synctv/server/handlers/websocket.go

package handlers

import (
	"io"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/gorilla/websocket"
	log "github.com/sirupsen/logrus"
	"github.com/synctv-org/synctv/internal/op"
	pb "github.com/synctv-org/synctv/proto/message"
	"github.com/synctv-org/synctv/server/middlewares"
	"github.com/synctv-org/synctv/server/model"
	"github.com/synctv-org/synctv/utils"
	"google.golang.org/protobuf/proto"
)

const maxInterval = 10

func NewWebSocketHandler(wss *utils.WebSocket) gin.HandlerFunc {
	return func(ctx *gin.Context) {
		token := ctx.GetHeader("Sec-WebSocket-Protocol")
		user, room, err := middlewares.AuthRoom(token)
		if err != nil {
			ctx.AbortWithStatusJSON(http.StatusUnauthorized, model.NewApiErrorResp(err))
			return
		}

		wss.Server(ctx.Writer, ctx.Request, []string{token}, NewWSMessageHandler(user, room))
	}
}

func NewWSMessageHandler(u *op.User, r *op.Room) func(c *websocket.Conn) error {
	return func(c *websocket.Conn) error {
		client, err := r.NewClient(u, c)
		if err != nil {
			log.Errorf("ws: register client error: %v", err)
			wc, err2 := c.NextWriter(websocket.BinaryMessage)
			if err2 != nil {
				return err2
			}
			defer wc.Close()
			em := op.ElementMessage{
				Type:    pb.ElementMessageType_ERROR,
				Message: err.Error(),
			}
			return em.Encode(wc)
		}
		log.Infof("ws: room %s user %s connected", r.Name, u.Username)
		defer func() {
			r.UnregisterClient(client)
			client.Close()
			log.Infof("ws: room %s user %s disconnected", r.Name, u.Username)
		}()
		go handleReaderMessage(client)
		return handleWriterMessage(client)
	}
}

func handleWriterMessage(c *op.Client) error {
	for v := range c.GetReadChan() {
		wc, err := c.NextWriter(v.MessageType())
		if err != nil {
			log.Debugf("ws: room %s user %s get next writer error: %v", c.Room().Name, c.User().Username, err)
			return err
		}

		if err = v.Encode(wc); err != nil {
			log.Debugf("ws: room %s user %s encode message error: %v", c.Room().Name, c.User().Username, err)
			return err
		}

		if err = wc.Close(); err != nil {
			return err
		}
	}
	return nil
}

func handleReaderMessage(c *op.Client) error {
	defer c.Close()
	for {
		t, rd, err := c.NextReader()
		if err != nil {
			log.Debugf("ws: room %s user %s get next reader error: %v", c.Room().Name, c.User().Username, err)
			return err
		}
		log.Debugf("ws: room %s user %s receive message type: %d", c.Room().Name, c.User().Username, t)
		switch t {
		case websocket.CloseMessage:
			log.Debugf("ws: room %s user %s receive close message", c.Room().Name, c.User().Username)
			return nil
		case websocket.BinaryMessage:
			var data []byte
			if data, err = io.ReadAll(rd); err != nil {
				log.Errorf("ws: room %s user %s read message error: %v", c.Room().Name, c.User().Username, err)
				if err := c.Send(&op.ElementMessage{
					Type:    pb.ElementMessageType_ERROR,
					Message: err.Error(),
				}); err != nil {
					log.Errorf("ws: room %s user %s send error message error: %v", c.Room().Name, c.User().Username, err)
					return err
				}
				continue
			}
			var msg pb.ElementMessage
			if err := proto.Unmarshal(data, &msg); err != nil {
				log.Errorf("ws: room %s user %s decode message error: %v", c.Room().Name, c.User().Username, err)
				if err := c.Send(&op.ElementMessage{
					Type:    pb.ElementMessageType_ERROR,
					Message: err.Error(),
				}); err != nil {
					log.Errorf("ws: room %s user %s send error message error: %v", c.Room().Name, c.User().Username, err)
					return err
				}
				continue
			}

