deepdrft/DeepDrftTests/OpusFormatSelectionTests.cs

using System.Net;
using DeepDrftModels.Enums;
using DeepDrftPublic.Client.Clients;
using DeepDrftPublic.Client.Services;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.JSInterop;
using Microsoft.JSInterop.Infrastructure;

namespace DeepDrftTests;

/// <summary>
/// Unit tests for the Phase 18.5 player-side format-selection seam
/// (<see cref="StreamingAudioPlayerService.ResolveStreamFormatAsync"/>): the default policy (OQ2) of "Opus
/// when the browser can decode Ogg Opus AND a sidecar exists, else lossless", the capability gate (AC7), and
/// the sidecar-absent → lossless fallback (C2). The seam is the single, overridable hook 18.6 will use to
/// inject the listener's quality preference; these tests pin the capability-gated default it falls through to.
///
/// The seam touches two collaborators: <see cref="AudioInteropService"/> (over a fake <see cref="IJSRuntime"/>
/// — <c>canDecodeOggOpus</c> + <c>setOpusSidecar</c>) and <see cref="TrackMediaClient"/> (over a stub HTTP
/// handler — the one-time sidecar fetch). Both are real instances wired over the fakes; only the network/JS
/// boundary is faked, so the selection logic under test is exercised exactly as it runs in the browser.
/// </summary>
[TestFixture]
public class OpusFormatSelectionTests
{
    // A scriptable JS runtime: canDecodeOggOpus returns a configured bool; setOpusSidecar returns a
    // configured success/failure; every other invocation returns default. Records the calls so a test can
    // assert the set-before-init contract was honoured (the sidecar was actually handed to the player).
    private sealed class FakeJsRuntime : IJSRuntime
    {
        private readonly bool _canDecode;
        private readonly bool _sidecarParseSucceeds;

        public FakeJsRuntime(bool canDecode, bool sidecarParseSucceeds)
        {
            _canDecode = canDecode;
            _sidecarParseSucceeds = sidecarParseSucceeds;
        }

        public int SetSidecarCallCount { get; private set; }

        public ValueTask<TValue> InvokeAsync<TValue>(string identifier, object?[]? args)
        {
            if (identifier == "DeepDrftAudio.canDecodeOggOpus")
                return ValueTask.FromResult((TValue)(object)_canDecode);

            if (identifier == "DeepDrftAudio.setOpusSidecar")
            {
                SetSidecarCallCount++;
                var result = new AudioOperationResult
                {
                    Success = _sidecarParseSucceeds,
                    Error = _sidecarParseSucceeds ? null : "Invalid Opus sidecar blob",
                };
                return ValueTask.FromResult((TValue)(object)result);
            }

            return ValueTask.FromResult<TValue>(default!);
        }

        public ValueTask<TValue> InvokeAsync<TValue>(string identifier, CancellationToken cancellationToken, object?[]? args)
            => InvokeAsync<TValue>(identifier, args);
    }

    // Returns a configured status (with a body) for GET api/track/{id}/opus/seekdata; any other request 404s.
    private sealed class StubSidecarHandler : HttpMessageHandler
    {
        private readonly HttpStatusCode _status;
        private readonly byte[] _body;

        public StubSidecarHandler(HttpStatusCode status, byte[]? body = null)
        {
            _status = status;
            _body = body ?? [];
        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            var response = new HttpResponseMessage(_status);
            if (_status == HttpStatusCode.OK)
                response.Content = new ByteArrayContent(_body);
            return Task.FromResult(response);
        }
    }

    private sealed class SingleClientFactory : IHttpClientFactory
    {
        private readonly HttpMessageHandler _handler;
        public SingleClientFactory(HttpMessageHandler handler) => _handler = handler;

        public HttpClient CreateClient(string name) =>
            new(_handler, disposeHandler: false) { BaseAddress = new Uri("https://content.test/") };
    }

