use crate::parser::Parser;

pub fn choice<P1, P2, I, O, E>(parser1: P1, parser2: P2) -> impl Parser<I, O, E>
where
    P1: Parser<I, O, E>,
    P2: Parser<I, O, E>,
    I: Copy,
{
    move |input| match parser1.parse(input) {
        ok @ Ok(..) => ok,
        Err(_e) => parser2.parse(input),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::combinators::one_or_more;
    use crate::primitives::literal;

    #[test]
    fn test_choice() {
        let p = choice(literal("gnostika").to(1), one_or_more(literal(" ")).to(2));
        assert_eq!(p.parse("gnostika twentynine"), Ok((1, " twentynine")));
    }
}