use std::fmt;

pub enum ApiFlavor {
    Foo,
    Bar,
}

impl fmt::Display for ApiFlavor {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            ApiFlavor::Foo => f.write_str("Foo"),
            ApiFlavor::Bar => f.write_str("Bar"),
        }
    }
}

pub struct Context {
    username: Option<String>,
    api_flavor: Option<ApiFlavor>,
}

pub fn print_ctx(ctx: &Context) {
    println!(
        "            API: {}",
        ctx.api_flavor.as_ref()
            .map(ApiFlavor::to_string)
            .unwrap_or_else(|| String::from("<none>"))
    );

    // better
    println!(
        "            API: {}",
        ctx.api_flavor.as_ref()
            .map_or_else(|| String::from("<none>"), ApiFlavor::to_string)
    );

    println!(
        "       Username: {}",
        ctx.username.as_ref().unwrap_or(&String::from("<none>"))
    );

    // better
    println!(
        "       Username: {}",
        ctx.username.as_ref()
            .map_or_else(|| String::from("<none>"), String::to_string)
    );
}

pub fn main() {
    print_ctx(&Context {
        username: Some("Alice".into()),
        api_flavor: Some(ApiFlavor::Foo),
    });

    print_ctx(&Context {
        username: None,
        api_flavor: None,
    });
}