feat: support download uploaded documents (#532)

part of #466

---------

Co-authored-by: MingWei Liu <[email protected]>

backend/app/api/main.py

@@ -7,6 +7,7 @@
     user,
     api_key,
     feedback,
+    document,
 )
 from app.api.admin_routes.knowledge_base.routes import (
     router as admin_knowledge_base_router,
@@ -52,6 +53,7 @@
 api_router.include_router(feedback.router, tags=["chat"])
 api_router.include_router(user.router, tags=["user"])
 api_router.include_router(api_key.router, tags=["auth"])
+api_router.include_router(document.router, tags=["documents"])
 api_router.include_router(admin_chat_engine.router, tags=["admin/chat_engine"])
 api_router.include_router(admin_document_router, tags=["admin/documents"])
 api_router.include_router(admin_feedback.router, tags=["admin/feedback"])

backend/app/api/routes/document.py

@@ -0,0 +1,34 @@
+from fastapi import FastAPI, HTTPException, APIRouter
+from fastapi.responses import StreamingResponse
+from sqlmodel import Session
+from app.api.deps import SessionDep
+from app.repositories import document_repo
+from app.file_storage import get_file_storage
+
+router = APIRouter()
+
+@router.get("/documents/{doc_id}/download")
+def download_file(
+    doc_id: int,
+    session: SessionDep
+):
+    doc = document_repo.must_get(session, doc_id)
+
+    name = doc.source_uri
+    filestorage = get_file_storage()
+    if filestorage.exists(name):
+        file_size = filestorage.size(name)
+        headers = {"Content-Length": str(file_size)}
+        def iterfile():
+            with filestorage.open(name) as f:
+                yield from f
+        return StreamingResponse(
+            iterfile(),
+            media_type = doc.mime_type,
+            headers = headers
+        )
+    else:
+        raise HTTPException(status_code = 404, detail = "File not found")
+
+
+