// examples/ch25/ch25_prod_cons.cpp
#include <iostream>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <queue>
#include <stop_token>

std::queue<int> q;
std::mutex m;

// Return the shared condition variable as a function-local static.
// Function-local statics are initialized on first use, so the
// condition variable never participates in dynamic initialization.
std::condition_variable_any& cv() {
    static std::condition_variable_any c;
    return c;
}

void producer(std::stop_token st) {
    int value = 0;
    while (!st.stop_requested()) {
        {
            std::scoped_lock lock(m);
            q.push(value++);
        }
        cv().notify_one();
        std::this_thread::sleep_for(std::chrono::milliseconds(5));
    }
    // notify consumer to finish
    cv().notify_one();
}

void consumer(std::stop_token st) {
    while (true) {
        std::unique_lock lock(m);
        cv().wait(lock, [&]{ return !q.empty() || st.stop_requested(); });
        if (st.stop_requested() && q.empty()) break;
        int v = q.front(); q.pop();
        lock.unlock();
        std::cout << "got " << v << std::endl;
        if (v >= 9) {
            // have enough, request stop via external means
            // In this demo, we just continue; main will request stop.
        }
    }
    std::cout << "consumer exit" << std::endl;
}

int main() {
    std::jthread prod(producer);
    std::jthread cons(consumer);
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
    prod.request_stop();
    cons.request_stop();
    return 0;
}