Merge pull request #153 from jonklein/fix/day_of_week_offsets

Fix/day of week offsets

parsedatetime/__init__.py

@@ -910,13 +910,31 @@ def _evalModifier(self, modifier, chunk1, chunk2, sourceTime):
                     sourceTime = sTime
                     ctx.updateAccuracy(ctx.ACU_HALFDAY)
             else:
+                # unless one of these modifiers is being applied to the
+                # day-of-week, we want to start with target as the day
+                # in the current week.
+                dowOffset = offset
+                if not modifier in ['next', 'last', 'prior', 'previous']:
+                    dowOffset = 0
+
                 wkdy = self.ptc.WeekdayOffsets[wkdy]
                 diff = self._CalculateDOWDelta(
-                    wd, wkdy, offset, self.ptc.DOWParseStyle,
+                    wd, wkdy, dowOffset, self.ptc.DOWParseStyle,
                     self.ptc.CurrentDOWParseStyle)
                 start = datetime.datetime(yr, mth, dy, startHour,
                                           startMinute, startSecond)
                 target = start + datetime.timedelta(days=diff)
+
+                if chunk1 != '':
+                    # consider "one day before thursday": we need to parse chunk1 ("one day")
+                    # and apply according to the offset ("before"), rather than allowing the
+                    # remaining parse step to apply "one day" without the offset direction.
+                    t, subctx = self.parse(chunk1, sourceTime, VERSION_CONTEXT_STYLE)
+                    if subctx.hasDateOrTime:
+                        delta = time.mktime(t) - time.mktime(sourceTime)
+                        target = start + datetime.timedelta(days=diff) + datetime.timedelta(seconds = delta * offset)
+                        chunk1 = ''
+
                 sourceTime = target.timetuple()
             ctx.updateAccuracy(ctx.ACU_DAY)
 

tests/TestSimpleOffsets.py

@@ -46,6 +46,40 @@ def testNow(self):
 
         self.assertExpectedResult(self.cal.parse('now', start), (target, 2))
 
+    def testOffsetFromDayOfWeek(self):
+        self.cal.ptc.StartTimeFromSourceTime = True
+
+        s = datetime.datetime(2016, 2, 16) # a Tuesday
+        t = datetime.datetime(2016, 2, 18) # Thursday of the same week
+        tPlusOffset = t + datetime.timedelta(hours=1)
+
+        start = s.timetuple()
+        target = t.timetuple()
+        targetPlusOffset = tPlusOffset.timetuple()
+
+        self.assertExpectedResult(
+            self.cal.parse('Thursday', start), (target, 1))
+
+        self.assertExpectedResult(
+            self.cal.parse('one hour from Thursday', start), (targetPlusOffset, 3))
+
+    def testOffsetBeforeDayOfWeek(self):
+        self.cal.ptc.StartTimeFromSourceTime = True
+
+        s = datetime.datetime(2016, 2, 16) # a Tuesday
+        t = datetime.datetime(2016, 2, 18) # Thursday of the same week
+        tPlusOffset = t + datetime.timedelta(hours=-1)
+
+        start = s.timetuple()
+        target = t.timetuple()
+        targetPlusOffset = tPlusOffset.timetuple()
+
+        self.assertExpectedResult(
+            self.cal.parse('Thursday', start), (target, 1))
+
+        self.assertExpectedResult(
+            self.cal.parse('one hour before Thursday', start), (targetPlusOffset, 3))
+
     def testMinutesFromNow(self):
         s = datetime.datetime.now()
         t = s + datetime.timedelta(minutes=5)