use once_cell::sync::Lazy;
use regex::{Captures, Regex};
use std::borrow::Cow;

static CURLY_BRACES: Lazy<Regex> = Lazy::new(|| Regex::new(r"(\\N\{[^}]+})|([{}])").unwrap());

pub(super) fn curly_escape(text: &str) -> Cow<'_, str> {
    // Match all curly braces. This will include named unicode escapes (like
    // \N{SNOWMAN}), which we _don't_ want to escape, so take care to preserve them.
    CURLY_BRACES.replace_all(text, |caps: &Captures| {
        if let Some(match_) = caps.get(1) {
            match_.as_str().to_string()
        } else {
            if &caps[2] == "{" {
                "{{".to_string()
            } else {
                "}}".to_string()
            }
        }
    })
}

static DOUBLE_CURLY_BRACES: Lazy<Regex> = Lazy::new(|| Regex::new(r"((\{\{)|(\}\}))").unwrap());

pub(super) fn curly_unescape(text: &str) -> Cow<'_, str> {
    // Match all double curly braces and replace with a single
    DOUBLE_CURLY_BRACES.replace_all(text, |caps: &Captures| {
        if &caps[1] == "{{" {
            "{".to_string()
        } else {
            "}".to_string()
        }
    })
}