feat(file-storage): add local and azure blob backends

surfsense_backend/app/file_storage/backends/azure.py

@@ -0,0 +1,54 @@
+"""Azure Blob Storage backend (the first production target)."""
+
+from __future__ import annotations
+
+from collections.abc import AsyncIterator
+
+from app.file_storage.backends.base import StorageBackend
+
+
+class AzureBlobBackend(StorageBackend):
+    """Stores objects as blobs in an Azure Blob Storage container."""
+
+    backend_name = "azure"
+
+    def __init__(self, *, connection_string: str, container: str) -> None:
+        self._connection_string = connection_string
+        self._container = container
+
+    def _service(self):
+        from azure.storage.blob.aio import BlobServiceClient
+
+        return BlobServiceClient.from_connection_string(self._connection_string)
+
+    async def put(
+        self, key: str, data: bytes, *, content_type: str | None = None
+    ) -> None:
+        from azure.storage.blob import ContentSettings
+
+        settings = ContentSettings(content_type=content_type) if content_type else None
+        async with self._service() as service:
+            blob = service.get_blob_client(self._container, key)
+            await blob.upload_blob(data, overwrite=True, content_settings=settings)
+
+    async def open_stream(self, key: str) -> AsyncIterator[bytes]:
+        async with self._service() as service:
+            blob = service.get_blob_client(self._container, key)
+            downloader = await blob.download_blob()
+            async for chunk in downloader.chunks():
+                yield chunk
+
+    async def delete(self, key: str) -> None:
+        from azure.core.exceptions import ResourceNotFoundError
+
+        async with self._service() as service:
+            blob = service.get_blob_client(self._container, key)
+            try:
+                await blob.delete_blob()
+            except ResourceNotFoundError:
+                pass
+
+    async def exists(self, key: str) -> bool:
+        async with self._service() as service:
+            blob = service.get_blob_client(self._container, key)
+            return await blob.exists()