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use crate::puppet_parser::{range::Range, IResult, Span};
use nom::branch::alt;
use nom::bytes::complete::{is_not, tag};
use nom::character::complete::anychar;
use nom::combinator::{map, recognize, verify};
use nom::multi::fold_many0;
use nom::sequence::{pair, tuple};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum StringFragment<'a> {
    Literal(Span<'a>),
    EscapedChar(Span<'a>),
}

fn parse_literal(input: Span) -> IResult<Span> {
    let not_quote_slash = is_not("/\\");
    verify(not_quote_slash, |s: &Span| !s.is_empty())(input)
}

fn parse_escaped_char(input: Span) -> IResult<Span> {
    recognize(pair(tag("\\"), anychar))(input)
}

fn parse_fragment(input: Span) -> IResult<StringFragment> {
    alt((
        map(parse_literal, StringFragment::Literal),
        map(parse_escaped_char, StringFragment::EscapedChar),
    ))(input)
}

pub fn parse(input: Span) -> IResult<crate::puppet_lang::expression::Regexp<Range>> {
    let build_regex = fold_many0(parse_fragment, String::new, |mut string, fragment| {
        match fragment {
            StringFragment::Literal(s) => string.push_str(&s),
            StringFragment::EscapedChar(s) => string.push_str(&s),
        }
        string
    });

    map(
        tuple((tag("/"), build_regex, tag("/"))),
        |(left_tag, data, right_tag)| crate::puppet_lang::expression::Regexp {
            data,
            extra: Range::from((left_tag, right_tag)),
        },
    )(input)
}

#[test]
fn test() {
    assert_eq!(
        parse(Span::new("//")).unwrap().1,
        crate::puppet_lang::expression::Regexp {
            data: "".to_owned(),
            extra: Range::new(0, 1, 1, 1, 1, 2)
        }
    );
    assert_eq!(
        parse(Span::new("/aaa/")).unwrap().1,
        crate::puppet_lang::expression::Regexp {
            data: "aaa".to_owned(),
            extra: Range::new(0, 1, 1, 4, 1, 5)
        }
    );
    assert_eq!(
        parse(Span::new("/\\//")).unwrap().1,
        crate::puppet_lang::expression::Regexp {
            data: "\\/".to_owned(),
            extra: Range::new(0, 1, 1, 3, 1, 4)
        }
    );
    assert_eq!(
        parse(Span::new("/\\d/")).unwrap().1,
        crate::puppet_lang::expression::Regexp {
            data: "\\d".to_owned(),
            extra: Range::new(0, 1, 1, 3, 1, 4)
        }
    );
}