API: Download doc api (#1354)

### What problem does this PR solve?

Adds download_document api

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

api/apps/dataset_api.py

 #  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
-
 import os
 import pathlib
 import re
 import warnings
+from io import BytesIO
 
-from flask import request
+from flask import request, send_file
 from flask_login import login_required, current_user
 from httpx import HTTPError
+from minio import S3Error
 
 from api.contants import NAME_LENGTH_LIMIT
 from api.db import FileType, ParserType, FileSource
         return construct_json_result(code=RetCode.DATA_ERROR, message=f"You try to upload {num_file_objs} files, "
                                                                       f"which exceeds the maximum number of uploading files: {MAXIMUM_OF_UPLOADING_FILES}")
 
+    # no dataset
+    exist, dataset = KnowledgebaseService.get_by_id(dataset_id)
+    if not exist:
+        return construct_json_result(message="Can't find this dataset", code=RetCode.DATA_ERROR)
+
     for file_obj in file_objs:
-        # the content of the file
-        file_content = file_obj.read()
         file_name = file_obj.filename
         # no name
         if not file_name:
         if 'http' in file_name:
             return construct_json_result(code=RetCode.ARGUMENT_ERROR, message="Remote files have not unsupported.")
 
-        # the content is empty, raising a warning
-        if file_content == b'':
-            warnings.warn(f"[WARNING]: The file {file_name} is empty.")
-
-    # no dataset
-    exist, dataset = KnowledgebaseService.get_by_id(dataset_id)
-    if not exist:
-        return construct_json_result(message="Can't find this dataset", code=RetCode.DATA_ERROR)
-
     # get the root_folder
     root_folder = FileService.get_root_folder(current_user.id)
     # get the id of the root_folder
             location = filename
             while MINIO.obj_exist(dataset_id, location):
                 location += "_"
+
             blob = file.read()
+            # the content is empty, raising a warning
+            if blob == b'':
+                warnings.warn(f"[WARNING]: The file {filename} is empty.")
+
             MINIO.put(dataset_id, location, blob)
+
             doc = {
                 "id": get_uuid(),
                 "kb_id": dataset.id,
     return value not in enum_class.__members__.values()
 
 # ----------------------------download a file-----------------------------------------------------
+@manager.route("/<dataset_id>/documents/<document_id>", methods=["GET"])
+@login_required
+def download_document(dataset_id, document_id):
+    try:
+        # Check whether there is this dataset
+        exist, _ = KnowledgebaseService.get_by_id(dataset_id)
+        if not exist:
+            return construct_json_result(code=RetCode.DATA_ERROR, message=f"This dataset '{dataset_id}' cannot be found!")
+
+        # Check whether there is this document
+        exist, document = DocumentService.get_by_id(document_id)
+        if not exist:
+            return construct_json_result(message=f"This document '{document_id}' cannot be found!",
+                                         code=RetCode.ARGUMENT_ERROR)
+
+        # The process of downloading
+        doc_id, doc_location = File2DocumentService.get_minio_address(doc_id=document_id)  # minio address
+        file_stream = MINIO.get(doc_id, doc_location)
+        if not file_stream:
+            return construct_json_result(message="This file is empty.", code=RetCode.DATA_ERROR)
+
+        file = BytesIO(file_stream)
+
+        # Use send_file with a proper filename and MIME type
+        return send_file(
+            file,
+            as_attachment=True,
+            download_name=document.name,
+            mimetype='application/octet-stream'  # Set a default MIME type
+        )
+
+    # Error
+    except Exception as e:
+        return construct_error_response(e)
 
 # ----------------------------start parsing-----------------------------------------------------
 
 
 # ----------------------------list the chunks of the file-----------------------------------------------------
 
-# ----------------------------delete the chunk-----------------------------------------------------
+# -- --------------------------delete the chunk-----------------------------------------------------
 
 # ----------------------------edit the status of the chunk-----------------------------------------------------
 
 
 # ----------------------------retrieval test-----------------------------------------------------
 
+
+

sdk/python/ragflow/ragflow.py

 #  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
-
 import json
 import os
 
 import requests
 
+from api.db.services.document_service import DocumentService
 from api.settings import RetCode
 
 
         return response.json()
 
     # ----------------------------download a file-----------------------------------------------------
-
+    def download_file(self, dataset_id, document_id):
+        endpoint = f"{self.dataset_url}/{dataset_id}/documents/{document_id}"
+        res = requests.get(endpoint, headers=self.authorization_header)
+
+        content = res.content  # binary data
+        # decode the binary data
+        try:
+            decoded_content = content.decode("utf-8")
+            json_data = json.loads(decoded_content)
+            return json_data  # message
+        except json.JSONDecodeError:  # binary data
+            _, document = DocumentService.get_by_id(document_id)
+            file_path = os.path.join(os.getcwd(), document.name)
+            with open(file_path, "wb") as file:
+                file.write(content)
+            return {"code": RetCode.SUCCESS, "data": content}
     # ----------------------------start parsing-----------------------------------------------------
 
