//! Play a sawtooth wave for several seconds.
//!
//! A rusty adaptation of the official PortAudio C "paex_saw.c" example by Phil Burk and Ross
//! Bencina.

extern crate portaudio;

use portaudio as pa;

const CHANNELS: i32 = 2;
const NUM_SECONDS: i32 = 5;
const SAMPLE_RATE: f64 = 44_100.0;
const FRAMES_PER_BUFFER: u32 = 64;

fn main() {
    match run() {
        Ok(_) => {}
        e => {
            eprintln!("Example failed with the following: {:?}", e);
        }
    }
}

fn run() -> Result<(), pa::Error> {
    println!(
        "PortAudio Test: output sawtooth wave. SR = {}, BufSize = {}",
        SAMPLE_RATE, FRAMES_PER_BUFFER
    );

    let mut left_saw = 0.0;
    let mut right_saw = 0.0;

    let pa = pa::PortAudio::new()?;

    let mut settings =
        pa.default_output_stream_settings(CHANNELS, SAMPLE_RATE, FRAMES_PER_BUFFER)?;
    // we won't output out of range samples so don't bother clipping them.
    settings.flags = pa::StreamFlags::CLIP_OFF;

    // This routine will be called by the PortAudio engine when audio is needed. It may called at
    // interrupt level on some machines so don't do anything that could mess up the system like
    // dynamic resource allocation or IO.
    let callback = move |pa::OutputStreamCallbackArgs { buffer, frames, .. }| {
        let mut idx = 0;
        for _ in 0..frames {
            buffer[idx] = left_saw;
            buffer[idx + 1] = right_saw;
            left_saw += 0.01;
            if left_saw >= 1.0 {
                left_saw -= 2.0;
            }
            right_saw += 0.03;
            if right_saw >= 1.0 {
                right_saw -= 2.0;
            }
            idx += 2;
        }
        pa::Continue
    };

    let mut stream = pa.open_non_blocking_stream(settings, callback)?;

    stream.start()?;

    println!("Play for {} seconds.", NUM_SECONDS);
    pa.sleep(NUM_SECONDS * 1_000);

    stream.stop()?;
    stream.close()?;

    println!("Test finished.");

    Ok(())
}