#include "libmin.h"

#define BLK_SIZE 16
#define ROUNDS 10

uint8_t sbox[256] = {
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b,
    0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
    0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26,
    0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2,
    0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
    0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed,
    0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f,
    0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
    0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec,
    0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14,
    0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
    0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d,
    0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f,
    0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
    0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11,
    0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f,
    0xb0, 0x54, 0xbb, 0x16,
};

uint8_t inv_sbox[256] = {
    0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38, 0xBF, 0x40, 0xA3, 0x9E,
    0x81, 0xF3, 0xD7, 0xFB, 0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87,
    0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB, 0x54, 0x7B, 0x94, 0x32,
    0xA6, 0xC2, 0x23, 0x3D, 0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,
    0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2, 0x76, 0x5B, 0xA2, 0x49,
    0x6D, 0x8B, 0xD1, 0x25, 0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16,
    0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92, 0x6C, 0x70, 0x48, 0x50,
    0xFD, 0xED, 0xB9, 0xDA, 0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,
    0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A, 0xF7, 0xE4, 0x58, 0x05,
    0xB8, 0xB3, 0x45, 0x06, 0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02,
    0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B, 0x3A, 0x91, 0x11, 0x41,
    0x4F, 0x67, 0xDC, 0xEA, 0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,
    0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85, 0xE2, 0xF9, 0x37, 0xE8,
    0x1C, 0x75, 0xDF, 0x6E, 0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89,
    0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B, 0xFC, 0x56, 0x3E, 0x4B,
    0xC6, 0xD2, 0x79, 0x20, 0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,
    0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31, 0xB1, 0x12, 0x10, 0x59,
    0x27, 0x80, 0xEC, 0x5F, 0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D,
    0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF, 0xA0, 0xE0, 0x3B, 0x4D,
    0xAE, 0x2A, 0xF5, 0xB0, 0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 0xE1, 0x69, 0x14, 0x63,
    0x55, 0x21, 0x0C, 0x7D};

void add_round_key(uint8_t *s, const uint8_t *round_key) {
  for (int i = 0; i < BLK_SIZE; i++)
    s[i] ^= round_key[i];
}

void sub_bytes(uint8_t *s) {
  for (int i = 0; i < BLK_SIZE; i++)
    s[i] = sbox[s[i]];
}

void inv_sub_bytes(uint8_t *s) {
  for (int i = 0; i < BLK_SIZE; i++)
    s[i] = inv_sbox[s[i]];
}

void shift_rows(uint8_t *s) {
  uint8_t res[BLK_SIZE];
  uint8_t idx[BLK_SIZE] = {0, 5,  10, 15, 4,  9, 14, 3,
                           8, 13, 2,  7,  12, 1, 6,  11};

  for (int i = 0; i < BLK_SIZE; i++)
    res[i] = s[idx[i]];

  for (int i = 0; i < BLK_SIZE; i++)
    s[i] = res[i];
}

void inv_shift_rows(uint8_t *s) {
  uint8_t res[BLK_SIZE];
  uint8_t idx[BLK_SIZE] = {0, 13, 10, 7,  4,  1, 14, 11,
                           8, 5,  2,  15, 12, 9, 6,  3};

  for (int i = 0; i < BLK_SIZE; i++)
    res[i] = s[idx[i]];

  for (int i = 0; i < BLK_SIZE; i++)
    s[i] = res[i];
}

/*
 * Multiply by 0x02 in GF(2^8) using the AES irreducible polynomial.
 * If the high bit is set, reduce the result modulo 0x11B by XORing with 0x1B.
 */
uint8_t gf256_mul2(uint8_t x) { return (x << 1) ^ ((x & 0x80) ? 0x1b : 0x00); }

void mix_columns(uint8_t *s) {
  for (int i = 0; i < 4; i++) {
    int c = i * 4;
    uint8_t a = s[c];
    uint8_t b = s[c + 1];
    uint8_t c1 = s[c + 2];
    uint8_t d = s[c + 3];
    uint8_t r = a ^ b ^ c1 ^ d;

    uint8_t x = a ^ b;
    x = gf256_mul2(x);
    s[c] ^= x ^ r;

    x = b ^ c1;
    x = gf256_mul2(x);
    s[c + 1] ^= x ^ r;

    x = c1 ^ d;
    x = gf256_mul2(x);
    s[c + 2] ^= x ^ r;

    x = d ^ a;
    x = gf256_mul2(x);
    s[c + 3] ^= x ^ r;
  }
}

void inv_mix_columns(uint8_t *s) {
  for (int i = 0; i < 4; i++) {
    int c = i * 4;
    uint8_t a = s[c];
    uint8_t b = s[c + 1];
    uint8_t c1 = s[c + 2];
    uint8_t d = s[c + 3];

    uint8_t a1 = gf256_mul2(gf256_mul2(a ^ c1));
    uint8_t b1 = gf256_mul2(gf256_mul2(b ^ d));

    s[c] ^= a1;
    s[c + 1] ^= b1;
    s[c + 2] ^= a1;
    s[c + 3] ^= b1;
  }
  mix_columns(s);
}

