Add ID-based pagination to logs using new decorators and an encrypted token

Fixes #599

data/model/__init__.py

@@ -95,4 +95,4 @@ config = Config()
 # moving the minimal number of things to _basequery
 # TODO document the methods and modules for each one of the submodules below.
 from data.model import (blob, build, image, log, notification, oauth, organization, permission,
-                        repository, storage, tag, team, token, user, release)
+                        repository, storage, tag, team, token, user, release, modelutil)

data/model/log.py

@@ -41,9 +41,7 @@ def get_aggregated_logs(start_time, end_time, performer=None, repository=None, n
   return query.group_by(date, LogEntry.kind)
 
 
-def list_logs(start_time, end_time, performer=None, repository=None, namespace=None, page=None,
-              count=None):
-
+def get_logs_query(start_time, end_time, performer=None, repository=None, namespace=None):
   Performer = User.alias()
   selections = [LogEntry, Performer]
 
@@ -52,10 +50,7 @@ def list_logs(start_time, end_time, performer=None, repository=None, namespace=N
                 .join(Performer, JOIN_LEFT_OUTER,
                   on=(LogEntry.performer == Performer.id).alias('performer')))
 
-  if page and count:
-    query = query.paginate(page, count)
-
-  return list(query.order_by(LogEntry.datetime.desc()))
+  return query
 
 
 def log_action(kind_name, user_or_organization_name, performer=None, repository=None,

data/model/modelutil.py

@@ -0,0 +1,29 @@
+def paginate(query, model, descending=False, page_token=None, limit=50):
+  """ Paginates the given query using an ID range, starting at the optional page_token.
+      Returns a *list* of matching results along with an unencrypted page_token for the
+      next page, if any. If descending is set to True, orders by the ID descending rather
+      than ascending.
+  """
+  query = query.limit(limit + 1)
+
+  if descending:
+    query = query.order_by(model.id.desc())
+  else:
+    query = query.order_by(model.id)
+
+  if page_token is not None:
+    start_id = page_token.get('start_id')
+    if start_id is not None:
+      if descending:
+        query = query.where(model.id <= start_id)
+      else:
+        query = query.where(model.id >= start_id)
+
+  results = list(query)
+  page_token = None
+  if len(results) > limit:
+    page_token = {
+      'start_id': results[limit].id
+    }
+
+  return results[0:limit], page_token