atome 0.8.8

use cpal::traits::DeviceTrait;
use cpal::{Device, Error, ErrorKind, SampleFormat, Stream, StreamConfig};
use ringbuf::traits::{Consumer, Producer, Split};
use ringbuf::{HeapCons, HeapProd, HeapRb};
use std::marker::PhantomData;
use std::sync::{Arc, Mutex, PoisonError};


pub mod clock;
pub mod mixer;
pub mod scheduler;
pub mod types;
pub mod utils;

pub use clock::PlayClock;
pub use mixer::{ClearSignal, MixCommand, Mixer, MixerHandle, Voices};
pub use scheduler::Scheduler;
pub use types::{OutputType, SampleRate, SampleType};
pub use utils::{
    default_device, device_name, find_device, get_host_by_id, get_host_by_name, get_host_in_name,
    list_device_names, list_devices, list_hosts,
};

/// Frames assumed when the caller asks for the device's default buffer size.
/// Only used to size the ring buffer — the stream itself still asks the device
/// for its own preferred size.
///
/// The ring holds exactly one buffer size, so this is a guess at a number the
/// device actually decides. If the device then picks a period *larger* than
/// this, the ring cannot hold a whole callback and every callback gets a
/// partially filled buffer. Pass an explicit `buffer_size` to make the two match.
pub(crate) const DEFAULT_BUFFER_FRAMES: i32 = 1024;

/// How many `MixCommand`s can be queued before `add_samples` starts refusing.
const COMMAND_QUEUE_LEN: usize = 256;

/// # OutputClass
///
/// Used to hold a stream to a single output.
///
/// `S` *is* the sample type this output speaks: `OutputClass<f32>`,
/// `OutputClass<i16>`, `OutputClass<cpal::I24>`, and so on. Fixing it at the
/// type level means the callback is picked once, when the stream is built,
/// instead of re-deciding on every audio callback, and `add_samples` can only
/// ever be handed matching data.

pub struct OutputClass<S: SampleType> {
    // Number of channels in this output
    channels: u16,
    // Output device to use
    device: Device,
    // Type of device
    out_type: OutputType,
    // The buffer size in frames, one for all outputs; `None` = device default
    buffer_size: Option<i32>,
    // The sample rate
    sample_rate: SampleRate,
    // stream for cpal
    stream: Option<Stream>,
    // Config the stream is (or will be) built with
    stream_config: StreamConfig,
    // Mixer input queue: `add_samples` writes indexed work here, never audio.
    // Shared with every `Scheduler`, so other threads can queue work too.
    commands: Arc<Mutex<HeapProd<MixCommand<S>>>>,
    // Consumer half of the audio ring buffer, sized to exactly one buffer size:
    // taken by `build_stream` and moved into the audio callback. The mixer owns
    // the producer half and keeps it topped up.
    consumer: Option<HeapCons<S>>,
    // Keeps the mixer thread running for as long as this output exists
    mixer: MixerHandle,
    // Where the stream is, as heard: advanced by the callback, read by anyone
    clock: PlayClock,
    // The sample type lives only in the type system; nothing is stored for it.
    sample_type: PhantomData<S>,
}

/// As [`OutputClass::resample`], writing into `out` instead of returning a fresh `Vec`.
///
/// `out` is cleared and refilled, so a caller that keeps one buffer around and hands it back each
/// time allocates once rather than per call — which is what the capture callback needs, since it
/// runs on the audio thread.
pub(crate) fn resample_into<S: SampleType>(
    samples: &[S],
    frames: usize,
    channels: usize,
    from: u32,
    to: u32,
    out: &mut Vec<S>,
) {
    out.clear();
    if frames == 0 || from == 0 || to == 0 {
        return;
    }

    let ratio = to as f64 / from as f64;
    let out_frames = ((frames as f64) * ratio).round().max(1.0) as usize;
    let last = frames - 1;

    out.reserve(out_frames * channels);
    for frame in 0..out_frames {
        // Where this output frame lands on the input timeline.
        let position = frame as f64 / ratio;
        let left = (position.floor() as usize).min(last);
        let right = (left + 1).min(last);
        let t = (position - position.floor()) as f32;
        for channel in 0..channels {
            let a = samples[left * channels + channel].to_f32();
            let b = samples[right * channels + channel].to_f32();
            out.push(S::from_f32(a + (b - a) * t));
        }
    }
}

