namespace ytLive.Services.Audio;

/// <summary>
/// Supplies the live-mix gain values (mic + loopback) as Func seams for
/// <see cref="AudioMixer"/>, sourced from the VM's volume/mute state. Read live
/// on every mix tick so slider drags and mutes take effect immediately on the
/// stream. Mute and zero volume can never disagree: 0 always reads as muted.
/// </summary>
public sealed class AudioGainProvider
{
    private readonly Func<bool> _micMuted;
    private readonly Func<double> _micVolume;
    private readonly Func<bool> _gameMuted;
    private readonly Func<double> _gameVolume;

    public AudioGainProvider(
        Func<bool> micMuted,
        Func<double> micVolume,
        Func<bool> gameMuted,
        Func<double> gameVolume)
    {
        _micMuted = micMuted;
        _micVolume = micVolume;
        _gameMuted = gameMuted;
        _gameVolume = gameVolume;
    }

    /// <summary>Mic gain for the live mix (0 = muted).</summary>
    public double MicGain() => _micMuted() ? 0 : _micVolume();

    /// <summary>Loopback (desktop/game) gain for the live mix (0 = muted).
    /// Honesty rule (2026-09-01): WASAPI loopback capture does NOT shrink with the
    /// endpoint volume — the creator dropped system volume to 20% and the captured
    /// level stayed pegged — so the mixer must multiply by GameAudioVolume itself
    /// for the stream to follow the knob (the old unity assumption left the stream
    /// at full desktop volume while the headphones went quiet; ai.md always
    /// specified loopbackGain = GameAudioVolume — the code had drifted).</summary>
    public double LoopbackGain() => _gameMuted() ? 0 : _gameVolume();
}