package opentsdbhttp

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

	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
	"github.com/VictoriaMetrics/metrics"
)

var (
	writeRequests = metrics.NewCounter(`vm_ingestserver_requests_total{type="opentsdbhttp", name="write", net="tcp"}`)
	writeErrors   = metrics.NewCounter(`vm_ingestserver_request_errors_total{type="opentsdbhttp", name="write", net="tcp"}`)
)

// Server represents HTTP OpenTSDB server.
type Server struct {
	s  *http.Server
	ln net.Listener
	wg sync.WaitGroup
}

// MustStart starts HTTP OpenTSDB server on the given addr.
//
// MustStop must be called on the returned server when it is no longer needed.
func MustStart(addr string, insertHandler func(r *http.Request) error) *Server {
	logger.Infof("starting HTTP OpenTSDB server at %q", addr)
	lnTCP, err := netutil.NewTCPListener("opentsdbhttp", addr, nil)
	if err != nil {
		logger.Fatalf("cannot start HTTP OpenTSDB collector at %q: %s", addr, err)
	}
	return MustServe(lnTCP, insertHandler)
}

// MustServe serves OpenTSDB HTTP put requests from ln.
//
// MustStop must be called on the returned server when it is no longer needed.
func MustServe(ln net.Listener, insertHandler func(r *http.Request) error) *Server {
	h := newRequestHandler(insertHandler)
	hs := &http.Server{
		Handler:           h,
		ReadHeaderTimeout: 5 * time.Second,
		IdleTimeout:       time.Minute,
		// Do not set ReadTimeout and WriteTimeout here,
		// since these timeouts must be controlled by request handler.
	}
	s := &Server{
		s:  hs,
		ln: ln,
	}
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		err := s.s.Serve(s.ln)
		if err == http.ErrServerClosed {
			return
		}
		if err != nil {
			logger.Fatalf("error serving HTTP OpenTSDB at %q: %s", s.ln.Addr(), err)
		}
	}()
	return s
}

// Wait waits until the server is stopped with MustStop.
func (s *Server) Wait() {
	s.wg.Wait()
}

// MustStop stops HTTP OpenTSDB server.
func (s *Server) MustStop() {
	logger.Infof("stopping HTTP OpenTSDB server at %q...", s.ln.Addr())
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	if err := s.s.Shutdown(ctx); err != nil {
		logger.Fatalf("cannot close HTTP OpenTSDB server at %q: %s", s.ln.Addr(), err)
	}
	s.wg.Wait()
	logger.Infof("OpenTSDB HTTP server at %q has been stopped", s.ln.Addr())
}

func newRequestHandler(insertHandler func(r *http.Request) error) http.Handler {
	rh := func(w http.ResponseWriter, r *http.Request) {
		writeRequests.Inc()
		if err := insertHandler(r); err != nil {
			writeErrors.Inc()
			httpserver.Errorf(w, r, "%s", err)
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
	return http.HandlerFunc(rh)
}