/// The rates to try for an output whose device will not take the one it was asked for: only rates
/// above it, nearest first.
///
/// Never downward. Resampling up keeps the whole band, while dropping to a lower rate throws the
/// top of it away — and a caller that asked for 44.1 kHz asked for it, so landing on 16 kHz would
/// be a quieter failure than refusing. Where nothing above will open, the caller keeps the rate it
/// asked for and reports the device's own refusal.
///
/// `native` is left out: the caller tries the rate the device is already running at first, that
/// being the one most likely to work.
pub(crate) fn fallback_rates(wanted: SampleRate, native: Option<SampleRate>) -> Vec<SampleRate> {
    let mut higher: Vec<SampleRate> = SampleRate::ALL
        .into_iter()
        .filter(|rate| rate.hz() > wanted.hz() && Some(*rate) != native)
        .collect();

    higher.sort_by_key(|rate| rate.hz() - wanted.hz());
    higher
}

impl<S: SampleType> OutputClass<S> {
    pub fn new(device: Option<Device>, out_type: OutputType, channels: u16, sample_rate:SampleRate, buffer_size: Option<i32>) -> Self {
        // `None` lets the device pick its own buffer size. We can't know that
        // size until the stream is built, so the ring buffer is sized off a
        // default instead.
        let buffer_size_form = match buffer_size {
            Some(frames) => cpal::BufferSize::Fixed(frames as u32),
            None => cpal::BufferSize::Default,
        };
        let frames = buffer_size.unwrap_or(DEFAULT_BUFFER_FRAMES).max(1) as usize;


        let stream_config = StreamConfig {
            channels,
            sample_rate: sample_rate as u32,
            buffer_size: buffer_size_form,
        };

        // Exactly one buffer size: this ring holds only the samples about to go
        // to CPAL, never more. Everything further ahead stays in the mixer's own
        // buffer, where later commands can still be summed into it.
        let capacity = frames * channels.max(1) as usize;
        let (audio_producer, consumer) = HeapRb::<S>::new(capacity).split();

        // add_samples -> commands -> mixer -> audio ring buffer -> callback.
        let (commands, pending) = HeapRb::<MixCommand<S>>::new(COMMAND_QUEUE_LEN).split();
        let mixer = MixerHandle::spawn(Mixer::new(pending, audio_producer));

        OutputClass {
            channels,
            device: device
                .unwrap_or_else(|| default_device().expect("no default output device available")),
            out_type,
            buffer_size,
            sample_rate,
            stream: None,
            stream_config,
            commands: Arc::new(Mutex::new(commands)),
            consumer: Some(consumer),
            mixer,
            clock: PlayClock::new(sample_rate as u32),
            sample_type: PhantomData,
        }
    }

    pub fn channels(&self) -> u16 {
        self.channels
    }
    pub fn device(&self) -> Device {
        self.device.clone()
    }
    pub fn name(&self) -> String {
        device_name(&self.device)
    }
    /// The configured buffer size in frames, or `None` if the device picks it.
    pub fn buffer_size(&self) -> Option<i32> {
        self.buffer_size
    }
    pub fn sample_rate(&self) -> i32 {
        self.sample_rate as i32
    }
    /// The value-level tag for `S`, for when a `SampleFormat` is needed at runtime.
    pub fn sample_format(&self) -> SampleFormat {
        S::format()
    }

    pub fn sample_type(&self) -> SampleFormat {
        S::format()
    }
    pub fn out_type(&self) -> OutputType {
        self.out_type
    }
    /// The body of the output callback.
    ///
    /// The ring buffer already holds `S`, so this pops one callback's worth of
    /// interleaved samples straight into the device's buffer — no conversion, no
    /// scratch buffer, no allocation on the audio thread. `add_samples` queues
    /// frames interleaved (L,R,L,R,…) and the ring buffer is FIFO, so they go
    /// out in exactly the order they came in.
    ///
    /// This is also the only place the ring buffer can be emptied — the mixer
    /// holds the producer half and cannot take anything back out — so a
    /// [`stop`](Self::stop) is finished here, not where it is asked for.
    ///
    /// The [`PlayClock`] moves on by what this takes out of the ring — played
    /// or thrown away by a stop — so it reads the mixer's index exactly. The
    /// mixer pads quiet stretches with silence, so that is every frame the
    /// device plays; only the padding for an underrun or a stop, which stands
    /// in for no index at all, is left off. Counting those would push the
    /// clock ahead of the mixer and make every later sound land that much late.
    fn data_callback(
        data: &mut [S],
        buffer: &mut HeapCons<S>,
        clear: &ClearSignal,
        cleared: &mut usize,
        clock: &PlayClock,
        channels: usize,
        latency: std::time::Duration,
    ) {
        let channels = channels.max(1);

