#include "sm4_core.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static void rk_crypto_cbc128_encrypt(void *ctx, const unsigned char *in,
                                     unsigned char *out, unsigned int len,
                                     unsigned char *ivec, block128_f block) {
  unsigned int n;
  const unsigned char *iv = ivec;

  while (len) {
    for (n = 0; n < SM4_BLOCK_SIZE && n < len; ++n)
      out[n] = in[n] ^ iv[n];
    for (; n < SM4_BLOCK_SIZE; ++n)
      out[n] = iv[n];
    (*block)((const unsigned char *)out, out, ctx);
    iv = out;
    if (len <= SM4_BLOCK_SIZE)
      break;
    len -= SM4_BLOCK_SIZE;
    in += SM4_BLOCK_SIZE;
    out += SM4_BLOCK_SIZE;
  }
  memcpy(ivec, iv, SM4_BLOCK_SIZE);
}

static void rk_crypto_cbc128_decrypt(void *ctx, const unsigned char *in,
                                     unsigned char *out, unsigned int len,
                                     unsigned char *ivec, block128_f block) {
  unsigned int n;
  unsigned char c;
  unsigned char tmp_buf[SM4_BLOCK_SIZE];

  memset(tmp_buf, 0x00, sizeof(tmp_buf));

  while (len) {
    (*block)(in, tmp_buf, ctx);
    for (n = 0; n < SM4_BLOCK_SIZE && n < len; ++n) {
      c = in[n];
      out[n] = tmp_buf[n] ^ ivec[n];
      ivec[n] = c;
    }
    if (len <= SM4_BLOCK_SIZE) {
      for (; n < SM4_BLOCK_SIZE; ++n)
        ivec[n] = in[n];
      break;
    }
    len -= SM4_BLOCK_SIZE;
    in += SM4_BLOCK_SIZE;
    out += SM4_BLOCK_SIZE;
  }
}

static int rk_crypto_cts_encrypt(void *ctx, const unsigned char *in,
                                 unsigned char *out, unsigned int length,
                                 unsigned char *ivec, const int enc,
                                 block128_f block) {
  int k = 0, r = 0;

  r = length % SM4_BLOCK_SIZE;
  if (r) {
    k = length - r - SM4_BLOCK_SIZE;
  } else {
    k = length;
  }

  if (enc) {
    unsigned char peniv[SM4_BLOCK_SIZE] = {0};
    memset(peniv, 0x00, sizeof(peniv));

    rk_crypto_cbc128_encrypt(ctx, in, out, k, ivec, block);

    if (r) {
      memcpy(peniv, in + k + SM4_BLOCK_SIZE, r);

      rk_crypto_cbc128_encrypt(ctx, in + k, out + k, SM4_BLOCK_SIZE, ivec,
                               block);
      memcpy(out + length - r, out + k, r);
      rk_crypto_cbc128_encrypt(ctx, peniv, out + k, SM4_BLOCK_SIZE, ivec,
                               block);
    } else {
      // swap last two block
      memcpy(peniv, out + length - SM4_BLOCK_SIZE, SM4_BLOCK_SIZE);
      memcpy(out + length - SM4_BLOCK_SIZE, out + length - 2 * SM4_BLOCK_SIZE,
             SM4_BLOCK_SIZE);
      memcpy(out + length - 2 * SM4_BLOCK_SIZE, peniv, SM4_BLOCK_SIZE);
    }
  } else {
    unsigned int i;
    unsigned char *pout_tmp = NULL;
    unsigned char tmp1[SM4_BLOCK_SIZE], tmp2[SM4_BLOCK_SIZE];

    memset(tmp1, 0x00, sizeof(tmp1));
    memset(tmp2, 0x00, sizeof(tmp2));

    if (r == 0) {
      rk_crypto_cbc128_decrypt(ctx, in, out, k - 2 * SM4_BLOCK_SIZE, ivec,
                               block);

      // swap last two block
      rk_crypto_cbc128_decrypt(ctx, in + length - SM4_BLOCK_SIZE,
                               out + length - 2 * SM4_BLOCK_SIZE,
                               SM4_BLOCK_SIZE, ivec, block);
      rk_crypto_cbc128_decrypt(ctx, in + length - 2 * SM4_BLOCK_SIZE,
                               out + length - SM4_BLOCK_SIZE, SM4_BLOCK_SIZE,
                               ivec, block);
    } else {
      rk_crypto_cbc128_decrypt(ctx, in, out, k, ivec, block);
      (*block)(in + k, tmp1, ctx);

      memcpy(tmp2, in + k + SM4_BLOCK_SIZE, r);
      memcpy(tmp2 + r, tmp1 + r, SM4_BLOCK_SIZE - r);

      // get last one plain text
      pout_tmp = out + k + SM4_BLOCK_SIZE;
      for (i = 0; i < SM4_BLOCK_SIZE; i++, pout_tmp++)
        *pout_tmp = tmp1[i] ^ tmp2[i];

      (*block)(tmp2, tmp2, ctx);

      // get sencond to last plain text
      pout_tmp = out + k;
      for (i = 0; i < SM4_BLOCK_SIZE; i++, pout_tmp++)
        *pout_tmp = tmp2[i] ^ ivec[i];
    }
  }

  return 0;
}

int rk_sm4_cts_encrypt(const unsigned char *in, unsigned char *out,
                       unsigned long length, const unsigned char *key,
                       const int key_len, unsigned char *ivec, const int enc) {
  sm4_context ctx;

  if (in == NULL || out == NULL || key == NULL)
    return -1;

  if (key_len != 16)
    return -2;

  if (length <= SM4_BLOCK_SIZE)
    return -3;

  if (enc) {
    rk_sm4_setkey_enc(&ctx, key);
  } else {
    rk_sm4_setkey_dec(&ctx, key);
  }

  rk_crypto_cts_encrypt((void *)(&ctx), in, out, length, ivec, enc,
                        rk_rk_sm4_crypt_ecb);

  return 0;
}