use std::borrow::Borrow;
use std::iter::FromIterator;
type Result<T> = std::result::Result<T, Box<std::error::Error>>;

pub struct Game {
    rolls: Vec<u8>,
}

impl Game {
    pub fn new<I>(rolls: I) -> Result<Self> where I: IntoIterator,
                                                  I::Item: Borrow<u8>, {
        Ok(Self {
            rolls: Vec::from_iter(rolls),
        })
    }

    pub fn score(&self) -> u16 {
        self.rolls
            .iter()
            .map(u16::from)
            .sum()
    }
}

#[test]
fn calc_no_rolls_returns_0() -> Result<()> {
    // given an empty `Rolls`
    let game = Game::new(&[])?;

    // when invoked
    let res = game.score();

    // the score should be 0
    assert_eq!(0, res);
    Ok(())
}