Golang 1.18 undo example

main.go

package main

import (
	"fmt"
)

func main() {
	fmt.Print("Hello, ", "playground\n")
	s := AppState{}
	a := ActionStack[AppState]{}
	fmt.Printf("%#v\n", s)
	a.ApplyDo(ChangeCountAction{amount: 2}, &s)
	fmt.Printf("%#v\n", s)
	a.ApplyDo(ChangeBirthdayAction(true), &s)
	fmt.Printf("%#v\n", s)
	a.ApplyUndo(&s)
	fmt.Printf("%#v\n", s)
	a.ApplyUndo(&s)
	fmt.Printf("%#v\n", s)
	a.ApplyUndo(&s)
	fmt.Printf("%#v\n", s)
}

type ActionStack[T any] struct {
	stack []Action[T]
}

func (a *ActionStack[T]) ApplyDo(action Action[T], state *T) {
	a.stack = append(a.stack, action)
	action.Do(state)
}

func (a *ActionStack[T]) ApplyUndo(state *T) {
	l := len(a.stack)
	if l == 0 {
		return
	}
	last := a.stack[l-1]
	a.stack = a.stack[:l-1]
	last.Undo(state)
}

type Action[T any] interface {
	Do(*T)
	Undo(*T)
}

type AppState struct {
	count      int
	isBirthday bool
}

type ChangeCountAction struct {
	amount int
}

func (c ChangeCountAction) Do(state *AppState) {
	state.count += c.amount
}

func (c ChangeCountAction) Undo(state *AppState) {
	state.count -= c.amount
}

type ChangeBirthdayAction bool

func (c ChangeBirthdayAction) Do(state *AppState) {
	state.isBirthday = bool(c)
}

func (c ChangeBirthdayAction) Undo(state *AppState) {
	state.isBirthday = !bool(c)
}