////
// Cryptopal set 1 chal 1 : https://cryptopals.com/sets/1/challenges/1
// Run with :
// cargo run -- 49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d
////

use std::env;

fn hex_to_char(s: &str) -> Result<char, std::num::ParseIntError> {
    u8::from_str_radix(s, 16).map(|n| n as char)
}

fn main() {
    let args: Vec<String> = env::args().collect();
    let input = &args[1];

    let char_vec: Vec<char> = input.chars().collect();
    let split = &char_vec.chunks(2)
        .map(|chunk| chunk.iter().collect::<String>())
        .collect::<Vec<_>>();

    // Printing the string in Ascii format - for decoding example
    for (i, s) in split.iter().enumerate() {
        match hex_to_char(s) {
            Ok(s) => print!("{}", s),
            Err(e) => println!("\nError decoding char '{}' at index {}", e, i),
        }
    }
    println!();

    // Now we can unroll the base64 algorithm
    // We need to : http://www.herongyang.com/Encoding/Base64-Encoding-Algorithm.html
}