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

Fixes #599

endpoints/api/__init__.py

@@ -1,5 +1,6 @@
 import logging
 import datetime
+import json
 
 from app import app, metric_queue
 from flask import Blueprint, request, make_response, jsonify, session
@@ -21,6 +22,7 @@ from auth.auth import process_oauth
 from endpoints.csrf import csrf_protect
 from endpoints.decorators import check_anon_protection
 from util.saas.metricqueue import time_decorator
+from util.security.aes import AESCipher
 
 
 logger = logging.getLogger(__name__)
@@ -209,6 +211,41 @@ def query_param(name, help_str, type=reqparse.text_type, default=None,
   return add_param
 
 
+def page_support(func):
+  """ Adds pagination support to an API endpoint. The decorated API will have an
+      added query parameter named 'next_page'. Works in tandem with the
+      modelutil paginate method.
+  """
+  @wraps(func)
+  @query_param('next_page', 'The page token for the next page', type=str)
+  def wrapper(self, query_args, *args, **kwargs):
+    page_token = None
+    unecrypted = None
+
+    if query_args['next_page']:
+      # Decrypt the page token.
+      cipher = AESCipher(app.config['PAGE_TOKEN_KEY'])
+      try:
+        unecrypted = cipher.decrypt(query_args['next_page'])
+      except TypeError:
+        pass
+
+      if unecrypted is not None:
+        try:
+          page_token = json.loads(unecrypted)
+        except ValueError:
+          pass
+
+    (result, next_page_token) = func(self, query_args, page_token, *args, **kwargs)
+    if next_page_token is not None:
+      cipher = AESCipher(app.config['PAGE_TOKEN_KEY'])
+      result['next_page'] = cipher.encrypt(json.dumps(next_page_token))
+
+    return result
+
+  return wrapper
+
+
 def parse_args(func):
   @wraps(func)
   def wrapper(self, *args, **kwargs):