package main
type IOtp interface {
	genRandomOPT(int) string
	saveOPTCache(string)
	getMessage(string) string
	sendNotification(string) error
}
type Otp struct {
	iOtp IOtp
}
func (o *Otp) genAndSendOPT(optLength int) error {
	opt := o.iOtp.genRandomOPT(optLength)
	o.iOtp.saveOPTCache(opt)
	message := o.iOtp.getMessage(opt)
	if err := o.iOtp.sendNotification(message); err != nil {
		return err
	}
	return nil
}

package main
import (
	"fmt"
)
type Sms struct {
	Otp
}
func (s *Sms) genRandomOPT(len int) string {
	randomOTP := "1234"
	fmt.Printf("SMS: generating random otp %s \n", randomOTP)
	return randomOTP
}
func (s *Sms) saveOPTCache(otp string) {
	fmt.Printf("SMS: saving otp %s", otp)
}
func (s *Sms) getMessage(otp string) string {
	return "SMS OTP for login is " + otp
}
func (s *Sms) sendNotification(message string) error {
	fmt.Printf("SMS: sending sms: %s\n", message)
	return nil
}

package main
import (
	"fmt"
)
type Email struct {
	Otp
}
func (s *Email) genRandomOPT(len int) string {
	randomOTP := "2345"
	fmt.Printf("Email: generating random otp %s \n", randomOTP)
	return randomOTP
}
func (s *Email) saveOPTCache(otp string) {
	fmt.Printf("Email: saving otp %s to cache", otp)
}
func (s *Email) getMessage(otp string) string {
	return "Email otp for login is " + otp
}
func (s *Email) sendNotification(message string) error {
	fmt.Printf("Email: sending email %s \n", message)
	return nil
}

package main
import "fmt"
func main() {
	smsOTP := &Sms{}
	o := Otp{
		iOtp: smsOTP,
	}
	o.genAndSendOPT(4)
	fmt.Println("")
	emailOtp := &Email{}
	o = Otp{
		iOtp: emailOtp,
	}
	o.genAndSendOPT(4)
}