Add methods to convert from Document to Weaviate data object and vice…

…versa

integrations/weaviate/src/haystack_integrations/document_stores/weaviate/document_store.py

@@ -1,6 +1,7 @@
 # SPDX-FileCopyrightText: 2023-present deepset GmbH <[email protected]>
 #
 # SPDX-License-Identifier: Apache-2.0
+import base64
 from dataclasses import asdict
 from typing import Any, Dict, List, Optional, Tuple, Union
 
@@ -12,6 +13,7 @@
 from weaviate.auth import AuthCredentials
 from weaviate.config import Config, ConnectionConfig
 from weaviate.embedded import EmbeddedOptions
+from weaviate.util import generate_uuid5
 
 Number = Union[int, float]
 TimeoutType = Union[Tuple[Number, Number], Number]
@@ -195,6 +197,28 @@ def count_documents(self) -> int:
     def filter_documents(self, filters: Optional[Dict[str, Any]] = None) -> List[Document]:  # noqa: ARG002
         return []
 
+    def _to_data_object(self, document: Document) -> Dict[str, Any]:
+        """
+        Convert a Document to a Weviate data object ready to be saved.
+        """
+        data = document.to_dict(flatten=False)
+        # Weaviate forces a UUID as an id.
+        # We don't know if the id of our Document is a UUID or not, so we save it on a different field
+        # and let Weaviate a UUID that we're going to ignore completely.
+        data["_original_id"] = data.pop("id")
+        if (blob := data.pop("blob")) is not None:
+            # Weaviate wants the blob data as a base64 encoded string
+            # See the official docs for more information:
+            # https://weaviate.io/developers/weaviate/config-refs/datatypes#datatype-blob
+            data["blob_data"] = base64.b64encode(bytes(blob.pop("data"))).decode()
+            data["blob_mime_type"] = blob.pop("mime_type")
+        # The embedding vector is stored separately from the rest of the data
+        del data["embedding"]
+
+        # Weaviate doesn't like empty objects, let's delete meta if it's empty
+        if data["meta"] == {}:
+            del data["meta"]
+
     def write_documents(
         self,
         documents: List[Document],  # noqa: ARG002