package discovery

import (
	"context"
	"net"
	"sync"

	"github.com/grandcat/zeroconf"
)

// 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(ctx context.Context) ([]Service, error) {
	var wg sync.WaitGroup

	wg.Add(1)

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

	services := make([]Service, 0)
	entries := make(chan *zeroconf.ServiceEntry)

	go func() {
		for e := range entries {
			var addr *net.IP
			if len(e.AddrIPv4) > 0 {
				addr = &e.AddrIPv4[0]
			}
			srv := Service{
				Name:   e.Instance,
				AddrV4: addr,
				Port:   e.Port,
			}
			services = append(services, srv)
		}
		wg.Done()
	}()

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

	wg.Wait()

	return services, nil

}