// makeHandler wraps our ResponseHandlers while timing requests, collecting,
// stats, logging, and handling errors.
func makeHandler(handler ResponseHandler) httprouter.Handle {
	return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
		start := time.Now()
		httpCode, err := handler(w, r, p)
		duration := time.Since(start)

		var msg string
		if err != nil {
			msg = err.Error()
		} else if httpCode != http.StatusOK {
			msg = http.StatusText(httpCode)
		}

		if len(msg) > 0 {
			http.Error(w, msg, httpCode)
			stats.RecordEvent(stats.ErroredRequest)
		}

		if len(msg) > 0 || glog.V(2) {
			reqString := r.URL.Path + " " + r.RemoteAddr
			if glog.V(3) {
				reqString = r.URL.RequestURI() + " " + r.RemoteAddr
			}

			if len(msg) > 0 {
				glog.Errorf("[API - %9s] %s (%d - %s)", duration, reqString, httpCode, msg)
			} else {
				glog.Infof("[API - %9s] %s (%d)", duration, reqString, httpCode)
			}
		}

		stats.RecordEvent(stats.HandledRequest)
		stats.RecordTiming(stats.ResponseTime, duration)
	}
}

func handleError(err error) (int, error) {
	if err == nil {
		return http.StatusOK, nil
	} else if _, ok := err.(models.NotFoundError); ok {
		stats.RecordEvent(stats.ClientError)
		return http.StatusNotFound, nil
	} else if _, ok := err.(models.ClientError); ok {
		stats.RecordEvent(stats.ClientError)
		return http.StatusBadRequest, nil
	}
	return http.StatusInternalServerError, err
}

// HandleAnnounce encapsulates all of the logic of handling a BitTorrent
// client's Announce without being coupled to any transport protocol.
func (tkr *Tracker) HandleAnnounce(ann *models.Announce, w Writer) (err error) {
	if tkr.Config.ClientWhitelistEnabled {
		if err = tkr.ClientApproved(ann.ClientID()); err != nil {
			return err
		}
	}

	if tkr.Config.JWKSetURI != "" {
		err := tkr.validateJWT(ann.JWT, ann.Infohash)
		if err != nil {
			return err
		}
	}

	torrent, err := tkr.FindTorrent(ann.Infohash)
	if err == models.ErrTorrentDNE && tkr.Config.CreateOnAnnounce {
		torrent = &models.Torrent{
			Infohash: ann.Infohash,
			Seeders:  models.NewPeerMap(true, tkr.Config),
			Leechers: models.NewPeerMap(false, tkr.Config),
		}

		tkr.PutTorrent(torrent)
		stats.RecordEvent(stats.NewTorrent)
	} else if err != nil {
		return err
	}

	ann.BuildPeer(torrent)

	_, err = tkr.updateSwarm(ann)
	if err != nil {
		return err
	}

	_, err = tkr.handleEvent(ann)
	if err != nil {
		return err
	}

	if tkr.Config.PurgeInactiveTorrents && torrent.PeerCount() == 0 {
		// Rather than deleting the torrent explicitly, let the tracker driver
		// ensure there are no race conditions.
		tkr.PurgeInactiveTorrent(torrent.Infohash)
		stats.RecordEvent(stats.DeletedTorrent)
	}

	stats.RecordEvent(stats.Announce)
	return w.WriteAnnounce(newAnnounceResponse(ann))
}

// connState is used by graceful in order to gracefully shutdown. It also
// keeps track of connection stats.
func (s *Server) connState(conn net.Conn, state http.ConnState) {
	switch state {
	case http.StateNew:
		stats.RecordEvent(stats.AcceptedConnection)

	case http.StateClosed:
		stats.RecordEvent(stats.ClosedConnection)

	case http.StateHijacked:
		panic("connection impossibly hijacked")

	// Ignore the following cases.
	case http.StateActive, http.StateIdle:

	default:
		glog.Errorf("Connection transitioned to unknown state %s (%d)", state, state)
	}
}

// handleTorrentError writes err to w if err is a models.ClientError.
func handleTorrentError(err error, w *Writer) {
	if err == nil {
		return
	}

	if models.IsPublicError(err) {
		w.WriteError(err)
		stats.RecordEvent(stats.ClientError)
	}
}

func handleTorrentError(err error, w *Writer) (int, error) {
	if err == nil {
		return http.StatusOK, nil
	} else if models.IsPublicError(err) {
		w.WriteError(err)
		stats.RecordEvent(stats.ClientError)
		return http.StatusOK, nil
	}

	return http.StatusInternalServerError, err
}

func (s *Storage) PurgeInactivePeers(purgeEmptyTorrents bool, before time.Time) error {
	unixtime := before.Unix()

