9 files changed, 966 insertions, 0 deletions

diff --git a/audio/Cargo.toml b/audio/Cargo.toml
new file mode 100644
index 0000000..58f18a2
--- /dev/null
+++ b/audio/Cargo.toml
@@ -0,0 +1,18 @@
+[package]
+name = "audio"
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+raylib.workspace = true
+
+[lints]
+workspace = true
+
+[features]
+default = []
+static = []
diff --git a/audio/src/channel.rs b/audio/src/channel.rs
new file mode 100644
index 0000000..7ed61a6
--- /dev/null
+++ b/audio/src/channel.rs
@@ -0,0 +1,199 @@
+use raylib::audio::RaylibAudio;
+
+type Music = raylib::audio::Music<'static>;
+
+macro_rules! load_audio {
+	($handle:expr, $filepath:expr) => {{
+		let mut audio = if cfg!(any(feature = "static", target_arch = "wasm32")) {
+			let bytes = include_bytes!(concat!("../../", $filepath));
+			let vec = Vec::from(bytes);
+			$handle.new_music_from_memory(".wav", &vec)?
+		} else {
+			$handle.new_music($filepath)?
+		};
+		audio.looping = true;
+		audio
+	}};
+}
+
+pub trait Channel {
+	fn stop(&self);
+	fn play(&self);
+	fn update(&self);
+	fn is_playing(&self) -> bool;
+	fn set_volume(&self, volume: f32);
+	fn set_pitch(&self, pitch: f32);
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DutyCycle {
+	Percent12,
+	Percent25,
+	Percent50,
+	Percent25Neg,
+}
+
+pub struct PulseChannel {
+	pulse_12: Music,
+	pulse_25: Music,
+	pulse_50: Music,
+	pulse_75: Music,
+	duty: DutyCycle,
+}
+impl PulseChannel {
+	pub fn load(handle: &'static RaylibAudio) -> crate::Result<Self> {
+		Ok(Self {
+			pulse_12: load_audio!(handle, "assets/wav/pulse_12.wav"),
+			pulse_25: load_audio!(handle, "assets/wav/pulse_25.wav"),
+			pulse_50: load_audio!(handle, "assets/wav/pulse_50.wav"),
+			pulse_75: load_audio!(handle, "assets/wav/pulse_50.wav"),
+			duty: DutyCycle::Percent50,
+		})
+	}
+
+	pub fn set_duty(&mut self, duty: DutyCycle) {
+		self.duty = duty;
+		if self.is_playing() {
+			self.stop();
+			self.play();
+		}
+	}
+}
+impl Channel for PulseChannel {
+	fn stop(&self) {
+		self.pulse_12.stop_stream();
+		self.pulse_25.stop_stream();
+		self.pulse_50.stop_stream();
+		self.pulse_75.stop_stream();
+	}
+
+	fn play(&self) {
+		use DutyCycle as D;
+		match self.duty {
+			D::Percent12 => self.pulse_12.play_stream(),
+			D::Percent25 => self.pulse_25.play_stream(),
+			D::Percent50 => self.pulse_50.play_stream(),
+			D::Percent25Neg => self.pulse_75.play_stream(),
+		}
+	}
+
+	fn update(&self) {
+		self.pulse_12.update_stream();
+		self.pulse_25.update_stream();
+		self.pulse_50.update_stream();
+		self.pulse_75.update_stream();
+	}
+
+	fn is_playing(&self) -> bool {
+		self.pulse_12.is_stream_playing()
+			|| self.pulse_25.is_stream_playing()
+			|| self.pulse_50.is_stream_playing()
+			|| self.pulse_75.is_stream_playing()
+	}
+
+	fn set_volume(&self, volume: f32) {
+		self.pulse_12.set_volume(volume);
+		self.pulse_25.set_volume(volume);
+		self.pulse_50.set_volume(volume);
+		self.pulse_75.set_volume(volume);
+	}
+
+	fn set_pitch(&self, pitch: f32) {
+		self.pulse_12.set_pitch(pitch);
+		self.pulse_25.set_pitch(pitch);
+		self.pulse_50.set_pitch(pitch);
+		self.pulse_75.set_pitch(pitch);
+	}
+}
+
+pub struct TriangleChannel {
+	inner: Music,
+}
+impl TriangleChannel {
+	pub fn load(handle: &'static RaylibAudio) -> crate::Result<Self> {
+		Ok(Self {
+			inner: load_audio!(handle, "assets/wav/triangle.wav"),
+		})
+	}
+}
+impl Channel for TriangleChannel {
+	fn stop(&self) {
+		self.inner.stop_stream();
