package server

import (
	"context"
	"net/http"
	"runtime"
	"sync/atomic"
	"time"

	"github.com/golang/glog"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	healthy int32
	ready   int32
)

type Server struct {
	mux *http.ServeMux
}

func NewServer(options ...func(*Server)) *Server {
	s := &Server{mux: http.NewServeMux()}

	for _, f := range options {
		f(s)
	}

	s.mux.HandleFunc("/", s.index)
	s.mux.HandleFunc("/healthz", s.healthz)
	s.mux.HandleFunc("/readyz", s.readyz)
	s.mux.HandleFunc("/readyz/enable", s.enable)
	s.mux.HandleFunc("/readyz/disable", s.disable)
	s.mux.HandleFunc("/echo", s.echo)
	s.mux.HandleFunc("/panic", s.panic)
	s.mux.HandleFunc("/version", s.version)
	s.mux.Handle("/metrics", promhttp.Handler())

	return s
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Server", runtime.Version())

	s.mux.ServeHTTP(w, r)
}

func ListenAndServe(port string, timeout time.Duration, stopCh <-chan struct{}) {
	inst := NewInstrument()
	srv := &http.Server{
		Addr:         ":" + port,
		Handler:      inst.Wrap(NewServer()),
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  15 * time.Second,
	}

	atomic.StoreInt32(&healthy, 1)
	atomic.StoreInt32(&ready, 1)

	// run server in background
	go func() {
		if err := srv.ListenAndServe(); err != http.ErrServerClosed {
			glog.Fatal(err)
		}
	}()

	// wait for SIGTERM or SIGINT
	<-stopCh
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	// all calls to /healthz and /readyz will fail from now on
	atomic.StoreInt32(&healthy, 0)
	atomic.StoreInt32(&ready, 0)

	glog.Infof("Shutting down HTTP server with timeout: %v", timeout)

	if err := srv.Shutdown(ctx); err != nil {
		glog.Errorf("HTTP server graceful shutdown failed with error: %v", err)
	} else {
		glog.Info("HTTP server stopped")
	}
}