audioview/frontend-core/src/components/player.rs

use crate::agents::audio_agent::{AudioAgent, AudioData};
use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
use cpal::{Device, Sample, SampleFormat, Stream, StreamConfig};
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;
use yew::prelude::*;
use yew::services::ConsoleService;

pub enum Status {
    Stopped,
    Playing,
}

pub struct Player {
    link: ComponentLink<Self>,
    status: Status,
    stream: Option<Stream>,
    _audio_agent: Box<dyn Bridge<AudioAgent>>,
    audio_data: Option<Arc<AudioData>>,
}

pub enum Msg {
    Play,
    AudioAgentMessage(Result<Arc<AudioData>, String>),
}

impl Component for Player {
    type Message = Msg;
    type Properties = ();

    fn create(_: Self::Properties, link: ComponentLink<Self>) -> Self {
        let cb = link.callback(Msg::AudioAgentMessage);

        Self {
            link,
            status: Status::Stopped,
            stream: None,
            _audio_agent: AudioAgent::bridge(cb),
            audio_data: None,
        }
    }

    fn rendered(&mut self, _first_render: bool) {}

    fn update(&mut self, msg: Self::Message) -> ShouldRender {
        match msg {
            Msg::Play => self.handle_play_button_clicked(),
            Msg::AudioAgentMessage(Ok(audio_data)) => self.handle_samples_loaded(audio_data),
            Msg::AudioAgentMessage(Err(err)) => self.handle_samples_loaded_error(&err),
        }
    }

    fn change(&mut self, _: Self::Properties) -> ShouldRender {
        false
    }

    fn view(&self) -> Html {
        html! {
            <div>
                <button onclick=self.link.callback(move |_| Msg::Play)>{self.button_text()}</button>
            </div>
        }
    }
}

impl Player {
    fn handle_samples_loaded(&mut self, audio_data: Arc<AudioData>) -> ShouldRender {
        ConsoleService::log("Player: samples loaded");
        self.audio_data = Some(audio_data);
        true
    }

    fn handle_samples_loaded_error(&mut self, err: &str) -> ShouldRender {
        ConsoleService::log(&format!("Player: error loading samples: {:?}", err));
        self.audio_data = None;
        false
    }

    fn play(&mut self) {
        if let Some(audio_data) = &self.audio_data {
            let host = cpal::default_host();
            let device = host.default_output_device().unwrap();

            let config = device.default_output_config().unwrap();
            ConsoleService::log(&format!("Using output config: {:?}", config));

            let stream = match config.sample_format() {
                SampleFormat::F32 => {
                    Player::run::<f32>(&device, &config.into(), audio_data.clone())
                }
                SampleFormat::I16 => {
                    Player::run::<i16>(&device, &config.into(), audio_data.clone())
                }
                SampleFormat::U16 => {
                    Player::run::<u16>(&device, &config.into(), audio_data.clone())
                }
            };

            self.stream = Some(stream);
        }
    }

    fn run<T>(device: &Device, config: &StreamConfig, audio_data: Arc<AudioData>) -> Stream
    where
        T: cpal::Sample,
    {
        let err_fn = |err| ConsoleService::warn(&format!("an error occurred on stream: {}", err));
        let num_channels = audio_data.num_channels as usize;

        // TODO: consider passing the link into the audio callback? Need to double check
        // performance implications.
        // https://discord.com/channels/701068342760570933/703449306497024049/753646647938121738
        let idx = Arc::new(AtomicUsize::new(0));
        let stream = device
            .build_output_stream(
                config,
                move |output: &mut [T], _| {
                    let frames = output.chunks_mut(num_channels);
                    let mut idx = idx.fetch_add(frames.len(), Ordering::Relaxed);

                    for frame in output.chunks_mut(num_channels) {
                        for (j, sample) in frame.iter_mut().enumerate() {
                            let buffer = &audio_data.buffers[j];
                            let value: T = Sample::from::<f32>(&buffer[idx]);
                            *sample = value;
                        }
                        idx += 1;
                    }
                },
                err_fn,
            )
            .unwrap();

        stream.play().unwrap();
        stream
    }

    fn handle_play_button_clicked(&mut self) -> ShouldRender {
        match self.status {
            Status::Stopped => {
                self.status = Status::Playing;
                self.play();
            }
            Status::Playing => self.status = Status::Stopped,
        }
        true
    }

    fn button_text(&self) -> &str {
        if let Status::Stopped = self.status {
            "Play"
        } else {
            "Pause"
        }
    }
}