teach abbreviate_time to understand timedelta

original review wanted to do this instead of depending on "humanize"

src/allmydata/test/test_util.py

@@ -3,6 +3,7 @@ def foo(): pass # keep the line number constant
 
 import os, time, sys
 from StringIO import StringIO
+from datetime import timedelta
 from twisted.trial import unittest
 from twisted.internet import defer, reactor
 from twisted.python.failure import Failure
@@ -75,6 +76,42 @@ class HumanReadable(unittest.TestCase):
                 hr(e) == "<NoArgumentException>" # python-2.4
                 or hr(e) == "NoArgumentException()") # python-2.5
 
+    def test_abbrev_time_1s(self):
+        diff = timedelta(seconds=1)
+        s = abbreviate.abbreviate_time(diff)
+        self.assertEqual('1 second ago', s)
+
+    def test_abbrev_time_25s(self):
+        diff = timedelta(seconds=25)
+        s = abbreviate.abbreviate_time(diff)
+        self.assertEqual('25 seconds ago', s)
+
+    def test_abbrev_time_future_5_minutes(self):
+        diff = timedelta(minutes=-5)
+        s = abbreviate.abbreviate_time(diff)
+        self.assertEqual('5 minutes in the future', s)
+
+    def test_abbrev_time_hours(self):
+        diff = timedelta(hours=4)
+        s = abbreviate.abbreviate_time(diff)
+        self.assertEqual('4 hours ago', s)
+
+    def test_abbrev_time_day(self):
+        diff = timedelta(hours=49)  # must be more than 2 days
+        s = abbreviate.abbreviate_time(diff)
+        self.assertEqual('2 days ago', s)
+
+    def test_abbrev_time_month(self):
+        diff = timedelta(days=91)
+        s = abbreviate.abbreviate_time(diff)
+        self.assertEqual('3 months ago', s)
+
+    def test_abbrev_time_year(self):
+        diff = timedelta(weeks=(5 * 52) + 1)
+        s = abbreviate.abbreviate_time(diff)
+        self.assertEqual('5 years ago', s)
+
+
 
 class MyList(list):
     pass

src/allmydata/util/abbreviate.py

@@ -1,5 +1,6 @@
 
 import re
+from datetime import timedelta
 
 HOUR = 3600
 DAY = 24*3600
@@ -8,24 +9,40 @@ MONTH = 30*DAY
 YEAR = 365*DAY
 
 def abbreviate_time(s):
+    postfix = ''
+    if isinstance(s, timedelta):
+        # this feels counter-intuitive that positive numbers in a
+        # time-delta are "the past"; but if you "do math" on two
+        # datetime instances as below, you get a "positve seconds"
+        # timedelta instance:
+        # a = datetime.utcnow()
+        # time.sleep(1)
+        # b = datetime.utcnow()
+        # print(b - a)  # 0:00:01.001203
+        s = s.total_seconds()
+        if s >= 0.0:
+            postfix = ' ago'
+        else:
+            postfix = ' in the future'
+            s = -s
     def _plural(count, unit):
         count = int(count)
         if count == 1:
-            return "%d %s" % (count, unit)
-        return "%d %ss" % (count, unit)
+            return "%d %s%s" % (count, unit, postfix)
+        return "%d %ss%s" % (count, unit, postfix)
     if s is None:
         return "unknown"
     if s < 120:
         return _plural(s, "second")
     if s < 3*HOUR:
-        return _plural(s/60, "minute")
+        return _plural(s / 60, "minute")
     if s < 2*DAY:
-        return _plural(s/HOUR, "hour")
+        return _plural(s / HOUR, "hour")
     if s < 2*MONTH:
-        return _plural(s/DAY, "day")
+        return _plural(s / DAY, "day")
     if s < 4*YEAR:
-        return _plural(s/MONTH, "month")
-    return _plural(s/YEAR, "year")
+        return _plural(s / MONTH, "month")
+    return _plural(s / YEAR, "year")
 
 def abbreviate_space(s, SI=True):
     if s is None: