#include <iostream>
#include <chrono>
#include <thread>
#include <atomic>
#include <cmath>

class CPUUsageController {
private:
    const double targetUsage;  // 目标 CPU 使用率 (0.0 到 1.0)
    const int cycleTimeMs;     // 每个周期的总时间（毫秒）
    std::atomic<bool> running; // 控制运行状态

    // 自旋等待函数，消耗 CPU
    void spinWait(std::chrono::milliseconds duration) {
        auto start = std::chrono::high_resolution_clock::now();
        while (std::chrono::high_resolution_clock::now() - start < duration) {
            // 执行一些计算以防止编译器优化
            volatile double x = std::sin(0.5);
        }
    }

public:
    // 简单的 clamp 函数实现
    static double clamp(double value, double low, double high) {
        if (value < low) return low;
        if (value > high) return high;
        return value;
    }

    CPUUsageController(double targetUsage = 0.7, int cycleTimeMs = 100)
        : targetUsage(clamp(targetUsage, 0.0, 1.0))
        , cycleTimeMs(cycleTimeMs)
        , running(false) {}

    void start() {
        running = true;
        while (running) {
            // 计算本周期内需要消耗 CPU 的时间
            int busyTimeMs = static_cast<int>(cycleTimeMs * targetUsage);
            int idleTimeMs = cycleTimeMs - busyTimeMs;

            // 消耗 CPU
            spinWait(std::chrono::milliseconds(busyTimeMs));

            // 休眠
            if (idleTimeMs > 0) {
                std::this_thread::sleep_for(std::chrono::milliseconds(idleTimeMs));
            }
        }
    }

    void stop() {
        running = false;
    }
};

int main(int argc, char* argv[]) {
    if (argc != 2) {
        std::cout << "Usage: " << argv[0] << " <target_cpu_usage>\n";
        std::cout << "Example: " << argv[0] << " 0.7\n";
        return 1;
    }

    double targetUsage = std::stod(argv[1]);
    std::cout << "Starting CPU usage controller with target usage: "
              << (targetUsage * 100) << "%\n";

    CPUUsageController controller(targetUsage);
    controller.start();

    return 0;
}