        let epoch = clear.epoch();
        if epoch != *cleared {
            // A stop is in flight: drop what was already committed and play
            // silence instead of it. This keeps happening until the mixer has
            // answered the same stop, because until then it may still be
            // flushing pre-stop samples into the ring behind us.
            let dropped = buffer.clear();
            data.fill(S::SILENCE);
            if clear.acked() == epoch {
                *cleared = epoch;
            }
            clock.advance((dropped / channels) as u64, latency);
            return;
        }

        let read = buffer.pop_slice(data);
        if read < data.len() {
            // Underrun: pad with silence rather than replaying stale audio.
            data[read..].fill(S::SILENCE);
        }
        clock.advance((read / channels) as u64, latency);
    }

    /// Whether this output's device will open at `rate`, found out by opening it.
    ///
    /// Asking the host instead does not work on Windows: `supported_output_configs` lists what
    /// the device could manage in exclusive mode, while a shared-mode stream only ever gets the
    /// rate the device is already mixing at. The stream built here is never played and is closed
    /// again before this returns.
    fn opens_at(&self, rate: SampleRate) -> bool {
        let config = StreamConfig {
            sample_rate: rate.hz(),
            ..self.stream_config
        };

        self.device
            .build_output_stream(
                config,
                move |_data: &mut [S], _info: &cpal::OutputCallbackInfo| {},
                |_error| {},
                None,
            )
            .is_ok()
    }

    /// The rate to open this output at: its own where the device will take it, the rate the
    /// device is already running at otherwise, and failing that the nearest rate it will take.
    ///
    /// Nothing is given up by moving: an output resamples whatever is scheduled on it to its own
    /// rate already (see [`align_samples`](Self::align_samples)), so the rate here is the one
    /// content lands on rather than a rate content has to be in. A device that will not run at
    /// the engine's rate plays at its own instead of staying silent.
    fn usable_rate(&self) -> SampleRate {
        // What the device is mixing at. Asked for that rate it cannot refuse, so the usual case —
        // an engine at the rate its devices run at — settles here without opening anything.
        let mixing_at = self.device.default_output_config().ok().map(|config| config.sample_rate());
        if mixing_at == Some(self.sample_rate.hz()) || self.opens_at(self.sample_rate) {
            return self.sample_rate;
        }

        let native = mixing_at
            .and_then(SampleRate::from_hz)
            .filter(|rate| *rate != self.sample_rate);
        if let Some(native) = native.filter(|rate| self.opens_at(*rate)) {
            return native;
        }

        // Then whatever else it will take — a device at a rate this enum does not name lands here.
        // Nothing at all opens: keep the rate asked for, so `build_stream` reports the device's
        // own refusal rather than one for a rate nobody chose.
        fallback_rates(self.sample_rate, native)
            .into_iter()
            .find(|rate| self.opens_at(*rate))
            .unwrap_or(self.sample_rate)
    }

    /// Moves this output to `rate`: the stream it will build, the rate content is aligned to, and
    /// the clock. Only before the stream is built.
    fn retune(&mut self, rate: SampleRate) {
        self.sample_rate = rate;
        self.stream_config.sample_rate = rate.hz();
        self.clock.retune(rate.hz());
    }

    /// Builds the cpal output stream for this output's device, pulling mixed
    /// samples out of its ring buffer and writing them as `S`. The resulting
    /// `Stream` is stored on `self` (streams must be kept alive to keep playing)
    /// and also returned.
    ///
    /// Opens at the rate this output was made with where the device will take it, and at a rate
    /// the device will take otherwise — [`sample_rate`](Self::sample_rate) then reports the rate
    /// it actually runs at, which is also the rate content is resampled to.
    ///
    /// Consumes the consumer half of the ring buffer, so it can only be called
    /// once per `OutputClass`.
    pub fn build_stream(&mut self) -> Result<&Stream, Error> {
        // Before the ring buffer is consumed: a failed build takes the consumer half with it, so
        // the rate has to be settled while there is still something to retry with.
        let usable = self.usable_rate();
        if usable != self.sample_rate {
            self.retune(usable);
        }

        let mut buffer = self.consumer.take().ok_or_else(|| {
            Error::with_message(
                ErrorKind::UnsupportedOperation,
                "stream already built for this output",
            )
        })?;

