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

bool IsPrime(uint64_t x) {
    if (x <= 1) {
        return false;
    }
    uint16_t num_threads = 8;
    if (x <= num_threads * 2) {
        num_threads = 1;
    }
    std::atomic<bool> is_prime = true;
    std::vector<std::thread> workers;
    uint64_t lower_bound = 2, upper_bound = static_cast<uint64_t>(sqrt(x));
    uint64_t from = 2, step = (upper_bound - lower_bound) / num_threads, to = from + step;
    for (size_t i = 0; i < num_threads; ++i) {
        workers.emplace_back([x, &is_prime, from, to] {
            for (size_t j = from; j <= to && is_prime; ++j) {
                if (x % j == 0) {
                    is_prime = false;
                    return;
                }
            }
        });
        from = to + 1;
        to = std::min(from + step, upper_bound);
    }
    for (auto& worker : workers) {
        worker.join();
    }
    return is_prime;
}