feat: add Kurigram property notification bot

src/property_bot/consumer.py

@@ -0,0 +1,72 @@
+from __future__ import annotations
+
+import asyncio
+from dataclasses import dataclass
+from datetime import UTC, datetime
+import json
+import logging
+from typing import Awaitable, Callable
+
+from websockets.asyncio.client import connect
+from websockets.exceptions import WebSocketException
+
+from .config import PropertyApiConfig
+from .listings import Listing, listing_from_event
+
+logger = logging.getLogger(__name__)
+ListingSink = Callable[[Listing], Awaitable[None]]
+
+
+@dataclass(slots=True)
+class ConnectionStatus:
+    connected: bool = False
+    last_connected_at: datetime | None = None
+    last_event_at: datetime | None = None
+    last_error: str | None = None
+
+
+class ListingEventConsumer:
+    def __init__(self, config: PropertyApiConfig, on_listing: ListingSink) -> None:
+        self._config = config
+        self._on_listing = on_listing
+        self.status = ConnectionStatus()
+
+    async def handle_message(self, raw_message: str | bytes) -> bool:
+        try:
+            payload = json.loads(raw_message)
+        except (TypeError, json.JSONDecodeError):
+            logger.warning("Ignoring invalid WebSocket JSON event")
+            return False
+        listing = listing_from_event(payload)
+        if listing is None:
+            return False
+        await self._on_listing(listing)
+        self.status.last_event_at = datetime.now(UTC)
+        return True
+
+    async def run(self) -> None:
+        delay = self._config.reconnect_initial_delay_seconds
+        while True:
+            try:
+                async with connect(
+                    self._config.websocket_url,
+                    open_timeout=self._config.connect_timeout_seconds,
+                    ping_interval=20,
+                    ping_timeout=20,
+                ) as websocket:
+                    self.status.connected = True
+                    self.status.last_connected_at = datetime.now(UTC)
+                    self.status.last_error = None
+                    delay = self._config.reconnect_initial_delay_seconds
+                    logger.info("Connected to property API: %s", self._config.websocket_url)
+                    async for message in websocket:
+                        await self.handle_message(message)
+            except asyncio.CancelledError:
+                raise
+            except (OSError, WebSocketException, TimeoutError) as error:
+                self.status.last_error = str(error)
+                logger.warning("Property API connection failed; retrying in %.1fs: %s", delay, error)
+            finally:
+                self.status.connected = False
+            await asyncio.sleep(delay)
+            delay = min(delay * 2, self._config.reconnect_max_delay_seconds)