use yap::Tokens;

use crate::parsing::{newline, parse_digit};

use super::model::SnailfishNumber;

pub fn parse_regular(tokens: &mut impl Tokens<Item = char>) -> Option<SnailfishNumber> {
    parse_digit(tokens).map(|digit: isize| digit.into())
}

pub fn parse_pair(tokens: &mut impl Tokens<Item = char>) -> Option<SnailfishNumber> {
    tokens.optional(|t| {
        if !t.token('[') {
            return None;
        }
        let lhs = parse_snailfish_number(t)?;
        if !t.token(',') {
            return None;
        }
        let rhs = parse_snailfish_number(t)?;
        if !t.token(']') {
            return None;
        }
        Some((lhs, rhs).into())
    })
}

pub fn parse_snailfish_number(tokens: &mut impl Tokens<Item = char>) -> Option<SnailfishNumber> {
    yap::one_of!(t from tokens;
        parse_regular(t),
        parse_pair(t),
    )
}

pub fn parse_number_list(tokens: &mut impl Tokens<Item = char>) -> Option<Vec<SnailfishNumber>> {
    tokens.optional(|t| {
        let vec: Vec<SnailfishNumber> = t
            .sep_by(|t| parse_snailfish_number(t), |t| newline(t))
            .collect();
        if !vec.is_empty() {
            Some(vec)
        } else {
            None
        }
    })
}

#[cfg(test)]
mod test {
    use yap::IntoTokens;

    #[test]
    fn test_parsing() {
        let number = super::parse_snailfish_number(
            &mut "[[[[1,3],[5,3]],[[1,3],[8,7]]],[[[4,9],[6,9]],[[8,2],[7,3]]]]".into_tokens(),
        );
        assert_eq!(
            number,
            Some(
                (
                    (((1, 3), (5, 3)), ((1, 3), (8, 7))),
                    (((4, 9), (6, 9)), ((8, 2), (7, 3)))
                )
                    .into()
            )
        );
    }
}