canape/backend/events/channel.go

package events

import (
	"net"
	"time"

	"git.quimbo.fr/odwrtw/canape/backend/models"
	"github.com/gorilla/websocket"
	"github.com/jmoiron/sqlx"
	"github.com/sirupsen/logrus"
)

// Channel represents the channel of the user and the server
type Channel struct {
	log *logrus.Entry
	// Channel where the eventer will write messages to
	serverEventStream chan ServerEvent
	// Channel where the eventer will write errors to
	serverErrorStream chan ServerError
	// Done channel when we need to stop the connection
	done chan struct{}
	// Underlying ws connection
	conn *websocket.Conn
	// A channel is directly linked to a user
	User *models.User `json:"user"`
	// List of events the user is listening to
	Events map[string]struct{} `json:"events"`
	ID     string              `json:"id"`
	db     *sqlx.DB
	closed bool
}

// go routine writing events to the websocket connection
func (c *Channel) writer() {
	// Create the ping timer that will ping the client every pingWait seconds
	// to check that he's still listening
	pingTicker := time.NewTicker(pingWait)
	defer pingTicker.Stop()

	// If we exit, close the connection to tell the reader to stop
	defer c.conn.Close()

	// Write loop
	for {
		select {
		case <-pingTicker.C:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				c.log.Warnf("error writing message: %s", err)
				return
			}
		case e := <-c.serverEventStream:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteJSON(e); err != nil {
				c.log.Warnf("error writing JSON message: %s", err)
				return
			}
		case err := <-c.serverErrorStream:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteJSON(err); err != nil {
				c.log.Warnf("error writing JSON error: %s", err)
				return
			}
		case <-c.done:
			c.log.Debug("all done finished")
			return
		}
	}
}

// go routine reading messages from the websocket connection
func (c *Channel) reader() {
	// Read loop
	c.conn.SetReadDeadline(time.Now().Add(pongWait))
	for {
		msg := ClientMessage{}

		// Read the client's message
		if err := c.conn.ReadJSON(&msg); err != nil {
			switch e := err.(type) {
			case *websocket.CloseError:
				c.log.Info("close error")
			case net.Error:
				if e.Timeout() {
					c.log.WithField(
						"error", err,
					).Warn("timeout")
				} else {
					c.log.WithField(
						"error", err,
					).Warn("unknown net error")
				}
			default:
				c.log.WithField(
					"error", err,
				).Warn("unknown error reading message")
			}

			// We got an error, we close all the subscribed events and stop the
			// writer goroutine
			c.close()
			return
		}

		e, ok := Eventers[msg.Message]
		if !ok {
			c.log.Warnf("no such event to subscribe %q", msg.Message)
			continue
		}

		switch msg.Type {
		case "subscribe":
			c.log.Debugf("subscribe to %s", msg.Message)
			if _, ok := c.Events[e.Name]; ok {
				c.log.Infof("user %s is already subscribed to %s", c.User.Name, e.Name)
				continue
			}
			if err := e.Subscribe(c); err != nil {
				c.Error(e.Name, err)
				continue
			}
			c.Events[e.Name] = struct{}{}
		case "unsubscribe":
			c.log.Debugf("unsubscribe from %s", msg.Message)
			if _, ok := c.Events[e.Name]; !ok {
				c.log.Infof("user %s is not subscribed to %s", c.User.Name, e.Name)
				continue
			}
			e.Unsubscribe(c)
		default:
			c.log.Warnf("invalid type: %s", msg.Type)
		}
	}
}

func (c *Channel) close() {
	// The channel is now closed
	c.closed = true

	// Unsubscribe from all Events
	for eventName := range c.Events {
		Eventers[eventName].Unsubscribe(c)
	}

	// Tell the writer to stop
	c.done <- struct{}{}
}

// Error sends an error into the errorStream channel
func (c *Channel) Error(name string, err error) {
	if c.closed {
		return
	}
	c.log.WithField("name", name).Warn(err)
	c.serverErrorStream <- ServerError{
		Event: Event{
			Type:   name,
			Status: Error,
		},
		ErrorEvent: ErrorEvent{
			Level:   WarningError,
			Message: err.Error(),
		},
	}
}

// FatalError sends an error into the errorStream channel
func (c *Channel) FatalError(name string, err error) {
	if c.closed {
		return
	}
	c.log.WithField("name", name).Warn(err)
	c.serverErrorStream <- ServerError{
		Event: Event{
			Type:   name,
			Status: Error,
		},
		ErrorEvent: ErrorEvent{
			Level:   FatalError,
			Message: err.Error(),
		},
	}
}

// SendEvent sends an event to the serverEvent channel
func (c *Channel) sendEvent(event ServerEvent) {
	if c.closed {
		return
	}
	c.serverEventStream <- event
}

// Unsubscribe unsubscribes a user from all eventers
func Unsubscribe(u *models.User) {
	chanl := &Channel{User: u}
	for _, event := range Eventers {
		event.Unsubscribe(chanl)
	}
}