        // Shared with the mixer thread so `stop` can reach the samples that are
        // already past it, sitting in the ring buffer.
        let clear = self.mixer.clear_signal();
        let mut cleared = clear.epoch();
        let clock = self.clock.clone();
        let channels = usize::from(self.channels);

        let stream = self.device.build_output_stream(
            self.stream_config,
            move |data: &mut [S], info: &cpal::OutputCallbackInfo| {
                // How long until what is written now is heard: the device's
                // buffering and the DAC, as cpal predicts them.
                let stamp = info.timestamp();
                let latency = stamp.playback.duration_since(stamp.callback);

                Self::data_callback(data, &mut buffer, &clear, &mut cleared, &clock, channels, latency)
            },
            Self::err_fn,
            None,
        )?;

        self.clock.opened();
        self.stream = Some(stream);
        Ok(self.stream.as_ref().unwrap())
    }

    /// Schedules interleaved samples for playback at absolute sample `index`,
    /// summing them with anything already scheduled there. They stay in this
    /// output's sample type the whole way — `&[i16]` into an `OutputClass<i16>`
    /// is queued, mixed, and played as `i16`, never converted.
    ///
    /// This only hands a [`MixCommand`] to the mixer — no audio touches the
    /// stream's ring buffer here. Returns the index just past the batch, ready
    /// to pass straight back in for the next one.
    ///
    /// Fails if the mixer's command queue is full, which means it is not
    /// draining fast enough; the whole batch is refused rather than half of it.
    pub fn add_samples(&mut self, samples: &[S], index: usize) -> Result<usize, Error> {
        
        
        let command = MixCommand {
            index,
            samples: samples.to_vec(),
            voice: None,
        };

        self.commands.lock().unwrap_or_else(PoisonError::into_inner).try_push(command).map_err(|_| {
            Error::with_message(ErrorKind::ResourceExhausted, "mixer command queue is full")
        })?;

        Ok(index + samples.len())
    }
    /// Schedules interleaved samples for playback at a `time`.
    /// Time is in secounds from now, so it will delay the start of the audio
    ///
    /// The index is `time * sample_rate * channels`, since an index counts
    /// interleaved samples rather than frames — a stereo second is twice as
    /// many indices as a mono one.
    ///
    /// Note that "from now" is measured from the *start of the stream*, not
    /// from wherever playback has reached: the mixer's play cursor is not
    /// visible from here, so calling this after playback has begun schedules
    /// into the past and the samples are dropped as late. Exposing the cursor
    /// through [`MixerHandle`] would be the way to make it truly relative.
    pub fn add_samples_time(&mut self, samples: &[S], time: usize) -> Result<usize, Error> {
        let index = time * self.sample_rate as usize * self.channels.max(1) as usize;

        let command = MixCommand {
            index,
            samples: samples.to_vec(),
            voice: None,
        };

        self.commands.lock().unwrap_or_else(PoisonError::into_inner).try_push(command).map_err(|_| {
            Error::with_message(ErrorKind::ResourceExhausted, "mixer command queue is full")
        })?;

        Ok(index + samples.len())
    }

    /// Deletes all samples that have been scheduled but not yet played, and resets the
    /// mixer to the current time. This is useful if you want to stop all audio
    /// immediately and start fresh.
    ///
    /// Both stages are cleared: the mixer's queued commands and accumulation
    /// buffer, and the ring buffer the audio callback is already reading from —
    /// otherwise up to one buffer of committed audio would still play out.
    ///
    /// The stream keeps running and plays silence; the output stays usable and
    /// [`add_samples`](Self::add_samples) works again straight away. It is not
    /// instant: the mixer answers on its next pass and the callback on its
    /// next, so the tail is at most one buffer long.
    ///
    /// The play cursor does not move: it is an absolute position in the stream,
    /// not a count of what got played, so anything scheduled behind it is still
    /// late after a stop.
    pub fn stop(&mut self) {
        self.mixer.clear_samples();
    }
    /// Drops the stream, stopping playback. The output can be re-used by calling
    /// [`build_stream`](Self::build_stream) again.
    pub fn close(&mut self) {
        self.stream.take();
        self.clock.closed();
    }

