package main

import (
	"context"
	"io"
	"log"
	"net"
	"os"
	"os/signal"
	"sync"
	"syscall"
	"time"

	"github.com/cloudflare/tableflip"

)

func handleConnection(ctx context.Context, wg *sync.WaitGroup, c net.Conn) {
	defer wg.Done()
	select {
	case <-ctx.Done():
		return
	default:
		io.WriteString(c, "topsecret")
	}
}

func handleDataStream(ctx context.Context, wg *sync.WaitGroup, upg *tableflip.Upgrader, addr string) {
	defer wg.Done()
	// i can handle parent listeners here if they was created with such arguments in parent process, or create new listener
	l, _ := upg.Fds.Listen("tcp", addr)

	for {
		select {
		case <-ctx.Done():
			return
		default:
			l.(*net.TCPListener).SetDeadline(time.Now().Add(time.Second * 3))
			c, err := l.Accept() // now i want to store all accepted connections in order to pass them on to the child process in the future
			if err != nil {
				continue
			}

			wg.Add(1)
			go handleConnection(ctx, wg, c)
		}
	}
}

func main() {
	wg := &sync.WaitGroup{}
	ctx, cancel := context.WithCancel(context.Background())

	upg, _ := tableflip.New(tableflip.Options{})
	defer upg.Stop()

	listenOn := []string{":8080", ":8085", "8090"}
	for _, addr := range listenOn {
		wg.Add(1)
		go handleDataStream(ctx, wg, upg, addr)
	}

	for _, c := range upg.InheritConnections() { // i want to continue processing all parent connections if they exist.
		wg.Add(1)
		go handleConnection(ctx, wg, c)
	}

	go func() {
		sig := make(chan os.Signal, 1)
		signal.Notify(sig, syscall.SIGHUP)

		<-sig
		cancel()
		wg.Wait()
		_ := upg.Upgrade()
	}()

	_ = upg.Ready()
	<-upg.Exit()
}