+	}
+
+	fn play(&self) {
+		self.inner.play_stream();
+	}
+
+	fn update(&self) {
+		self.inner.update_stream();
+	}
+
+	fn is_playing(&self) -> bool {
+		self.inner.is_stream_playing()
+	}
+
+	fn set_volume(&self, volume: f32) {
+		self.inner.set_volume(volume);
+	}
+
+	fn set_pitch(&self, pitch: f32) {
+		self.inner.set_pitch(pitch);
+	}
+}
+
+pub struct NoiseChannel {
+	noise_0: Music,
+	noise_1: Music,
+	mode: bool,
+}
+impl NoiseChannel {
+	pub fn load(handle: &'static RaylibAudio) -> crate::Result<Self> {
+		Ok(Self {
+			noise_0: load_audio!(handle, "assets/wav/noise_0.wav"),
+			noise_1: load_audio!(handle, "assets/wav/noise_1.wav"),
+			mode: false,
+		})
+	}
+
+	pub fn set_mode(&mut self, mode: bool) {
+		self.mode = mode;
+		if self.is_playing() {
+			self.stop();
+			self.play();
+		}
+	}
+}
+impl Channel for NoiseChannel {
+	fn stop(&self) {
+		self.noise_0.stop_stream();
+		self.noise_1.stop_stream();
+	}
+
+	fn play(&self) {
+		if self.mode {
+			self.noise_1.play_stream();
+		} else {
+			self.noise_0.play_stream();
+		}
+	}
+
+	fn update(&self) {
+		self.noise_0.update_stream();
+		self.noise_0.update_stream();
+	}
+
+	fn is_playing(&self) -> bool {
+		self.noise_0.is_stream_playing() || self.noise_1.is_stream_playing()
+	}
+
+	fn set_volume(&self, volume: f32) {
+		self.noise_0.set_volume(volume);
+		self.noise_1.set_volume(volume);
+	}
+
+	fn set_pitch(&self, pitch: f32) {
+		self.noise_0.set_pitch(pitch);
+		self.noise_1.set_pitch(pitch);
+	}
+}
diff --git a/audio/src/data.rs b/audio/src/data.rs
new file mode 100644
index 0000000..2d1bdc5
--- /dev/null
+++ b/audio/src/data.rs
@@ -0,0 +1,30 @@
+use crate::program::Program;
+use std::fs;
+
+macro_rules! load_asm {
+	($path:tt) => {{
+		if cfg!(any(feature = "static", target_arch = "wasm32")) {
+			let src = include_str!(concat!("../../", $path));
+			Program::parse(src, true)?
+		} else {
+			let src = fs::read_to_string($path)?;
+			Program::parse(&src, true)?
+		}
+	}};
+    ($first:tt, $($arg:tt)*) => {
+		load_asm!($first)$(.merge(load_asm!($arg)))*
+	};
+}
+
+pub struct Data {
+	pub megalovania: Program,
+}
+impl Data {
+	pub fn load() -> crate::Result<Self> {
+		let megalovania = load_asm!(
+			"assets/asm/megalovania_melody.asm",
+			"assets/asm/megalovania_base.asm"
+		);
+		Ok(Self { megalovania })
+	}
+}
diff --git a/audio/src/lib.rs b/audio/src/lib.rs
new file mode 100644
index 0000000..b2d3e87
--- /dev/null
+++ b/audio/src/lib.rs
@@ -0,0 +1,97 @@
+//! The `audio` crate stores all audio assets that need to be loaded during runtime
+
+use raylib::audio::RaylibAudio;
+use std::time::{Duration, Instant};
+
+use channel::{Channel, NoiseChannel, PulseChannel, TriangleChannel};
+use data::Data;
+
+mod channel;
+mod data;
+mod parse;
+mod program;
+
+/// The `Error` type used within this crate
+pub type Error = Box<dyn std::error::Error>;
+
+/// The `Result` type used witin this crate
+pub type Result<T> = std::result::Result<T, crate::Error>;
+
+const AUDIO_FPS: u32 = 60;
+const TIME_SLICE: Duration = Duration::from_millis(1000 / AUDIO_FPS as u64);
+
+/// Holds each audio channel
+pub struct Channels {
+	pub pulse_a: PulseChannel,
+	pub pulse_b: PulseChannel,
+	pub triangle: TriangleChannel,
+	pub noise: NoiseChannel,
+}
+impl Channels {
+	pub(crate) fn load() -> crate::Result<Self> {
+		// Phantom handle to the raylib audio subsystem
+		// Raylib doesnt use a handle, but the rust bindings
+		// have one to ensure memory safety.
