Add download hook

Change-Id: I46644ced4e2aaf64392be70133538b0a48478772

glare/engine.py

@@ -399,7 +399,7 @@ class Engine(object):
         blob_name = "%s[%s]" % (field_name, blob_key)\
             if blob_key else field_name
 
-        # check if property is downloadable
+        # check if field is downloadable
         if blob_key is None and not af.is_blob(field_name):
             msg = _("%s is not a blob") % field_name
             raise exception.BadRequest(msg)
@@ -440,4 +440,17 @@ class Engine(object):
             data = store_api.load_from_store(uri=blob['url'], context=context)
             meta['size'] = blob.get('size')
             meta['content_type'] = blob.get('content_type')
-        return data, meta
+
+        path = None
+        try:
+            try:
+                # call download hook first
+                data, path = af.validate_download(
+                    context, af, field_name, data)
+            except Exception as e:
+                raise exception.BadRequest(message=str(e))
+
+            return data, meta
+        finally:
+            if path:
+                os.remove(path)

glare/objects/base.py

@@ -619,7 +619,7 @@ class BaseArtifact(base.VersionedObject):
         :param context: user context
         :param af: artifact object targeted for deletion
         """
-        cls.validate_deletion(context, af)
+        cls.validate_delete(context, af)
         # marking artifact as deleted
         cls.db_api.update(context, af.id, {'status': cls.STATUS.DELETED})
 
@@ -829,13 +829,18 @@ class BaseArtifact(base.VersionedObject):
         """Validation hook for uploading."""
         return fd, None
 
+    @classmethod
+    def validate_download(cls, context, af, field_name, fd):
+        """Validation hook for downloading."""
+        return fd, None
+
     @classmethod
     def validate_publish(cls, context, af):
         """Validation hook for publishing."""
         pass
 
     @classmethod
-    def validate_deletion(cls, context, af):
+    def validate_delete(cls, context, af):
         """Validation hook for deletion."""
         pass