Random Cron Scheduler

main.go

package main

import (
	"fmt"
	"time"
	"math/rand"
	"bytes"
	"gopkg.in/robfig/cron.v2"
)


func PrintTheTime(name string) {
	fmt.Printf("I am %s and the time is %s\n", name, time.Now())
}

func randomNumber(min, max int) (int) {
	rand.Seed(time.Now().UTC().UnixNano())
	i := rand.Intn(max-min) + min
	return i
}

 func listOfNumbers(min, max, count int) string {
	 var buffer bytes.Buffer
	 for i := 0; i < count; i++ {
		 if count > 1 {
			 if i != 0  {
				 buffer.WriteString(fmt.Sprintf(","))
			 }
		 }
		 buffer.WriteString(fmt.Sprintf("%d", randomNumber(min, max)))
	 }
	 s := buffer.String()
	 return s
 }

func GetSpec(duration int) string {

	var spec string

	switch {
	case duration == 1:
		spec = fmt.Sprintf("%s * * * * *", listOfNumbers(1, 59, 1))
	case duration == 5:
		spec = fmt.Sprintf("%s %s * * * *", listOfNumbers(1, 59, 1), listOfNumbers(1, 59, 12))
	case duration == 15:
		spec = fmt.Sprintf("%s %s * * * *", listOfNumbers(1, 59, 1), listOfNumbers(1, 59, 4))
	case duration == 30:
		spec = fmt.Sprintf("%s %s * * * *", listOfNumbers(1, 59, 1), listOfNumbers(1, 59, 2))
	case duration == 60:
		spec = fmt.Sprintf("%s %s * * * *", listOfNumbers(1, 59, 1), listOfNumbers(1, 59, 1))
	}

	return spec
}

func main() {

	c := cron.New()
	c.Start()

	for i := 0; i < 500; i++ {
		spec := GetSpec(5)
		fmt.Printf("%s\n", spec)
		c.AddFunc(spec, func() {PrintTheTime(spec)})
	}
	select{}
}