use core::fmt;

#[derive(Debug, Clone)]
pub enum Inst<'a> {
    Set(&'a str),
    Var(&'a str),
    Num(f64),
    Call,
    Block(Vec<Inst<'a>>),
}

impl fmt::Display for Inst<'_> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Inst::Set(v) => write!(f, "→{v}"),
            Inst::Var(v) => write!(f, "{v}"),
            Inst::Num(n) => write!(f, "{n}"),
            Inst::Call => write!(f, "!"),
            Inst::Block(insts) => {
                write!(f, "(")?;
                if insts.len() == 1 {
                    write!(f, "{}", insts[0])?;
                } else if !insts.is_empty() {
                    for window in insts.windows(2) {
                        match window {
                            [a, Inst::Call] => write!(f, "{a}")?,
                            [a, _] => write!(f, "{a} ")?,
                            [last] => write!(f, "{last}")?,
                            _ => unreachable!(),
                        }
                    }
                    write!(f, "{}", insts.last().unwrap())?;
                }
                write!(f, ")")
            }
        }
    }
}