use crate::span::Pos;
#[derive(Debug, Clone)]
pub struct Scanner<'a> {
source: &'a str,
offset: usize,
line: usize,
column: usize,
pub has_line_break: bool,
}
impl<'a> Scanner<'a> {
pub fn new(source: &'a str) -> Self {
Scanner {
source,
offset: 0,
line: 1,
column: 0,
has_line_break: false,
}
}
pub fn peek(&self) -> Option<char> {
self.source[self.offset..].chars().next()
}
pub fn peek_ahead(&self, n: usize) -> Option<char> {
let mut chars = self.source[self.offset..].chars();
for _ in 0..n {
chars.next()?;
}
chars.next()
}
pub fn advance(&mut self) -> Option<char> {
let ch = self.peek()?;
self.offset += ch.len_utf8();
match ch {
'\r' => {
self.line += 1;
self.column = 0;
self.has_line_break = true;
if self.peek() == Some('\n') {
self.offset += '\n'.len_utf8();
}
}
'\n' => {
self.line += 1;
self.column = 0;
self.has_line_break = true;
}
_ => {
self.column += 1;
}
}
Some(ch)
}
pub fn advance_if(&mut self, pred: impl FnOnce(char) -> bool) -> Option<char> {
match self.peek() {
Some(ch) if pred(ch) => self.advance(),
_ => None,
}
}
pub fn advance_if_eq(&mut self, ch: char) -> bool {
self.advance_if(|c| c == ch).is_some()
}
pub fn position(&self) -> Pos {
Pos::new(self.offset, self.line, self.column)
}
pub fn slice(&self, start: Pos) -> &'a str {
&self.source[start.offset..self.offset]
}
pub fn slice_from(&self, start: usize) -> &'a str {
&self.source[start..self.offset]
}
pub fn remaining(&self) -> &'a str {
&self.source[self.offset..]
}
pub fn is_eof(&self) -> bool {
self.offset >= self.source.len()
}
}