#include <iostream>
#include <mutex>
#include <queue>
#include <cstdlib>
#include <unistd.h>
#include <thread>

using namespace std;

// 打印日志
void printMsg(string msg) {

    cout << msg + "\n";

}

// 线程安全类，该类会被用来初始化一次，然后通过引用传递，给多个线程轮流操作
class ThreadSafeQueue {

    private:

        // int队列
        queue<int> rawQueue;
        // 排他锁
        mutex m;
    
    public:

        // 打印包含线程名的日志
        void printLocalMsg(string msg, string name) {

            printMsg("[" + name + "] " + msg);

        }

        // 从队列取值
        void retrieveAndDelete(int sleepSec, string name) {

            int frontValue = 0;

            // 取值之前，加上排他锁，防止其他线程并行操作
            m.lock();
            printLocalMsg("Lock pop", name);
            if (!rawQueue.empty()) {

                frontValue = rawQueue.front();
                printLocalMsg("Retrieved front value " + to_string(frontValue), name);
                rawQueue.pop();
                printLocalMsg("Front value popped", name);

            }
            // 取值完成后，释放锁，使其他线程可以继续操作
            printLocalMsg("Unlock pop", name);
            m.unlock();

        }

        // 向队列里存放值
        void push(int val, int sleepSec, string name) {

            // 存放值之前，加上排他锁，防止其他线程并行操作
            m.lock();
            printLocalMsg("Lock push", name);
            printLocalMsg("Sleep for " + to_string(sleepSec), name);
            sleep(sleepSec);
            printLocalMsg("Push " + to_string(val), name);
            rawQueue.push(val);
            // 存放值完成后，释放锁，使其他线程可以继续操作
            printLocalMsg("Unlock push", name);
            m.unlock();

        }

};

// 定义线程操作
void run(int tid, string name, ThreadSafeQueue & tsq) {

    // 取随机数 1-5
    int random = rand() % 5 + 1;

    string msg;
    msg = "Start thread " + to_string(tid) + ":" + name
            + " with random " + to_string(random);
    tsq.printLocalMsg(msg, name);

    // 从线程取值
    tsq.retrieveAndDelete(random, name);
    // 向线程存放值
    tsq.push(random, random, name);

}

int main() {

    // Get random int from 1-5
    int random = rand() % 5 + 1;

    ThreadSafeQueue tsq;
    tsq.push(0, 0, "main");

    thread t0(run, 1, "Red", ref(tsq));
    thread t1(run, 2, "Green", ref(tsq));
    thread t2(run, 3, "Blue", ref(tsq));
    thread t3(run, 4, "Yellow", ref(tsq));

    t0.join();
    t1.join();
    t2.join();
    t3.join();

    tsq.retrieveAndDelete(0, "main");

}