    /// Where this output's stream is, as heard, readable from any thread —
    /// what a video engine follows so pictures stay on the sound. Cheap to
    /// clone, and live before the stream is built: it reads zero and stopped
    /// until the first callback.
    ///
    /// Its timeline is the mixer's. A sound scheduled at interleaved index `i`
    /// with [`add_samples`](Self::add_samples) is heard at
    /// `i / channels / sample_rate` seconds on this clock.
    pub fn clock(&self) -> PlayClock {
        self.clock.clone()
    }
    /// A handle other threads can schedule this output's audio through —
    /// cheap to clone, `Send` and `Sync`. What a video engine uses to play a
    /// film's soundtrack in step with its pictures.
    pub fn scheduler(&self) -> Scheduler<S> {
        Scheduler::new(
            Arc::clone(&self.commands),
            self.mixer.voices(),
            self.clock.clone(),
            self.channels,
            self.sample_rate as u32,
        )
    }

    /// Handle to the mixer thread feeding this output.
    pub fn mixer(&self) -> &MixerHandle {
        &self.mixer
    }
    /// Aligns the samples to the output's sample rate and channel count.
    ///
    /// Set `interleaved` to describe what you are handing in: `true` for frames
    /// (L,R,L,R,…), `false` for planar data, where each channel is one
    /// contiguous run. Planar input is woven into frames before anything else
    /// happens to it.
    ///
    /// The result is always interleaved at `self.channels` / `self.sample_rate`,
    /// ready to hand to [`add_samples`](Self::add_samples). Fails if `channels`
    /// is zero or `samples` does not hold a whole number of frames.
    pub fn align_samples(&self, samples: &[S], sample_rate: SampleRate, channels: u16, interleaved: bool) -> Result<Vec<S>, Error> {
        if channels == 0 {
            return Err(Error::with_message(
                ErrorKind::InvalidInput,
                "sample data must have at least one channel",
            ));
        }
        let src_channels = channels as usize;
        if samples.len() % src_channels != 0 {
            return Err(Error::with_message(
                ErrorKind::InvalidInput,
                "sample count is not a whole number of frames",
            ));
        }
        // The device always takes interleaved data, so interleaved input that
        // already matches the output needs nothing done to it.
        if sample_rate == self.sample_rate && channels == self.channels && interleaved {
            return Ok(samples.to_vec());
        }

        let dst_channels = self.channels.max(1) as usize;
        let frames = samples.len() / src_channels;

        // Weave first: everything after this point indexes by frame, so planar
        // input has to become frames before it can be remapped or resampled.
        // One channel is the same bytes either way, so it skips the copy.
        let mut buffer = if interleaved || src_channels == 1 {
            samples.to_vec()
        } else {
            Self::weave(samples, frames, src_channels)
        };

        if src_channels != dst_channels {
            buffer = Self::map_channels(&buffer, frames, src_channels, dst_channels);
        }

        if sample_rate != self.sample_rate {
            buffer = Self::resample(
                &buffer,
                frames,
                dst_channels,
                sample_rate as u32,
                self.sample_rate as u32,
            );
        }

        Ok(buffer)
    }

    /// Weaves planar samples — channel 0's `frames` samples, then channel 1's,
    /// and so on — into interleaved frames (L,R,L,R,…), the only layout the
    /// mixer and the device ever see.
    fn weave(samples: &[S], frames: usize, channels: usize) -> Vec<S> {
        let mut out = Vec::with_capacity(samples.len());
        for frame in 0..frames {
            for channel in 0..channels {
                out.push(samples[(channel * frames) + frame]);
            }
        }
        out
    }

