package emlid

import (
	"net"
	"sync"
	"time"

	"github.com/oleksandr/bonjour"
)

// Service is a ReachRS service discovered via MDNS-SD
type Service struct {
	Name   string
	AddrV4 net.IP
	Port   int
}

// Discover tries to discover ReachRS services on the local network via MDNS-SD
func Discover(timeout time.Duration) ([]Service, error) {

	var wg sync.WaitGroup

	wg.Add(1)

	resolver, err := bonjour.NewResolver(nil)
	if err != nil {
		return nil, err
	}

	services := make([]Service, 0)
	entries := make(chan *bonjour.ServiceEntry)
	timer := time.NewTimer(timeout)
	defer timer.Stop()

	stop := func() {
		resolver.Exit <- true
		wg.Done()
	}

	go func() {
		for {
			select {

			case e, ok := <-entries:
				if !ok {
					stop()
					return
				}
				services = append(services, Service{
					Name:   e.Instance,
					AddrV4: e.AddrIPv4,
					Port:   e.Port,
				})

			case <-timer.C:
				stop()
				return
			}
		}
	}()

	if err = resolver.Browse("_reach._tcp", ".local", entries); err != nil {
		return nil, err
	}

	wg.Wait()

	return services, nil

}