package main

import (
	"context"
	"fmt"
	"github.com/choria-io/fisk"
	"github.com/nats-io/jsm.go/natscontext"
	"github.com/nats-io/nats.go"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"
)

var (
	subject string
	nctx    string

	interval time.Duration
	ctx      context.Context
	cancel   context.CancelFunc
)

func main() {
	app := fisk.New("ct", "NATS connection latency test")
	app.Flag("context", "NATS Context to connect with").StringVar(&nctx)

	publisher := app.Command("publish", "Start a publisher").Alias("pub").Action(runPublisher)
	publisher.Arg("subject", "Subject to test on").Required().StringVar(&subject)
	publisher.Flag("interval", "Publish interval").Short('i').Default("1s").DurationVar(&interval)

	subscriber := app.Commandf("subscribe", "Start a subscriber").Alias("sub").Action(runSubscriber)
	subscriber.Arg("subject", "Subject to test on").Required().StringVar(&subject)

	ctx, cancel = context.WithCancel(context.Background())

	go interruptWatcher()

	app.MustParseWithUsage(os.Args[1:])
}

func connectNats() (*nats.Conn, error) {
	return natscontext.Connect(nctx)
}

func runPublisher(_ *fisk.ParseContext) error {
	nc, err := connectNats()
	if err != nil {
		return err
	}

	var (
		errs         int
		corruptions  int
		symmetryHist []float64
		rttHist      []time.Duration
		platHist     []time.Duration
	)

	ticker := time.NewTicker(interval)
	for {
		select {
		case <-ticker.C:
			start := time.Now()

			to, cancel := context.WithTimeout(ctx, 2*time.Second)
			res, err := nc.RequestWithContext(to, subject, []byte(fmt.Sprintf("%d", start.UnixNano())))
			cancel()
			if err != nil {
				fmt.Printf("Error publishing: %v\n", err)
				errs++
				continue
			}

			parts := strings.Split(string(res.Data), " ")
			if len(parts) != 2 {
				fmt.Printf("Invalid response %q\n", res.Data)
				corruptions++
				continue
			}

			ns, err := strconv.Atoi(parts[1])
			if err != nil {
				fmt.Printf("Invalid response: %q: %v", res.Data, err)
				corruptions++
				continue
			}

			since := time.Since(start)
			pubRtt := time.Duration(ns)
			symmetry := float64(since) / float64(pubRtt)

			if len(rttHist) == 51 {
				rttHist = rttHist[1:]
			}
			if len(platHist) == 51 {
				platHist = platHist[1:]
			}
			if len(symmetryHist) == 51 {
				symmetryHist = symmetryHist[1:]
			}

			rttHist = append(rttHist, since)
			platHist = append(platHist, pubRtt)
			symmetryHist = append(symmetryHist, symmetry)

			fmt.Printf("%v roundtrip time: %v (%v) publish latency: %v (%v) rtt symmetry: %0.3f (%0.3f)\n",
				start.Format(time.RFC3339),
				since.Round(time.Microsecond), avgDuration(rttHist).Round(time.Microsecond),
				pubRtt.Round(time.Microsecond), avgDuration(platHist).Round(time.Microsecond),
				symmetry, avgFloats(symmetryHist))

		case <-ctx.Done():
			return nil
		}
	}
}

func avgFloats(d []float64) float64 {
	sum := float64(0)
	for _, i := range d {
		sum += i
	}
	return sum / float64(len(d))
}
func avgDuration(d []time.Duration) time.Duration {
	sum := time.Duration(0)
	for _, i := range d {
		sum += i
	}
	return time.Duration(int(sum) / len(d))
}
func runSubscriber(_ *fisk.ParseContext) error {
	nc, err := connectNats()
	if err != nil {
		return err
	}

	_, err = nc.Subscribe(subject, func(msg *nats.Msg) {
		ns, err := strconv.Atoi(string(msg.Data))
		if err != nil {
			fmt.Printf("Invalid request: %q: %v", msg.Data, err)
			return
		}

		plat := time.Since(time.Unix(0, int64(ns)))
		fmt.Printf("%v Received a message with publish latency: %v\n", time.Now().Format(time.RFC3339), plat.Round(time.Microsecond))
		err = msg.Respond([]byte(fmt.Sprintf("%d %d", time.Now().UnixNano(), plat)))
		if err != nil {
			fmt.Printf("Reply failed: %v", err)
			return
		}
	})
	if err != nil {
		return err
	}
	<-ctx.Done()

	return nil
}

func interruptWatcher() {
	sigs := make(chan os.Signal, 1)
	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)

	for {
		select {
		case sig := <-sigs:
			switch sig {
			case syscall.SIGINT, syscall.SIGTERM:
				cancel()
			}

		case <-ctx.Done():
			return
		}
	}
}