    /// Re-lays `frames` interleaved frames of `src_channels` into `dst_channels`.
    ///
    /// Mono input fans out to every output channel and a mono output sums the
    /// input down; anything else keeps channel `n` as channel `n`, dropping
    /// the extras when narrowing and filling with silence when widening. That
    /// is deliberately dumb about channel *meaning* — a 5.1 stream narrowed to
    /// stereo keeps front-left/front-right and loses the rest rather than
    /// folding them in.
    fn map_channels(samples: &[S], frames: usize, src_channels: usize, dst_channels: usize) -> Vec<S> {
        let mut out = Vec::with_capacity(frames * dst_channels);
        for frame in 0..frames {
            let start = frame * src_channels;
            if src_channels == 1 {
                out.extend(std::iter::repeat(samples[start]).take(dst_channels));
            } else if dst_channels == 1 {
                // Summed with the format's own `mix`, so an `i16` source stays
                // `i16` the whole way down — no float round-trip. Folding N
                // channels into one is correspondingly louder and can overflow
                // the format, so attenuate before calling if the source is hot.
                let mut sum = S::SILENCE;
                for sample in &samples[start..start + src_channels] {
                    sum = sum.mix(*sample);
                }
                out.push(sum);
            } else {
                for channel in 0..dst_channels {
                    out.push(if channel < src_channels {
                        samples[start + channel]
                    } else {
                        S::SILENCE
                    });
                }
            }
        }
        out
    }

    /// Resamples interleaved `frames` from `from` Hz to `to` Hz, linearly
    /// interpolating between the two input frames each output frame falls
    /// between.
    ///
    /// Linear interpolation is cheap and has no pre-ring, but it is not
    /// band-limited: downsampling folds anything above the new Nyquist back
    /// into the audible range, so low-pass filter first if the source has real
    /// content up there.
    fn resample(samples: &[S], frames: usize, channels: usize, from: u32, to: u32) -> Vec<S> {
        let mut out = Vec::new();
        resample_into(samples, frames, channels, from, to, &mut out);
        out
    }

    fn err_fn(err: cpal::Error) {
        eprintln!("audio output stream error: {}", err);
    }

}

#[cfg(test)]
mod rate_tests {
    use super::*;

    /// Falling back climbs and never drops: a caller that asked for 44.1 kHz would rather be
    /// refused than quietly handed 16 kHz.
    #[test]
    fn a_fallback_only_reaches_for_higher_rates() {
        let order = fallback_rates(SampleRate::Hz44_1k, None);

        assert_eq!(order[0], SampleRate::Hz48k, "the next rate up, first");
        assert_eq!(order[1], SampleRate::Hz88_2k);
        assert!(order.iter().all(|rate| rate.hz() > SampleRate::Hz44_1k.hz()), "{order:?}");
        assert!(!order.contains(&SampleRate::Hz44_1k), "the rate that failed is not retried");
    }

    /// The rate the device is already running at is the caller's first move, so it is not repeated.
    #[test]
    fn a_fallback_leaves_out_the_rate_already_tried() {
        let order = fallback_rates(SampleRate::Hz44_1k, Some(SampleRate::Hz48k));

        assert!(!order.contains(&SampleRate::Hz48k));
        assert_eq!(order[0], SampleRate::Hz88_2k, "the next one up after it");
    }

    /// Nothing is above the top rate, so there is nowhere to climb to.
    #[test]
    fn the_top_rate_has_nowhere_to_fall_back_to() {
        assert!(fallback_rates(SampleRate::Hz352_8, None).is_empty());
    }

    /// An output ends up at a rate its device will take, whatever was asked for, and says which.
    ///
    /// Every rate opens on a machine whose host converts for us (Windows's shared-mode engine
    /// does, since cpal 0.18.2), so on those this asserts that nothing was moved needlessly. On a
    /// host that refuses, it asserts the fallback landed somewhere the device accepts. A machine
    /// with no output device tests nothing and still passes.
    #[test]
    fn an_output_opens_at_a_rate_its_device_will_take() {
        let Some(device) = default_device() else { return };
        let channels = device.default_output_config().map(|config| config.channels()).unwrap_or(2);

        for asked in [SampleRate::Hz44_1k, SampleRate::Hz48k, SampleRate::Hz88_2k] {
            let mut output =
                OutputClass::<f32>::new(Some(device.clone()), OutputType::WASAPI, channels, asked, Some(512));

            // Whatever `build_stream` reports, the rate it settled on is the one it opened with.
            let built = output.build_stream().is_ok();
            let got = output.sample_rate() as u32;

            if built {
                assert!(
                    SampleRate::from_hz(got).is_some(),
                    "opened at {got} Hz, which is not one of atome's rates"
                );
            } else {
                // Nothing opened at all: the rate asked for is kept, so the error is about that.
                assert_eq!(got, asked.hz(), "a refused output should keep the rate it was asked for");
            }
        }
    }
}