use yap::Tokens;

use crate::parsing::{parse_n, parse_number};

use super::model::TargetArea;

pub fn parse_target_area(tokens: &mut impl Tokens<Item = char>) -> Option<TargetArea> {
    tokens.optional(|t| {
        if !t.tokens("target area: x=".chars()) {
            return None;
        }
        let x = parse_bounds(t)?;
        if !t.tokens(", y=".chars()) {
            return None;
        }
        let y = parse_bounds(t)?;
        Some(TargetArea(x, y))
    })
}

pub fn parse_bounds(tokens: &mut impl Tokens<Item = char>) -> Option<(isize, isize)> {
    tokens.optional(|t| {
        let numbers: Option<[isize; 2]> =
            parse_n(t, |t| parse_number(t), |t| t.tokens("..".chars()));
        numbers.map(|numbers| (numbers[0], numbers[1]))
    })
}

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

    use crate::day_17::model::TargetArea;

    const EXAMPLE: &str = "target area: x=20..30, y=-10..-5";

    #[test]
    fn parse_example() {
        let example = super::parse_target_area(&mut EXAMPLE.into_tokens());
        assert_eq!(example, Some(TargetArea((20, 30), (-10, -5))));
    }
}