extern crate anyhow;
extern crate cpal;

use cpal::traits::{DeviceTrait, StreamTrait, HostTrait};

fn main() -> Result<(), anyhow::Error> {
    let host = cpal::default_host();
    let device = host.default_output_device().expect("failed to find a default output device");
    let format = device.default_output_format()?;
    let sample_rate = format.sample_rate.0 as f32;
    let channels = format.channels;
    let mut sample_clock = 0f32;

    // Produce a sinusoid of maximum amplitude.
    let mut next_value = move || {
        sample_clock = (sample_clock + 1.0) % sample_rate;
        (sample_clock * 440.0 * 2.0 * 3.141592 / sample_rate).sin()
    };

    let stream = device.build_output_stream(&format, move |data| {
        match data {
            cpal::StreamData::Output { buffer: cpal::UnknownTypeOutputBuffer::U16(mut buffer) } => {
                for sample in buffer.chunks_mut(channels as usize) {
                    let value = ((next_value() * 0.5 + 0.5) * std::u16::MAX as f32) as u16;
                    for out in sample.iter_mut() {
                        *out = value;
                    }
                }
            },
            cpal::StreamData::Output { buffer: cpal::UnknownTypeOutputBuffer::I16(mut buffer) } => {
                for sample in buffer.chunks_mut(channels as usize) {
                    let value = (next_value() * std::i16::MAX as f32) as i16;
                    for out in sample.iter_mut() {
                        *out = value;
                    }
                }
            },
            cpal::StreamData::Output { buffer: cpal::UnknownTypeOutputBuffer::F32(mut buffer) } => {
                for sample in buffer.chunks_mut(channels as usize) {
                    let value = next_value();
                    for out in sample.iter_mut() {
                        *out = value;
                    }
                }
            },
            _ => (),
        }
    }, move |err| {
        eprintln!("an error occurred on stream: {}", err);
    })?;
    stream.play()?;

    std::thread::sleep(std::time::Duration::from_millis(1000));

    Ok(())
}