const OP_TABLE: [[usize; 10]; 10] = [
    [0, 3, 1, 7, 5, 9, 8, 6, 4, 2],
    [7, 0, 9, 2, 1, 5, 4, 8, 6, 3],
    [4, 2, 0, 6, 8, 7, 1, 3, 5, 9],
    [1, 7, 5, 0, 9, 8, 3, 4, 2, 6],
    [6, 1, 2, 3, 0, 4, 5, 9, 7, 8],
    [3, 6, 7, 4, 2, 0, 9, 5, 8, 1],
    [5, 8, 6, 9, 7, 2, 0, 1, 3, 4],
    [8, 9, 4, 5, 3, 6, 2, 0, 1, 7],
    [9, 4, 3, 8, 6, 1, 7, 2, 0, 5],
    [2, 5, 8, 1, 4, 3, 6, 7, 9, 0]
];

/// Calculates the check digit for a given ID
fn check_digit(input: &[usize]) -> usize {
    let mut interim = 0;
    for &digit in input.iter() {
        interim = OP_TABLE[interim][digit];
    }
    interim
}

/// Is an ID valid?
pub fn verify(id: &[usize]) -> bool {
    check_digit(id) == 0
}

/// Append a checksum to an existing ID
pub fn id(mut input: Vec<usize>) -> Vec<usize> {
    let id = check_digit(&input);
    input.push(id);
    input
}

fn main() {
    let mut id = vec![ 7, 8, 9, 3, 5, 7, 2 ];
    let sum = check_digit(&id);
    id.push(sum);
    //println!("{:?}, {}", id, );
    println!("{}", verify(&id));
}