// Simple 128-bit key expansion for 10 rounds
void key_expansion(const uint8_t *key, uint8_t *round_keys) {
  static const uint8_t rcon[10] = {0x01, 0x02, 0x04, 0x08, 0x10,
                                   0x20, 0x40, 0x80, 0x1B, 0x36};
  for (int i = 0; i < BLK_SIZE; i++)
    round_keys[i] = key[i];

  for (int i = 1; i <= ROUNDS; i++) {
    uint8_t *prev = &round_keys[BLK_SIZE * (i - 1)];
    uint8_t *curr = &round_keys[BLK_SIZE * i];
    curr[0] = prev[0] ^ sbox[prev[13]] ^ rcon[i - 1];
    curr[1] = prev[1] ^ sbox[prev[14]];
    curr[2] = prev[2] ^ sbox[prev[15]];
    curr[3] = prev[3] ^ sbox[prev[12]];
    for (int j = 4; j < BLK_SIZE; j++)
      curr[j] = curr[j - 4] ^ prev[j];
  }
}

void aes_encrypt(uint8_t *data, const uint8_t *key) {
  uint8_t round_keys[(ROUNDS + 1) * BLK_SIZE];
  key_expansion(key, round_keys);

  add_round_key(data, round_keys);
  for (int round = 1; round < ROUNDS; round++) {
    sub_bytes(data);
    shift_rows(data);
    mix_columns(data);
    add_round_key(data, round_keys + round * BLK_SIZE);
  }
  sub_bytes(data);
  shift_rows(data);
  add_round_key(data, round_keys + ROUNDS * BLK_SIZE);
}

void aes_decrypt(uint8_t *data, const uint8_t *key) {
  uint8_t round_keys[(ROUNDS + 1) * BLK_SIZE];
  key_expansion(key, round_keys);

  add_round_key(data, round_keys + ROUNDS * BLK_SIZE);
  for (int round = 9; round > 0; round--) {
    inv_shift_rows(data);
    inv_sub_bytes(data);
    add_round_key(data, round_keys + round * BLK_SIZE);
    inv_mix_columns(data);
  }
  inv_shift_rows(data);
  inv_sub_bytes(data);
  add_round_key(data, round_keys + 0 * BLK_SIZE);
}

int main(void) {
  uint8_t key[16] = {0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6,
                     0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c};

  char *plaintext = "This is a test!!";
  if (libmin_strlen(plaintext) != BLK_SIZE) {
    libmin_fail(1);
  }

  uint8_t ciphertext[BLK_SIZE];
  uint8_t decrypted[BLK_SIZE];

  libmin_memcpy(ciphertext, plaintext, BLK_SIZE);
  aes_encrypt(ciphertext, key);

  uint8_t ref_ciphertext[BLK_SIZE] = {0xf8, 0x6e, 0x9e, 0x4e, 0x8d, 0x38,
                                      0x05, 0xe9, 0x72, 0x9f, 0xf1, 0x55,
                                      0xe5, 0x17, 0xbd, 0x65};

  for (int i = 0; i < BLK_SIZE; i++) {
    if (ref_ciphertext[i] != ciphertext[i]) {
      libmin_printf("Ciphertext mismatch at byte %d\n", i);
      libmin_printf("Expected: %02x, Got: %02x\n", ref_ciphertext[i],
                    ciphertext[i]);
      libmin_fail(2);
    }
  }

  libmin_memcpy(decrypted, ciphertext, BLK_SIZE);
  aes_decrypt(decrypted, key);

  libmin_printf("AES Cipher results:\n");
  libmin_printf("  plaintext:  %s\n", plaintext);
  libmin_printf("  ciphertext: ");
  for (int i = 0; i < BLK_SIZE; i++) {
    libmin_printf("%02x ", ciphertext[i]);
  }

  libmin_printf("\n");

  libmin_printf("  decrypted:  ");
  for (int i = 0; i < BLK_SIZE; i++) {
    libmin_printf("%c", decrypted[i]);
  }
  libmin_printf("\n");

  for (int i = 0; i < BLK_SIZE; i++) {
    if (decrypted[i] != plaintext[i]) {
      libmin_fail(3);
    }
  }

  libmin_success();
  return 0;
}

