Tera Function Add

use tera::Tera;

fn main() {
    let mut urls: HashMap<String, String> = HashMap::new();
    let mut tera = match Tera::new("templates/**/*.html") {
        Ok(t) => t,
        Err(e) => {
            println!("Parsing error(s): {}", e);
            ::std::process::exit(1);
        }
    };

    urls.insert("home".to_string(), "http://address.com/home".to_string());

    //Register our function here with External types
    tera.register_function("url_for", make_url(urls));
}

fn make_url(urls: HashMap<String, String>) -> impl Function {
    //Boxed closure for Function
    Box::new(
        move |args: &HashMap<String, Value>| -> Result<Value, tera::Error> {
            //cloning the urls otherwise it needs to be a &'static
            let urls = urls.clone();
            //getting the name argument from the args list which is returned by tera
            let name = args
                .get("name")
                .ok_or_else(|| tera::Error::msg("`name` must Exist in url_for"))?
                .as_str()
                .ok_or_else(|| tera::Error::msg("`name` must be a string in url_for"))?
                .trim();
            //getting our url from out urls hashmap.
            let url = urls
                .get(&name.to_string())
                .ok_or_else(|| tera::Error::msg(format!("`{}` is not a valid url", name)))?
                .as_str();
            //Transforming url into json string value.
            let value = to_value(url)
                .map_err(|_| tera::Error::msg("failed to convert url to json value"))?;
            Ok(value)
        },
    )
}