// Copyright 2018 Google Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#ifndef FAKE_RANDOM_H_

#define FAKE_RANDOM_H_

#include <sodium.h>

#include <assert.h>

#include <stdint.h>

#include <string.h>

#include <algorithm>

static const unsigned char * SEED_DATA;

static size_t SEED_SIZE;

static const char *

fake_implementation_name(void) {

  return "fake_random";

}

static void

fake_random_buffer(void * const buf, const size_t size) {

  static unsigned char seed[randombytes_SEEDBYTES];

  memset(seed, '0', randombytes_SEEDBYTES);

  size_t boundary = std::min((size_t) randombytes_SEEDBYTES, SEED_SIZE);

  memcpy(&seed, SEED_DATA, boundary);

  randombytes_buf_deterministic(buf, size, seed);

}

struct randombytes_implementation fake_random = {

  .implementation_name = fake_implementation_name,

  .random = NULL,

  .stir = NULL,

  .uniform = NULL,

  .buf = fake_random_buffer,

  .close = NULL

};

void

setup_fake_random(const unsigned char * seed, const size_t seed_size) {

  SEED_DATA = seed;

  SEED_SIZE = seed_size;

  int fake_random_set = randombytes_set_implementation(&fake_random);

  assert(fake_random_set == 0);

  assert(strcmp(randombytes_implementation_name(), "fake_random") == 0);

  int initialized = sodium_init();

  assert(initialized >= 0);

}

#endif // FAKE_RANDOM_H_