package drone

import (
	"log"
	"net"
	"sync"
	"time"
)

// An uninteresting service.
type Service struct {
	ch        chan bool
	waitGroup *sync.WaitGroup
}

// Make a new Service.
func NewService() *Service {
	s := &Service{
		ch:        make(chan bool),
		waitGroup: &sync.WaitGroup{},
	}
	s.waitGroup.Add(1)
	return s
}

// Accept connections and spawn a goroutine to serve each one.  Stop listening
// if anything is received on the service's channel.
func (s *Service) Serve(listener *net.TCPListener) {
	defer s.waitGroup.Done()
	for {
		select {
		case <-s.ch:
			log.Println("stopping listening on", listener.Addr())
			listener.Close()
			return
		default:
		}
		listener.SetDeadline(time.Now().Add(1e9))
		conn, err := listener.AcceptTCP()
		if nil != err {
			if opErr, ok := err.(*net.OpError); ok && opErr.Timeout() {
				continue
			}
			log.Println(err)
		}
		log.Println(conn.RemoteAddr(), "connected")
		s.waitGroup.Add(1)
		go s.serve(conn)
	}
}

// Stop the service by closing the service's channel.  Block until the service
// is really stopped.
func (s *Service) Stop() {
	close(s.ch)
	s.waitGroup.Wait()
}

// Serve a connection by reading and writing what was read.  That's right, this
// is an echo service.  Stop reading and writing if anything is received on the
// service's channel but only after writing what was read.
func (s *Service) serve(conn *net.TCPConn) {
	defer conn.Close()
	defer s.waitGroup.Done()
	for {
		select {
		case <-s.ch:
			log.Println("disconnecting", conn.RemoteAddr())
			return
		default:
		}
		conn.SetDeadline(time.Now().Add(1e9))
		buf := make([]byte, 4096)
		if _, err := conn.Read(buf); nil != err {
			if opErr, ok := err.(*net.OpError); ok && opErr.Timeout() {
				continue
			}
			log.Println(err)
			return
		}

		// fixed
		// $$GPS, 년월일, 시분초, 위도, 경도, 고도, 속도, 방향, A, LTE 통신 상태, EMM 오류 정보, ESM 오류 정보, 신호세기, 위성 갯수, 위성 ID-신호세기, 위성 ID-신호세기, 위성 ID-신호세기, 위성 ID-신호세기
		// $$GPS,20190718,050519,37396586,126968913,798,0,0,A,2,255,255,-53,13,17-44,19-43,6-42,28-41

		// unfixed
		// $$GPS,,,,,,,, V, LTE 통신 상태, EMM 오류 정보, ESM 오류 정보, 신호세기, 위성 갯수, 위성 ID-신호세기, 위성 ID-신호세기, 위성 ID-신호세기, 위성 ID-신호세기
		// $$GPS,,,,,,,,V,2,255,255,-53,4,17-44,19-42,6-40,28-40

		// if _, err := conn.Write(buf); nil != err {
		// 	log.Println(err)
		// 	return
		// }
	}
}