service.go

package zeroconf

import (
	"fmt"
	"net"
	"sync"
	"time"
)

// ServiceRecord contains the basic description of a service, which contains instance name, service type & domain
type ServiceRecord struct {
	Instance string   `json:"name"`     // Instance name (e.g. "My web page")
	Service  string   `json:"type"`     // Service name (e.g. _http._tcp.)
	Subtypes []string `json:"subtypes"` // Service subtypes
	Domain   string   `json:"domain"`   // If blank, assumes "local"

	// private variable populated on ServiceRecord creation
	serviceName         string
	serviceInstanceName string
	serviceTypeName     string
}

// ServiceName returns a complete service name (e.g. _foobar._tcp.local.), which is composed
// of a service name (also referred as service type) and a domain.
func (s *ServiceRecord) ServiceName() string {
	return s.serviceName
}

// ServiceInstanceName returns a complete service instance name (e.g. MyDemo\ Service._foobar._tcp.local.),
// which is composed from service instance name, service name and a domain.
func (s *ServiceRecord) ServiceInstanceName() string {
	return s.serviceInstanceName
}

// ServiceTypeName returns the complete identifier for a DNS-SD query.
func (s *ServiceRecord) ServiceTypeName() string {
	return s.serviceTypeName
}

// newServiceRecord constructs a ServiceRecord.
func newServiceRecord(instance, service string, domain string) *ServiceRecord {
	service, subtypes := parseSubtypes(service)
	s := &ServiceRecord{
		Instance:    instance,
		Service:     service,
		Domain:      domain,
		serviceName: fmt.Sprintf("%s.%s.", trimDot(service), trimDot(domain)),
	}

	for _, subtype := range subtypes {
		s.Subtypes = append(s.Subtypes, fmt.Sprintf("%s._sub.%s", trimDot(subtype), s.serviceName))
	}

	// Cache service instance name
	if instance != "" {
		s.serviceInstanceName = fmt.Sprintf("%s.%s", trimDot(s.Instance), s.ServiceName())
	}

	// Cache service type name domain
	typeNameDomain := "local"
	if len(s.Domain) > 0 {
		typeNameDomain = trimDot(s.Domain)
	}
	s.serviceTypeName = fmt.Sprintf("_services._dns-sd._udp.%s.", typeNameDomain)

	return s
}

// lookupParams contains configurable properties to create a service discovery request
type lookupParams struct {
	ServiceRecord
	Entries chan<- *ServiceEntry // Entries Channel
	Removed chan<- *ServiceEntry // Expired and Removed Channel

	isBrowsing  bool
	stopProbing chan struct{}
	once        sync.Once
}

// newLookupParams constructs a lookupParams.
func newLookupParams(instance, service, domain string, isBrowsing bool, entries, removed chan<- *ServiceEntry) *lookupParams {
	p := &lookupParams{
		ServiceRecord: *newServiceRecord(instance, service, domain),
		Entries:       entries,
		Removed:       removed,
		isBrowsing:    isBrowsing,
	}
	if !isBrowsing {
		p.stopProbing = make(chan struct{})
	}
	return p
}

// Notify subscriber that no more entries will arrive. Mostly caused
// by an expired context.
func (l *lookupParams) done() {
	close(l.Entries)
	close(l.Removed)
}

func (l *lookupParams) disableProbing() {
	l.once.Do(func() { close(l.stopProbing) })
}

// ServiceEntry represents a browse/lookup result for client API.
// It is also used to configure service registration (server API), which is
// used to answer multicast queries.
type ServiceEntry struct {
	ServiceRecord
	HostName string    `json:"hostname"` // Host machine DNS name
	Port     int       `json:"port"`     // Service Port
	Text     []string  `json:"text"`     // Service info served as a TXT record
	Expiry   time.Time `json:"expiry"`   // Expiry of the service entry, will be converted to a TTL value
	AddrIPv4 []net.IP  `json:"-"`        // Host machine IPv4 address
	AddrIPv6 []net.IP  `json:"-"`        // Host machine IPv6 address
}

// newServiceEntry constructs a ServiceEntry.
func newServiceEntry(instance, service string, domain string) *ServiceEntry {
	return &ServiceEntry{
		ServiceRecord: *newServiceRecord(instance, service, domain),
	}
}