package main

import "fmt"

type Filter struct {
	alive      *bool
	id         *int
	externalId *string
}

func NewFilter() *Filter {
	return &Filter{}
}

func (f *Filter) Dump() {
	fmt.Println("Filter non-nil options:")
	if f.alive != nil {
		fmt.Printf("  Alive: %v\n", *f.alive)
	}
	if f.id != nil {
		fmt.Printf("  Id: %v\n", *f.id)
	}
	if f.externalId != nil {
		fmt.Printf("  ExternalId: %v\n", *f.externalId)
	}
}

func (f *Filter) Alive(alive bool) *Filter {
	f.alive = &alive
	return f
}

func (f *Filter) Id(id int) *Filter {
	f.id = &id
	return f
}

func (f *Filter) ExternalId(externalId string) *Filter {
	f.externalId = &externalId
	return f
}

func main() {
	var f *Filter

	f = NewFilter().ExternalId("some-external-id")
	f.Dump()

	fmt.Println("-------------------")

	f = NewFilter().Id(123).Alive(true).ExternalId("some-external-id")
	f.Dump()
}