    // Exposes the protected seam for direct assertion. The 18.6 override will replace this same method.
    private sealed class TestablePlayer : StreamingAudioPlayerService
    {
        public TestablePlayer(AudioInteropService interop, TrackMediaClient media)
            : base(interop, media, NullLogger<StreamingAudioPlayerService>.Instance) { }

        public Task<AudioFormat> ResolveFormatForTest(string entryKey) =>
            ResolveStreamFormatAsync(entryKey, CancellationToken.None);
    }

    private static TestablePlayer BuildPlayer(
        bool canDecode, bool sidecarParseSucceeds, HttpStatusCode sidecarStatus, byte[]? sidecarBody)
    {
        var js = new FakeJsRuntime(canDecode, sidecarParseSucceeds);
        var interop = new AudioInteropService(js);
        var media = new TrackMediaClient(new SingleClientFactory(new StubSidecarHandler(sidecarStatus, sidecarBody)));
        return new TestablePlayer(interop, media);
    }

    private static readonly byte[] SidecarBytes = "setup-header+seek-index"u8.ToArray();

    // Capable browser + present sidecar → Opus. The happy path: the default policy picks the low-data format.
    [Test]
    public async Task ResolveStreamFormat_CapableBrowser_SidecarPresent_ChoosesOpus()
    {
        var player = BuildPlayer(canDecode: true, sidecarParseSucceeds: true,
            HttpStatusCode.OK, SidecarBytes);

        var format = await player.ResolveFormatForTest("track-1");

        Assert.That(format, Is.EqualTo(AudioFormat.Opus));
    }

    // Capability gate (AC7): a browser that cannot decode Ogg Opus always gets lossless, and the sidecar is
    // never even fetched/injected — Opus is off the table before any sidecar work.
    [Test]
    public async Task ResolveStreamFormat_IncapableBrowser_ChoosesLossless_AndDoesNotInjectSidecar()
    {
        var js = new FakeJsRuntime(canDecode: false, sidecarParseSucceeds: true);
        var interop = new AudioInteropService(js);
        var media = new TrackMediaClient(new SingleClientFactory(
            new StubSidecarHandler(HttpStatusCode.OK, SidecarBytes)));
        var player = new TestablePlayer(interop, media);

        var format = await player.ResolveFormatForTest("track-1");

        Assert.Multiple(() =>
        {
            Assert.That(format, Is.EqualTo(AudioFormat.Lossless), "incapable browser must fall back to lossless");
            Assert.That(js.SetSidecarCallCount, Is.Zero, "no sidecar should be injected when Opus is gated out");
        });
    }

    // C2 fallback: capable browser but no sidecar (legacy / not-yet-transcoded track, 404) → lossless.
    [Test]
    public async Task ResolveStreamFormat_CapableBrowser_NoSidecar_FallsBackToLossless()
    {
        var player = BuildPlayer(canDecode: true, sidecarParseSucceeds: true,
            HttpStatusCode.NotFound, sidecarBody: null);

        var format = await player.ResolveFormatForTest("track-1");

        Assert.That(format, Is.EqualTo(AudioFormat.Lossless),
            "a capable browser with no Opus sidecar must request lossless, not Opus");
    }

    // A present-but-unparseable sidecar (the JS decoder rejects the bytes) → lossless, so a malformed sidecar
    // never breaks playback. The injection was attempted (set-before-init), but its failure degrades safely.
    [Test]
    public async Task ResolveStreamFormat_SidecarPresentButUnparseable_FallsBackToLossless()
    {
        var js = new FakeJsRuntime(canDecode: true, sidecarParseSucceeds: false);
        var interop = new AudioInteropService(js);
        var media = new TrackMediaClient(new SingleClientFactory(
            new StubSidecarHandler(HttpStatusCode.OK, SidecarBytes)));
        var player = new TestablePlayer(interop, media);

        var format = await player.ResolveFormatForTest("track-1");

        Assert.Multiple(() =>
        {
            Assert.That(format, Is.EqualTo(AudioFormat.Lossless), "an unparseable sidecar must degrade to lossless");
            Assert.That(js.SetSidecarCallCount, Is.EqualTo(1), "the player attempted the set-before-init injection");
        });
    }
}