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//! Tokenizer for the DSL.
use super::ParseError;
#[derive(Debug, Clone, PartialEq)]
pub enum TokenKind {
Num(f64),
Ident(String),
Str(String),
Op(String),
LParen,
RParen,
LBracket,
RBracket,
Comma,
Eq,
Let,
Eof,
}
#[derive(Debug, Clone, PartialEq)]
pub struct Token {
pub kind: TokenKind,
pub line: usize,
pub col: usize,
}
pub fn lex(src: &str) -> Result<Vec<Token>, ParseError> {
let chars: Vec<char> = src.chars().collect();
let mut i = 0;
let mut line = 1;
let mut col = 1;
let mut out = Vec::new();
let bump = |i: &mut usize, col: &mut usize| {
*i += 1;
*col += 1;
};
while i < chars.len() {
let c = chars[i];
match c {
' ' | '\t' | '\r' => bump(&mut i, &mut col),
'\n' => {
i += 1;
line += 1;
col = 1;
}
'#' => {
while i < chars.len() && chars[i] != '\n' {
i += 1;
}
}
'(' => {
out.push(Token {
kind: TokenKind::LParen,
line,
col,
});
bump(&mut i, &mut col);
}
')' => {
out.push(Token {
kind: TokenKind::RParen,
line,
col,
});
bump(&mut i, &mut col);
}
'[' => {
out.push(Token {
kind: TokenKind::LBracket,
line,
col,
});
bump(&mut i, &mut col);
}
']' => {
out.push(Token {
kind: TokenKind::RBracket,
line,
col,
});
bump(&mut i, &mut col);
}
',' => {
out.push(Token {
kind: TokenKind::Comma,
line,
col,
});
bump(&mut i, &mut col);
}
'=' => {
out.push(Token {
kind: TokenKind::Eq,
line,
col,
});
bump(&mut i, &mut col);
}
'>' | '<' => {
let (start_line, start_col) = (line, col);
let mut s = c.to_string();
bump(&mut i, &mut col);
if i < chars.len() && chars[i] == '=' {
s.push('=');
bump(&mut i, &mut col);
}
out.push(Token {
kind: TokenKind::Op(s),
line: start_line,
col: start_col,
});
}
'+' | '-' | '*' | '/' => {
out.push(Token {
kind: TokenKind::Op(c.to_string()),
line,
col,
});
bump(&mut i, &mut col);
}
'"' => {
let (start_line, start_col) = (line, col);
bump(&mut i, &mut col);
let mut s = String::new();
while i < chars.len() && chars[i] != '"' {
s.push(chars[i]);
bump(&mut i, &mut col);
}
if i >= chars.len() {
return Err(ParseError {
line: start_line,
col: start_col,
message: "unterminated string".into(),
});
}
bump(&mut i, &mut col); // closing quote
out.push(Token {
kind: TokenKind::Str(s),
line: start_line,
col: start_col,
});
}
c if c.is_ascii_digit() => {
let (start_line, start_col) = (line, col);
let mut s = String::new();
while i < chars.len() {
let d = chars[i];
if d.is_ascii_digit() || d == '_' || d == '.' {
if d != '_' {
s.push(d);
}
bump(&mut i, &mut col);
} else if (d == 'e' || d == 'E')
&& i + 1 < chars.len()
&& (chars[i + 1].is_ascii_digit()
|| ((chars[i + 1] == '+' || chars[i + 1] == '-')
&& i + 2 < chars.len()
&& chars[i + 2].is_ascii_digit()))
{
s.push('e');
bump(&mut i, &mut col);
if chars[i] == '+' || chars[i] == '-' {
s.push(chars[i]);
bump(&mut i, &mut col);
}
} else {
break;
}
}
let value = s.parse::<f64>().map_err(|_| ParseError {
line: start_line,
col: start_col,
message: format!("invalid number `{s}`"),
})?;
out.push(Token {
kind: TokenKind::Num(value),
line: start_line,
col: start_col,
});
}
c if c.is_ascii_alphabetic() || c == '_' => {
let (start_line, start_col) = (line, col);
let mut s = String::new();
while i < chars.len() && (chars[i].is_ascii_alphanumeric() || chars[i] == '_') {
s.push(chars[i]);
bump(&mut i, &mut col);
}
let kind = if s == "let" {
TokenKind::Let
} else {
TokenKind::Ident(s)
};
out.push(Token {
kind,
line: start_line,
col: start_col,
});
}
other => {
return Err(ParseError {
line,
col,
message: format!("unexpected character `{other}`"),
});
}
}
}
out.push(Token {
kind: TokenKind::Eof,
line,
col,
});
Ok(out)
}
#[cfg(test)]
mod tests {
use super::*;
fn kinds(src: &str) -> Vec<TokenKind> {
lex(src).unwrap().into_iter().map(|t| t.kind).collect()
}
#[test]
fn lexes_comparison_and_call() {
use TokenKind::*;
assert_eq!(
kinds("close > sma(close, 2)"),
vec![
Ident("close".into()),
Op(">".into()),
Ident("sma".into()),
LParen,
Ident("close".into()),
Comma,
Num(2.0),
RParen,
Eof,
]
);
}
#[test]
fn handles_let_comment_underscore_and_scientific() {
use TokenKind::*;
let toks = kinds("let x = 1_000_000 # note\nx >= 5e8");
assert_eq!(
toks,
vec![
Let,
Ident("x".into()),
Eq,
Num(1_000_000.0),
Ident("x".into()),
Op(">=".into()),
Num(500_000_000.0),
Eof,
]
);
}
#[test]
fn tracks_position_and_rejects_bad_char() {
let err = lex("a $ b").unwrap_err();
assert_eq!((err.line, err.col), (1, 3));
}
}