use hex::{AsHexBytes, HexDigest};

#[derive(Debug)]
pub enum FixedXORError {
    Bad,
}

pub fn fixed(a: &str, b: &str) -> Result<String, FixedXORError> {
    let a_decoded = a.hex_bytes().valid();
    let b_decoded = b.hex_bytes().valid();
    let xor: Vec<u8> = a_decoded.zip(b_decoded).map(|(x, y)| x ^ y).collect();
    Ok(xor.hex_digest())
}

#[cfg(test)]
mod tests {
    use hex::AsHexBytes;
    use std::char;
    use super::fixed;

    #[test]
    fn cryptopals() {
        let a = "1c0111001f010100061a024b53535009181c";
        let b = "686974207468652062756c6c277320657965";
        let ex_output = "746865206b696420646f6e277420706c6179";
        let output = fixed(a, b);
        assert_eq!(output.unwrap(), ex_output);
    }

    static ENGLISH_LETTER_FREQ: &'static str = "EARIOTNSLCUDPMHGBFYWKVXZJQ";

    fn letter_freq_score(input: &str) -> f32 {
        let mut score: f32 = 0.0;
        score
    }

    #[test]
    fn cryptopals13() {
        let input = "1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736";
        for key in 32u32..127 {
            let possible_output = input.hex_bytes().valid()
                .map(|c| char::from_u32(c as u32 ^ key))
                .take_while(|c| c.is_some())
                .map(|c| c.unwrap())
                .collect::<String>();
            println!("{}: {}", key, possible_output);
        }
    }
}