extern crate cpal;
extern crate failure;

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

fn main() -> Result<(), failure::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 event_loop = host.event_loop();
    let stream_id = event_loop.build_output_stream(&device, &format)?;
    event_loop.play_stream(stream_id.clone())?;

    let sample_rate = format.sample_rate.0 as f32;
    let mut sample_clock = 0f32;

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

    event_loop.run(move |id, result| {
        let data = match result {
            Ok(data) => data,
            Err(err) => {
                eprintln!("an error occurred on stream {:?}: {}", id, err);
                return;
            }
        };

        match data {
            cpal::StreamData::Output { buffer: cpal::UnknownTypeOutputBuffer::U16(mut buffer) } => {
                for sample in buffer.chunks_mut(format.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(format.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(format.channels as usize) {
                    let value = next_value();
                    for out in sample.iter_mut() {
                        *out = value;
                    }
                }
            },
            _ => (),
        }
    });
}