//   Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
//
// 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.

#include "cached_gaussian_sampling.h"

namespace DeepES{

CachedGaussianSampling::CachedGaussianSampling() {}

CachedGaussianSampling::~CachedGaussianSampling() {
  delete[] _noise_cache;
}

bool CachedGaussianSampling::load_config(const DeepESConfig& config) {
  bool success = true;
  _std = config.gaussian_sampling().std();
  success = set_seed(config.seed());
  CHECK(success) << "[DeepES] Fail to set seed while load config.";
  _cache_size = config.gaussian_sampling().cache_size();
  _noise_cache = new float [_cache_size];
  memset(_noise_cache, 0, _cache_size * sizeof(float));
  success = _create_noise_cache();
  CHECK(success) << "[DeepES] Fail to create noise_cache while load config.";
  return success;
}

bool CachedGaussianSampling::sampling(int* key, float* noise, int64_t size) {
  bool success = true;
  if (_noise_cache == nullptr) {
    LOG(ERROR) << "[DeepES] Please use load_config() first.";
    success = false;
    return success;
  }
  if (noise == nullptr) {
    LOG(ERROR) << "[DeepES] Input noise array cannot be nullptr.";
    success = false;
    return success;
  }
  if ((size >= _cache_size) || (size < 0)) {
    LOG(ERROR) << "[DeepES] Input size " << size << " is out of bounds [0, " << _cache_size << "), cache_size: " << _cache_size;
    success = false;
    return success;
  }
  int rand_key = rand();
  std::default_random_engine generator(rand_key);
  std::uniform_int_distribution<unsigned int> uniform(0, _cache_size - size);
  int index = uniform(generator);
  *key = index;
  for (int64_t i = 0; i < size; ++i) {
    *(noise + i) = *(_noise_cache + index + i);
  }
  return success;
}

bool CachedGaussianSampling::resampling(int key, float* noise, int64_t size) {
  bool success = true;
  if (_noise_cache == nullptr) {
    LOG(ERROR) << "[DeepES] Please use load_config() first.";
    success = false;
    return success;
  }
  if (noise == nullptr) {
    LOG(ERROR) << "[DeepES] Input noise array cannot be nullptr.";
    success = false;
    return success;
  }
  if ((size >= _cache_size) || (size < 0)) {
    LOG(ERROR) << "[DeepES] Input size " << size << " is out of bounds [0, " << _cache_size << "), cache_size: " << _cache_size;
    success = false;
    return success;
  }
  if ((key > _cache_size - size) || (key < 0)) {
    LOG(ERROR) << "[DeepES] Resampling key " << key << " is out of bounds [0, " << _cache_size - size << "], cache_size: " << _cache_size << ", size: " << size;
    success = false;
    return success;
  }
  for (int64_t i = 0; i < size; ++i) {
    *(noise + i) = *(_noise_cache + key + i);
  }
  return success;
}

bool CachedGaussianSampling::_create_noise_cache() {
  std::default_random_engine generator(_seed);
  std::normal_distribution<float> norm;
  for (int64_t i = 0; i < _cache_size; ++i) {
    *(_noise_cache + i) = norm(generator) * _std;
  }
  return true;
}

}