package main

import "fmt"

type SetFilterFunc func(options *FilterOptions)

type FilterOptions struct {
	Alive      *bool
	Id         *int
	ExternalId *string
}

type Filter struct {
	Options FilterOptions
}

func (f *Filter) Dump() {
	if f.Options.Alive != nil {
		fmt.Printf("Alive: %v\n", *f.Options.Alive)
	}
	if f.Options.Id != nil {
		fmt.Printf("Id: %v\n", *f.Options.Id)
	}
	if f.Options.ExternalId != nil {
		fmt.Printf("ExternalId: %v\n", *f.Options.ExternalId)
	}
}

func WithAlive(options *FilterOptions) {
	alive := true
	options.Alive = &alive
}

func WithId(id int) SetFilterFunc {
	return func(options *FilterOptions) {
		options.Id = &id
	}
}

func WithExternalId(externalId string) SetFilterFunc {
	return func(options *FilterOptions) {
		options.ExternalId = &externalId
	}
}

func NewFilter(opts ...SetFilterFunc) *Filter {
	f := Filter{Options: FilterOptions{}}
	for _, fn := range opts {
		fn(&f.Options)
	}
	return &f
}

func main() {
	var f *Filter

	f = NewFilter()
	f.Dump()

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

	f = NewFilter(WithId(123), WithAlive, WithExternalId("some-external-id"))
	f.Dump()
}