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use crate::error::Error;
#[derive(Debug, Clone, PartialEq)]
pub enum Token {
Number(f64),
Identifier(String),
String(String),
True,
False,
Null,
Plus,
Minus,
Star,
Slash,
Percent,
Caret,
Bang,
Dot,
SafeNavigation, // &.
Ellipsis,
LParen,
RParen,
Comma,
Colon,
DoubleColon,
LBracket,
RBracket,
LBrace,
RBrace,
Greater,
Less,
Ge,
Le,
EqEq,
NotEq,
And,
Or,
AndAnd,
OrOr,
QMark,
Semicolon,
ColonEquals,
Eof,
}
#[derive(Clone)]
pub struct Lexer<'a> {
input: &'a [u8],
pos: usize,
last_start: usize,
last_end: usize,
}
impl<'a> Lexer<'a> {
pub fn new(input: &'a str) -> Self {
Self {
input: input.as_bytes(),
pos: 0,
last_start: 0,
last_end: 0,
}
}
fn peek(&self) -> Option<u8> {
self.input.get(self.pos).copied()
}
fn bump(&mut self) -> Option<u8> {
let b = self.peek()?;
self.pos += 1;
Some(b)
}
fn skip_ws(&mut self) {
while matches!(self.peek(), Some(b' ' | b'\t' | b'\n' | b'\r')) {
self.pos += 1;
}
}
fn number(&mut self, first: u8) -> Result<Token, Error> {
let start = self.pos - 1;
let mut end = self.pos;
let mut has_dot = first == b'.';
while let Some(c) = self.peek() {
match c {
b'0'..=b'9' => {
end += 1;
self.pos += 1;
}
b'.' if !has_dot => {
// Only consume the dot if it's followed by a digit (for decimals like 1.23)
// Don't consume it if it's followed by a letter (for method calls like 1.abs)
if let Some(&next) = self.input.get(self.pos + 1) {
if matches!(next, b'0'..=b'9') {
has_dot = true;
end += 1;
self.pos += 1;
} else {
// Don't consume the dot - it's likely a method call
break;
}
} else {
// End of input, consume the dot as it could be a valid decimal like "1."
has_dot = true;
end += 1;
self.pos += 1;
}
}
_ => break,
}
}
// Avoid UTF-8 conversion - parse directly from bytes for common numbers
let n = if end - start <= 10 && !has_dot {
// Fast path for small integers
let mut result = 0.0;
for i in start..end {
result = result * 10.0 + (self.input[i] - b'0') as f64;
}
result
} else {
// Fallback to string parsing for complex numbers
let s = std::str::from_utf8(&self.input[start..end])
.map_err(|_| Error::new("Invalid UTF-8 in number", Some(start)))?;
s.parse()
.map_err(|_| Error::new("Invalid number", Some(start)))?
};
self.last_start = start;
self.last_end = end;
Ok(Token::Number(n))
}
fn identifier(&mut self, _first: u8) -> Result<Token, Error> {
let start = self.pos - 1;
let mut end = self.pos;
while let Some(c) = self.peek() {
match c {
b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' | b'_' => {
end += 1;
self.pos += 1;
}
_ => break,
}
}
self.last_start = start;
self.last_end = end;
// Fast path for common keywords - avoid string allocation
let len = end - start;
let bytes = &self.input[start..end];
// Check common keywords by length first, then bytes
let token = match len {
4 => {
if bytes.eq_ignore_ascii_case(b"TRUE") {
Token::True
} else if bytes.eq_ignore_ascii_case(b"NULL") {
Token::Null
} else {
// Convert to string only if not a keyword
let s = std::str::from_utf8(bytes)
.map_err(|_| Error::new("Invalid UTF-8 in identifier", Some(start)))?
.to_string();
Token::Identifier(s)
}
}
5 => {
if bytes.eq_ignore_ascii_case(b"FALSE") {
Token::False
} else {
let s = std::str::from_utf8(bytes)
.map_err(|_| Error::new("Invalid UTF-8 in identifier", Some(start)))?
.to_string();
Token::Identifier(s)
}
}
_ => {
// For other identifiers, convert to string
let s = std::str::from_utf8(bytes)
.map_err(|_| Error::new("Invalid UTF-8 in identifier", Some(start)))?
