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use std::ascii::AsciiExt;
use super::{Token, Parser};
pub fn parse_nth(input: &mut Parser) -> Result<(i32, i32), ()> {
match try!(input.next()) {
Token::Number(value) => Ok((0, try!(value.int_value.ok_or(())) as i32)),
Token::Dimension(value, unit) => {
let a = try!(value.int_value.ok_or(())) as i32;
match_ignore_ascii_case! { unit,
"n" => parse_b(input, a),
"n-" => parse_signless_b(input, a, -1),
_ => Ok((a, try!(parse_n_dash_digits(&*unit))))
}
}
Token::Ident(value) => {
match_ignore_ascii_case! { value,
"even" => Ok((2, 0)),
"odd" => Ok((2, 1)),
"n" => parse_b(input, 1),
"-n" => parse_b(input, -1),
"n-" => parse_signless_b(input, 1, -1),
"-n-" => parse_signless_b(input, -1, -1),
_ => if value.starts_with("-") {
Ok((-1, try!(parse_n_dash_digits(&value[1..]))))
} else {
Ok((1, try!(parse_n_dash_digits(&*value))))
}
}
}
Token::Delim('+') => match try!(input.next_including_whitespace()) {
Token::Ident(value) => {
match_ignore_ascii_case! { value,
"n" => parse_b(input, 1),
"n-" => parse_signless_b(input, 1, -1),
_ => Ok((1, try!(parse_n_dash_digits(&*value))))
}
}
_ => Err(())
},
_ => Err(())
}
}
fn parse_b(input: &mut Parser, a: i32) -> Result<(i32, i32), ()> {
let start_position = input.position();
match input.next() {
Ok(Token::Delim('+')) => parse_signless_b(input, a, 1),
Ok(Token::Delim('-')) => parse_signless_b(input, a, -1),
Ok(Token::Number(ref value)) if value.has_sign => {
Ok((a, try!(value.int_value.ok_or(())) as i32))
}
_ => {
input.reset(start_position);
Ok((a, 0))
}
}
}
fn parse_signless_b(input: &mut Parser, a: i32, b_sign: i32) -> Result<(i32, i32), ()> {
match try!(input.next()) {
Token::Number(ref value) if !value.has_sign => {
Ok((a, b_sign * (try!(value.int_value.ok_or(())) as i32)))
}
_ => Err(())
}
}
fn parse_n_dash_digits(string: &str) -> Result<i32, ()> {
if string.len() >= 3
&& string[..2].eq_ignore_ascii_case("n-")
&& string[2..].chars().all(|c| matches!(c, '0'...'9'))
{
Ok(string[1..].parse().unwrap())
} else {
Err(())
}
}