fix(cp): use json.Marshal for error messages to properly escape special characters

Author: rgarcia

cmd/api/api/cp.go

@@ -100,21 +100,24 @@ func (s *ApiService) CpHandler(w http.ResponseWriter, r *http.Request) {
 	msgType, message, err := ws.ReadMessage()
 	if err != nil {
 		log.ErrorContext(ctx, "failed to read cp request", "error", err)
-		ws.WriteMessage(websocket.TextMessage, []byte(fmt.Sprintf(`{"type":"error","message":"failed to read request: %v"}`, err)))
+		errMsg, _ := json.Marshal(CpError{Type: "error", Message: fmt.Sprintf("failed to read request: %v", err)})
+		ws.WriteMessage(websocket.TextMessage, errMsg)
 		return
 	}
 
 	if msgType != websocket.TextMessage {
 		log.ErrorContext(ctx, "expected text message with JSON request", "type", msgType)
-		ws.WriteMessage(websocket.TextMessage, []byte(`{"type":"error","message":"first message must be JSON text"}`))
+		errMsg, _ := json.Marshal(CpError{Type: "error", Message: "first message must be JSON text"})
+		ws.WriteMessage(websocket.TextMessage, errMsg)
 		return
 	}
 
 	// Parse JSON request
 	var cpReq CpRequest
 	if err := json.Unmarshal(message, &cpReq); err != nil {
 		log.ErrorContext(ctx, "invalid JSON request", "error", err)
-		ws.WriteMessage(websocket.TextMessage, []byte(fmt.Sprintf(`{"type":"error","message":"invalid JSON: %v"}`, err)))
+		errMsg, _ := json.Marshal(CpError{Type: "error", Message: fmt.Sprintf("invalid JSON: %v", err)})
+		ws.WriteMessage(websocket.TextMessage, errMsg)
 		return
 	}