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use super::{Error, Result};
pub mod token;
pub use token::Token;
fn is_class_byte(c: u8) -> bool {
matches!(
c,
b'a' | b'c'
| b'd'
| b'g'
| b'l'
| b'p'
| b's'
| b'u'
| b'w'
| b'x'
| b'A'
| b'C'
| b'D'
| b'G'
| b'L'
| b'P'
| b'S'
| b'U'
| b'W'
| b'X'
)
}
fn is_escapable_magic_byte(c: u8) -> bool {
matches!(
c,
b'(' | b')' | b'.' | b'%' | b'[' | b']' | b'*' | b'+' | b'-' | b'?' | b'^' | b'$'
)
}
pub struct Lexer<'a> {
input: &'a [u8],
pos: usize,
capture_depth: usize,
set_depth: usize,
}
impl<'a> Lexer<'a> {
pub fn new(input: &'a str) -> Self {
Lexer {
input: input.as_bytes(),
pos: 0,
capture_depth: 0,
set_depth: 0,
}
}
fn peek(&self) -> Option<u8> {
self.input.get(self.pos).copied()
}
fn advance(&mut self) -> Option<u8> {
let byte = self.peek();
if byte.is_some() {
self.pos += 1
}
byte
}
pub fn next_token(&mut self) -> Result<Option<Token>> {
let Some(byte) = self.advance() else {
return Ok(None);
};
match byte {
b'(' => {
self.capture_depth += 1;
Ok(Some(Token::LParen))
}
b')' => {
if self.capture_depth > 0 {
self.capture_depth -= 1;
Ok(Some(Token::RParen))
} else {
Ok(Some(Token::Literal(b')')))
}
}
b'.' => Ok(Some(Token::Any)),
b'[' => {
self.set_depth += 1;
Ok(Some(Token::LBracket))
}
b']' => {
if self.set_depth > 0 {
self.set_depth -= 1;
Ok(Some(Token::RBracket))
} else {
Ok(Some(Token::Literal(byte)))
}
}
b'^' => Ok(Some(Token::Caret)),
b'$' => Ok(Some(Token::Dollar)),
b'*' => {
if self.set_depth > 0 {
Ok(Some(Token::Literal(b'*')))
} else {
Ok(Some(Token::Star))
}
}
b'+' => {
if self.set_depth > 0 {
Ok(Some(Token::Literal(b'+')))
} else {
Ok(Some(Token::Plus))
}
}
b'?' => {
if self.set_depth > 0 {
Ok(Some(Token::Literal(b'?')))
} else {
Ok(Some(Token::Question))
}
}
b'-' => {
if self.set_depth > 0 {
Ok(Some(Token::Literal(b'-')))
} else {
Ok(Some(Token::Minus))
}
}
b'%' => {
if self.set_depth > 0 {
if let Some(next_byte) = self.peek() {
match next_byte {
byte if is_class_byte(next_byte) => Ok(Some(Token::Class(byte))),
byte if is_escapable_magic_byte(next_byte) => {
self.advance();
Ok(Some(Token::EscapedLiteral(byte)))
}
b'%' => {
self.advance();
Ok(Some(Token::EscapedLiteral(b'%')))
}
_ => Err(Error::Lexer(format!(
"malformed pattern (invalid escape sequence in set: %{})",
next_byte
))),
}
} else {
Err(Error::Lexer(
"malformed pattern (ends with '%' inside set)".to_string(),
))
}
} else {
let Some(next_byte) = self.advance() else {
return Err(Error::Lexer(
"malformed pattern (ends with '%')".to_string(),
));
};
match next_byte {
c if is_escapable_magic_byte(c) => Ok(Some(Token::EscapedLiteral(c))),
c if is_class_byte(c) => Ok(Some(Token::Class(c))),
b'%' => {
self.advance();
Ok(Some(Token::EscapedLiteral(b'%')))
}
b'b' => {
let Some(d1) = self.advance() else {
return Err(Error::Lexer(
"malformed pattern (%b needs two characters)".to_string(),
));
};
let Some(d2) = self.advance() else {
return Err(Error::Lexer(
"malformed pattern (%b needs two characters)".to_string(),
));
};
Ok(Some(Token::Balanced(d1, d2)))
}
b'f' => Ok(Some(Token::Frontier)),
d @ b'1'..=b'9' => Ok(Some(Token::CaptureRef(d - b'0'))),
_ => Err(Error::Lexer(format!(
"malformed pattern (invalid escape sequence in set: %{})",
next_byte
))),
}
}
}
_ => Ok(Some(Token::Literal(byte))),
}
}
}
impl Iterator for Lexer<'_> {
type Item = Result<Token>;
fn next(&mut self) -> Option<Self::Item> {
match self.next_token() {
Ok(Some(token)) => Some(Ok(token)),
Ok(None) => None,
Err(e) => Some(Err(e)),
}
}
}