outrig 0.1.0

//! Shared `${VAR}` parser used by `ApiKeyRef` and `EnvValue`. Variable names
//! match `^[A-Z_][A-Z0-9_]*$`; the regex is anchored on both ends, so a value
//! either *is* `${VAR}` whole or it isn't.

use std::sync::OnceLock;

use regex::Regex;

/// If `raw` whole-matches `${VAR}`, return `Some(VAR)`; otherwise `None`.
pub(crate) fn parse_env_ref(raw: &str) -> Option<&str> {
    static RE: OnceLock<Regex> = OnceLock::new();
    let re = RE
        .get_or_init(|| Regex::new(r"^\$\{([A-Z_][A-Z0-9_]*)\}$").expect("env-ref regex compiles"));
    re.captures(raw).map(|caps| caps.get(1).unwrap().as_str())
}

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

    #[test]
    fn accepts_simple_uppercase() {
        assert_eq!(parse_env_ref("${FOO}"), Some("FOO"));
    }

    #[test]
    fn accepts_leading_underscore_and_digits() {
        assert_eq!(parse_env_ref("${_VAR_2}"), Some("_VAR_2"));
    }

    #[test]
    fn rejects_lowercase() {
        assert_eq!(parse_env_ref("${foo}"), None);
    }

    #[test]
    fn rejects_digit_first() {
        assert_eq!(parse_env_ref("${1FOO}"), None);
    }

    #[test]
    fn rejects_empty_braces() {
        assert_eq!(parse_env_ref("${}"), None);
    }

    #[test]
    fn rejects_no_braces() {
        assert_eq!(parse_env_ref("$FOO"), None);
    }

    #[test]
    fn rejects_trailing_junk() {
        assert_eq!(parse_env_ref("${FOO} extra"), None);
    }

    #[test]
    fn rejects_leading_junk() {
        assert_eq!(parse_env_ref("prefix-${FOO}"), None);
    }

    #[test]
    fn rejects_empty_string() {
        assert_eq!(parse_env_ref(""), None);
    }

    #[test]
    fn rejects_bare_name() {
        assert_eq!(parse_env_ref("FOO"), None);
    }
}