#include "is_prime.h"
#include <cmath>
#include <algorithm>
#include <thread>

static std::atomic<bool> is_prime = true;

void IsDividedBySmth(size_t x, size_t begin, size_t end, size_t num_threads) {
    if (x <= 1) {
        is_prime.store(false);
        return;
    }
    for (size_t i = begin; i < end; i += num_threads) {
        if (x % i == 0) {
            is_prime.store(false);
        }
        if (!is_prime.load()) {
            return;
        }
    }
}

bool IsPrime(uint64_t x) {
    is_prime.store(true);

    unsigned begin = 2;
    unsigned end = static_cast<uint64_t>(sqrt(x)) + 1;
    unsigned num_threads = std::thread::hardware_concurrency();

    std::vector<std::thread> workers;
    for (size_t i = 0; i < num_threads; ++i) {
        workers.emplace_back(IsDividedBySmth, x, begin + i, end, num_threads);
    }
    for (std::thread& thread : workers) {
        thread.join();
    }

    return is_prime;
}