package main

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"os/signal"
	"syscall"
	"time"
	_ "time/tzdata"
)

func handler() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, r *http.Request) { fmt.Fprintln(w, "ok") })
	return mux
}
func run() error {
	if len(os.Args) == 2 && os.Args[1] == "--selftest" {
		w := httptest.NewRecorder()
		handler().ServeHTTP(w, httptest.NewRequest(http.MethodGet, "/healthz", nil))
		loc, err := time.LoadLocation("Asia/Shanghai")
		if err != nil {
			return err
		}
		fmt.Printf("health=%d body=%q timezone=%s\n", w.Code, w.Body.String(), loc)
		return nil
	}
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	srv := &http.Server{Addr: ":8080", Handler: handler(), ReadHeaderTimeout: 5 * time.Second}
	result := make(chan error, 1)
	go func() { result <- srv.ListenAndServe() }()
	select {
	case err := <-result:
		return err
	case <-ctx.Done():
	}
	stop()
	drain, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	if err := srv.Shutdown(drain); err != nil {
		_ = srv.Close()
		return err
	}
	if err := <-result; !errors.Is(err, http.ErrServerClosed) {
		return err
	}
	return nil
}
func main() {
	if err := run(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}