#[cfg(test)]
mod tests;

use bytes::{Buf, BufMut};

use crate::{
    aead::ocb3::Ocb3Marker,
    block::{BlockCipher, BlockCipherMarker},
    error::{CryptoError, CryptoResult},
};

const SKIPJACK_KEY_SIZE: usize = 10;
const SKIPJACK_BLOCK_SIZE: usize = 8;

static SBOX: [u8; 256] = [
    0xa3, 0xd7, 0x09, 0x83, 0xf8, 0x48, 0xf6, 0xf4, 0xb3, 0x21, 0x15, 0x78, 0x99, 0xb1, 0xaf, 0xf9,
    0xe7, 0x2d, 0x4d, 0x8a, 0xce, 0x4c, 0xca, 0x2e, 0x52, 0x95, 0xd9, 0x1e, 0x4e, 0x38, 0x44, 0x28,
    0x0a, 0xdf, 0x02, 0xa0, 0x17, 0xf1, 0x60, 0x68, 0x12, 0xb7, 0x7a, 0xc3, 0xe9, 0xfa, 0x3d, 0x53,
    0x96, 0x84, 0x6b, 0xba, 0xf2, 0x63, 0x9a, 0x19, 0x7c, 0xae, 0xe5, 0xf5, 0xf7, 0x16, 0x6a, 0xa2,
    0x39, 0xb6, 0x7b, 0x0f, 0xc1, 0x93, 0x81, 0x1b, 0xee, 0xb4, 0x1a, 0xea, 0xd0, 0x91, 0x2f, 0xb8,
    0x55, 0xb9, 0xda, 0x85, 0x3f, 0x41, 0xbf, 0xe0, 0x5a, 0x58, 0x80, 0x5f, 0x66, 0x0b, 0xd8, 0x90,
    0x35, 0xd5, 0xc0, 0xa7, 0x33, 0x06, 0x65, 0x69, 0x45, 0x00, 0x94, 0x56, 0x6d, 0x98, 0x9b, 0x76,
    0x97, 0xfc, 0xb2, 0xc2, 0xb0, 0xfe, 0xdb, 0x20, 0xe1, 0xeb, 0xd6, 0xe4, 0xdd, 0x47, 0x4a, 0x1d,
    0x42, 0xed, 0x9e, 0x6e, 0x49, 0x3c, 0xcd, 0x43, 0x27, 0xd2, 0x07, 0xd4, 0xde, 0xc7, 0x67, 0x18,
    0x89, 0xcb, 0x30, 0x1f, 0x8d, 0xc6, 0x8f, 0xaa, 0xc8, 0x74, 0xdc, 0xc9, 0x5d, 0x5c, 0x31, 0xa4,
    0x70, 0x88, 0x61, 0x2c, 0x9f, 0x0d, 0x2b, 0x87, 0x50, 0x82, 0x54, 0x64, 0x26, 0x7d, 0x03, 0x40,
    0x34, 0x4b, 0x1c, 0x73, 0xd1, 0xc4, 0xfd, 0x3b, 0xcc, 0xfb, 0x7f, 0xab, 0xe6, 0x3e, 0x5b, 0xa5,
    0xad, 0x04, 0x23, 0x9c, 0x14, 0x51, 0x22, 0xf0, 0x29, 0x79, 0x71, 0x7e, 0xff, 0x8c, 0x0e, 0xe2,
    0x0c, 0xef, 0xbc, 0x72, 0x75, 0x6f, 0x37, 0xa1, 0xec, 0xd3, 0x8e, 0x62, 0x8b, 0x86, 0x10, 0xe8,
    0x08, 0x77, 0x11, 0xbe, 0x92, 0x4f, 0x24, 0xc5, 0x32, 0x36, 0x9d, 0xcf, 0xf3, 0xa6, 0xbb, 0xac,
    0x5e, 0x6c, 0xa9, 0x13, 0x57, 0x25, 0xb5, 0xe3, 0xbd, 0xa8, 0x3a, 0x01, 0x05, 0x59, 0x2a, 0x46,
];

static KEYSTEP: [usize; 10] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
static IKEYSTEP: [usize; 10] = [9, 0, 1, 2, 3, 4, 5, 6, 7, 8];

/// Skipjack block cipher implement as defined in
/// <https://en.wikipedia.org/wiki/Skipjack_(cipher)>
pub struct Skipjack {
    key: [u8; 10],
}

impl BlockCipherMarker for Skipjack {}
impl Ocb3Marker for Skipjack {}

impl Skipjack {
    pub fn new(key: &[u8]) -> CryptoResult<Self> {
        if key.len() != SKIPJACK_KEY_SIZE {
            return Err(CryptoError::InvalidKeySize {
                expected: "10",
                actual: key.len(),
            });
        }

        let mut skey = [0u8; 10];
        skey.copy_from_slice(&key[..10]);

