fix: prevent concurrent write to websocket connection

- refactor client handling and message broadcasting
- replace Client struct
- implement SendMessage method in Client struct for safer message sending
- update client map to use *models.Client instead of bool
- adjust BroadcastMessage and RunPomodoroTimer functions to use new client type

🤖

internal/broadcast/broadcast.go

@@ -8,7 +8,7 @@ import (
 )
 
 // BroadcastMessage sends a message to all connected WebSocket clients.
-func BroadcastMessage(clients map[*websocket.Conn]bool, message models.BroadcastMessage) {
+func BroadcastMessage(clients map[*websocket.Conn]*models.Client, message models.BroadcastMessage) {
 	// Marshal the message into JSON format
 	jsonMessage, err := json.Marshal(message)
 	if err != nil {
@@ -17,12 +17,11 @@ func BroadcastMessage(clients map[*websocket.Conn]bool, message models.Broadcast
 	}
 
 	// Iterate over all connected clients and broadcast the message
-	for client := range clients {
-		err := client.WriteMessage(websocket.TextMessage, jsonMessage)
+	for _, client := range clients {
+		err := client.SendMessage(websocket.TextMessage, jsonMessage)
 		if err != nil {
 			log.Printf("Error broadcasting to client: %v", err)
-			client.Close()
-			delete(clients, client) // Remove the client if an error occurs
+			// The client is responsible for closing itself on error
 		}
 	}
 }