+		//
+		// We must leak this handle after allocating it,
+		// if we dont then all audio will be unloaded :(
+		//
+		// NOTE: would this cause issues if `Audio::load` was
+		// called multiple times?
+		let handle = Box::leak(Box::new(RaylibAudio::init_audio_device()?));
+
+		let pulse_a = PulseChannel::load(handle)?;
+		pulse_a.set_volume(0.0);
+		pulse_a.play();
+		let pulse_b = PulseChannel::load(handle)?;
+		pulse_b.set_volume(0.0);
+		pulse_b.play();
+		let triangle = TriangleChannel::load(handle)?;
+		triangle.set_volume(0.0);
+		triangle.play();
+		let noise = NoiseChannel::load(handle)?;
+		noise.set_volume(0.0);
+		noise.play();
+
+		Ok(Self {
+			pulse_a,
+			pulse_b,
+			triangle,
+			noise,
+		})
+	}
+}
+
+/// The `Audio` container initalizes the audio subsystem
+/// for raylib, leaks it (to gurentee audio is statically loaded),
+/// then loads all needed audio samples
+pub struct Audio {
+	channels: Channels,
+	last: Instant,
+	pub data: Data,
+}
+impl Audio {
+	pub fn load() -> crate::Result<Self> {
+		let channels = Channels::load()?;
+		let last = Instant::now();
+		let data = Data::load()?;
+
+		Ok(Self {
+			channels,
+			last,
+			data,
+		})
+	}
+
+	pub fn update(&mut self) {
+		if self.last.elapsed() >= TIME_SLICE {
+			self.data.megalovania.exec(&mut self.channels);
+			self.last = Instant::now();
+		}
+
+		self.channels.pulse_a.update();
+		self.channels.pulse_b.update();
+		self.channels.triangle.update();
+		self.channels.noise.update();
+	}
+}
diff --git a/audio/src/parse/lex.rs b/audio/src/parse/lex.rs
new file mode 100644
index 0000000..0ef8d47
--- /dev/null
+++ b/audio/src/parse/lex.rs
@@ -0,0 +1,218 @@
+use std::{
+	fmt::Display,
+	iter::Peekable,
+	str::{Chars, FromStr},
+};
+
+use super::Result;
+use crate::{channel::DutyCycle, program::ChanSpec};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Token {
+	Eof,
+	LineSeparator,
+	Pause(usize),
+	PauseLen(u32),
+	Jump(usize),
+	ChanSpec(ChanSpec),
+	SetVolume(u8),
+	SetPitch(u8),
+	SetNoiseMode(bool),
+	SetPulseDuty(DutyCycle),
+}
+impl Token {
+	pub const fn is_eol(self) -> bool {
+		matches!(self, Self::Eof | Self::LineSeparator)
+	}
+}
+
+pub struct Lexer<'s> {
+	src: &'s str,
+	chars: Peekable<Chars<'s>>,
+	pos: usize,
+}
+impl<'s> Lexer<'s> {
+	pub fn new(src: &'s str) -> Self {
+		let chars = src.chars().peekable();
+		Self { src, chars, pos: 0 }
+	}
+
+	fn filter_char(&mut self, ch: Option<char>, advance: bool) -> Result<char> {
+		match ch {
+			Some(c) if c.is_control() && !matches!(c, '\n' | '\r' | '\t') => {
+				Err(invalid_char(c))
+			}
+			Some(c) => {
+				if advance {
+					self.pos += c.len_utf8();
+				}
+				Ok(c)
+			}
+			None => Ok('\0'),
+		}
+	}
+
+	fn peek(&mut self) -> Result<char> {
+		let c = self.chars.peek().copied();
+		self.filter_char(c, false)
+	}
+
+	fn next(&mut self) -> Result<char> {
+		let c = self.chars.next();
+		self.filter_char(c, true)
+	}
+
+	fn next_int<T>(&mut self) -> Result<T>
+	where
+		T: FromStr,
+		<T as FromStr>::Err: Display,
+	{
+		let start = self.pos;
+		while self.peek()?.is_ascii_digit() {
+			self.next()?;
+		}
+		let str = &self.src[start..self.pos];
