[Predator] Move time_util from common/ to lib/, split code review related part to code_review_util

appengine/findit/lib/time_util.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import calendar
 from datetime import datetime
 from datetime import time
 from datetime import timedelta
 
 import pytz
@@ skipping 48 matching lines @@
 
   Args:
     timezone_name (str): The name of any timezone supported by pytz.
     date_time (datetime.datetime): The optional datetime to be converted into
         the new timezone.
 
   Returns:
     A datetime.datetime of the given one in the specified timezone.
   """
   return date_time.astimezone(pytz.timezone(timezone_name))
+
+
+class TimeZoneInfo(object):

[stgao, 2016/11/03 22:14:05]

Can we make this a simple function like the other above?

[wrengr, 2016/11/03 22:17:58]

Why?

[stgao, 2016/11/03 23:04:52]

The current version of it looks simpler to me:
https://chromium.googlesource.com/infra/infra/+/master/appengine/findit/lib/g...

[Sharu Jiang, 2016/11/04 01:02:34]

Actually I prefer this one, because it's more expandable, we can easily add
something like UTCToLocal method and if we want to convert multiple local times
to utc (though, we don't have this kind of use cases right now), this would be
more efficient.

Simplified this class a little bit :)

[wrengr, 2016/11/04 20:24:26]

That's the direction I was thinking, whence my question. Timezone stuff (like
all time stuff) gets really hairy really quickly, so it makes sense to me to try
and encapsulate all that complexity in a class.

+  """Gets time zone info from string like: +0800.
+
+  The string is HHMM offset relative to UTC timezone."""
+
+  def __init__(self, offset_str):
+    super(TimeZoneInfo, self).__init__()
+    self._utcoffset = self.GetOffsetFromStr(offset_str)
+
+  def GetOffsetFromStr(self, offset_str):
+    offset = int(offset_str[-4:-2]) * 60 + int(offset_str[-2:])
+    if offset_str[0] == '-':
+      offset = -offset
+    return timedelta(minutes=offset)
+
+  @property
+  def utcoffset(self):
+    return self._utcoffset
+
+  def LocalToUTC(self, naive_time):
+    """Localizes naive datetime and converts it to utc naive datetime.
+
+    Args:
+      naive_time(datetime): naive time in local time zone, for example '+0800'.
+
+    Return:
+      A naive datetime object in utc time zone.
+      For example:
+      For TimeZoneInfo('+0800'), and naive local time is
+      datetime(2016, 9, 1, 10, 0, 0), the returned result should be
+      datetime(2016, 9, 1, 18, 0, 0) in utc time.

[stgao, 2016/11/03 22:14:05]

Is this true? Shouldn't it be datetime(2016, 9, 1, 2, 0, 0) in UTC for
datetime(2016, 9, 1, 10, 0, 0) at timezone +8?

[Sharu Jiang, 2016/11/04 01:02:34]

Oops, updated.

+    """
+    return naive_time - self.utcoffset