#include <string.h>
#include <openssl/evp.h>

#include "gost_lcl.h"
#include "e_gost_err.h"

/*
 * Function expects that out is a preallocated buffer of length
 * defined as sum of shared_len and mac length defined by mac_nid
 * */
int gost_kexp15(const unsigned char *shared_key, const int shared_len,
    int cipher_nid, const unsigned char *cipher_key, const size_t cipher_key_len,
    int mac_nid, unsigned char *mac_key, const size_t mac_key_len,
    const char *iv, const size_t ivlen,
    unsigned char *out, int *out_len
)
{
  /* out_len = key_len + mac_len */
  unsigned char iv_full[16], mac_buf[8];
  unsigned int mac_len;

  EVP_CIPHER_CTX *ciph = NULL;
  EVP_MD_CTX *mac = NULL;

  int ret = 0;
  int len;

  /* we expect IV of half length */
  memset(iv_full, 0, 16);
  memcpy(iv_full, iv, ivlen);

  mac = EVP_MD_CTX_new();
  if (mac == NULL) {
    GOSTerr(GOST_F_GOST_KEXP15, ERR_R_MALLOC_FAILURE);
    goto err;
  }

  if(EVP_DigestInit_ex(mac, EVP_get_digestbynid(mac_nid), NULL) <= 0
  || EVP_MD_CTX_ctrl(mac, EVP_MD_CTRL_SET_KEY, mac_key_len, mac_key) <= 0
  || EVP_DigestUpdate(mac, shared_key, shared_len) <= 0
  || EVP_DigestFinal_ex(mac, mac_buf, &mac_len) <= 0) {
    GOSTerr(GOST_F_GOST_KEXP15, ERR_R_INTERNAL_ERROR);
    goto err;
  }

  ciph = EVP_CIPHER_CTX_new();
  if (ciph == NULL) {
    GOSTerr(GOST_F_GOST_KEXP15, ERR_R_MALLOC_FAILURE);
    goto err;
  }

  if (EVP_CipherInit_ex(ciph, EVP_get_cipherbynid(cipher_nid), NULL, NULL, NULL, 1) <= 0
  || EVP_CipherInit_ex(ciph, NULL, NULL, cipher_key, iv_full, 1) <= 0
  || EVP_CipherUpdate(ciph, out, &len, shared_key, shared_len) <= 0
  || EVP_CipherUpdate(ciph, out + shared_len, &len, mac_buf, mac_len) <= 0
  || EVP_CipherFinal_ex(ciph, out + shared_len + len, out_len) <= 0) {
    GOSTerr(GOST_F_GOST_KEXP15, ERR_R_INTERNAL_ERROR);
    goto err;
  }

  *out_len = shared_len + mac_len;

  ret = 1;

 err:
  /* TODO clear mac_buf */
  EVP_MD_CTX_free(mac);
  EVP_CIPHER_CTX_free(ciph);

  return ret;
}

int gost_kimp15(const char *expkey, const size_t expkeylen,
    int cipher_nid, const char *cipher_key, const size_t cipher_key_len,
    int mac_nid, const char *mac_key, const size_t mac_key_len,
    const char *iv, const size_t ivlen,
    char *shared_key, size_t *shared_len
)
{
  return 0;
}

/*
 * keyout expected to be 64 bytes
 * */
int gost_keg(const unsigned char *seckey, const size_t seckey_len,
    const EC_POINT *pub, const unsigned char *h,
    unsigned char *keyout)
{
    return 0;
}

#ifdef ENABLE_UNIT_TESTS
# include <stdio.h>
# include <string.h>
# include <openssl/obj_mac.h>

static void hexdump(FILE *f, const char *title, const unsigned char *s, int l)
{
    int n = 0;

    fprintf(f, "%s", title);
    for (; n < l; ++n) {
        if ((n % 16) == 0)
            fprintf(f, "\n%04x", n);
        fprintf(f, " %02x", s[n]);
    }
    fprintf(f, "\n");
}

int main(void)
{
    const unsigned char key[] = {
        0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF,
        0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
        0xFE, 0xDC, 0xBA, 0x98, 0x76, 0x54, 0x32, 0x10,
        0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF
    };

    const unsigned char magma_key[] = {
0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
    };

    unsigned char mac_key[] = {
0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F,
    };

		const unsigned char iv[] = {0x67, 0xBE, 0xD6, 0x54};

    unsigned char buf[32+8];
    int ret;
    int outlen = 40;

    ret = gost_kexp15(key, 32,
    NID_magma_ctr, magma_key, 32,
    NID_magma_mac, mac_key, 32,
    iv, 4,
    buf, &outlen);

  return 0;
}

#endif