feat: upgrade NostrClient to bidirectional (publish + subscribe)

Add receive queue, subscription management, and event deduplication
to support incoming NIP-52 calendar events from relays.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

nostr/nostr_client.py

@@ -1,30 +1,36 @@
 """
-Publish-only Nostr client for the events extension.
+Bidirectional Nostr client for the events extension.
 
 Connects to the nostrclient extension's internal WebSocket to publish
-NIP-52 calendar events. No subscription/receive capabilities — this
-is a stripped-down version of nostrmarket's NostrClient.
+and subscribe to NIP-52 calendar events. Based on nostrmarket's
+NostrClient pattern.
 """
 
 import asyncio
 import json
 from asyncio import Queue
+from collections import OrderedDict
 from typing import Optional
 
 from loguru import logger
 from websocket import WebSocketApp
 
-from lnbits.helpers import encrypt_internal_message
+from lnbits.helpers import encrypt_internal_message, urlsafe_short_hash
 from lnbits.settings import settings
 
 from .event import NostrEvent
 
+MAX_SEEN_EVENTS = 500
+
 
 class NostrClient:
     def __init__(self):
+        self.receive_event_queue: Queue = Queue()
         self.send_req_queue: Queue = Queue()
         self.ws: Optional[WebSocketApp] = None
+        self.subscription_id = "events-" + urlsafe_short_hash()[:32]
         self.running = False
+        self._seen_events: OrderedDict[str, None] = OrderedDict()
 
     @property
     def is_websocket_connected(self):
@@ -45,8 +51,10 @@ class NostrClient:
             logger.info("[EVENTS] Connected to nostrclient WebSocket")
 
         def on_message(_, message):
-            # Log relay responses (OK, NOTICE) but don't process
-            logger.debug(f"[EVENTS] Relay response: {message[:200]}")
+            try:
+                self.receive_event_queue.put_nowait(message)
+            except Exception as e:
+                logger.error(f"[EVENTS] Failed to queue message: {e}")
 
         def on_error(_, error):
             logger.warning(f"[EVENTS] WebSocket error: {error}")
@@ -55,6 +63,9 @@ class NostrClient:
             logger.warning(
                 f"[EVENTS] WebSocket closed: {status_code} {message}"
             )
+            self.receive_event_queue.put_nowait(
+                ValueError("WebSocket closed")
+            )
 
         ws = WebSocketApp(
             ws_url,
@@ -87,11 +98,44 @@ class NostrClient:
                 logger.warning(f"[EVENTS] NostrClient error: {ex}")
                 await asyncio.sleep(60)
 
+    def is_duplicate_event(self, event_id: str) -> bool:
+        """Check if an event has been seen recently."""
+        if event_id in self._seen_events:
+            return True
+        self._seen_events[event_id] = None
+        if len(self._seen_events) > MAX_SEEN_EVENTS:
+            self._seen_events.popitem(last=False)
+        return False
+
+    async def get_event(self):
+        """Get next event from the receive queue."""
+        value = await self.receive_event_queue.get()
+        if isinstance(value, ValueError):
+            raise value
+        return value
+
     async def publish_nostr_event(self, e: NostrEvent):
         await self.send_req_queue.put(["EVENT", e.dict()])
 
+    async def subscribe(self, filters: list[dict]):
+        """Subscribe to events matching the given filters."""
+        self.subscription_id = "events-" + urlsafe_short_hash()[:32]
+        await self.send_req_queue.put(
+            ["REQ", self.subscription_id] + filters
+        )
+        logger.info(
+            f"[EVENTS] Subscribed to NIP-52 events "
+            f"(sub: {self.subscription_id[:20]}...)"
+        )
+
+    async def unsubscribe(self):
+        """Unsubscribe from current subscription."""
+        await self.send_req_queue.put(["CLOSE", self.subscription_id])
+
     async def stop(self):
+        await self.unsubscribe()
         self.running = False
+        await asyncio.sleep(2)
         if self.ws:
             try:
                 self.ws.close()