plugin.go

package main

import "log"

type AB interface {
	Append(AB) AB
	DoA()
	DoB()
}

// empty
type empty struct{}

func (ab empty) Append(AB) AB {
	return empty{}
}

func (ab empty) DoA() {}
func (ab empty) DoB() {}

// log
type logAB struct {
	AB
}

func (l logAB) Append(ab AB) AB {
	l.AB = ab
	return l
}

func (l logAB) DoA() {
	log.Println("DoA")
	l.AB.DoA()
}

func (l logAB) DoB() {
	log.Println("DoB")
	l.AB.DoB()
}

func Compose(abs ...AB) AB {
	if len(abs) <= 0 {
		return empty{}
	}

	ab := abs[len(abs)-1]
	for i := len(abs) - 2; i >= 0; i-- {
		ab = abs[i].Append(ab)
	}
	return ab
}

func main() {
	ab := Compose(logAB{}, logAB{}, empty{})
	ab.DoA()
	ab.DoB()
}