        Ok(Skipjack { key: skey })
    }

    fn g_func(w: u16, kp: &mut usize, key: &[u8]) -> u16 {
        let mut g1 = (w >> 8) as u8;
        let mut g2 = (w & 0xff) as u8;

        g1 ^= SBOX[(g2 ^ key[*kp]) as usize];
        *kp = KEYSTEP[*kp];
        g2 ^= SBOX[(g1 ^ key[*kp]) as usize];
        *kp = KEYSTEP[*kp];
        g1 ^= SBOX[(g2 ^ key[*kp]) as usize];
        *kp = KEYSTEP[*kp];
        g2 ^= SBOX[(g1 ^ key[*kp]) as usize];
        *kp = KEYSTEP[*kp];

        ((g1 as u16) << 8) | (g2 as u16)
    }

    fn ig_func(w: u16, kp: &mut usize, key: &[u8]) -> u16 {
        let mut g1 = (w >> 8) as u8;
        let mut g2 = (w & 0xff) as u8;

        *kp = IKEYSTEP[*kp];
        g2 ^= SBOX[(g1 ^ key[*kp]) as usize];
        *kp = IKEYSTEP[*kp];
        g1 ^= SBOX[(g2 ^ key[*kp]) as usize];
        *kp = IKEYSTEP[*kp];
        g2 ^= SBOX[(g1 ^ key[*kp]) as usize];
        *kp = IKEYSTEP[*kp];
        g1 ^= SBOX[(g2 ^ key[*kp]) as usize];

        ((g1 as u16) << 8) | (g2 as u16)
    }

    fn encrypt_block(&self, inout: &mut [u8]) {
        let mut buf = &*inout;
        let mut w1 = buf.get_u16();
        let mut w2 = buf.get_u16();
        let mut w3 = buf.get_u16();
        let mut w4 = buf.get_u16();

        let mut kp = 0;

        for x in 1..9 {
            let tmp = Self::g_func(w1, &mut kp, &self.key);
            w1 = tmp ^ w4 ^ x;
            w4 = w3;
            w3 = w2;
            w2 = tmp;
        }

        for x in 9..17 {
            let tmp = Self::g_func(w1, &mut kp, &self.key);
            let tmp1 = w4;
            w4 = w3;
            w3 = w1 ^ w2 ^ x;
            w1 = tmp1;
            w2 = tmp;
        }

        for x in 17..25 {
            let tmp = Self::g_func(w1, &mut kp, &self.key);
            w1 = tmp ^ w4 ^ x;
            w4 = w3;
            w3 = w2;
            w2 = tmp;
        }

        for x in 25..33 {
            let tmp = Self::g_func(w1, &mut kp, &self.key);
            let tmp1 = w4;
            w4 = w3;
            w3 = w1 ^ w2 ^ x;
            w1 = tmp1;
            w2 = tmp;
        }

        let mut buf = inout;
        buf.put_u16(w1);
        buf.put_u16(w2);
        buf.put_u16(w3);
        buf.put_u16(w4);
    }

    fn decrypt_block(&self, inout: &mut [u8]) {
        let mut buf = &*inout;
        let mut w1 = buf.get_u16();
        let mut w2 = buf.get_u16();
        let mut w3 = buf.get_u16();
        let mut w4 = buf.get_u16();

        let mut kp = 8;

        for x in (25..33).rev() {
            let tmp = Self::ig_func(w2, &mut kp, &self.key);
            w2 = tmp ^ w3 ^ x;
            w3 = w4;
            w4 = w1;
            w1 = tmp;
        }

        for x in (17..25).rev() {
            let tmp = w1 ^ w2 ^ x;
            w1 = Self::ig_func(w2, &mut kp, &self.key);
            w2 = w3;
            w3 = w4;
            w4 = tmp;
        }

        for x in (9..17).rev() {
            let tmp = Self::ig_func(w2, &mut kp, &self.key);
            w2 = tmp ^ w3 ^ x;
            w3 = w4;
            w4 = w1;
            w1 = tmp;
        }

        for x in (1..9).rev() {
            let tmp = w1 ^ w2 ^ x;
            w1 = Self::ig_func(w2, &mut kp, &self.key);
            w2 = w3;
            w3 = w4;
            w4 = tmp;
        }

        let mut buf = inout;
        buf.put_u16(w1);
        buf.put_u16(w2);
        buf.put_u16(w3);
        buf.put_u16(w4);
    }
}

impl BlockCipher for Skipjack {
    fn block_size(&self) -> usize {
        SKIPJACK_BLOCK_SIZE
    }

    fn encrypt_block(&self, inout: &mut [u8]) {
        self.encrypt_block(inout);
    }

    fn decrypt_block(&self, inout: &mut [u8]) {
        self.decrypt_block(inout);
    }
}
