use regex::Regex;
use std::path::PathBuf;
use once_cell::sync::Lazy;

static PATH_REGEX: Lazy<Regex> = Lazy::new(|| {
    Regex::new(r"^[+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?$").unwrap()
});

pub fn path_exists(s: &str) -> Result<PathBuf, String> {
    let p = PathBuf::from(s);
    p.exists().then_some(p).ok_or("path does not exist".to_string())
}

pub fn valid_possible_path(s: &str) -> Result<PathBuf, String>
{
    let lower = s.to_ascii_lowercase();

    if lower == "true" || lower == "false" {
        return Err("boolean literal is not allowed".into());
    }

    if PATH_REGEX.is_match(s) {
        return Err("numeric literal is not allowed".into());
    }

    Ok(PathBuf::from(s))
}