use crate::ast;

fn parse_expr(tokens: &mut Vec<LocatedToken>) -> Result<ast::Expr, Error> {
    todo!()
}

enum Error {
    UnexpectedToken(LocatedToken),
    UnexpectedEndOfInput,
}

fn parse_definition(tokens: &mut Vec<LocatedToken>) -> Result<ast::Definition, Error> {
    if let Some(start) = tokens.pop_if(|tok| tok.token == Token::Let) {
        if let Some(LocatedToken {
            token: Token::Identifier(identifier),
            ..
        }) = tokens.pop_if(|tok| match tok.token {
            Token::Identifier(_) => true,
            _ => false,
        }) {
            if let Some(_eq) = tokens.pop_if(|tok| tok.token == Token::Equals) {
                let expr = parse_expr(tokens)?;
                Ok(ast::Definition {
                    name: ast::Name(identifier),
                    expr,
                })
            } else {
                Err(Error::UnexpectedToken(start))
            }
        } else {
            Err(Error::UnexpectedToken(start))
        }
    } else {
        Err(Error::UnexpectedEndOfInput)
    }
}