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     28 
     29 from google.appengine.ext import db
     30 
     31 from datetime import timedelta, datetime
     32 import time
     33 
     34 from model.queuepropertymixin import QueuePropertyMixin
     35 
     36 
     37 class ActiveWorkItems(db.Model, QueuePropertyMixin):
     38     queue_name = db.StringProperty()
     39     item_ids = db.ListProperty(int)
     40     item_dates = db.ListProperty(float)
     41     date = db.DateTimeProperty(auto_now_add=True)
     42 
     43     # The id/date pairs should probably just be their own class.
     44     def _item_time_pairs(self):
     45         return zip(self.item_ids, self.item_dates)
     46 
     47     def _set_item_time_pairs(self, pairs):
     48         if pairs:
     49             # The * operator raises on an empty list.
     50             # db.Model does not tuples, we have to make lists.
     51             self.item_ids, self.item_dates = map(list, zip(*pairs))
     52         else:
     53             self.item_ids = []
     54             self.item_dates = []
     55 
     56     def _append_item_time_pair(self, pair):
     57         self.item_ids.append(pair[0])
     58         self.item_dates.append(pair[1])
     59 
     60     def _remove_item(self, item_id):
     61         nonexpired_pairs = [pair for pair in self._item_time_pairs() if pair[0] != item_id]
     62         self._set_item_time_pairs(nonexpired_pairs)
     63 
     64     @classmethod
     65     def key_for_queue(cls, queue_name):
     66         return "active-work-items-%s" % (queue_name)
     67 
     68     @classmethod
     69     def lookup_by_queue(cls, queue_name):
     70         return cls.get_or_insert(key_name=cls.key_for_queue(queue_name), queue_name=queue_name)
     71 
     72     @staticmethod
     73     def _expire_item(key, item_id):
     74         active_work_items = db.get(key)
     75         active_work_items._remove_item(item_id)
     76         active_work_items.put()
     77 
     78     def expire_item(self, item_id):
     79         return db.run_in_transaction(self._expire_item, self.key(), item_id)
     80 
     81     def deactivate_expired(self, now):
     82         one_hour_ago = time.mktime((now - timedelta(minutes=60)).timetuple())
     83         nonexpired_pairs = [pair for pair in self._item_time_pairs() if pair[1] > one_hour_ago]
     84         self._set_item_time_pairs(nonexpired_pairs)
     85 
     86     def next_item(self, work_item_ids, now):
     87         for item_id in work_item_ids:
     88             if item_id not in self.item_ids:
     89                 self._append_item_time_pair([item_id, time.mktime(now.timetuple())])
     90                 return item_id
     91         return None
     92 
     93     def time_for_item(self, item_id):
     94         for active_item_id, time in self._item_time_pairs():
     95             if active_item_id == item_id:
     96                 return datetime.fromtimestamp(time)
     97         return None
     98