package main

import (
	"context"
	"log"
	"time"

	"github.com/nats-io/go-nats"
)

func main() {
	nc, err := nats.Connect("nats://127.0.0.1:4222")
	if err != nil {
		log.Fatalf("Failed to connect: %s\n", err)
	}

	nc.Subscribe("help", func(m *nats.Msg) {
		log.Printf("Received help request: %s\n", string(m.Data))

		for i := 0; i < 100; i++ {
			if i >= 3 {
				time.Sleep(300 * time.Millisecond)
			}
			nc.Publish(m.Reply, []byte("ok can help"))
			log.Printf("Replied to help request (times=%d)\n", i)
		}
	})

	// Parent context
	ctx := context.Background()

	// Hard deadline for the whole context
	ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
	defer cancel() // must be called always

	// Probe deadline will be expanded as we gather replies
	timer := time.AfterFunc(250*time.Millisecond, func() {
		cancel()
	})

	replies := make([]interface{}, 0)

	// RequestWithContext is actually syntax sugar for something like this
	inbox := nats.NewInbox()
	sub, err := nc.SubscribeSync(inbox)
	defer sub.Unsubscribe()
	if err != nil {
		log.Fatalf("Failed to make request: %s\n", err)
	}

	start := time.Now()
	err = nc.PublishRequest("help", inbox, []byte("please help!"))
	if err != nil {
		log.Fatalf("Failed to create request: %s\n", err)
	}
	for {
		// Wait to receive all messages we can until we stop
		// hearing from members for over 250ms
		result, err := sub.NextMsgWithContext(ctx)
		if err != nil {
			log.Printf("Stopped waiting for replies (reason=%q)", err)
			break
		}
		replies = append(replies, result)
		timer.Reset(250 * time.Millisecond)
	}
	log.Printf("Received %d messages in %.3f seconds", len(replies), time.Since(start).Seconds())
}