feat: add live traffic stats (#530) (#616)

internal/app/api/core/middleware/logging/writer.go

@@ -1,6 +1,8 @@
 package logging
 
 import (
+	"bufio"
+	"net"
 	"net/http"
 )
 
@@ -38,6 +40,12 @@ func (w *writerWrapper) Write(data []byte) (int, error) {
 	return n, err
 }
 
+// Hijack wraps the Hijack method of the ResponseWriter and returns the hijacked connection.
+// This is required for websockets to work.
+func (w *writerWrapper) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return http.NewResponseController(w.ResponseWriter).Hijack()
+}
+
 // newWriterWrapper returns a new writerWrapper that wraps the given http.ResponseWriter.
 // It initializes the StatusCode to http.StatusOK.
 func newWriterWrapper(w http.ResponseWriter) *writerWrapper {

internal/app/api/v0/handlers/endpoint_websocket.go

@@ -0,0 +1,100 @@
+package handlers
+
+import (
+	"context"
+	"net/http"
+	"strings"
+	"sync"
+
+	"github.com/go-pkgz/routegroup"
+	"github.com/gorilla/websocket"
+
+	"github.com/h44z/wg-portal/internal/app"
+	"github.com/h44z/wg-portal/internal/config"
+	"github.com/h44z/wg-portal/internal/domain"
+)
+
+type WebsocketEventBus interface {
+	Subscribe(topic string, fn any) error
+	Unsubscribe(topic string, fn any) error
+}
+
+type WebsocketEndpoint struct {
+	authenticator Authenticator
+	bus           WebsocketEventBus
+
+	upgrader websocket.Upgrader
+}
+
+func NewWebsocketEndpoint(cfg *config.Config, auth Authenticator, bus WebsocketEventBus) *WebsocketEndpoint {
+	return &WebsocketEndpoint{
+		authenticator: auth,
+		bus:           bus,
+		upgrader: websocket.Upgrader{
+			ReadBufferSize:  1024,
+			WriteBufferSize: 1024,
+			CheckOrigin: func(r *http.Request) bool {
+				origin := r.Header.Get("Origin")
+				return strings.HasPrefix(origin, cfg.Web.ExternalUrl)
+			},
+		},
+	}
+}
+
+func (e WebsocketEndpoint) GetName() string {
+	return "WebsocketEndpoint"
+}
+
+func (e WebsocketEndpoint) RegisterRoutes(g *routegroup.Bundle) {
+	g.With(e.authenticator.LoggedIn()).HandleFunc("GET /ws", e.handleWebsocket())
+}
+
+// wsMessage represents a message sent over websocket to the frontend
+type wsMessage struct {
+	Type string `json:"type"` // either "peer_stats" or "interface_stats"
+	Data any    `json:"data"` // domain.TrafficDelta
+}
+
+func (e WebsocketEndpoint) handleWebsocket() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		conn, err := e.upgrader.Upgrade(w, r, nil)
+		if err != nil {
+			return
+		}
+		defer conn.Close()
+
+		ctx, cancel := context.WithCancel(r.Context())
+		defer cancel()
+
+		writeMutex := sync.Mutex{}
+		writeJSON := func(msg wsMessage) error {
+			writeMutex.Lock()
+			defer writeMutex.Unlock()
+			return conn.WriteJSON(msg)
+		}
+
+		peerStatsHandler := func(status domain.TrafficDelta) {
+			_ = writeJSON(wsMessage{Type: "peer_stats", Data: status})
+		}
+		interfaceStatsHandler := func(status domain.TrafficDelta) {
+			_ = writeJSON(wsMessage{Type: "interface_stats", Data: status})
+		}
+
+		_ = e.bus.Subscribe(app.TopicPeerStatsUpdated, peerStatsHandler)
+		defer e.bus.Unsubscribe(app.TopicPeerStatsUpdated, peerStatsHandler)
+		_ = e.bus.Subscribe(app.TopicInterfaceStatsUpdated, interfaceStatsHandler)
+		defer e.bus.Unsubscribe(app.TopicInterfaceStatsUpdated, interfaceStatsHandler)
+
+		// Keep connection open until client disconnects or context is cancelled
+		go func() {
+			for {
+				if _, _, err := conn.ReadMessage(); err != nil {
+					cancel()
+					return
+				}
+			}
+		}()
+
+		<-ctx.Done()
+	}
+}