feat（channels）: support WeChat and WeCom image and file attachments

backend/app/api/channels.py

@@ -2,12 +2,15 @@
 
 import json
 import logging
+import re
 import secrets
 import threading
 import time
 from datetime import timedelta
+from urllib.parse import quote
 
 from fastapi import APIRouter, Depends, HTTPException, Query, Response
+from fastapi.responses import Response as FastAPIResponse
 from sqlalchemy import case, text, update
 from sqlalchemy.exc import IntegrityError
 from sqlmodel import Session, select
@@ -94,6 +97,23 @@
 router = APIRouter(prefix="/api/enterprise/channels", tags=["enterprise:channels"])
 
 
+def _channel_attachment_metadata(metadata: object) -> list[ChannelConversationAttachmentRead]:
+    if not isinstance(metadata, dict):
+        return []
+    raw_attachments = metadata.get("attachments")
+    if not isinstance(raw_attachments, list):
+        return []
+    attachments: list[ChannelConversationAttachmentRead] = []
+    for raw in raw_attachments:
+        if not isinstance(raw, dict):
+            continue
+        try:
+            attachments.append(ChannelConversationAttachmentRead.model_validate(raw))
+        except ValueError:
+            continue
+    return attachments
+
+
 def _patch_binding_config_key(
     db: Session,
     tenant_id: str,
@@ -1332,17 +1352,65 @@ def list_channel_conversation_messages(
             role=row.role,
             content=row.content,
             created_at=row.created_at.isoformat(),
-            attachments=[
-                ChannelConversationAttachmentRead(
-                    id=item.get("id"),
-                    filename=item.get("filename"),
-                    content_type=item.get("content_type"),
-                    size=item.get("size"),
-                    kind=item.get("kind"),
-                )
-                for item in ((row.metadata_json or {}).get("attachments") or [])
-            ]
-            or None,
+            attachments=_channel_attachment_metadata(row.metadata_json) or None,
         )
         for row in rows
     ]
+
+
+@router.get("/{binding_id}/conversations/{session_id}/messages/{message_id}/attachments/{attachment_id}")
+def get_channel_conversation_attachment(
+    binding_id: str,
+    session_id: str,
+    message_id: str,
+    attachment_id: str,
+    tenant_id: str = Query(...),
+    current_user: User = Depends(get_current_user),
+    db: Session = Depends(get_session),
+) -> FastAPIResponse:
+    from app.session.attachment_store import read_staged_chat_attachment
+    from app.session.session_schema import ChatAttachmentRead
+
+    ensure_current_user_tenant(tenant_id, current_user)
+    binding = _get_binding(db, tenant_id, binding_id)
+    _ensure_binding_manager(db, tenant_id, binding, current_user)
+    session_ids = {row.id for row in _binding_channel_sessions(db, binding)}
+    if session_id not in session_ids:
+        raise HTTPException(status_code=404, detail="Channel conversation not found")
+    message = db.get(Message, message_id)
+    if not message or message.tenant_id != tenant_id or message.session_id != session_id:
+        raise HTTPException(status_code=404, detail="Channel message not found")
+    raw_attachments = (message.metadata_json or {}).get("attachments")
+    if not isinstance(raw_attachments, list):
+        raise HTTPException(status_code=404, detail="Attachment not found")
+    raw = next(
+        (item for item in raw_attachments if isinstance(item, dict) and item.get("id") == attachment_id),
+        None,
+    )
+    session = db.get(ChatSession, session_id)
+    if raw is None or not session or not session.user_id:
+        raise HTTPException(status_code=404, detail="Attachment not found")
+    try:
+        attachment = ChatAttachmentRead.model_validate(raw)
+    except ValueError as exc:
+        raise HTTPException(status_code=404, detail="Attachment not found") from exc
+    data = read_staged_chat_attachment(
+        attachment,
+        tenant_id=tenant_id,
+        user_id=session.user_id,
+    )
+    if data is None:
+        raise HTTPException(status_code=404, detail="Attachment content not found")
+    filename = attachment.filename or "attachment"
+    ascii_filename = re.sub(r"[^\x20-\x7e]", "_", filename).replace('"', "'")
+    encoded_filename = quote(filename, safe="")
+    return FastAPIResponse(
+        content=data,
+        media_type=attachment.content_type or "application/octet-stream",
+        headers={
+            "Content-Disposition": (
+                f'attachment; filename="{ascii_filename}"; '
+                f"filename*=UTF-8''{encoded_filename}"
+            )
+        },
+    )