package main

import "fmt"

/*
实例：
汤宝宝坚信搭积木是人类的未来，因此开办了一家积木厂。
*/

// 抽象Node接口 Shape
type Shape interface {
	Accept(visitor Visitor)
	ClaimShape()
}

type Circle struct{}

func (c *Circle) Accept(visitor Visitor) {
	visitor.VisitCircle(c)
}

func (c *Circle) ClaimShape() {
	fmt.Println("I am a Circle")
}

type Square struct{}

func (s *Square) Accept(visitor Visitor) {
	visitor.VisitSquare(s)
}

func (s *Square) ClaimShape() {
	fmt.Println("I am a Square")
}

type Triangle struct{}

func (t *Triangle) Accept(visitor Visitor) {
	visitor.VisitTriangle(t)
}

func (t *Triangle) ClaimShape() {
	fmt.Println("I am a Triangle")
}

// 抽象NodeVisitor接口 Visitor
type Visitor interface {
	VisitCircle(c *Circle)
	VisitSquare(s *Square)
	VisitTriangle(t *Triangle)
}

type ShapeVisitor struct{}

func (sv *ShapeVisitor) VisitCircle(c *Circle) {
	fmt.Print("Visiting Circle: ")
	c.ClaimShape()
}

func (sv *ShapeVisitor) VisitSquare(s *Square) {
	fmt.Print("Visiting Square: ")
	s.ClaimShape()
}

func (sv *ShapeVisitor) VisitTriangle(t *Triangle) {
	fmt.Print("Visiting Triangle: ")
	t.ClaimShape()
}

func main() {
	fmt.Println("========== 访问者模式 ==========")
	shapes := []Shape{&Circle{}, &Square{}, &Triangle{}}
	visitor := &ShapeVisitor{}

	for _, shape := range shapes {
		shape.Accept(visitor)
	}
	fmt.Println()
	fmt.Println("======== 访问者模式结束 ========")
}