Fix V2 catalog and tag pagination

endpoints/v2/v2util.py

@@ -1,19 +1,42 @@
 from flask import request
 from app import get_app_url
+from util.pagination import encrypt_page_token, decrypt_page_token
+import urllib
+import logging
 
-_MAX_RESULTS_PER_PAGE = 100
+_MAX_RESULTS_PER_PAGE = 50
 
 def add_pagination(query, url):
   """ Adds optional pagination to the given query by looking for the Docker V2 pagination request
-      args. """
-  limit = request.args.get('n', None)
-  page = request.args.get('page', 1)
+      args.
+  """
+  try:
+    requested_limit = int(request.args.get('n', _MAX_RESULTS_PER_PAGE))
+  except ValueError:
+    requested_limit = 0
 
-  if limit is None:
-    return None, query
+  limit = max(min(requested_limit, _MAX_RESULTS_PER_PAGE), 1)
+  next_page_token = request.args.get('next_page', None)
 
-  limit = max(limit, _MAX_RESULTS_PER_PAGE)
+  # Decrypt the next page token, if any.
+  offset = 0
+  page_info = decrypt_page_token(next_page_token)
+  if page_info is not None:
+    # Note: we use offset here instead of ID >= n because one of the V2 queries is a UNION.
+    offset = page_info.get('offset', 0)
+    query = query.offset(offset)
+
+  query = query.limit(limit + 1)
   url = get_app_url() + url
-  query = query.paginate(page, limit)
-  link = url + '?n=%s&last=%s; rel="next"' % (limit, page + 1)
-  return link, query
+
+  results = list(query)
+  if len(results) <= limit:
+    return None, results
+
+  # Add a link to the next page of results.
+  page_info = dict(offset=limit + offset)
+  next_page_token = encrypt_page_token(page_info)
+
+  link = url + '?' + urllib.urlencode(dict(n=limit, next_page=next_page_token))
+  link = link + '; rel="next"'
+  return link, results[0:-1]