rsco/src/parser.rs

use nom::{
    branch::alt,
    bytes::complete::{escaped, is_not},
    bytes::complete::{tag, take_until},
    character::complete::char,
    character::complete::multispace0,
    character::complete::{alpha1, alphanumeric1, digit1, one_of, space0},
    combinator::value,
    combinator::{cut, map, map_res, recognize},
    error::{context, convert_error, ContextError, ErrorKind, ParseError, VerboseError},
    multi::{fold_many0, many0, separated_list0},
    number::complete::double,
    sequence::pair,
    sequence::{delimited, preceded, terminated, tuple},
    IResult, Parser,
};

use crate::ast::*;

fn sc<'a, E>(i: &'a str) -> IResult<&'a str, (), E>
where
    E: ParseError<&'a str>,
{
    alt((value((), multispace0), pinline_comment, peol_comment))(i)
}

fn pinline_comment<'a, E>(i: &'a str) -> IResult<&'a str, (), E>
where
    E: ParseError<&'a str>,
{
    value(
        (), // Output is thrown away.
        tuple((tag("/*"), take_until("*/"), tag("*/"))),
    )(i)
}

fn peol_comment<'a, E: ParseError<&'a str>>(i: &'a str) -> IResult<&'a str, (), E> {
    value(
        (), // Output is thrown away.
        pair(char('/'), is_not("\n\r")),
    )(i)
}

fn braces<'a, P, O, E>(a: P) -> impl FnMut(&'a str) -> IResult<&'a str, O, E>
where
    P: Parser<&'a str, O, E>,
    E: ParseError<&'a str>,
{
    delimited(char('{'), a, char('}'))
}

fn parens<'a, P, O, E>(a: P) -> impl FnMut(&'a str) -> IResult<&'a str, O, E>
where
    P: Parser<&'a str, O, E>,
    E: ParseError<&'a str>,
{
    delimited(
        tuple((tag("("), recognize(sc))),
        a,
        tuple((recognize(sc), tag(")"))),
    )
}

fn identifier(input: &str) -> IResult<&str, &str> {
    recognize(pair(
        alt((alpha1, tag("_"))),
        many0(alt((alphanumeric1, tag("_")))),
    ))(input)
}

fn parse_str<'a>(i: &'a str) -> IResult<&'a str, &'a str> {
    escaped(alphanumeric1, '\\', one_of("\"n\\"))(i)
}

fn string<'a>(i: &'a str) -> IResult<&'a str, &'a str> {
    preceded(char('\"'), cut(terminated(parse_str, char('\"'))))(i)
}

fn boolean<'a>(i: &'a str) -> IResult<&'a str, bool> {
    println!("boolean: {}", i);
    alt((map(tag("true"), |_| true), map(tag("false"), |_| false)))(i)
}

fn call<'a>(i: &'a str) -> IResult<&'a str, (Identifier, Vec<Expr>)> {
    println!("call: {}", i);
    map(
        tuple((
            identifier,
            delimited(
                char('('),
                separated_list0(tuple((sc, tag(","), sc)), expr),
                char(')'),
            ),
        )),
        |(i, v)| (i.to_string(), v),
    )(i)
}

fn num(i: &str) -> IResult<&str, Expr> {
    println!("num: {}", i);
    map(double, Expr::LNum)(i)
}

fn parens_bin(i: &str) -> IResult<&str, Expr> {
    delimited(space0, delimited(tag("("), expr, tag(")")), space0)(i)
}

fn factor_bin(i: &str) -> IResult<&str, Expr> {
    alt((delimited(space0, num, space0), parens_bin))(i)
}

fn bin_less_greater(i: &str) -> IResult<&str, Expr> {
    let (i, init) = factor_bin(i)?;

    fold_many0(
        pair(alt((char('<'), char('>'))), factor_bin),
        move || init.clone(),
        |acc, (op, val): (char, Expr)| {
            if op == '<' {
                Expr::Binary(BinOp::LessThan, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::GreaterThan, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}
fn bin_equal_not(i: &str) -> IResult<&str, Expr> {
    let (i, init) = bin_less_greater(i)?;

    fold_many0(
        pair(alt((char('<'), char('>'))), bin_less_greater),
        move || init.clone(),
        |acc, (op, val): (char, Expr)| {
            if op == '<' {
                Expr::Binary(BinOp::LessThan, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::GreaterThan, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}
fn bin_mult_div(i: &str) -> IResult<&str, Expr> {
    let (i, init) = bin_equal_not(i)?;

    fold_many0(
        pair(alt((char('*'), char('/'))), bin_equal_not),
        move || init.clone(),
        |acc, (op, val): (char, Expr)| {
            if op == '*' {
                Expr::Binary(BinOp::Mult, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::Div, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}
fn binary<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("binary: {}", i);
    let (i, init) = bin_mult_div(i)?;

    fold_many0(
        pair(alt((char('+'), char('-'))), bin_mult_div),
        move || init.clone(),
        |acc, (op, val): (char, Expr)| {
            if op == '+' {
                Expr::Binary(BinOp::Plus, Box::new(acc), Box::new(val))
            } else {
                Expr::Binary(BinOp::Minus, Box::new(acc), Box::new(val))
            }
        },
    )(i)
}
fn receive<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    map(pair(tag("<-"), expr), |(_, expr)| {
        Expr::Receive(Box::new(expr))
    })(i)
}

pub fn expr<'a>(i: &'a str) -> IResult<&'a str, Expr> {
    println!("expr: {}", i);
    preceded(
        sc,
        alt((
            parens(expr),
            map(call, |(i, v)| Expr::Call(i, v)),
            map(identifier, |i| Expr::Var(i.to_string())),
            receive,
            binary,
            map(tag("null"), |_| Expr::LNull),
            map(string, |s| Expr::LStr(String::from(s))),
            num,
        )),
    )(i)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn can_parse_string_lit() {
        let a = r#""hey"  "#;
        let (rest, res) = string(a).unwrap();

        assert_eq!(res, "hey");
        assert_eq!(rest, "  ");
    }

    #[test]
    fn can_parse_binary_op() {
        let a = "3 +3 +  6";
        let (_rest, res) = binary(a).unwrap();

        assert_eq!(
            res,
            Expr::Binary(
                BinOp::Plus,
                Box::new(Expr::Binary(
                    BinOp::Plus,
                    Box::new(Expr::LNum(3.0)),
                    Box::new(Expr::LNum(3.0)),
                )),
                Box::new(Expr::LNum(6.0))
            )
        );
    }

    #[test]
    fn can_parse_empty_call() {
        let a = "hello()";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(res, Expr::Call("hello".to_string(), vec![]));
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_call() {
        let a = "hello(1.0, 45 , yeah)";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Call(
                "hello".to_string(),
                vec![
                    Expr::LNum(1.0),
                    Expr::LNum(45.0),
                    Expr::Var("yeah".to_string())
                ]
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse_call_with_bin_op() {
        let a = "hello(1.0, 45 + 33, yeah)";
        let (rest, res) = expr(a).unwrap();

        assert_eq!(
            res,
            Expr::Call(
                "hello".to_string(),
                vec![
                    Expr::LNum(1.0),
                    Expr::Binary(
                        BinOp::Plus,
                        Box::new(Expr::LNum(45.0)),
                        Box::new(Expr::LNum(33.0))
                    ),
                    Expr::Var("yeah".to_string())
                ]
            )
        );
        assert_eq!(rest, "");
    }

    #[test]
    fn can_parse() {
        let a = r#"let hello = ("hey" + 0.5)"#;
    }
}