feat(channels): upload file attachments via IM channels (Slack, Telegram, Feishu) (#1040)

backend/src/channels/slack.py

@@ -9,7 +9,7 @@ from typing import Any
 from markdown_to_mrkdwn import SlackMarkdownConverter
 
 from src.channels.base import Channel
-from src.channels.message_bus import InboundMessageType, MessageBus, OutboundMessage
+from src.channels.message_bus import InboundMessageType, MessageBus, OutboundMessage, ResolvedAttachment
 
 logger = logging.getLogger(__name__)
 
@@ -128,6 +128,27 @@ class SlackChannel(Channel):
                 pass
         raise last_exc  # type: ignore[misc]
 
+    async def send_file(self, msg: OutboundMessage, attachment: ResolvedAttachment) -> bool:
+        if not self._web_client:
+            return False
+
+        try:
+            kwargs: dict[str, Any] = {
+                "channel": msg.chat_id,
+                "file": str(attachment.actual_path),
+                "filename": attachment.filename,
+                "title": attachment.filename,
+            }
+            if msg.thread_ts:
+                kwargs["thread_ts"] = msg.thread_ts
+
+            await asyncio.to_thread(self._web_client.files_upload_v2, **kwargs)
+            logger.info("[Slack] file uploaded: %s to channel=%s", attachment.filename, msg.chat_id)
+            return True
+        except Exception:
+            logger.exception("[Slack] failed to upload file: %s", attachment.filename)
+            return False
+
     # -- internal ----------------------------------------------------------
 
     def _add_reaction(self, channel_id: str, timestamp: str, emoji: str) -> None: