function secNSec2ms(secNSec: Array<number>|number) {
    if (Array.isArray(secNSec)) {
        return secNSec[0] * 1000 + secNSec[1] / 1000000;
    }
    return secNSec / 1000;
}

class CpuTracker {
    private cpuPercent: number = 0;

    constructor() {
        let time  = process.hrtime.bigint()
        let usage = process.cpuUsage()
        setInterval(() => {
            let elapTime = process.hrtime.bigint();
            let elapUsage = process.cpuUsage(usage)
            usage = process.cpuUsage()

            let elapTimeMS = elapTime - time;
            let elapUserMS = secNSec2ms(elapUsage.user)
            let elapSystMS = secNSec2ms(elapUsage.system)
            this.cpuPercent = Math.round(100 * (elapUserMS + elapSystMS) / Number(elapTimeMS) * 1000000)

            time = elapTime;
            /*console.log('elapsed time ms:  ', elapTimeMS)
            console.log('elapsed user ms:  ', elapUserMS)
            console.log('elapsed system ms:', elapSystMS)
            console.log('cpu percent:      ', this.cpuPercent)*/
        }, 500);
    }

    public getCpuPercent(): number {
        return this.cpuPercent;
    }
}

const cpuTracker = new CpuTracker();

export { cpuTracker };