refactor upload_to

anchor/admin.py

@@ -1,11 +1,7 @@
-import os
-from typing import Any
-
 from django import forms
 from django.conf import settings
 from django.contrib import admin
 from django.template.defaultfilters import filesizeformat
-from django.utils import timezone
 from django.utils.html import format_html
 
 from anchor.models import Attachment, Blob, VariantRecord
@@ -31,19 +27,16 @@ def save(self, commit=True):
         return Blob.objects.create(
             file=self.cleaned_data["file"],
             backend=self.cleaned_data["backend"],
-            key=self.get_key(self.cleaned_data["file"]),
+            key=Blob.key_with_upload_to(
+                upload_to=anchor_settings.ADMIN_UPLOAD_TO,
+                instance=None,
+                file=self.cleaned_data["file"],
+            ),
         )
 
     def save_m2m(self):
         pass
 
-    def get_key(self, file: Any) -> str:
-        if anchor_settings.ADMIN_UPLOAD_TO:
-            dirname = timezone.now().strftime(anchor_settings.ADMIN_UPLOAD_TO)
-            return os.path.join(dirname, Blob.generate_key())
-
-        return Blob.generate_key()
-
 
 @admin.register(Attachment)
 class AttachmentAdmin(admin.ModelAdmin):

anchor/models/blob/blob.py

@@ -3,7 +3,6 @@
 import logging
 import mimetypes
 import os
-from secrets import token_bytes
 from typing import Any, Optional
 
 from django.core.files import File as DjangoFile
@@ -16,6 +15,7 @@
 from anchor.settings import anchor_settings
 from anchor.support.signing import AnchorSigner
 
+from .keys import KeysMixin
 from .representations import RepresentationsMixin
 
 logger = logging.getLogger("anchor")
@@ -48,7 +48,7 @@ def from_path(self, path: str, **kwargs):
             return self.create(file=f, **kwargs)
 
 
-class Blob(RepresentationsMixin, BaseModel):
+class Blob(KeysMixin, RepresentationsMixin, BaseModel):
     """
     Stores metadata for files stored by Django Anchor.
     """
@@ -271,24 +271,6 @@ def storage(self) -> Storage:
         """
         return storages.create_storage(storages.backends[self.backend])
 
-    @classmethod
-    def generate_key(cls):
-        """
-        Generates a random key to store this blob in the storage backend.
-
-        Keys are hard to guess, but shouldn't be shared directly with users,
-        preferring to use :py:attr:`signed_id` instead, which can be expired.
-
-        They use the base32 encoding to ensure no compatibility issues arise in
-        case insensitive file systems.
-        """
-        return (
-            base64.b32encode(token_bytes(cls.KEY_LENGTH))
-            .decode("utf-8")
-            .replace("=", "")
-            .lower()
-        )
-
     def url(self, expires_in: timezone.timedelta = None, disposition: str = "inline"):
         """
         Returns a URL to the file's location in the storage backend.

anchor/models/blob/keys.py

@@ -0,0 +1,47 @@
+import base64
+import os
+from secrets import token_bytes
+from typing import Any, Callable
+
+from django.db import models
+from django.utils import timezone
+
+FileLike = Any
+UploadToCallable = Callable[[models.Model, FileLike], str] | str | None
+
+
+class KeysMixin:
+    @classmethod
+    def generate_key(cls):
+        """
+        Generates a random key to store this blob in the storage backend.
+
+        Keys are hard to guess, but shouldn't be shared directly with users,
+        preferring to use :py:attr:`signed_id` instead, which can be expired.
+
+        They use the base32 encoding to ensure no compatibility issues arise in
+        case insensitive file systems.
+        """
+        return (
+            base64.b32encode(token_bytes(cls.KEY_LENGTH))
+            .decode("utf-8")
+            .replace("=", "")
+            .lower()
+        )
+
+    @classmethod
+    def key_with_upload_to(
+        cls,
+        upload_to: UploadToCallable = None,
+        instance: models.Model = None,
+        file: FileLike = None,
+    ) -> str:
+        if upload_to is None:
+            return cls.generate_key()
+        elif isinstance(upload_to, str) and file is not None:
+            dir = timezone.now().strftime(str(upload_to))
+            return os.path.join(dir, cls.generate_key())
+        elif callable(upload_to):
+            return upload_to(instance, file)
+        else:
+            raise ValueError("upload_to must be a string or a callable")

anchor/models/fields/single_attachment.py

@@ -1,12 +1,10 @@
-import os
 from typing import Any, Callable
 
 from django.contrib.contenttypes.fields import GenericRel, GenericRelation
 from django.contrib.contenttypes.models import ContentType
 from django.db import models
 from django.db.models import Model
 from django.db.models.fields.related_descriptors import ReverseOneToOneDescriptor
-from django.utils import timezone
 from django.utils.functional import cached_property
 from django.utils.text import capfirst
 
@@ -82,7 +80,9 @@ def __set__(self, instance, value):
             blob = value
         elif hasattr(value, "read"):  # quacks like a file?
             blob = Blob.objects.create(
-                file=value, backend=self.backend, key=self.get_key(value)
+                file=value,
+                backend=self.backend,
+                key=Blob.key_with_upload_to(self.upload_to, value),
             )
         else:
             raise ValueError(
@@ -138,17 +138,6 @@ def instance_attr(i):
             False,
         )
 
-    def get_key(self, value: Any):
-        if self.upload_to is None:
-            return Blob.generate_key()
-        elif isinstance(self.upload_to, str):
-            dir = timezone.now().strftime(str(self.upload_to))
-            return os.path.join(dir, Blob.generate_key())
-        elif callable(self.upload_to):
-            return self.upload_to(self.model, value)
-        else:
-            raise ValueError("upload_to must be a string or a callable")
-
 
 class SingleAttachmentField(GenericRelation):
     """