+		str.parse::<T>().map_err(|e| e.to_string())
+	}
+
+	fn next_note(&mut self) -> Result<u8> {
+		if self.peek()?.is_ascii_digit() {
+			return self.next_int();
+		}
+
+		let note = match self.next()? {
+			'a' => 80,
+			'b' => 82,
+			'c' => 83,
+			'd' => 85,
+			'e' => 87,
+			'f' => 88,
+			'g' => 90,
+			c => unexpected(c)?,
+		};
+
+		let octave = {
+			let c = self.next()?;
+			c.to_digit(10).ok_or_else(|| format!("invalid octave: {c}"))
+		}?;
+
+		let off = match self.peek()? {
+			'#' => {
+				self.next()?;
+				1
+			}
+			'b' => {
+				self.next()?;
+				-1
+			}
+			_ => 0,
+		};
+
+		let pitch_u32 = (note + octave * 12).wrapping_add_signed(off);
+		let pitch = u8::try_from(pitch_u32).map_err(|e| format!("{e}"))?;
+
+		Ok(pitch)
+	}
+
+	fn next_bool(&mut self) -> Result<bool> {
+		match self.next_int()? {
+			0 => Ok(false),
+			_ => Ok(true),
+		}
+	}
+
+	fn next_duty_cycle(&mut self) -> Result<DutyCycle> {
+		match self.next_int()? {
+			12 => Ok(DutyCycle::Percent12),
+			25 => Ok(DutyCycle::Percent25),
+			50 => Ok(DutyCycle::Percent50),
+			75 => Ok(DutyCycle::Percent25Neg),
+			n => Err(format!("invalid duty cycle: {n}")),
+		}
+	}
+
+	fn skip_comment(&mut self) -> Result<()> {
+		loop {
+			let next = self.next()?;
+			if next == '\n' || next == '\0' {
+				break;
+			}
+		}
+		Ok(())
+	}
+
+	fn next_pause(&mut self) -> Result<Token> {
+		let mut count = 1;
+		if self.peek()?.is_ascii_digit() {
+			count = self.next_int()?;
+		}
+		Ok(Token::Pause(count))
+	}
+
+	pub fn next_token(&mut self) -> Result<Token> {
+		use Token as T;
+		loop {
+			let peek = self.peek()?;
+			if peek == ';' {
+				self.skip_comment()?;
+			} else if matches!(peek, ' ' | '\t' | '\r') {
+				self.next()?;
+			} else {
+				break;
+			}
+		}
+		let token = match self.next()? {
+			// chan spec
+			'a' => Token::ChanSpec(ChanSpec::PulseA),
+			'b' => Token::ChanSpec(ChanSpec::PulseB),
+			't' => Token::ChanSpec(ChanSpec::Triangle),
+			'n' => Token::ChanSpec(ChanSpec::Noise),
+			// volume
+			'v' => T::SetVolume(self.next_int()?),
+			// pitch
+			'p' => T::SetPitch(self.next_note()?),
+			// duty cycle
+			'd' => T::SetPulseDuty(self.next_duty_cycle()?),
+			// noise mode
+			'm' => T::SetNoiseMode(self.next_bool()?),
+			// pause
+			'-' => self.next_pause()?,
+			// jump
+			'j' => T::Jump(self.next_int()?),
+			// pause len
+			'P' => T::PauseLen(self.next_int()?),
+			// eof
+			'\0' => T::Eof,
+			// new line
+			'\n' => T::LineSeparator,
+			// unexpected
+			c => unexpected(c)?,
+		};
+		Ok(token)
+	}
+}
+impl Iterator for Lexer<'_> {
+	type Item = Result<Token>;
+
+	fn next(&mut self) -> Option<Self::Item> {
+		Some(self.next_token())
+	}
+}
+
+fn invalid_char(ch: char) -> String {
+	match ch as u32 {
+		c @ 0x00..=0x7f => format!("invalid character (codepoint 0x{c:2x})"),
+		c => format!("invalid character (codepoint U+{c:04x})"),
+	}
+}
+
+fn unexpected<T>(c: char) -> Result<T> {
+	let msg = match c {
+		'\0' => "unexpected end of file".to_owned(),
+		'\n' => "unexpected newline character".to_owned(),
+		'\t' => "unexpected tab character".to_owned(),
+		'\r' => "unexpected return character".to_owned(),
