feat: notify document updates over websocket

apps/server/internal/httpserver/websocket.go

@@ -0,0 +1,88 @@
+package httpserver
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gorilla/websocket"
+
+	"github.com/tim/md-hub-secure/apps/server/internal/realtime"
+)
+
+const (
+	wsWriteWait  = 10 * time.Second
+	wsPongWait   = 60 * time.Second
+	wsPingPeriod = 45 * time.Second
+)
+
+var wsUpgrader = websocket.Upgrader{
+	ReadBufferSize:  1024,
+	WriteBufferSize: 1024,
+	CheckOrigin: func(r *http.Request) bool {
+		origin := r.Header.Get("Origin")
+		if origin == "" {
+			return true
+		}
+		return origin == "http://"+r.Host || origin == "https://"+r.Host
+	},
+}
+
+func (s *Server) handleWebSocket(w http.ResponseWriter, r *http.Request) {
+	conn, err := wsUpgrader.Upgrade(w, r, nil)
+	if err != nil {
+		s.logger.Warn("upgrade websocket", "error", err)
+		return
+	}
+
+	client := s.hub.NewClient(16)
+	s.hub.Register(client)
+
+	go s.readWebSocket(conn, client)
+	s.writeWebSocket(conn, client)
+}
+
+func (s *Server) readWebSocket(conn *websocket.Conn, client *realtime.Client) {
+	defer func() {
+		s.hub.Unregister(client)
+		_ = conn.Close()
+	}()
+	conn.SetReadLimit(1024)
+	_ = conn.SetReadDeadline(time.Now().Add(wsPongWait))
+	conn.SetPongHandler(func(string) error {
+		return conn.SetReadDeadline(time.Now().Add(wsPongWait))
+	})
+
+	for {
+		if _, _, err := conn.NextReader(); err != nil {
+			return
+		}
+	}
+}
+
+func (s *Server) writeWebSocket(conn *websocket.Conn, client *realtime.Client) {
+	ticker := time.NewTicker(wsPingPeriod)
+	defer func() {
+		ticker.Stop()
+		s.hub.Unregister(client)
+		_ = conn.Close()
+	}()
+
+	for {
+		select {
+		case message, ok := <-client.Send():
+			_ = conn.SetWriteDeadline(time.Now().Add(wsWriteWait))
+			if !ok {
+				_ = conn.WriteMessage(websocket.CloseMessage, []byte{})
+				return
+			}
+			if err := conn.WriteMessage(websocket.TextMessage, message); err != nil {
+				return
+			}
+		case <-ticker.C:
+			_ = conn.SetWriteDeadline(time.Now().Add(wsWriteWait))
+			if err := conn.WriteMessage(websocket.PingMessage, nil); err != nil {
+				return
+			}
+		}
+	}
+}