Random.cpp

///---------------------------------------------------------------------------------------------------------------------
/// Random.cpp
///
/// Authors: Tutors
///---------------------------------------------------------------------------------------------------------------------

#include "Random.hpp"

#include <stdexcept>
#include <iostream>
#include <cstdlib>
#include <sstream>
#include <string>

using Oop::Random;

///---------------------------------------------------------------------------------------------------------------------
std::string const Random::CARD_SEED{"RAND_SEED"};
std::string const Random::ORIENTATION_SEED{"RAND_SEED"};
size_t const Random::ORIENTATION_MIN{0};
size_t const Random::ORIENTATION_MAX{3};

///---------------------------------------------------------------------------------------------------------------------
Random::Random() :
  card_mersenne_twister_{getSeed(CARD_SEED)},
  orientation_mersenne_twister_{getSeed(ORIENTATION_SEED)},
  orientations_{ORIENTATION_MIN, ORIENTATION_MAX}
{
}

///---------------------------------------------------------------------------------------------------------------------
Random& Random::getInstance()
{
  static Random instance{};
  return instance;
}

///---------------------------------------------------------------------------------------------------------------------
size_t Random::getRandomCard(size_t const number_of_cards_left)
{
  std::uniform_int_distribution<size_t> normal_distribution{1, number_of_cards_left};
  return normal_distribution(card_mersenne_twister_);
}

///---------------------------------------------------------------------------------------------------------------------
size_t Random::getRandomOrientation()
{
  return orientations_(orientation_mersenne_twister_);
}

///---------------------------------------------------------------------------------------------------------------------
size_t Random::getSeed(std::string const environment_variable)
{
  size_t seed{};

  try
  {
    seed = getEnvironmentSeed(environment_variable);
  }
  catch (std::runtime_error& exception)
  {
    seed = getHardwareSeed();
  }

  return seed;
}

///---------------------------------------------------------------------------------------------------------------------
size_t Random::getEnvironmentSeed(std::string const environment_variable)
{
  char* environment_seed{getenv(environment_variable.c_str())};

  if (environment_seed)
  {
    return parseSeed(environment_seed);
  }

  throw  std::runtime_error{"Environment variable \"" + environment_variable + "\" does not exist."};
}

///---------------------------------------------------------------------------------------------------------------------
size_t Random::getHardwareSeed()
{
  std::random_device seed_from_hardware{};
  return seed_from_hardware();
}

///---------------------------------------------------------------------------------------------------------------------
size_t Random::parseSeed(std::string const seed)
{
  std::stringstream seed_stream{seed};
  size_t seed_value{};

  seed_stream >> seed_value;

  if (seed_stream.eof() && !seed_stream.bad())
  {
    return seed_value;
  }

  throw  std::runtime_error{"Could not parse the seed \"" + seed + "\"."};
}