Initialize LineUp app server

internal/hub.go

@@ -0,0 +1,60 @@
+package internal
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/gorilla/websocket"
+)
+
+// Client represents a connected user WebSocket connection.
+type Client struct {
+	UID  string
+	Conn *websocket.Conn
+}
+
+// Hub manages connected clients and their WebSocket connections.
+type Hub struct {
+	mu      sync.RWMutex
+	clients map[string]*Client // uid -> client
+}
+
+// NewHub creates a new Hub.
+func NewHub() *Hub {
+	return &Hub{clients: make(map[string]*Client)}
+}
+
+// Register adds a client connection.
+func (h *Hub) Register(uid string, conn *websocket.Conn) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	// Close existing connection if any
+	if old, ok := h.clients[uid]; ok {
+		old.Conn.Close()
+	}
+	h.clients[uid] = &Client{UID: uid, Conn: conn}
+}
+
+// Unregister removes a client connection.
+func (h *Hub) Unregister(uid string) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	delete(h.clients, uid)
+}
+
+// GetClient returns a client by uid.
+func (h *Hub) GetClient(uid string) *Client {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+	return h.clients[uid]
+}
+
+// PushToClient sends a JSON message to a specific client.
+// Returns an error if the client is not connected.
+func (h *Hub) PushToClient(uid string, msg []byte) error {
+	client := h.GetClient(uid)
+	if client == nil {
+		return fmt.Errorf("client %s not connected", uid)
+	}
+	return client.Conn.WriteMessage(websocket.TextMessage, msg)
+}