1 files changed, 156 insertions, 0 deletions
diff --git a/users/tazjin/rlox/src/bytecode/compiler/mod.rs b/users/tazjin/rlox/src/bytecode/compiler/mod.rs
new file mode 100644
index 000000000000..813cf2e26df0
--- /dev/null
+++ b/users/tazjin/rlox/src/bytecode/compiler/mod.rs
@@ -0,0 +1,156 @@
+use super::chunk::Chunk;
+use super::errors::{Error, ErrorKind, LoxResult};
+use super::opcode::OpCode;
+use super::value::Value;
+use crate::scanner::{self, Token, TokenKind};
+
+#[cfg(test)]
+mod tests;
+
+struct Compiler<T: Iterator<Item = Token>> {
+    tokens: T,
+    chunk: Chunk,
+    panic: bool,
+    errors: Vec<Error>,
+
+    // TODO(tazjin): Restructure so that these don't need to be Option?
+    current: Option<Token>,
+    previous: Option<Token>,
+}
+
+#[derive(Debug, PartialEq, PartialOrd)]
+enum Precedence {
+    None,
+    Assignment, // =
+    Or,         // or
+    And,        // and
+    Equality,   // == !=
+    Comparison, // < > <= >=
+    Term,       // + -
+    Factor,     // * /
+    Unary,      // ! -
+    Call,       // . ()
+    Primary,
+}
+
+impl<T: Iterator<Item = Token>> Compiler<T> {
+    fn compile(&mut self) -> LoxResult<()> {
+        self.advance();
+        self.expression()?;
+        self.consume(
+            &TokenKind::Eof,
+            ErrorKind::ExpectedToken("Expected end of expression"),
+        )?;
+
+        self.end_compiler()
+    }
+
+    fn advance(&mut self) {
+        self.previous = self.current.take();
+        self.current = self.tokens.next();
+    }
+
+    fn expression(&mut self) -> LoxResult<()> {
+        self.parse_precedence(Precedence::Assignment)
+    }
+
+    // TODO(tazjin): Assumption is that we have access to the previous
+    // token wherever this ends up invoked. True?
+    fn number(&mut self, num: f64) {
+        self.emit_constant(num);
+    }
+
+    fn grouping(&mut self, num: f64) -> LoxResult<()> {
+        self.expression()?;
+        self.consume(
+            &TokenKind::RightParen,
+            ErrorKind::ExpectedToken("Expected ')' after expression"),
+        )
+    }
+
+    fn unary(&mut self, kind: &TokenKind) -> LoxResult<()> {
+        // Compile the operand
+        self.parse_precedence(Precedence::Unary)?;
+
+        // Emit operator instruction
+        match kind {
+            TokenKind::Minus => self.emit_op(OpCode::OpNegate),
+            _ => unreachable!("only called for unary operator tokens"),
+        }
+
+        Ok(())
+    }
+
+    fn parse_precedence(&mut self, precedence: Precedence) -> LoxResult<()> {
+        unimplemented!("what goes here?")
+    }
+
+    fn consume(
+        &mut self,
+        expected: &TokenKind,
+        err: ErrorKind,
+    ) -> LoxResult<()> {
+        unimplemented!()
+    }
+
+    fn current_chunk(&mut self) -> &mut Chunk {
+        &mut self.chunk
+    }
+
+    fn end_compiler(&mut self) -> LoxResult<()> {
+        self.emit_op(OpCode::OpReturn);
+        Ok(())
+    }
+
+    fn emit_op(&mut self, op: OpCode) {
+        let line = self.previous().line;
+        self.current_chunk().add_op(op, line);
+    }
+
+    fn emit_constant(&mut self, val: Value) {
+        let idx = self.chunk.add_constant(val);
+        self.emit_op(OpCode::OpConstant(idx));
+    }
+
+    fn previous(&self) -> &Token {
+        self.previous
+            .as_ref()
+            .expect("invalid internal compiler state: missing previous token")
+    }
+
+    fn error_at(&mut self, token: &Token, kind: ErrorKind) {
+        if self.panic {
+            return;
+        }
+
+        self.panic = true;
+        self.errors.push(Error {
+            kind,
+            line: token.line,
+        })
+    }
+}
+
+pub fn compile(code: &str) -> Result<Chunk, Vec<Error>> {
+    let chars = code.chars().collect::<Vec<char>>();
+    let tokens = scanner::scan(&chars).map_err(|errors| {
+        errors.into_iter().map(Into::into).collect::<Vec<Error>>()
+    })?;
+
+    let mut compiler = Compiler {
+        tokens: tokens.into_iter().peekable(),
+        chunk: Default::default(),
+        panic: false,
+        errors: vec![],
+        current: None,
+        previous: None,
+    };
+
+    compiler.compile()?;
+
+    if compiler.errors.is_empty() {
+        Ok(unimplemented!())
+    } else {
+        Err(compiler.errors)
+    }
+}