extern crate cpal;
extern crate futures;

use futures::Future;
use futures::stream::Stream;

fn main() {
    let endpoint = cpal::get_default_endpoint().expect("Failed to get default endpoint");
    let format = endpoint.get_supported_formats_list().unwrap().next().expect("Failed to get endpoint format");

    let event_loop = cpal::EventLoop::new();

    let (mut voice, stream) = cpal::Voice::new(&endpoint, &format, &event_loop).expect("Failed to create a voice");

    // Produce a sinusoid of maximum amplitude.
    let samples_rate = format.samples_rate.0 as f32;
    let mut data_source = (0u64..).map(move |t| t as f32 * 440.0 * 2.0 * 3.141592 / samples_rate)     // 440 Hz
                                  .map(move |t| t.sin());

    voice.play();
    stream.for_each(move |buffer| -> Result<_, ()> {
        match buffer {
            cpal::UnknownTypeBuffer::U16(mut buffer) => {
                for (sample, value) in buffer.chunks_mut(format.channels.len()).zip(&mut data_source) {
                    let value = ((value * 0.5 + 0.5) * std::u16::MAX as f32) as u16;
                    for out in sample.iter_mut() { *out = value; }
                }
            },

            cpal::UnknownTypeBuffer::I16(mut buffer) => {
                for (sample, value) in buffer.chunks_mut(format.channels.len()).zip(&mut data_source) {
                    let value = (value * std::i16::MAX as f32) as i16;
                    for out in sample.iter_mut() { *out = value; }
                }
            },

            cpal::UnknownTypeBuffer::F32(mut buffer) => {
                for (sample, value) in buffer.chunks_mut(format.channels.len()).zip(&mut data_source) {
                    for out in sample.iter_mut() { *out = value; }
                }
            },
        };

        Ok(())
    }).forget();

    event_loop.run();
}