1 files changed, 100 insertions, 0 deletions
diff --git a/graphics/src/audio/parse/parser.rs b/graphics/src/audio/parse/parser.rs
new file mode 100644
index 0000000..fbe5f4c
--- /dev/null
+++ b/graphics/src/audio/parse/parser.rs
@@ -0,0 +1,100 @@
+use std::iter::Peekable;
+
+use crate::audio::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));
+				}
+				_ => self.parse_line(&mut prog)?,
+			}
+		}
+		Ok(prog)
+	}
+}
+
+fn unexpected<T>(t: Token) -> Result<T> {
+	let msg = format!("unexpected token: {t:?}");
+	Err(msg)
+}