#include <stdint.h>

#include <openssl/type_check.h>

#include "params.h"
#include "poly.h"
#include "ntt.h"
#include "reduce.h"
#include "cbd.h"
#include "symmetric.h"

#include "../../../internal.h"

/*************************************************
* Name:        poly_compress
*
* Description: Compression and subsequent serialization of a polynomial
*
* Arguments:   - uint8_t *r: pointer to output byte array
*                            (of length KYBER_POLYCOMPRESSEDBYTES)
*              - const poly *a: pointer to input polynomial
**************************************************/
void poly_compress(ml_kem_params *params, uint8_t *r, const poly *a)
{
  unsigned int i,j;
  int32_t u;
  uint32_t d0;
  uint8_t t[8];

  assert((params->poly_compressed_bytes == 128) ||
         (params->poly_compressed_bytes == 160));

  if (params->poly_compressed_bytes == 128) {
    for(i=0;i<KYBER_N/8;i++) {
      for(j=0;j<8;j++) {
        // map to positive standard representatives
        u  = a->coeffs[8*i+j];
        u += (u >> 15) & KYBER_Q;
        // t[j] = ((((uint16_t)u << 4) + KYBER_Q/2)/KYBER_Q) & 15;
        d0 = u << 4;
        d0 += 1665;
        d0 *= 80635;
        d0 >>= 28;
        t[j] = d0 & 0xf;
      }
  
      r[0] = t[0] | (t[1] << 4);
      r[1] = t[2] | (t[3] << 4);
      r[2] = t[4] | (t[5] << 4);
      r[3] = t[6] | (t[7] << 4);
      r += 4;
    }
  } else {
    for(i=0;i<KYBER_N/8;i++) {
      for(j=0;j<8;j++) {
        // map to positive standard representatives
        u  = a->coeffs[8*i+j];
        u += (u >> 15) & KYBER_Q;
        // t[j] = ((((uint32_t)u << 5) + KYBER_Q/2)/KYBER_Q) & 31;
        d0 = u << 5;
        d0 += 1664;
        d0 *= 40318;
        d0 >>= 27;
        t[j] = d0 & 0x1f;
      }
  
      r[0] = (t[0] >> 0) | (t[1] << 5);
      r[1] = (t[1] >> 3) | (t[2] << 2) | (t[3] << 7);
      r[2] = (t[3] >> 1) | (t[4] << 4);
      r[3] = (t[4] >> 4) | (t[5] << 1) | (t[6] << 6);
      r[4] = (t[6] >> 2) | (t[7] << 3);
      r += 5;
    }
  }
}

/*************************************************
* Name:        poly_decompress
*
* Description: De-serialization and subsequent decompression of a polynomial;
*              approximate inverse of poly_compress
*
* Arguments:   - poly *r: pointer to output polynomial
*              - const uint8_t *a: pointer to input byte array
*                                  (of length KYBER_POLYCOMPRESSEDBYTES bytes)
**************************************************/
void poly_decompress(ml_kem_params *params, poly *r, const uint8_t *a)
{
  unsigned int i;

  assert((params->poly_compressed_bytes == 128) ||
         (params->poly_compressed_bytes == 160));

  if (params->poly_compressed_bytes == 128) {
    for(i=0;i<KYBER_N/2;i++) {
      r->coeffs[2*i+0] = (((uint16_t)(a[0] & 15)*KYBER_Q) + 8) >> 4;
      r->coeffs[2*i+1] = (((uint16_t)(a[0] >> 4)*KYBER_Q) + 8) >> 4;
      a += 1;
    }
  } else {
    unsigned int j;
    uint8_t t[8];
    for(i=0;i<KYBER_N/8;i++) {
      t[0] = (a[0] >> 0);
      t[1] = (a[0] >> 5) | (a[1] << 3);
      t[2] = (a[1] >> 2);
      t[3] = (a[1] >> 7) | (a[2] << 1);
      t[4] = (a[2] >> 4) | (a[3] << 4);
      t[5] = (a[3] >> 1);
      t[6] = (a[3] >> 6) | (a[4] << 2);
      t[7] = (a[4] >> 3);
      a += 5;

      for(j=0;j<8;j++)
        r->coeffs[8*i+j] = ((uint32_t)(t[j] & 31)*KYBER_Q + 16) >> 5;
    }
  }
}

