Chore: share one base class for the method-mapped permission classes

ViewDocumentsPermissions, TrashPermissions, PaperlessNotePermissions and
AcknowledgeTasksPermissions each repeated the same has_permission body and
disagreed on HTTP methods missing from their perms_map.

GlobalPermissionsByMethod now holds that logic once. HEAD is checked
against the GET entry and a method missing from the map is denied. The
task acknowledge map gains OPTIONS, now requiring change_paperlesstask
like POST instead of being open to any authenticated user. The global
statistics and system status checks also share their active and
authenticated preamble.

src/documents/permissions.py

@@ -1,4 +1,6 @@
 from typing import Any
+from typing import ClassVar
+from typing import TypeGuard
 from typing import TypeVar
 
 from django.contrib.auth.models import Group
@@ -62,28 +64,23 @@ class PaperlessAdminPermissions(BasePermission):
         return request.user.is_active and request.user.is_staff
 
 
-def has_global_statistics_permission(user: User | None) -> bool:
-    if (
-        user is None
-        or not getattr(user, "is_active", False)
-        or not getattr(user, "is_authenticated", False)
-    ):
-        return False
+def _is_active_and_authenticated(user: User | None) -> TypeGuard[User]:
+    return (
+        user is not None
+        and getattr(user, "is_active", False)
+        and getattr(user, "is_authenticated", False)
+    )
 
-    return getattr(user, "is_superuser", False) or user.has_perm(
-        "paperless.view_global_statistics",
+
+def has_global_statistics_permission(user: User | None) -> bool:
+    return _is_active_and_authenticated(user) and (
+        getattr(user, "is_superuser", False)
+        or user.has_perm("paperless.view_global_statistics")
     )
 
 
 def has_system_status_permission(user: User | None) -> bool:
-    if (
-        user is None
-        or not getattr(user, "is_active", False)
-        or not getattr(user, "is_authenticated", False)
-    ):
-        return False
-
-    return (
+    return _is_active_and_authenticated(user) and (
         getattr(user, "is_superuser", False)
         or getattr(user, "is_staff", False)
         or user.has_perm("paperless.view_system_monitoring")
@@ -705,7 +702,26 @@ def has_perms_owner_aware(user, perms, obj):
     return obj.owner is None or obj.owner == user or checker.has_perm(perms, obj)
 
 
-class ViewDocumentsPermissions(BasePermission):
+class GlobalPermissionsByMethod(BasePermission):
+    """
+    Requires the global (model-level) permissions listed in ``perms_map`` for
+    the request's HTTP method. HEAD is checked against the ``"GET"`` entry,
+    since DRF runs the GET handler for it. A method missing from
+    ``perms_map`` is denied.
+    """
+
+    perms_map: ClassVar[dict[str, list[str]]]
+
+    def has_permission(self, request: Any, view: Any) -> bool:
+        if not request.user or not request.user.is_authenticated:
+            return False
+
+        method = "GET" if request.method == "HEAD" else request.method
+        perms = self.perms_map.get(method)
+        return perms is not None and request.user.has_perms(perms)
+
+
+class ViewDocumentsPermissions(GlobalPermissionsByMethod):
     """
     Permissions class that checks for model permissions for only viewing Documents.
     """
@@ -716,31 +732,18 @@ class ViewDocumentsPermissions(BasePermission):
         "POST": ["documents.view_document"],
     }
 
-    def has_permission(self, request, view):
-        if not request.user or (not request.user.is_authenticated):  # pragma: no cover
-            return False
 
-        return request.user.has_perms(self.perms_map.get(request.method, []))
-
-
-class TrashPermissions(BasePermission):
+class TrashPermissions(GlobalPermissionsByMethod):
     """Check the global document permission for each trash operation."""
 
     perms_map = {
         "OPTIONS": ["documents.view_document"],
-        "HEAD": ["documents.view_document"],
         "GET": ["documents.view_document"],
         "POST": ["documents.delete_document"],
     }
 
-    def has_permission(self, request, view):
-        if not request.user or not request.user.is_authenticated:  # pragma: no cover
-            return False
 
-        return request.user.has_perms(self.perms_map.get(request.method, []))
-
-
-class PaperlessNotePermissions(BasePermission):
+class PaperlessNotePermissions(GlobalPermissionsByMethod):
     """
     Permissions class that checks for model permissions for Notes.
     """
@@ -760,28 +763,13 @@ class PaperlessNotePermissions(BasePermission):
         ],
     }
 
-    def has_permission(self, request, view):
-        if not request.user or (not request.user.is_authenticated):  # pragma: no cover
-            return False
 
-        perms = self.perms_map[request.method]
-
-        return request.user.has_perms(perms)
-
-
-class AcknowledgeTasksPermissions(BasePermission):
+class AcknowledgeTasksPermissions(GlobalPermissionsByMethod):
     """
     Permissions class that checks for model permissions for acknowledging tasks.
     """
 
     perms_map = {
+        "OPTIONS": ["documents.change_paperlesstask"],
         "POST": ["documents.change_paperlesstask"],
     }
-
-    def has_permission(self, request: Any, view: Any) -> bool:
-        if not request.user or not request.user.is_authenticated:  # pragma: no cover
-            return False
-
-        perms = self.perms_map.get(request.method, [])
-
-        return request.user.has_perms(perms)