+		c => format!("unexpected character {c}"),
+	};
+	Err(msg)
+}
diff --git a/audio/src/parse/macros.rs b/audio/src/parse/macros.rs
new file mode 100644
index 0000000..1dc33eb
--- /dev/null
+++ b/audio/src/parse/macros.rs
@@ -0,0 +1,103 @@
+use std::{borrow::Cow, collections::HashMap, str::Lines};
+
+struct PreProcessor<'s> {
+	src: &'s str,
+	pos: usize,
+	lines: Lines<'s>,
+	macros: HashMap<&'s str, &'s str>,
+}
+impl<'s> PreProcessor<'s> {
+	fn new(src: &'s str) -> Self {
+		let lines = src.lines();
+		let macros = HashMap::new();
+		Self {
+			src,
+			pos: 0,
+			lines,
+			macros,
+		}
+	}
+
+	fn next(&mut self) -> Option<&'s str> {
+		self.lines.next().map(|line| {
+			self.pos += line.len() + 1;
+			line.trim()
+		})
+	}
+
+	fn read_macro(&mut self, full_name: &'s str) {
+		let name = &full_name[8..];
+		let start = self.pos;
+		let mut end = start;
+		while let Some(line) = self.next()
+			&& !matches!(line, "%end")
+		{
+			end = self.pos;
+		}
+		let str = &self.src[start..end];
+		self.macros.insert(name, str);
+	}
+
+	fn read_macros(&mut self) -> String {
+		let mut buf = String::new();
+		while let Some(line) = self.next() {
+			if line.starts_with("%define ") {
+				self.read_macro(line);
+			} else {
+				buf.push_str(line);
+				buf.push('\n');
+			}
+		}
+		buf
+	}
+
+	fn process(&mut self) -> String {
+		let rest = self.read_macros();
+		let mut lines = rest.lines().map(Cow::Borrowed).collect::<Vec<_>>();
+		loop {
+			let mut count = 0;
+			for (name, body) in &self.macros {
+				count += fill_macro(&mut lines, name, body);
+			}
+			if count == 0 {
+				break;
+			}
+		}
+		lines.join("\n")
+	}
+}
+
+fn fill_macro(contents: &mut Vec<Cow<'_, str>>, name: &str, body: &str) -> usize {
+	let mut count = 0;
+	let mut idx = 0;
+	loop {
+		if idx >= contents.len() {
+			break;
+		}
+		let line = &contents[idx];
+		if line.starts_with(name) {
+			fill_macro_once(contents, idx, body);
+			count += 1;
+		}
+		idx += 1;
+	}
+	count
+}
+
+fn fill_macro_once(contents: &mut Vec<Cow<'_, str>>, idx: usize, body: &str) {
+	let invoke_line = contents.remove(idx);
+	let args = invoke_line.split_whitespace().skip(1).collect::<Vec<_>>();
+
+	for line in body.lines().rev() {
+		let mut buf = String::from(line);
+		for (idx, arg) in args.iter().enumerate() {
+			let key = format!("${}", idx + 1);
+			buf = buf.replace(&key, arg);
+		}
+		contents.insert(idx, Cow::Owned(buf));
+	}
+}
+
+pub fn process(src: &str) -> String {
+	PreProcessor::new(src).process()
+}
diff --git a/audio/src/parse/mod.rs b/audio/src/parse/mod.rs
new file mode 100644
index 0000000..726aaa2
--- /dev/null
+++ b/audio/src/parse/mod.rs
@@ -0,0 +1,13 @@
+use crate::program::Instruction;
+use parser::Parser;
+
+pub type Result<T> = std::result::Result<T, String>;
+
+mod lex;
+mod macros;
+mod parser;
+
+pub fn parse(raw_src: &str) -> Result<Vec<Instruction>> {
+	let src = macros::process(raw_src);
+	Parser::new(&src).parse()
+}
diff --git a/audio/src/parse/parser.rs b/audio/src/parse/parser.rs
new file mode 100644
index 0000000..b46e707
--- /dev/null
+++ b/audio/src/parse/parser.rs
@@ -0,0 +1,104 @@
+use std::iter::Peekable;
+