	// Build a list of keys to process.
	index := 0
	maxkeys := s.Len()
	keys := make([]string, maxkeys)
	for i := range s.shards {
		shard := &s.shards[i]
		shard.RLock()
		for infohash := range shard.torrents {
			keys[index] = infohash
			index++
			if index >= maxkeys {
				break
			}
		}
		shard.RUnlock()
		if index >= maxkeys {
			break
		}
	}

	// Process the keys while allowing other goroutines to run.
	for _, infohash := range keys {
		runtime.Gosched()
		shard := s.getTorrentShard(infohash, false)
		torrent := shard.torrents[infohash]

		if torrent == nil {
			// The torrent has already been deleted since keys were computed.
			shard.Unlock()
			continue
		}

		torrent.Seeders.Purge(unixtime)
		torrent.Leechers.Purge(unixtime)

		peers := torrent.PeerCount()
		shard.Unlock()

		if purgeEmptyTorrents && peers == 0 {
			s.PurgeInactiveTorrent(infohash)
			stats.RecordEvent(stats.ReapedTorrent)
		}
	}

	return nil
}

// HandleScrape encapsulates all the logic of handling a BitTorrent client's
// scrape without being coupled to any transport protocol.
func (tkr *Tracker) HandleScrape(scrape *models.Scrape, w Writer) (err error) {
	var torrents []*models.Torrent
	for _, infohash := range scrape.Infohashes {
		torrent, err := tkr.FindTorrent(infohash)
		if err != nil {
			return err
		}
		torrents = append(torrents, torrent)
	}

	stats.RecordEvent(stats.Scrape)
	return w.WriteScrape(&models.ScrapeResponse{
		Files: torrents,
	})
}

// HandleScrape encapsulates all the logic of handling a BitTorrent client's
// scrape without being coupled to any transport protocol.
func (tkr *Tracker) HandleScrape(scrape *models.Scrape, w Writer) (err error) {
	if tkr.Config.PrivateEnabled {
		if _, err = tkr.FindUser(scrape.Passkey); err != nil {
			return err
		}
	}

	var torrents []*models.Torrent
	for _, infohash := range scrape.Infohashes {
		torrent, err := tkr.FindTorrent(infohash)
		if err != nil {
			return err
		}
		torrents = append(torrents, torrent)
	}

	stats.RecordEvent(stats.Scrape)
	return w.WriteScrape(&models.ScrapeResponse{
		Files: torrents,
	})
}

// HandleAnnounce encapsulates all of the logic of handling a BitTorrent
// client's Announce without being coupled to any transport protocol.
func (tkr *Tracker) HandleAnnounce(ann *models.Announce, w Writer) (err error) {
	if tkr.Config.ClientWhitelistEnabled {
		if err = tkr.ClientApproved(ann.ClientID()); err != nil {
			return err
		}
	}

	var user *models.User
	if tkr.Config.PrivateEnabled {
		if user, err = tkr.FindUser(ann.Passkey); err != nil {
			return err
		}
	}

	torrent, err := tkr.FindTorrent(ann.Infohash)

	if err == models.ErrTorrentDNE && tkr.Config.CreateOnAnnounce {
		torrent = &models.Torrent{
			Infohash: ann.Infohash,
			Seeders:  models.NewPeerMap(true, tkr.Config),
			Leechers: models.NewPeerMap(false, tkr.Config),
		}

		tkr.PutTorrent(torrent)
		stats.RecordEvent(stats.NewTorrent)
	} else if err != nil {
		return err
	}

	ann.BuildPeer(user, torrent)
	var delta *models.AnnounceDelta

	if tkr.Config.PrivateEnabled {
		delta = newAnnounceDelta(ann, torrent)
	}

	created, err := tkr.updateSwarm(ann)
	if err != nil {
		return err
	}

	snatched, err := tkr.handleEvent(ann)
	if err != nil {
		return err
	}

	if tkr.Config.PrivateEnabled {
		delta.Created = created
		delta.Snatched = snatched
		if err = tkr.Backend.RecordAnnounce(delta); err != nil {
			return err
		}
	} else if tkr.Config.PurgeInactiveTorrents && torrent.PeerCount() == 0 {
		// Rather than deleting the torrent explicitly, let the tracker driver
		// ensure there are no race conditions.
		tkr.PurgeInactiveTorrent(torrent.Infohash)
		stats.RecordEvent(stats.DeletedTorrent)
	}

	stats.RecordEvent(stats.Announce)
	return w.WriteAnnounce(newAnnounceResponse(ann))
}