//备忘录是一种行为设计模式， 允许生成对象状态的快照并在以后将其还原。
//
//备忘录不会影响它所处理的对象的内部结构， 也不会影响快照中保存的数据。
//
//概念示例
//备忘录模式让我们可以保存对象状态的快照。 你可使用这些快照来将对象恢复到之前的状态。 这在需要在对象上实现撤销-重做操作时非常实用。

package main

import "fmt"

type originator struct {
	state string
}

func (e *originator) createMemento() *memento {
	return &memento{state: e.state}
}

func (e *originator) restoreMemento(m *memento) {
	e.state = m.getSavedState()
}

func (e *originator) setState(state string) {
	e.state = state
}

func (e *originator) getState() string {
	return e.state
}

type memento struct {
	state string
}

func (m *memento) getSavedState() string {
	return m.state
}

type caretaker struct {
	mementoArray []*memento
}

func (c *caretaker) addMemento(m *memento) {
	c.mementoArray = append(c.mementoArray, m)
}

func (c *caretaker) getMemento(index int) *memento {
	return c.mementoArray[index]
}

func main() {

	caretaker := &caretaker{
		mementoArray: make([]*memento, 0),
	}

	originator := &originator{
		state: "A",
	}

	fmt.Printf("Originator Current State: %s\n", originator.getState())
	caretaker.addMemento(originator.createMemento())

	originator.setState("B")
	fmt.Printf("Originator Current State: %s\n", originator.getState())
	caretaker.addMemento(originator.createMemento())

	originator.setState("C")
	fmt.Printf("Originator Current State: %s\n", originator.getState())
	caretaker.addMemento(originator.createMemento())

	originator.restoreMemento(caretaker.getMemento(1))
	fmt.Printf("Restored to State: %s\n", originator.getState())

	originator.restoreMemento(caretaker.getMemento(0))
	fmt.Printf("Restored to State: %s\n", originator.getState())

}