feat: handle unsubscribe

src/usecase/subscription/handle_unsubscription.py

@@ -0,0 +1,49 @@
+import datetime
+import logging
+from typing import TYPE_CHECKING
+
+from src import domain
+
+if TYPE_CHECKING:
+    from .. import Usecase
+
+log = logging.getLogger(__name__)
+
+
+async def handle_unsubscription(self: 'Usecase', user_telegram_id: int, channel_telegram_id: int) -> None:
+    async with self.database.transaction():
+        subscriber = await self.database.get_subscriber(user_telegram_id)
+        if not subscriber:
+            log.warning('Subscriber not found for telegram_id: %s', user_telegram_id)
+            return
+
+        subscriptions = await self.database.get_active_subscriptions_by_subscriber_and_channel(
+            subscriber.id, channel_telegram_id
+        )
+
+        if not subscriptions:
+            log.info(
+                'No active subscriptions found for subscriber %s (telegram_id: %s) in channel %s',
+                subscriber.id,
+                user_telegram_id,
+                channel_telegram_id,
+            )
+            return
+
+        for subscription in subscriptions:
+            subscription.status = domain.SubscriptionStatus.UNSUBSCRIBED
+            subscription.unsubscribed_at = datetime.datetime.now(datetime.UTC)
+            await self.database.update_subscription(subscription)
+
+            # Декрементируем счётчик подписок у закупа
+            placement = subscription.placement
+            if placement.subscriptions_count > 0:
+                placement.subscriptions_count -= 1
+                await self.database.update_placement(placement)
+
+            log.info(
+                'Subscription marked as unsubscribed: subscriber %s (telegram_id: %s) unsubscribed from placement %s',
+                subscriber.id,
+                user_telegram_id,
+                placement.id,
+            )