use std::collections::HashMap;

pub fn format_env_display(env: Option<&HashMap<String, String>>, env_vars: &[String]) -> String {
    let mut parts: Vec<String> = Vec::new();

    if let Some(map) = env {
        let mut pairs: Vec<_> = map.iter().collect();
        pairs.sort_by(|(a, _), (b, _)| a.cmp(b));
        parts.extend(
            pairs
                .into_iter()
                .map(|(key, value)| format!("{key}={value}")),
        );
    }

    if !env_vars.is_empty() {
        parts.extend(env_vars.iter().map(|var| format!("{var}=${var}")));
    }

    if parts.is_empty() {
        "-".to_string()
    } else {
        parts.join(", ")
    }
}

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

    #[test]
    fn returns_dash_when_empty() {
        assert_eq!(format_env_display(None, &[]), "-");

        let empty_map = HashMap::new();
        assert_eq!(format_env_display(Some(&empty_map), &[]), "-");
    }

    #[test]
    fn formats_sorted_env_pairs() {
        let mut env = HashMap::new();
        env.insert("B".to_string(), "two".to_string());
        env.insert("A".to_string(), "one".to_string());

        assert_eq!(format_env_display(Some(&env), &[]), "A=one, B=two");
    }

    #[test]
    fn formats_env_vars_with_dollar_prefix() {
        let vars = vec!["TOKEN".to_string(), "PATH".to_string()];

        assert_eq!(format_env_display(None, &vars), "TOKEN=$TOKEN, PATH=$PATH");
    }

    #[test]
    fn combines_env_pairs_and_vars() {
        let mut env = HashMap::new();
        env.insert("HOME".to_string(), "/tmp".to_string());
        let vars = vec!["TOKEN".to_string()];

        assert_eq!(
            format_env_display(Some(&env), &vars),
            "HOME=/tmp, TOKEN=$TOKEN"
        );
    }
}