using DeepDrftPublic.Client.Services;

namespace DeepDrftTests;

/// <summary>
/// Unit tests for the Theater-Mode auto-exit invariant on <see cref="WaveformVisualizerControlState"/>
/// (Phase 20 bug fix): when both subsystems are disabled, <see cref="WaveformVisualizerControlState.CoerceTheaterMode"/>
/// must force <c>TheaterMode = false</c> so observers never see a stranded-theater state.
/// </summary>
[TestFixture]
public class WaveformVisualizerControlStateTests
{
    private WaveformVisualizerControlState _state = null!;

    [SetUp]
    public void SetUp() => _state = new WaveformVisualizerControlState();

    // ── CoerceTheaterMode guard ──

    // Both off + Theater on → coerce exits theater.
    [Test]
    public void CoerceTheaterMode_BothOff_TheaterBecomesFalse()
    {
        _state.TheaterMode = true;
        _state.LavaEnabled = false;
        _state.WaveformEnabled = false;

        _state.CoerceTheaterMode();

        Assert.That(_state.TheaterMode, Is.False);
    }

    // Lava still on → theater is left alone even if waveform is off.
    [Test]
    public void CoerceTheaterMode_LavaOnWaveformOff_TheaterPreserved()
    {
        _state.TheaterMode = true;
        _state.LavaEnabled = true;
        _state.WaveformEnabled = false;

        _state.CoerceTheaterMode();

        Assert.That(_state.TheaterMode, Is.True);
    }

    // Waveform still on → theater is left alone even if lava is off.
    [Test]
    public void CoerceTheaterMode_WaveformOnLavaOff_TheaterPreserved()
    {
        _state.TheaterMode = true;
        _state.LavaEnabled = false;
        _state.WaveformEnabled = true;

        _state.CoerceTheaterMode();

        Assert.That(_state.TheaterMode, Is.True);
    }

    // Theater already false + both off → no change (no false-positive write).
    [Test]
    public void CoerceTheaterMode_TheaterAlreadyFalse_NoChange()
    {
        _state.TheaterMode = false;
        _state.LavaEnabled = false;
        _state.WaveformEnabled = false;

        _state.CoerceTheaterMode();

        Assert.That(_state.TheaterMode, Is.False);
    }

    // ── Changed event fires once with coerced state visible ──

    // Verify that after coercion, the Changed notification carries the already-corrected TheaterMode
    // value — all observers see a consistent state in the single Changed cycle.
    [Test]
    public void NotifyChanged_AfterCoerce_ObserverSeesTheaterFalse()
    {
        _state.TheaterMode = true;
        _state.LavaEnabled = false;
        _state.WaveformEnabled = false;

        bool? observedTheaterMode = null;
        _state.Changed += () => observedTheaterMode = _state.TheaterMode;

        _state.CoerceTheaterMode();
        _state.NotifyChanged();

        Assert.That(observedTheaterMode, Is.False);
    }

    // ── ApplyCapabilityDefault: the one-time HW-accel default-set ──

    // No HW accel → lava defaults off, waveform stays on (the whole point of the feature).
    [Test]
    public void ApplyCapabilityDefault_NoHardwareAccel_LavaOffWaveformOn()
    {
        _state.ApplyCapabilityDefault(hardwareAccelerated: false);

        Assert.Multiple(() =>
        {
            Assert.That(_state.LavaEnabled, Is.False);
            Assert.That(_state.WaveformEnabled, Is.True);
        });
    }

    // HW accel present → no change; lava keeps its shipped on-default (the common case is untouched).
    [Test]
    public void ApplyCapabilityDefault_HardwareAccelerated_LavaStaysOn()
    {
        _state.ApplyCapabilityDefault(hardwareAccelerated: true);

        Assert.Multiple(() =>
        {
            Assert.That(_state.LavaEnabled, Is.True);
            Assert.That(_state.WaveformEnabled, Is.True);
        });
    }

    // No HW accel raises Changed once so the controls UI / bridge / theater observers all react.
    [Test]
    public void ApplyCapabilityDefault_NoHardwareAccel_RaisesChanged()
    {
        var raised = 0;
        _state.Changed += () => raised++;

        _state.ApplyCapabilityDefault(hardwareAccelerated: false);

        Assert.That(raised, Is.EqualTo(1));
    }

    // HW accel present must not churn observers — no Changed when nothing changed.
    [Test]
    public void ApplyCapabilityDefault_HardwareAccelerated_DoesNotRaiseChanged()
    {
        var raised = 0;
        _state.Changed += () => raised++;

        _state.ApplyCapabilityDefault(hardwareAccelerated: true);

        Assert.That(raised, Is.Zero);
    }

    // Guarded to once per session: a second call cannot re-clobber, even with a different verdict.
    [Test]
    public void ApplyCapabilityDefault_SecondCall_IsNoOp()
    {
        _state.ApplyCapabilityDefault(hardwareAccelerated: true); // first call wins (accelerated → on)
        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // must be ignored

        Assert.That(_state.LavaEnabled, Is.True);
    }

    // Must not override an explicit in-session toggle: once applied, a user re-enabling lava on a
    // software renderer sticks — a later (guarded) call never reverts it.
    [Test]
    public void ApplyCapabilityDefault_DoesNotOverrideExplicitUserToggle()
    {
        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // default: lava off
        _state.LavaEnabled = true;                                 // user re-enables at their own risk

        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // guarded → no-op

        Assert.That(_state.LavaEnabled, Is.True);
    }

    // No HW accel while Theater Mode is on with only lava active → coercion exits theater in the same
    // cycle (lava off + waveform off would strand theater; here waveform stays on, but verify the
    // coercion path is exercised when it WOULD strand).
    [Test]
    public void ApplyCapabilityDefault_NoHardwareAccel_CoercesStrandedTheater()
    {
        _state.WaveformEnabled = false; // only lava active
        _state.TheaterMode = true;

        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // lava off → both off → strand

        Assert.That(_state.TheaterMode, Is.False);
    }
}