     # ----------------------------stop parsing-----------------------------------------------------
     # ----------------------------get a specific chunk-----------------------------------------------------
 
     # ----------------------------retrieval test-----------------------------------------------------
+

sdk/python/test/common.py

 
 
-API_KEY = 'ImFhMmJhZmUwMmQxNzExZWZhZDdmMzA0M2Q3ZWU1MzdlIg.ZnDsIQ.u-0-_qCRU6a4WICxyAPsjaafyOo'
+API_KEY = 'IjJkOGQ4ZDE2MzkyMjExZWZhYTk0MzA0M2Q3ZWU1MzdlIg.ZoUfug.RmqcYyCrlAnLtkzk6bYXiXN3eEY'
 HOST_ADDRESS = 'http://127.0.0.1:9380'

sdk/python/test/test_document.py

 from ragflow import RAGFlow
 import pytest
 from common import API_KEY, HOST_ADDRESS
-from api.contants import NAME_LENGTH_LIMIT
 
 
 class TestFile(TestSdk):
         update_res = ragflow.update_file(created_res_id, doc_id, **params)
         assert (update_res["code"] == RetCode.DATA_ERROR and
                 update_res["message"] == "Illegal value ? for 'template_type' field.")
+
 # ----------------------------download a file-----------------------------------------------------
 
+    def test_download_nonexistent_document(self):
+        """
+        Test downloading a document which does not exist.
+        """
+        # create a dataset
+        ragflow = RAGFlow(API_KEY, HOST_ADDRESS)
+        created_res = ragflow.create_dataset("test_download_nonexistent_document")
+        created_res_id = created_res["data"]["dataset_id"]
+        res = ragflow.download_file(created_res_id, "imagination")
+        assert res["code"] == RetCode.ARGUMENT_ERROR and res["message"] == f"This document 'imagination' cannot be found!"
+
+    def test_download_document_in_nonexistent_dataset(self):
+        """
+        Test downloading a document whose dataset is nonexistent.
+        """
+        # create a dataset
+        ragflow = RAGFlow(API_KEY, HOST_ADDRESS)
+        created_res = ragflow.create_dataset("test_download_nonexistent_document")
+        created_res_id = created_res["data"]["dataset_id"]
+        # upload files
+        file_paths = ["test_data/test.txt"]
+        uploading_res = ragflow.upload_local_file(created_res_id, file_paths)
+        # get the doc_id
+        data = uploading_res["data"][0]
+        doc_id = data["id"]
+        # download file
+        res = ragflow.download_file("imagination", doc_id)
+        assert res["code"] == RetCode.DATA_ERROR and res["message"] == f"This dataset 'imagination' cannot be found!"
+
+    def test_download_document_with_success(self):
+        """
+        Test the downloading of a document with success.
+        """
+        # create a dataset
+        ragflow = RAGFlow(API_KEY, HOST_ADDRESS)
+        created_res = ragflow.create_dataset("test_download_nonexistent_document")
+        created_res_id = created_res["data"]["dataset_id"]
+        # upload files
+        file_paths = ["test_data/test.txt"]
+        uploading_res = ragflow.upload_local_file(created_res_id, file_paths)
+        # get the doc_id
+        data = uploading_res["data"][0]
+        doc_id = data["id"]
+        # download file
+        with open("test_data/test.txt", "rb") as file:
+            binary_data = file.read()
+        res = ragflow.download_file(created_res_id, doc_id)
+        assert res["code"] == RetCode.SUCCESS and res["data"] == binary_data
+
+    def test_download_an_empty_document(self):
+        """
+        Test the downloading of an empty document.
+        """
+        # create a dataset
+        ragflow = RAGFlow(API_KEY, HOST_ADDRESS)
+        created_res = ragflow.create_dataset("test_download_nonexistent_document")
+        created_res_id = created_res["data"]["dataset_id"]
+        # upload files
+        file_paths = ["test_data/empty.txt"]
+        uploading_res = ragflow.upload_local_file(created_res_id, file_paths)
+        # get the doc_id
+        data = uploading_res["data"][0]
+        doc_id = data["id"]
+        # download file
+        res = ragflow.download_file(created_res_id, doc_id)
+        assert res["code"] == RetCode.DATA_ERROR and res["message"] == "This file is empty."
+
 # ----------------------------start parsing-----------------------------------------------------
 
 # ----------------------------stop parsing-----------------------------------------------------