/*************************************************
* Name:        poly_tobytes
*
* Description: Serialization of a polynomial
*
* Arguments:   - uint8_t *r: pointer to output byte array
*                            (needs space for KYBER_POLYBYTES bytes)
*              - const poly *a: pointer to input polynomial
**************************************************/
void poly_tobytes(uint8_t r[KYBER_POLYBYTES], const poly *a)
{
  unsigned int i;
  uint16_t t0, t1;

  for(i=0;i<KYBER_N/2;i++) {
    // map to positive standard representatives
    t0  = a->coeffs[2*i];
    t0 += ((int16_t)t0 >> 15) & KYBER_Q;
    t1 = a->coeffs[2*i+1];
    t1 += ((int16_t)t1 >> 15) & KYBER_Q;
    r[3*i+0] = (t0 >> 0);
    r[3*i+1] = (t0 >> 8) | (t1 << 4);
    r[3*i+2] = (t1 >> 4);
  }
}

/*************************************************
* Name:        poly_frombytes
*
* Description: De-serialization of a polynomial;
*              inverse of poly_tobytes
*
* Arguments:   - poly *r: pointer to output polynomial
*              - const uint8_t *a: pointer to input byte array
*                                  (of KYBER_POLYBYTES bytes)
**************************************************/
void poly_frombytes(poly *r, const uint8_t a[KYBER_POLYBYTES])
{
  unsigned int i;
  for(i=0;i<KYBER_N/2;i++) {
    r->coeffs[2*i]   = ((a[3*i+0] >> 0) | ((uint16_t)a[3*i+1] << 8)) & 0xFFF;
    r->coeffs[2*i+1] = ((a[3*i+1] >> 4) | ((uint16_t)a[3*i+2] << 4)) & 0xFFF;
  }
}

/*************************************************
* Name:        poly_frommsg
*
* Description: Convert 32-byte message to polynomial
*
* Arguments:   - poly *r: pointer to output polynomial
*              - const uint8_t *msg: pointer to input message
**************************************************/
void poly_frommsg(poly *r, const uint8_t msg[KYBER_INDCPA_MSGBYTES])
{
  unsigned int i,j;
  crypto_word_t mask;

#if (KYBER_INDCPA_MSGBYTES != KYBER_N/8)
#error "KYBER_INDCPA_MSGBYTES must be equal to KYBER_N/8 bytes!"
#endif

  for(i=0;i<KYBER_N/8;i++) {
    for(j=0;j<8;j++) {
      mask = constant_time_is_zero_w((msg[i] >> j) & 1);
      // We cast the result of constant_time_select_w, which is a crypto_word_t,
      // to int16_t. The constants must be within the range of int16_t.
      OPENSSL_STATIC_ASSERT(((KYBER_Q+1)/2) <= INT16_MAX,
                            value_exceeds_int16_max);
      r->coeffs[8*i+j] = (int16_t) constant_time_select_w(mask,
                                                          0, ((KYBER_Q+1)/2));
    }
  }
}

/*************************************************
* Name:        poly_tomsg
*
* Description: Convert polynomial to 32-byte message
*
* Arguments:   - uint8_t *msg: pointer to output message
*              - const poly *a: pointer to input polynomial
**************************************************/
void poly_tomsg(uint8_t msg[KYBER_INDCPA_MSGBYTES], const poly *a)
{
  unsigned int i,j;
  uint32_t t;

  for(i=0;i<KYBER_N/8;i++) {
    msg[i] = 0;
    for(j=0;j<8;j++) {
      t  = a->coeffs[8*i+j];
      // t += ((int16_t)t >> 15) & KYBER_Q;
      // t  = (((t << 1) + KYBER_Q/2)/KYBER_Q) & 1;
      t <<= 1;
      t += 1665;
      t *= 80635;
      t >>= 28;
      t &= 1;
      msg[i] |= t << j;
    }
  }
}

/*************************************************
* Name:        poly_getnoise_eta1
*
* Description: Sample a polynomial deterministically from a seed and a nonce,
*              with output polynomial close to centered binomial distribution
*              with parameter KYBER_ETA1
*
* Arguments:   - poly *r: pointer to output polynomial
*              - const uint8_t *seed: pointer to input seed
*                                     (of length KYBER_SYMBYTES bytes)
*              - uint8_t nonce: one-byte input nonce
**************************************************/
void poly_getnoise_eta1(ml_kem_params *params, poly *r, const uint8_t seed[KYBER_SYMBYTES], uint8_t nonce)
{
  uint8_t buf[KYBER_ETA1_MAX*KYBER_N/4];
  prf(buf, sizeof(buf), seed, nonce);
  poly_cbd_eta1(params, r, buf);
}

