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// GM/T 0002-2012 SM4分组密码算法标准（中文版本）
// https://github.com/guanzhi/GM-Standards/blob/master/GMT%E6%AD%A3%E5%BC%8F%E6%A0%87%E5%87%86/GMT%200002-2012%20SM4%E5%88%86%E7%BB%84%E5%AF%86%E7%A0%81%E7%AE%97%E6%B3%95.pdf
// 
// GM/T 0002-2012 SM4 Block Cipher Algorithm （English Version）
// http://www.gmbz.org.cn/upload/2018-04-04/1522788048733065051.pdf
// http://sca.hainan.gov.cn/xxgk/bzhgf/201804/W020180409400793061524.pdf
// 
// The SM4 Blockcipher Algorithm And Its Modes Of Operations
//            draft-ribose-cfrg-sm4-10
// 
// https://tools.ietf.org/html/draft-ribose-cfrg-sm4-10
use crate::mem::Zeroize;


const FK: [u32; 4]  = [ 0xa3b1_bac6, 0x56aa_3350, 0x677d_9197, 0xb270_22dc ];
const CK: [u32; 32] = [
    0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269, 0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
    0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249, 0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
    0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229, 0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
    0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209, 0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279,
];
const SBOX: [u8; 256] = [
    0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
    0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
    0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
    0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
    0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
    0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
    0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
    0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
    0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
    0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
    0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
    0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
    0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
    0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
    0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
    0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48,
];

macro_rules! SM4_T {
    ($x:expr) => {
        {
            let t = sub_bytes($x);
            t ^ t.rotate_left(2) ^ t.rotate_left(10) ^ t.rotate_left(18) ^ t.rotate_left(24)
        }
    }
}

macro_rules! SM4_ROUNDS_ENC {
    ($i:expr, $rk:expr, $x:expr) => {
        $x[0] ^= SM4_T!($x[1] ^ $x[2] ^ $x[3] ^ $rk[$i][0]);
        $x[1] ^= SM4_T!($x[0] ^ $x[2] ^ $x[3] ^ $rk[$i][1]);
        $x[2] ^= SM4_T!($x[0] ^ $x[1] ^ $x[3] ^ $rk[$i][2]);
        $x[3] ^= SM4_T!($x[0] ^ $x[1] ^ $x[2] ^ $rk[$i][3]);
    }
}

macro_rules! SM4_ROUNDS_DEC {
    ($i:expr, $rk:expr, $x:expr) => {
        $x[0] ^= SM4_T!($x[1] ^ $x[2] ^ $x[3] ^ $rk[$i][3]);
        $x[1] ^= SM4_T!($x[0] ^ $x[2] ^ $x[3] ^ $rk[$i][2]);
        $x[2] ^= SM4_T!($x[0] ^ $x[1] ^ $x[3] ^ $rk[$i][1]);
        $x[3] ^= SM4_T!($x[0] ^ $x[1] ^ $x[2] ^ $rk[$i][0]);
    }
}

#[inline]
fn sub_bytes(input: u32) -> u32 {
    let mut octets = input.to_be_bytes();
    octets[0] = SBOX[octets[0] as usize];
    octets[1] = SBOX[octets[1] as usize];
    octets[2] = SBOX[octets[2] as usize];
    octets[3] = SBOX[octets[3] as usize];
    u32::from_be_bytes(octets)
}


/// GM/T 0002-2012 SM4分组密码算法
#[derive(Clone)]
pub struct Sm4 {
    pub(crate) rk: [[u32; 4]; Self::NR],
}

impl Zeroize for Sm4 {
    fn zeroize(&mut self) {
        self.rk.zeroize();
    }
}

impl Drop for Sm4 {
    fn drop(&mut self) {
        self.zeroize();
    }
}

impl core::fmt::Debug for Sm4 {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.debug_struct("Sm4").finish()
    }
}

impl Sm4 {
    pub const KEY_LEN: usize   = 16;
    pub const BLOCK_LEN: usize = 16;
    
    pub const NR: usize = 8; // Rounds
    
    
    pub fn new(key: &[u8]) -> Self {
        assert_eq!(key.len(), Self::KEY_LEN);