.to_string();
Token::Identifier(s)
}
};
Ok(token)
}
fn string(&mut self, quote: u8) -> Result<Token, Error> {
let start0 = self.pos - 1;
// consume until matching quote, support escapes \" \\ \n \t; preserve UTF-8 bytes
let mut buf: Vec<u8> = Vec::new();
while let Some(c) = self.bump() {
if c == quote {
self.last_start = start0;
self.last_end = self.pos;
return Ok(Token::String(String::from_utf8(buf).map_err(|_| {
Error::new("Invalid UTF-8 in string", Some(self.pos))
})?));
}
if c == b'\\' {
match self.bump() {
Some(b'\\') => buf.push(b'\\'),
Some(b'"') => buf.push(b'"'),
Some(b'\'') => buf.push(b'\''),
Some(b'n') => buf.push(b'\n'),
Some(b't') => buf.push(b'\t'),
Some(x) => buf.push(x),
None => {
return Err(Error::new("Unterminated escape in string", Some(self.pos)))
}
}
} else {
buf.push(c);
}
}
Err(Error::new("Unterminated string literal", Some(self.pos)))
}
pub fn next_token(&mut self) -> Result<Token, Error> {
self.skip_ws();
let ch = match self.bump() {
Some(c) => c,
None => return Ok(Token::Eof),
};
let tok = match ch {
b'0'..=b'9' => return self.number(ch),
b'a'..=b'z' | b'A'..=b'Z' | b'_' => return self.identifier(ch),
b'.' => {
// Ellipsis '...'
if matches!(self.peek(), Some(b'.')) {
let save = self.pos;
self.bump();
if matches!(self.peek(), Some(b'.')) {
self.bump();
self.last_start = self.pos - 3;
self.last_end = self.pos;
Token::Ellipsis
} else {
// Was just two dots, backtrack second
self.pos = save;
self.last_start = self.pos - 1;
self.last_end = self.pos;
Token::Dot
}
} else if matches!(self.peek(), Some(b'0'..=b'9')) {
return self.number(ch);
} else {
self.last_start = self.pos - 1;
self.last_end = self.pos;
Token::Dot
}
}
b'+' => Token::Plus,
b'-' => Token::Minus,
b'*' => Token::Star,
b'/' => Token::Slash,
b'%' => Token::Percent,
b'^' => Token::Caret,
b'"' => return self.string(ch),
b'\'' => return self.string(ch),
b'!' => {
if matches!(self.peek(), Some(b'=')) {
self.bump();
Token::NotEq
} else {
Token::Bang
}
}
b'?' => Token::QMark,
b'(' => Token::LParen,
b')' => Token::RParen,
b'[' => Token::LBracket,
b']' => Token::RBracket,
b'{' => Token::LBrace,
b'}' => Token::RBrace,
b',' => Token::Comma,
b':' => {
if matches!(self.peek(), Some(b':')) {
self.bump();
Token::DoubleColon
} else if matches!(self.peek(), Some(b'=')) {
self.bump();
Token::ColonEquals
} else {
Token::Colon
}
}
b'>' => {
if matches!(self.peek(), Some(b'=')) {
self.bump();
Token::Ge
} else {
Token::Greater
}
}
b'<' => {
if matches!(self.peek(), Some(b'=')) {
self.bump();
Token::Le
} else {
Token::Less
}
}
b'=' => {
// Both '=' and '==' are valid for equality (leading '=' is stripped earlier)
if matches!(self.peek(), Some(b'=')) {
self.bump();
Token::EqEq
} else {
Token::EqEq
}
}
b'&' => {
if matches!(self.peek(), Some(b'&')) {
self.bump();
Token::AndAnd
} else if matches!(self.peek(), Some(b'.')) {
self.bump();
Token::SafeNavigation
} else {
return Err(Error::new("Unexpected '&'", Some(self.pos - 1)));
}
}
b'|' => {
if matches!(self.peek(), Some(b'|')) {
self.bump();
Token::OrOr
} else {
return Err(Error::new("Unexpected '|'", Some(self.pos - 1)));
}
}
b';' => Token::Semicolon,
_ => return Err(Error::new("Unexpected character", Some(self.pos - 1))),
};
// For single-char tokens not handled above, mark last positions
if matches!(
tok,
Token::Plus
| Token::Minus
| Token::Star
| Token::Slash
| Token::Percent
| Token::Caret
| Token::Bang
| Token::QMark
| Token::LParen
| Token::RParen
| Token::LBracket
| Token::RBracket
| Token::LBrace
| Token::RBrace
| Token::Comma
| Token::Colon
| Token::Greater
| Token::Less
| Token::Semicolon
) {
self.last_start = self.pos - 1;
self.last_end = self.pos;
} else if matches!(
tok,
Token::ColonEquals
| Token::DoubleColon
| Token::Ge
| Token::Le
| Token::EqEq
| Token::NotEq
| Token::AndAnd
| Token::OrOr
| Token::SafeNavigation
) {
self.last_start = self.pos - 2;
self.last_end = self.pos;
}
Ok(tok)
}
pub fn last_start(&self) -> usize {
self.last_start
}
pub fn last_end(&self) -> usize {
self.last_end
}
}