pub struct HashResult {
    result: [u64; 4],
}

impl HashResult {
    pub fn hex(&self) {
        for i in 0..4 {
            print!("{:016X}", self.result[i]);
        }
        println!();
    }
}

pub fn ascon256(input: &[u8]) -> HashResult {
    let mut state = [0u64; 5];
    state[0] = 0x00400c0000000100;
    state = permutate(state);
    let mut chunked_iterator = input.chunks_exact(8);
    let mut sized_chunk = [0u8; 8];
    for chunk in &mut chunked_iterator {
        sized_chunk.copy_from_slice(chunk);
        state[0] ^= u64::from_be_bytes(sized_chunk);
        state = permutate(state);
    }
    let remainder = chunked_iterator.remainder();
    if !remainder.is_empty() {
        sized_chunk = [0u8; 8];
        sized_chunk[..remainder.len()].copy_from_slice(remainder);
        sized_chunk[remainder.len()] |= 0x80;
        state[0] ^= u64::from_be_bytes(sized_chunk);
    }
    let mut res = HashResult { result: [0u64; 4] };
    state = permutate(state);
    for i in 0..3 {
        res.result[i] = state[0];
        state = permutate(state);
    }
    res.result[3] = state[0];
    res
}

fn permutate(input: [u64; 5]) -> [u64; 5] {
    let mut state = input;
    for i in 0..12 {
        state = diffusion(sbox(add_constants(i, state)));
    }
    state
}

fn diffusion(input: [u64; 5]) -> [u64; 5] {
    let [mut x0, mut x1, mut x2, mut x3, mut x4] = input;
    x0 ^= x0.rotate_right(19) ^ x0.rotate_right(28);
    x1 ^= x1.rotate_right(61) ^ x1.rotate_right(39);
    x2 ^= x2.rotate_right(1) ^ x2.rotate_right(6);
    x3 ^= x3.rotate_right(10) ^ x3.rotate_right(17);
    x4 ^= x4.rotate_right(7) ^ x4.rotate_right(41);

    [x0, x1, x2, x3, x4]
}

fn add_constants(round: u64, mut input: [u64; 5]) -> [u64; 5] {
    input[2] ^= ((0b1111 - round) << 4) | round;
    input
}

fn sbox(input: [u64; 5]) -> [u64; 5] {
    let [mut x0, mut x1, mut x2, mut x3, mut x4] = input;
    x0 ^= x4;
    x4 ^= x3;
    x2 ^= x1;

    let mut t0 = !x0;
    let mut t1 = !x1;
    let mut t2 = !x2;
    let mut t3 = !x3;
    let mut t4 = !x4;

    t0 &= x1;
    t1 &= x2;
    t2 &= x3;
    t3 &= x4;
    t4 &= x0;

    x0 ^= t1;
    x1 ^= t2;
    x2 ^= t3;
    x3 ^= t4;
    x4 ^= t0;

    x1 ^= x0;
    x0 ^= x4;
    x3 ^= x2;

    [x0, x1, !x2, x3, x4]
}