package main

import (
	"context"
	"flag"
	"log"
	"net/http"
	"os"
	"os/exec"
	"os/signal"
	"path/filepath"
	"sync"
	"syscall"
	"time"
)

var (
	devMode = flag.Bool("dev", false, "Run yarn autoreload underneath Go")
)

const (
	publicWebPath = "./web/public/"
)

func main() {
	flag.Parse()
	var wg sync.WaitGroup
	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)

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

	go func() {
		oscall := <-c
		log.Printf("system call:%+v", oscall)
		cancel()
	}()

	wg.Add(1)
	go serveHTTP(ctx, &wg)
	if *devMode {
		wg.Add(1)
		go runYarn(ctx, &wg)
	}
	wg.Wait()
}

func serveHTTP(ctx context.Context, wg *sync.WaitGroup) {

	fs := http.FileServer(http.Dir(publicWebPath))
	mux := http.NewServeMux()
	mux.Handle("/", fs)

	srv := &http.Server{
		Addr:    ":5000",
		Handler: mux,
	}

	go func() {
		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("listen:%+s\n", err)
		}
	}()

	log.Printf("Listening on port :5000")

	<-ctx.Done()

	log.Printf("server stopped")

	ctxShutDown, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	if err := srv.Shutdown(ctxShutDown); err != nil {
		if err != http.ErrServerClosed {
			log.Fatalf("server Shutdown Failed:%+s", err)
		}
	}

	log.Printf("server exited properly")

	wg.Done()
	return
}

func runYarn(ctx context.Context, wg *sync.WaitGroup) {
	var err error
	cmd := exec.Command("yarn", "dev")
	cmd.Env = append(cmd.Env, "SKIP_SERVE=1")
	cmd.Dir, err = filepath.Abs("./web/")
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err != nil {
		panic(err)
	}
	err = cmd.Start()
	if err != nil {
		panic(err)
	}
	<-ctx.Done()
	log.Println("closing")
	err = syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
	if err != nil {
		panic(err)
	}
	wg.Done()
	return
}