peuler 0.1.0

use crate::Solution;
use std::str;

problem!(Problem0059, 59, "XOR Decryption");

impl Solution for Problem0059 {
    fn solve(&self) -> String {
        const INPUT: &str = include_str!("0059_cipher.txt");
        let bytes = INPUT
            .split(',')
            .map(|s| s.parse::<u8>().unwrap())
            .collect::<Vec<_>>();
        let mut decrypted = bytes.clone();
        let mut key = [0u8; 3];
        let mut sum: u32 = 0;

        'outer: for a in b'a'..(b'z' + 1) {
            key[0] = a;
            for b in b'a'..(b'z' + 1) {
                key[1] = b;
                for c in b'a'..(b'z' + 1) {
                    key[2] = c;
                    decrypt(&bytes, &mut decrypted, &key);
                    let decrypted_str = unsafe { str::from_utf8_unchecked(&decrypted) };
                    if decrypted_str.contains(" the ") {
                        sum = decrypted.iter().map(|&b| b as u32).sum();
                        break 'outer;
                    }
                }
            }
        }

        sum.to_string()
    }
}

fn decrypt(bytes: &[u8], decrypted: &mut [u8], key: &[u8]) {
    for (i, d_byte) in decrypted.iter_mut().enumerate() {
        *d_byte = bytes[i] ^ key[i % key.len()];
    }
}