/*************************************************
* Name:        poly_getnoise_eta2
*
* Description: Sample a polynomial deterministically from a seed and a nonce,
*              with output polynomial close to centered binomial distribution
*              with parameter KYBER_ETA2
*
* Arguments:   - poly *r: pointer to output polynomial
*              - const uint8_t *seed: pointer to input seed
*                                     (of length KYBER_SYMBYTES bytes)
*              - uint8_t nonce: one-byte input nonce
**************************************************/
void poly_getnoise_eta2(poly *r, const uint8_t seed[KYBER_SYMBYTES], uint8_t nonce)
{
  uint8_t buf[KYBER_ETA2*KYBER_N/4];
  prf(buf, sizeof(buf), seed, nonce);
  poly_cbd_eta2(r, buf);
}


/*************************************************
* Name:        poly_ntt
*
* Description: Computes negacyclic number-theoretic transform (NTT) of
*              a polynomial in place;
*              inputs assumed to be in normal order, output in bitreversed order
*
* Arguments:   - uint16_t *r: pointer to in/output polynomial
**************************************************/
void poly_ntt(poly *r)
{
  ntt(r->coeffs);
  poly_reduce(r);
}

/*************************************************
* Name:        poly_invntt_tomont
*
* Description: Computes inverse of negacyclic number-theoretic transform (NTT)
*              of a polynomial in place;
*              inputs assumed to be in bitreversed order, output in normal order
*
* Arguments:   - uint16_t *a: pointer to in/output polynomial
**************************************************/
void poly_invntt_tomont(poly *r)
{
  invntt(r->coeffs);
}

/*************************************************
* Name:        poly_basemul_montgomery
*
* Description: Multiplication of two polynomials in NTT domain
*
* Arguments:   - poly *r: pointer to output polynomial
*              - const poly *a: pointer to first input polynomial
*              - const poly *b: pointer to second input polynomial
**************************************************/
void poly_basemul_montgomery(poly *r, const poly *a, const poly *b)
{
  unsigned int i;
  for(i=0;i<KYBER_N/4;i++) {
    basemul(&r->coeffs[4*i], &a->coeffs[4*i], &b->coeffs[4*i], zetas[64+i]);
    basemul(&r->coeffs[4*i+2], &a->coeffs[4*i+2], &b->coeffs[4*i+2], -zetas[64+i]);
  }
}

/*************************************************
* Name:        poly_tomont
*
* Description: Inplace conversion of all coefficients of a polynomial
*              from normal domain to Montgomery domain
*
* Arguments:   - poly *r: pointer to input/output polynomial
**************************************************/
void poly_tomont(poly *r)
{
  unsigned int i;
  const int16_t f = (1ULL << 32) % KYBER_Q;
  for(i=0;i<KYBER_N;i++)
    r->coeffs[i] = montgomery_reduce((int32_t)r->coeffs[i]*f);
}

/*************************************************
* Name:        poly_reduce
*
* Description: Applies Barrett reduction to all coefficients of a polynomial
*              for details of the Barrett reduction see comments in reduce.c
*
* Arguments:   - poly *r: pointer to input/output polynomial
**************************************************/
void poly_reduce(poly *r)
{
  unsigned int i;
  for(i=0;i<KYBER_N;i++)
    r->coeffs[i] = barrett_reduce(r->coeffs[i]);
}

/*************************************************
* Name:        poly_add
*
* Description: Add two polynomials; no modular reduction is performed
*
* Arguments: - poly *r: pointer to output polynomial
*            - const poly *a: pointer to first input polynomial
*            - const poly *b: pointer to second input polynomial
**************************************************/
void poly_add(poly *r, const poly *a, const poly *b)
{
  unsigned int i;
  for(i=0;i<KYBER_N;i++)
    r->coeffs[i] = a->coeffs[i] + b->coeffs[i];
}

/*************************************************
* Name:        poly_sub
*
* Description: Subtract two polynomials; no modular reduction is performed
*
* Arguments: - poly *r:       pointer to output polynomial
*            - const poly *a: pointer to first input polynomial
*            - const poly *b: pointer to second input polynomial
**************************************************/
void poly_sub(poly *r, const poly *a, const poly *b)
{
  unsigned int i;
  for(i=0;i<KYBER_N;i++)
    r->coeffs[i] = a->coeffs[i] - b->coeffs[i];
}
