pips 0.2.5

Library for analyzing dice roll expressions in TTRPGs
Documentation 
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use nom;
use nom::digit;
use nom::types::CompleteStr;

use std::str::FromStr;

use crate::expression::Expression;
use Expression::{Constant, Die, Sum};

named!(
    parse_eval_signs<CompleteStr, char>,
    map!(
        take_while!(call!(|c| c == '+' || c == '-')),
        |input: CompleteStr| {
            let neg_count = input.chars().filter(|&x| x == '-').count();
            match neg_count % 2 {
                1 => '-',
                _ => '+',
            }
        }
    )
);

named!(
    pub parse_unsigned_number<CompleteStr, u32>,
    map_res!(
        recognize!(digit),
        |CompleteStr(string)| u32::from_str(string)

    )
);

named!(
    pub parse_signed_number<CompleteStr, i32>,
    map!(
        pair!(
            opt!(parse_eval_signs),
            parse_unsigned_number
        ),
        |(sign, value): (Option<char>, u32)| {
            match sign {
                Some('-') => -1 * value as i32,
                _ => 1 * value as i32
            }
        }
    )
);

named!(
    pub parse_constant<CompleteStr, Expression>,
    ws!(
        map!(parse_signed_number, |num: i32| Constant(num))
    )
);

named!(
    parse_die_single<CompleteStr, Expression>,
    do_parse!(
             ws!(tag!("d"))        >>
        num: parse_unsigned_number >>
        (Die(num))
    )
);

named!(
    parse_die_coefficient<CompleteStr, Expression>,
    map!(
        do_parse!(
            coefficient: ws!(parse_unsigned_number) >>
                         tag!("d")                  >>
            num:         parse_unsigned_number      >>
            (coefficient, num)
        ),
        |(coefficient, num)| {
            if coefficient == 0 {
                return Constant(0)
            }

            (0..coefficient-1).fold(Die(num), |acc, _| {
                Sum(Box::new(acc), Box::new(Die(num)))
            })
        }
    )
);

named!(
    pub parse_die<CompleteStr, Expression>,
    alt_complete!(parse_die_single | parse_die_coefficient)
);

#[cfg(test)]
mod tests {
    use super::*;
    use crate::parser::test_helpers::test_parser;

    #[test]
    fn test_parse_number_success() {
        let cases = vec![
            ("-999999999", -999999999),
            ("-1234", -1234),
            ("---10", -10),
            ("-10", -10),
            ("-1", -1),
            ("0", 0),
            ("1", 1),
            ("+++--1", 1),
            ("10", 10),
            ("1234", 1234),
            ("--1234", 1234),
            ("999999999", 999999999),
        ];

        test_parser(parse_signed_number, cases);
    }

    #[test]
    fn test_parse_constant() {
        let cases = vec![
            ("4", Constant(4)),
            ("  5  ", Constant(5)),
            ("\n\t --10  ", Constant(10)),
            ("\n\t ---10  ", Constant(-10)),
        ];

        test_parser(parse_constant, cases);
    }

    #[test]
    fn test_parse_die() {
        let cases = vec![
            ("d4", Die(4)),
            ("  d6", Die(6)),
            (" d10", Die(10)),
            ("\nd12", Die(12)),
            ("\td20  ", Die(20)),
            (" 2d6 ", Sum(Box::new(Die(6)), Box::new(Die(6)))),
            (
                "4d6",
                Sum(
                    Box::new(Sum(
                        Box::new(Sum(Box::new(Die(6)), Box::new(Die(6)))),
                        Box::new(Die(6)),
                    )),
                    Box::new(Die(6)),
                ),
            ),
            (
                "6d6",
                Sum(
                    Box::new(Sum(
                        Box::new(Sum(
                            Box::new(Sum(
                                Box::new(Sum(Box::new(Die(6)), Box::new(Die(6)))),
                                Box::new(Die(6)),
                            )),
                            Box::new(Die(6)),
                        )),
                        Box::new(Die(6)),
                    )),
                    Box::new(Die(6)),
                ),
            ),
        ];

        test_parser(parse_die, cases);
    }
}