refactor: clean separation between lib and CLI

raust-cli/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "raust-cli"
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+homepage.workspace = true
+repository.workspace = true
+license.workspace = true
+
+[dependencies]
+anyhow = { workspace = true }
+clap = { version = "4.6.7", features = ["derive"] }
+cpal = { workspace = true }
+raust-engine = { workspace = true }
+
+[lints]
+workspace = true

raust-cli/src/main.rs

@@ -0,0 +1,43 @@
+use clap::Parser;
+use cpal::traits::DeviceTrait;
+use raust_engine::{AudioPlayer, Note};
+
+/// Play a single tone through the default audio output device.
+#[derive(Parser, Debug)]
+#[command(version, about, long_about = None)]
+struct Args {
+    /// Frequency of the tone to play, in Hertz.
+    #[arg(short, long, default_value = "440.0")]
+    frequency: f32,
+
+    /// How long to play the tone, in milliseconds.
+    #[arg(short, long, default_value = "1000")]
+    length_milli: u64,
+}
+
+fn main() -> anyhow::Result<()> {
+    let args = Args::parse();
+    let note = Note {
+        pitch: args.frequency,
+        length: args.length_milli,
+    };
+    let (device, config) = raust_engine::get_device_and_config()?;
+    println!("Output device: {}", device.id()?);
+    println!("Default output config: {config:?}");
+    let mut clock = 0f32;
+    // Sample rates are a few hundred kHz at most, nowhere near f32's
+    // 24-bit exact-integer range, so this cast never loses precision.
+    #[allow(clippy::cast_precision_loss, clippy::as_conversions)]
+    let sample_rate = config.sample_rate() as f32;
+    let generator = move || {
+        clock = (clock + 1.0) % sample_rate;
+        (clock * note.pitch * 2.0 * std::f32::consts::PI / sample_rate).sin()
+    };
+    let audio_player = AudioPlayer::try_new(&device, config, Box::new(generator))?;
+
+    audio_player.play()?;
+    std::thread::sleep(std::time::Duration::from_millis(note.length));
+    audio_player.pause()?;
+
+    Ok(())
+}