Simplify API permission validators

api/permissions.py

@@ -3,11 +3,9 @@ from rest_framework import permissions
 from datasources import models
 
 
-# TODO make permission class factory
-# TODO write permission tests
-
-class ViewPermission(permissions.BasePermission):
+class BaseUserPermission(permissions.BasePermission):
     message = 'You do not have permission to access this resource.'
+    permission_level = models.UserPermissionLevels.NONE
 
     def has_object_permission(self, request, view, obj):
         if not obj.access_control:
@@ -19,64 +17,27 @@ class ViewPermission(permissions.BasePermission):
                 datasource=obj
             )
 
-            return permission.granted >= models.UserPermissionLevels.VIEW
+            return permission.granted >= self.permission_level
 
         except models.UserPermissionLink.DoesNotExist:
             return False
 
 
-class MetadataPermission(permissions.BasePermission):
-    message = 'You do not have permission to access the metadata of this resource.'
-
-    def has_object_permission(self, request, view, obj):
-        if not obj.access_control:
-            return True
-
-        try:
-            permission = models.UserPermissionLink.objects.get(
-                user=request.user,
-                datasource=obj
-            )
+class ViewPermission(BaseUserPermission):
+    message = 'You do not have permission to access this resource.'
+    permission_level = models.UserPermissionLevels.VIEW
 
-            return permission.granted >= models.UserPermissionLevels.META
 
-        except models.UserPermissionLink.DoesNotExist:
-            return False
+class MetadataPermission(BaseUserPermission):
+    message = 'You do not have permission to access the metadata of this resource.'
+    permission_level = models.UserPermissionLevels.META
 
 
-class DataPermission(permissions.BasePermission):
+class DataPermission(BaseUserPermission):
     message = 'You do not have permission to access the data of this resource.'
+    permission_level = models.UserPermissionLevels.DATA
 
-    def has_object_permission(self, request, view, obj):
-        if not obj.access_control:
-            return True
-
-        try:
-            permission = models.UserPermissionLink.objects.get(
-                user=request.user,
-                datasource=obj
-            )
-
-            return permission.granted >= models.UserPermissionLevels.DATA
 
-        except models.UserPermissionLink.DoesNotExist:
-            return False
-
-
-class ProvPermission(permissions.BasePermission):
+class ProvPermission(BaseUserPermission):
     message = 'You do not have permission to access the prov data of this resource.'
-
-    def has_object_permission(self, request, view, obj):
-        if not obj.access_control:
-            return True
-
-        try:
-            permission = models.UserPermissionLink.objects.get(
-                user=request.user,
-                datasource=obj
-            )
-
-            return permission.granted >= models.UserPermissionLevels.PROV
-
-        except models.UserPermissionLink.DoesNotExist:
-            return False
+    permission_level = models.UserPermissionLevels.PROV