail_Open_When_Caller_Cancels()
    {
        HttpRemoteStreamProber prober = ProberReturning(HttpStatusCode.OK);

        using var cts = new CancellationTokenSource();
        await cts.CancelAsync();

        bool result = await prober.IsAvailable(Url, cts.Token);

        result.ShouldBeTrue();
    }

    private static HttpRemoteStreamProber ProberReturning(HttpStatusCode statusCode) =>
        new(
            new StubHttpClientFactory(new StatusCodeHttpMessageHandler(statusCode)),
            Substitute.For<ILogger<HttpRemoteStreamProber>>());

    private sealed class StubHttpClientFactory(HttpMessageHandler handler) : IHttpClientFactory
    {
        public HttpClient CreateClient(string name) => new(handler, disposeHandler: false);
    }

    private sealed class StatusCodeHttpMessageHandler(HttpStatusCode statusCode) : HttpMessageHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken)
        {
            cancellationToken.ThrowIfCancellationRequested();
            return Task.FromResult(new HttpResponseMessage(statusCode));
        }
    }

    private sealed class ThrowingHttpMessageHandler(Exception exception) : HttpMessageHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken) =>
            Task.FromException<HttpResponseMessage>(exception);
    }
}