--- a/libervia/pages/_browser/bridge.py	Sat Apr 08 13:44:11 2023 +0200
+++ b/libervia/pages/_browser/bridge.py	Mon May 22 11:57:44 2023 +0200
@@ -1,4 +1,4 @@
-from browser import window, timer, console as log
+from browser import window, aio, timer, console as log
 import time
 import random
 import json
@@ -11,6 +11,29 @@
 log.info(f"TAB ID is {tab_id}")
 
 
+class BridgeException(Exception):
+    """An exception which has been raised from the backend and arrived to the frontend."""
+
+    def __init__(self, name, message="", condition=""):
+        """
+
+        @param name (str): full exception class name (with module)
+        @param message (str): error message
+        @param condition (str) : error condition
+        """
+        Exception.__init__(self)
+        self.fullname = str(name)
+        self.message = str(message)
+        self.condition = str(condition) if condition else ""
+        self.module, __, self.classname = str(self.fullname).rpartition(".")
+
+    def __str__(self):
+        return f"{self.classname}: {self.message or ''}"
+
+    def __eq__(self, other):
+        return self.classname == other
+
+
 class WebSocket:
 
     def __init__(self, broadcast_channel):
@@ -243,12 +266,12 @@
         })
 
 
-class bridge:
+class Bridge:
     bc: BroadcastChannel | None = None
 
     def __init__(self) -> None:
-        if bridge.bc is None:
-            bridge.bc = BroadcastChannel()
+        if Bridge.bc is None:
+            Bridge.bc = BroadcastChannel()
 
     def __getattr__(self, attr):
         return lambda *args, **kwargs: self.call(attr, *args, **kwargs)
@@ -268,7 +291,7 @@
                 errback(ret)
         else:
             log.error(
-                f"bridge called failed: code: {xhr.response}, text: {xhr.statusText}"
+                f"bridge call failed: code: {xhr.response}, text: {xhr.statusText}"
             )
             if errback is not None:
                 errback({"fullname": "BridgeInternalError", "message": xhr.statusText})
@@ -289,3 +312,37 @@
     def register_signal(self, signal: str, handler, iface=None) -> None:
         BroadcastChannel.handlers.setdefault(signal, []).append(handler)
         log.debug(f"signal {signal} has been registered")
+
+
+class AsyncBridge:
+
+    def __getattr__(self, attr):
+        return lambda *args, **kwargs: self.call(attr, *args, **kwargs)
+
+    async def call(self, method_name, *args, **kwargs):
+        print(f"calling {method_name}")
+        data = javascript.JSON.stringify({
+            "args": args,
+            "kwargs": kwargs,
+        })
+        url = f"/_bridge/{method_name}"
+        r = await aio.post(
+            url,
+            headers={
+                'X-Csrf-Token': window.csrf_token,
+            },
+            data=data,
+        )
+
+        if r.status == 200:
+            return javascript.JSON.parse(r.data)
+        elif r.status == 502:
+            ret = javascript.JSON.parse(r.data)
+            raise BridgeException(ret['fullname'], ret['message'], ret['condition'])
+        else:
+            print(f"bridge called failed: code: {r.status}, text: {r.statusText}")
+            raise BridgeException("InternalError", r.statusText)
+
+    def register_signal(self, signal: str, handler, iface=None) -> None:
+        BroadcastChannel.handlers.setdefault(signal, []).append(handler)
+        log.debug(f"signal {signal} has been registered")