+use crate::program::{ChanSpec, Instruction};
+
+use super::{
+	Result,
+	lex::{Lexer, Token},
+};
+
+pub struct Parser<'s> {
+	lexer: Peekable<Lexer<'s>>,
+}
+impl<'s> Parser<'s> {
+	pub fn new(src: &'s str) -> Self {
+		Self {
+			lexer: Lexer::new(src).peekable(),
+		}
+	}
+
+	fn next(&mut self) -> Result<Token> {
+		self.lexer
+			.next()
+			.unwrap_or_else(|| Err("should not happen".to_owned()))
+	}
+
+	fn peek(&mut self) -> Result<Token> {
+		self.lexer
+			.peek()
+			.map_or_else(|| Err("should not happen".to_owned()), Result::clone)
+	}
+
+	fn parse_chan_spec(&mut self) -> Result<ChanSpec> {
+		match self.next()? {
+			Token::ChanSpec(spec) => Ok(spec),
+			t => Err(format!("expected channel specifier, got {t:?}")),
+		}
+	}
+
+	fn parse_ins(&mut self, spec: ChanSpec) -> Result<Instruction> {
+		use Token as T;
+		let t = self.next()?;
+		let ins = match t {
+			T::SetPitch(pitch) => Instruction::SetPitch(spec, pitch),
+			T::SetVolume(volume) => Instruction::SetVolume(spec, volume),
+			T::SetNoiseMode(mode) if spec == ChanSpec::Noise => {
+				Instruction::SetNoiseMode(mode)
+			}
+			T::SetPulseDuty(duty_cycle) if spec == ChanSpec::PulseA => {
+				Instruction::SetPulseDutyA(duty_cycle)
+			}
+			T::SetPulseDuty(duty_cycle) if spec == ChanSpec::PulseB => {
+				Instruction::SetPulseDutyB(duty_cycle)
+			}
+			_ => unexpected(t)?,
+		};
+		Ok(ins)
+	}
+
+	fn parse_line(&mut self, prog: &mut Vec<Instruction>) -> Result<()> {
+		let spec = self.parse_chan_spec()?;
+		loop {
+			prog.push(self.parse_ins(spec)?);
+			let peek = self.peek()?;
+			if peek.is_eol() || matches!(peek, Token::Pause(_)) {
+				break;
+			}
+		}
+		Ok(())
+	}
+
+	pub fn parse(&mut self) -> Result<Vec<Instruction>> {
+		let mut prog = vec![];
+		loop {
+			let t = self.peek()?;
+			match t {
+				Token::Eof => break,
+				Token::LineSeparator => {
+					self.next()?;
+				}
+				Token::Pause(count) => {
+					self.next()?;
+					for _ in 0..count {
+						prog.push(Instruction::Pause);
+					}
+				}
+				Token::Jump(pc) => {
+					self.next()?;
+					prog.push(Instruction::Jump(pc));
+				}
+				Token::PauseLen(pause_len) => {
+					self.next()?;
+					prog.push(Instruction::PauseLen(pause_len));
+				}
+				_ => self.parse_line(&mut prog)?,
+			}
+		}
+		Ok(prog)
+	}
+}
+
+fn unexpected<T>(t: Token) -> Result<T> {
+	let msg = format!("unexpected token: {t:?}");
+	Err(msg)
+}
diff --git a/audio/src/program.rs b/audio/src/program.rs
new file mode 100644
index 0000000..28a5f41
--- /dev/null
+++ b/audio/src/program.rs
@@ -0,0 +1,184 @@
+use crate::{
+	Channels,
+	channel::{Channel, DutyCycle},
+	parse,
+};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ChanSpec {
+	PulseA,
+	PulseB,
+	Triangle,
+	Noise,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Instruction {
+	Pause,
+	PauseLen(u32),
+	Jump(usize),
+	SetVolume(ChanSpec, u8),
+	SetPitch(ChanSpec, u8),
+	SetPulseDutyA(DutyCycle),
+	SetPulseDutyB(DutyCycle),
+	SetNoiseMode(bool),
+}
+
+fn map_pitch(pitch: u8) -> f32 {
+	const HALF_STEP: f32 = 1.059_463_1;
+	HALF_STEP.powf(pitch as f32 - 128.0)
+}
+
+const fn map_volume(volume: u8) -> f32 {
+	if volume > 100 {
+		1.0
+	} else {