			log.Debugf("ws: receive room %s user %s message: %+v", c.Room().Name, c.User().Username, msg.String())
			if err = handleElementMsg(c, &msg); err != nil {
				log.Errorf("ws: room %s user %s handle message error: %v", c.Room().Name, c.User().Username, err)
				return err
			}

		default:
			log.Errorf("ws: room %s user %s receive unknown message type: %d", c.Room().Name, c.User().Username, t)
			continue
		}
	}
}

func handleElementMsg(cli *op.Client, msg *pb.ElementMessage) error {
	var send = func(em *pb.ElementMessage) error {
		em.Sender = cli.User().Username
		return cli.Send((*op.ElementMessage)(em))
	}
	var broadcast = func(em *pb.ElementMessage, bc ...op.BroadcastConf) error {
		em.Sender = cli.User().Username
		return cli.Broadcast((*op.ElementMessage)(em), bc...)
	}
	var timeDiff float64
	if msg.Time != 0 {
		timeDiff = time.Since(time.UnixMilli(msg.Time)).Seconds()
	} else {
		timeDiff = 0.0
	}
	if timeDiff < 0 {
		timeDiff = 0
	} else if timeDiff > 1.5 {
		timeDiff = 1.5
	}
	switch msg.Type {
	case pb.ElementMessageType_CHAT_MESSAGE:
		if len(msg.Message) > 4096 {
			send(&pb.ElementMessage{
				Type:    pb.ElementMessageType_ERROR,
				Message: "message too long",
			})
			return nil
		}
		broadcast(&pb.ElementMessage{
			Type:    pb.ElementMessageType_CHAT_MESSAGE,
			Message: msg.Message,
		})
	case pb.ElementMessageType_PLAY:
		status := cli.Room().SetStatus(true, msg.Seek, msg.Rate, timeDiff)
		broadcast(&pb.ElementMessage{
			Type: pb.ElementMessageType_PLAY,
			Seek: status.Seek,
			Rate: status.Rate,
		}, op.WithIgnoreClient(cli))
	case pb.ElementMessageType_PAUSE:
		status := cli.Room().SetStatus(false, msg.Seek, msg.Rate, timeDiff)
		broadcast(&pb.ElementMessage{
			Type: pb.ElementMessageType_PAUSE,
			Seek: status.Seek,
			Rate: status.Rate,
		}, op.WithIgnoreClient(cli))
	case pb.ElementMessageType_CHANGE_RATE:
		status := cli.Room().SetSeekRate(msg.Seek, msg.Rate, timeDiff)
		broadcast(&pb.ElementMessage{
			Type: pb.ElementMessageType_CHANGE_RATE,
			Seek: status.Seek,
			Rate: status.Rate,
		}, op.WithIgnoreClient(cli))
	case pb.ElementMessageType_CHANGE_SEEK:
		status := cli.Room().SetSeekRate(msg.Seek, msg.Rate, timeDiff)
		broadcast(&pb.ElementMessage{
			Type: pb.ElementMessageType_CHANGE_SEEK,
			Seek: status.Seek,
			Rate: status.Rate,
		}, op.WithIgnoreClient(cli))
	case pb.ElementMessageType_CHECK_SEEK:
		status := cli.Room().Current().Status
		if status.Seek+maxInterval < msg.Seek+timeDiff {
			send(&pb.ElementMessage{
				Type: pb.ElementMessageType_TOO_FAST,
				Seek: status.Seek,
				Rate: status.Rate,
			})
		} else if status.Seek-maxInterval > msg.Seek+timeDiff {
			send(&pb.ElementMessage{
				Type: pb.ElementMessageType_TOO_SLOW,
				Seek: status.Seek,
				Rate: status.Rate,
			})
		} else {
			send(&pb.ElementMessage{
				Type: pb.ElementMessageType_CHECK_SEEK,
				Seek: status.Seek,
				Rate: status.Rate,
			})
		}
	}
	return nil
}