From c4ff75f44c0575394e2998c89813c2219210cfb8 Mon Sep 17 00:00:00 2001
From: Kevin Barnard <kbarnard@mbari.org>
Date: Thu, 12 Oct 2023 13:16:34 -0700
Subject: [PATCH] Implements #7

---
 lcm_websocket_server/app.py       |  9 ++++++++-
 lcm_websocket_server/lcmpubsub.py | 24 +++++++++++++++++++++---
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/lcm_websocket_server/app.py b/lcm_websocket_server/app.py
index 4688299..5362e58 100644
--- a/lcm_websocket_server/app.py
+++ b/lcm_websocket_server/app.py
@@ -15,6 +15,7 @@
 import asyncio
 import queue
 from signal import SIGINT, SIGTERM
+from urllib.parse import unquote
 
 from websockets import serve
 
@@ -44,8 +45,14 @@ async def republish_lcm(websocket, path):
         ip, port = websocket.remote_address[:2]
         logger.info(f"Client connected from {ip}:{port} at {path}")
 
+        # Extract channel regex
+        channel_regex = unquote(path.lstrip('/'))
+        if not channel_regex:  # empty path -> subscribe to all channels
+            channel_regex = '.*'
+
         # Create an LCM observer for this client
-        observer = LCMObserver()
+        observer = LCMObserver(channel_regex=channel_regex)
+        logger.debug(f"Created LCM observer with channel regex {channel_regex}")
         
         # Subscribe the observer to the LCM republisher
         lcm_republisher.subscribe(observer)
diff --git a/lcm_websocket_server/lcmpubsub.py b/lcm_websocket_server/lcmpubsub.py
index eb92049..837edc4 100644
--- a/lcm_websocket_server/lcmpubsub.py
+++ b/lcm_websocket_server/lcmpubsub.py
@@ -5,6 +5,7 @@
 import lcm
 
 import queue
+import re
 from threading import Thread
 
 from lcm_websocket_server.log import get_logger
@@ -15,12 +16,28 @@ class LCMObserver:
     """
     Observer for an LCMObservable. Puts received events in a thread-safe queue.
     """
-    def __init__(self):
+    def __init__(self, channel_regex: str = ".*"):
         self._queue = queue.Queue()
+        self._channel_regex = channel_regex
     
+    def match(self, channel: str) -> bool:
+        """
+        Check if the observer matches a given channel.
+
+        Args:
+            channel: Channel name
+        
+        Returns:
+            True if the observer matches the channel, False otherwise.
+        """
+        try:
+            return re.fullmatch(self._channel_regex, channel) is not None
+        except:
+            return False
+
     def handle(self, event):
         """
-        Handles an LCM event.
+        Handle an LCM event.
         """
         self._queue.put(event)
     
@@ -91,4 +108,5 @@ def _handler(self, channel, data):
             data: The LCM data
         """
         for subscriber in self._subscribers:
-            subscriber.handle((channel, data))
\ No newline at end of file
+            if subscriber.match(channel):
+                subscriber.handle((channel, data))
\ No newline at end of file