#[derive(Debug)]
enum Method {
    Head,
    Option,
    Get,
    Post,
    Patch,
    Put,
    Delete,
}

struct Router;

impl Router {
    pub fn to<H, P>(&self, method: Method, handler: H) -> &Self
    where
        H: HandlerFactory<P>,
    {
        println!("handle route {:?}", method);
        self
    }
}

trait HandlerFactory<P> {
    fn call(&self, _: P) -> String;
}

impl<F> HandlerFactory<()> for F
where
    F: Fn() -> String,
{
    fn call(&self, _: ()) -> String {
        (self)()
    }
}

impl<F> HandlerFactory<(Token,)> for F
where
    F: Fn(Token) -> String,
{
    fn call(&self, params: (Token,)) -> String {
        (self)(params.0)
    }
}

struct Token {}

fn public_route() -> String {
    "hello world".into()
}
fn private_route(token: Token) -> String {
    "hello private world".into()
}

fn main() {
    let router = Router {};
    router
        .to(Method::Get, public_route)
        .to(Method::Post, private_route);
}