use std::fs::read_to_string;

fn main() {
    let invalid_sum: u64 = read_to_string("../input.txt")
        .expect("failed to open input file")
        .split(',')
        .flat_map(|range| {
            let (first_id, last_id) = range.split_once('-').expect("failed to parse range");
            let (first_id, last_id): (u64, u64) = (
                first_id.parse().expect("failed to parse first ID"),
                last_id.trim_end().parse().expect("failed to parse last ID"),
            );

            first_id..=last_id
        })
        .filter(|id| {
            let id = id.to_string();
            let digit_count = id.len();
            (1..=(digit_count / 2))
                .any(|pattern_len| id[0..pattern_len].repeat(digit_count / pattern_len) == id)
        })
        .sum();
    println!("The sum of all invalid IDs is {invalid_sum}!")
}