+		(volume as f32) / 100.0
+	}
+}
+
+#[derive(Debug, Clone)]
+pub struct Program {
+	ins: Vec<Instruction>,
+	pc: usize,
+	looping: bool,
+	pause_cnt: u32,
+	pause_len: u32,
+}
+impl Program {
+	pub const fn new(ins: Vec<Instruction>, looping: bool) -> Self {
+		let pc = ins.len();
+		Self {
+			ins,
+			pc,
+			looping,
+			pause_cnt: 0,
+			pause_len: 4,
+		}
+	}
+
+	pub fn parse(src: &str, looping: bool) -> parse::Result<Self> {
+		let ins = parse::parse(src)?;
+		Ok(Self::new(ins, looping))
+	}
+
+	pub fn merge(self, other: Self) -> Self {
+		let mut res = vec![];
+
+		let mut l = 0;
+		let mut r = 0;
+		let l_ins = self.ins;
+		let r_ins = other.ins;
+
+		loop {
+			if l >= l_ins.len() && r >= r_ins.len() {
+				// were done here
+				break;
+			}
+
+			let mut has_pause = false;
+			while l < l_ins.len() {
+				let ins = l_ins[l];
+				l += 1;
+				if matches!(ins, Instruction::Pause) {
+					has_pause = true;
+					break;
+				}
+				res.push(ins);
+			}
+			while r < r_ins.len() {
+				let ins = r_ins[r];
+				r += 1;
+				if matches!(ins, Instruction::Pause) {
+					has_pause = true;
+					break;
+				}
+				res.push(ins);
+			}
+			if has_pause {
+				res.push(Instruction::Pause);
+			}
+		}
+
+		Self::new(res, self.looping)
+	}
+
+	fn exec_ins(&mut self, channels: &mut Channels, ins: Instruction) {
+		use Instruction as I;
+		match ins {
+			I::Pause => {
+				self.pause_cnt = self.pause_len;
+			}
+			I::PauseLen(pause_len) => {
+				self.pause_len = pause_len;
+			}
+			I::Jump(pc) => {
+				self.pc = pc;
+			}
+			I::SetVolume(chan_spec, volume) => {
+				// set the volume (amplitude) on a given channel
+				use ChanSpec as C;
+				let v = map_volume(volume);
+				match chan_spec {
+					C::PulseA => channels.pulse_a.set_volume(v),
+					C::PulseB => channels.pulse_b.set_volume(v),
+					C::Triangle => channels.triangle.set_volume(v),
+					C::Noise => channels.noise.set_volume(v),
+				}
+			}
+			I::SetPitch(chan_spec, pitch) => {
+				// set the pitch (freq) on a given channel
+				use ChanSpec as C;
+				let p = map_pitch(pitch);
+				match chan_spec {
+					C::PulseA => channels.pulse_a.set_pitch(p),
+					C::PulseB => channels.pulse_b.set_pitch(p),
+					C::Triangle => channels.triangle.set_pitch(p),
+					C::Noise => channels.noise.set_pitch(p),
+				}
+			}
+			I::SetPulseDutyA(duty_cycle) => {
+				channels.pulse_a.set_duty(duty_cycle);
+			}
+			I::SetPulseDutyB(duty_cycle) => {
+				channels.pulse_b.set_duty(duty_cycle);
+			}
+			I::SetNoiseMode(mode) => {
+				channels.noise.set_mode(mode);
+			}
+		}
+	}
+
+	pub fn exec(&mut self, channels: &mut Channels) {
+		if self.pause_cnt > 0 {
+			self.pause_cnt -= 1;
+		}
+		loop {
+			if self.pause_cnt > 0 {
+				break;
+			}
+			if self.finished() {
+				if self.looping {
+					self.pc = 0;
+				} else {
+					break;
+				}
+			}
+			let ins = self.ins[self.pc];
+			self.exec_ins(channels, ins);
+			self.pc += 1;
+		}
+	}
+
+	pub const fn finished(&self) -> bool {
+		self.pc >= self.ins.len()
+	}
+
+	pub const fn play(&mut self) {
+		self.pc = 0;
+	}
+
+	pub const fn set_looping(&mut self, looping: bool) {
+		self.looping = looping;
+	}
+}