builders.go

package main

import "fmt"

type MessageBuilder interface {
	WithOwner(string) MessageBuilder
	WithWebinar(string) MessageBuilder
	WithViewer(string, string) MessageBuilder
	Build() *Message
}

type messageBuilder struct {
	message *Message
}

func (m *messageBuilder) WithOwner(email string) MessageBuilder {
	m.message.owner = Owner{email}
	return m
}

func (m *messageBuilder) WithViewer(email string, language string) MessageBuilder {
	m.message.viewer = Viewer{email,language}
	return m
}

func (m *messageBuilder) WithWebinar(cover_url string) MessageBuilder {
	m.message.webinar = Webinar{cover_url}
	return m
}

func (m *messageBuilder) Build() *Message {
	return m.message
}

func NewMessageBuider(eventId string) MessageBuilder{
	message := &Message{event_id:eventId}
	return &messageBuilder{message}
}

type Webinar struct {
	coverl_url string
}

type Owner struct {
	email string
}

type Message struct {
	event_id string
	viewer    Viewer
	webinar Webinar
	owner Owner
}

type Viewer struct {
    email string
    language string
}


func main() {
	builder := NewMessageBuider("webinar_started")
	oneMessage := builder.WithOwner("owner").Build()
	anotherBuilder := NewMessageBuider("webinar_canceled")
	anotherMessage := anotherBuilder.WithOwner("owner").WithViewer("email","language").Build()
	fmt.Println(oneMessage)
	fmt.Println(anotherMessage)
}