        let mut k: [u32; 4] = [
            u32::from_be_bytes([key[ 0], key[ 1], key[ 2], key[ 3]]) ^ FK[0],
            u32::from_be_bytes([key[ 4], key[ 5], key[ 6], key[ 7]]) ^ FK[1],
            u32::from_be_bytes([key[ 8], key[ 9], key[10], key[11]]) ^ FK[2],
            u32::from_be_bytes([key[12], key[13], key[14], key[15]]) ^ FK[3],
        ];

        let mut rk = [[0u32; 4]; Self::NR];
        for i in 0..Self::NR {
            // Linear operation L'
            let t1 = sub_bytes(k[1] ^ k[2] ^ k[3] ^ CK[i * 4 + 0]);
            k[0] ^= t1 ^ t1.rotate_left(13) ^ t1.rotate_left(23);

            let t2 = sub_bytes(k[2] ^ k[3] ^ k[0] ^ CK[i * 4 + 1]);
            k[1] ^= t2 ^ t2.rotate_left(13) ^ t2.rotate_left(23);

            let t3 = sub_bytes(k[3] ^ k[0] ^ k[1] ^ CK[i * 4 + 2]);
            k[2] ^= t3 ^ t3.rotate_left(13) ^ t3.rotate_left(23);

            let t4 = sub_bytes(k[0] ^ k[1] ^ k[2] ^ CK[i * 4 + 3]);
            k[3] ^= t4 ^ t4.rotate_left(13) ^ t4.rotate_left(23);

            rk[i] = k;
        }

        Self { rk }
    }

    pub fn encrypt(&self, block: &mut [u8]) {
        debug_assert_eq!(block.len(), Self::BLOCK_LEN);

        let mut x: [u32; 4] = [
            u32::from_be_bytes([block[ 0], block[ 1], block[ 2], block[ 3]]),
            u32::from_be_bytes([block[ 4], block[ 5], block[ 6], block[ 7]]),
            u32::from_be_bytes([block[ 8], block[ 9], block[10], block[11]]),
            u32::from_be_bytes([block[12], block[13], block[14], block[15]]),
        ];

        SM4_ROUNDS_ENC!(0, self.rk, x);
        SM4_ROUNDS_ENC!(1, self.rk, x);
        SM4_ROUNDS_ENC!(2, self.rk, x);
        SM4_ROUNDS_ENC!(3, self.rk, x);
        SM4_ROUNDS_ENC!(4, self.rk, x);
        SM4_ROUNDS_ENC!(5, self.rk, x);
        SM4_ROUNDS_ENC!(6, self.rk, x);
        SM4_ROUNDS_ENC!(7, self.rk, x);

        block[ 0.. 4].copy_from_slice(&x[3].to_be_bytes());
        block[ 4.. 8].copy_from_slice(&x[2].to_be_bytes());
        block[ 8..12].copy_from_slice(&x[1].to_be_bytes());
        block[12..16].copy_from_slice(&x[0].to_be_bytes());
    }

    pub fn decrypt(&self, block: &mut [u8]) {
        debug_assert_eq!(block.len(), Self::BLOCK_LEN);

        let mut x: [u32; 4] = [
            u32::from_be_bytes([block[ 0], block[ 1], block[ 2], block[ 3]]),
            u32::from_be_bytes([block[ 4], block[ 5], block[ 6], block[ 7]]),
            u32::from_be_bytes([block[ 8], block[ 9], block[10], block[11]]),
            u32::from_be_bytes([block[12], block[13], block[14], block[15]]),
        ];

        SM4_ROUNDS_DEC!(7, self.rk, x);
        SM4_ROUNDS_DEC!(6, self.rk, x);
        SM4_ROUNDS_DEC!(5, self.rk, x);
        SM4_ROUNDS_DEC!(4, self.rk, x);
        SM4_ROUNDS_DEC!(3, self.rk, x);
        SM4_ROUNDS_DEC!(2, self.rk, x);
        SM4_ROUNDS_DEC!(1, self.rk, x);
        SM4_ROUNDS_DEC!(0, self.rk, x);

        block[ 0.. 4].copy_from_slice(&x[3].to_be_bytes());
        block[ 4.. 8].copy_from_slice(&x[2].to_be_bytes());
        block[ 8..12].copy_from_slice(&x[1].to_be_bytes());
        block[12..16].copy_from_slice(&x[0].to_be_bytes());
    }
}