mod upc_code {
    use std::io;

    pub struct UPCCode {
        pub code: Vec<i8>,
        pub check_digit: i8,
    }

    impl UPCCode {
        fn validate_nums(&self) -> bool {
            for code in &self.code {
                if !is_1_digit(*code) {
                    return false;
                }
            }

            is_1_digit(self.check_digit)
        }

        fn add_odd_total(&self) -> (i8, i8) {
            let mut result: (i8, i8) = (0, 0);

            for code in &self.code {
                if code % 2 == 0 {
                    result.0 += code;
                } else {
                    result.1 += code;
                }
            }

            result
        }

        pub fn check_code(&self) -> Result<bool, io::Error> {
            if !&self.validate_nums() {
                return Err(io::Error::new(
                    io::ErrorKind::Other,
                    "A number used isn\'t 1 digit!",
                ));
            }

            let mut total: i8 = 0;
            let (even_nums, odd_nums): &(i8, i8) = &self.add_odd_total();

            total += ((odd_nums * 3) + even_nums) % 10;

            if (total == 0 && self.check_digit == 0) || (10 - total == self.check_digit) {
                return Ok(true);
            }

            Ok(false)
        }
    }

    fn is_1_digit(num: i8) -> bool {
        num < 0 || num > 9
    }
}

fn main() {
    println!("Hello");

    let code: Vec<i8> = vec![2, 3, 4, 5, 5, 6, 6, 3, 2, 1];
    let check_digit: i8 = 3;

    let my_upc = upc_code::UPCCode {
        code: code,
        check_digit: check_digit,
    };

    println!("Result: {}", my_upc.check_code().unwrap());
}