use rocket::request::FromParam;
use phf::phf_map;


pub struct RequestLanguage {
    pub language: String,
    pub simple_language: String,
}


fn find_key_for_value<'a>(map: &'a phf::Map<&'a str, &'a str>, value: &str) -> Option<&'a str> {
    map.into_iter()
        .find_map(|(key, &val)| if val == value { Some(*key) } else { None })
}

static LANG_TO_CODES: phf::Map<&'static str, &'static str> = phf_map! {
    "cs" => "cs-CZ",
    "en" => "en-US",
};

impl<'r> FromParam<'r> for RequestLanguage {
    type Error = &'r str;

    fn from_param(param: &'r str) -> Result<Self, Self::Error> {
        match LANG_TO_CODES.get(param) {
            Some(val) => Ok(RequestLanguage {
                language: val.to_string(),
                simple_language: find_key_for_value(&LANG_TO_CODES, val).unwrap_or("un").to_string(),
            }),
            None => Ok(RequestLanguage {
                language: LANG_TO_CODES["en"].to_string(),
                simple_language: "en".to_string(),
            }),
        }
    }
}