use nom::{
    IResult,
    Parser,
    branch::alt,
    multi::many0,
    combinator::all_consuming,
    bytes::complete::{tag, take_while1},
    character::complete::multispace1,
};


#[derive(Debug,PartialEq)]
pub enum Token {
    ParOpen,
    ParClose,
    Num(i32),
    Sym(String),
    Whitespace(String),
}

use Token::*;
use crate::parse::util::*;

fn parse_token(s: &str) -> IResult<&str, Token> {
    alt((
            tag("(").map(|_| ParOpen),
            tag(")").map(|_| ParClose),
            multispace1.map(whitespace),
            nom::character::complete::i32.map(Num),
            take_while1(|c| !(" \n\t()".contains(c))).map(sym),
    )).parse(s)
}

fn tokenize(s: &str) -> Result<Vec<Token>, String> {
    match many0(parse_token).parse(s) {
        Ok(("", res)) => Ok(res),
        Ok((rest, _)) => Err(format!("all data should be tokenizable, '{rest}' was not")),
        Err(e) => Err(e.to_string()),
    }
}

#[cfg(test)]
mod private_parsing_tests {
    use super::{*, parse_token};

    #[test]
    fn test_parse_token() {
        assert_eq!(parse_token("()"), Ok((")", ParOpen)));
        assert_eq!(parse_token(")"), Ok(("", ParClose)));

        assert_eq!(parse_token(" \t\n"), Ok(("", whitespace(" \t\n"))));

        assert_eq!(parse_token("1 23"), Ok((" 23", Num(1))));
        assert_eq!(parse_token("23"), Ok(("", Num(23))));

        assert_eq!(parse_token("Nil a"), Ok((" a", sym("Nil"))));
        assert_eq!(parse_token("a"), Ok(("", sym("a"))));

        assert!(parse_token("").is_err())
    }

    #[test]
    fn test_tokenize() {
        assert_eq!(
            tokenize("(+ 1 2 (\t\n a)").unwrap(),
            vec![
                ParOpen,
                sym("+"), whitespace(" "),
                Num(1), whitespace(" "),
                Num(2), whitespace(" "),
                ParOpen, whitespace("\t\n "),
                sym("a"),
                ParClose
            ]
        );
    }

}