// Copyright 2021 The Tint Authors.
//
// 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 FUZZERS_MERSENNE_TWISTER_ENGINE_H_
#define FUZZERS_MERSENNE_TWISTER_ENGINE_H_

#include <random>

#include "fuzzers/random_generator_engine.h"

namespace tint {
namespace fuzzers {

/// Standard MT based random number generation
class MersenneTwisterEngine : public RandomGeneratorEngine {
 public:
  /// @brief Initializes using provided seed
  /// @param seed - seed value to use
  explicit MersenneTwisterEngine(uint64_t seed);
  ~MersenneTwisterEngine() override = default;

  /// Generate random uint32_t value from uniform distribution.
  /// @param lower - lower bound of integer generated
  /// @param upper - upper bound of integer generated
  /// @returns i, where lower <= i < upper
  uint32_t RandomUInt32(uint32_t lower, uint32_t upper) override;

  /// Get random uint64_t value from uniform distribution.
  /// @param lower - lower bound of integer generated
  /// @param upper - upper bound of integer generated
  /// @returns i, where lower <= i < upper
  uint64_t RandomUInt64(uint64_t lower, uint64_t upper) override;

  /// Get N bytes of pseudo-random data
  /// @param dest - memory location to store data
  /// @param n - number of bytes of data to generate
  void RandomNBytes(uint8_t* dest, size_t n) override;

 private:
  // Disallow copy & assign
  MersenneTwisterEngine(const MersenneTwisterEngine&) = delete;
  MersenneTwisterEngine& operator=(const MersenneTwisterEngine&) = delete;

  std::mt19937_64 engine_;

};  // class MersenneTwisterEngine

}  // namespace fuzzers
}  // namespace tint

#endif  // FUZZERS_MERSENNE_TWISTER_ENGINE_H_