# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1332713662 -7200
# Node ID b8f1a2cc8866491f6cac60bc660d747551af14ec
# Parent  fe647b8e49e4dabaa63aaafa104cb3ccc211e5e1
Fixed the Olson zone offset calculation to produce correct offsets for zones
west of the prime meridian in a form consistent with those generated using
explicit offsets (where the sign of the hours and minutes is always the same).
Changed the subtraction of dates, months and non-time objects to produce the
actual difference between those objects.
Added explicit subtraction support for times.
Added some tests.

diff -r fe647b8e49e4 -r b8f1a2cc8866 DateSupport.py
--- a/DateSupport.py	Sun Mar 25 21:19:17 2012 +0200
+++ b/DateSupport.py	Mon Mar 26 00:14:22 2012 +0200
@@ -29,7 +29,7 @@
 month_regexp_str = ur'(?P<year>[0-9]{4})-(?P<month>[0-9]{2})'
 date_regexp_str = ur'(?P<year>[0-9]{4})-(?P<month>[0-9]{2})-(?P<day>[0-9]{2})'
 time_regexp_str = ur'(?P<hour>[0-2][0-9]):(?P<minute>[0-5][0-9])(?::(?P<second>[0-6][0-9]))?'
-timezone_offset_str = ur'(?P<offset>(UTC)?(?:(?P<sign>[-+])(?P<hours>[0-9]{2})(?::?(?P<minutes>[0-9]{2}))?))'
+timezone_offset_str = ur'(?P<offset>(UTC)?(?:(?P<sign>[-+])?(?P<hours>[0-9]{2})(?::?(?P<minutes>[0-9]{2}))?))'
 timezone_olson_str = ur'(?P<olson>[a-zA-Z]+(?:/[-_a-zA-Z]+){1,2})'
 timezone_utc_str = ur'UTC'
 timezone_regexp_str = ur'(?P<zone>' + timezone_offset_str + '|' + timezone_olson_str + '|' + timezone_utc_str + ')'
@@ -56,6 +56,12 @@
 
 # Utility functions.
 
+def sign(x):
+    if x < 0:
+        return -1
+    else:
+        return 1
+
 def int_or_none(x):
     if x is None:
         return x
@@ -164,10 +170,12 @@
         else:
             data = self.as_tuple()
             other_data = other.as_tuple()
+            direction = self < other and 1 or -1
+
             if len(data) < len(other_data):
-                return len(self.until(other))
+                return (len(self.until(other)) - 1) * direction
             else:
-                return len(other.until(self))
+                return (len(other.until(self)) - 1) * -direction
 
     def _until(self, start, end, nextfn, prevfn):
 
@@ -442,6 +450,25 @@
 
         return Date.__cmp__(this, other)
 
+    def __sub__(self, other):
+
+        """
+        Return the difference between this object and the 'other' object at the
+        highest common accuracy of both objects.
+        """
+
+        if not isinstance(other, Temporal):
+            return NotImplemented
+        elif not other.has_time():
+            return self.as_date() - other
+        else:
+            utc = self.to_utc()
+            other = other.to_utc()
+            days = utc.as_date() - other.as_date()
+            h1, m1, s1 = utc.as_tuple()[3:6]
+            h2, m2, s2 = other.as_tuple()[3:6]
+            return days * 24 * 3600 + (h1 - h2) * 3600 + (m1 - m2) * 60 + s1 - s2
+
     def has_time(self):
 
         """
@@ -546,12 +573,12 @@
         match = timezone_offset_regexp.match(zone)
         if match:
             if match.group("sign") == "-":
-                sign = -1
+                offset_sign = -1
             else:
-                sign = 1
+                offset_sign = 1
 
-            hours = int(match.group("hours")) * sign
-            minutes = int(match.group("minutes") or 0) * sign
+            hours = int(match.group("hours")) * offset_sign
+            minutes = int(match.group("minutes") or 0) * offset_sign
             return hours, minutes
 
         # Attempt to handle Olson time zone identifiers.
@@ -559,9 +586,9 @@
         dt = self.as_olson_datetime()
         if dt:
             seconds = dt.utcoffset().seconds + dt.utcoffset().days * 24 * 3600
-            hours = seconds / 3600
-            minutes = (seconds % 3600) / 60
-            return hours, minutes
+            hours = abs(seconds) / 3600
+            minutes = (abs(seconds) % 3600) / 60
+            return sign(seconds) * hours, sign(seconds) * minutes
 
         # Otherwise return None.
 
diff -r fe647b8e49e4 -r b8f1a2cc8866 tests/test_dates.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test_dates.py	Mon Mar 26 00:14:22 2012 +0200
@@ -0,0 +1,60 @@
+#!/usr/bin/env python
+
+from DateSupport import *
+
+d1 = DateTime((2012, 3, 25, 20, 45, 30, "Europe/Oslo"))
+d2 = DateTime((2012, 3, 25, 21, 05, 25, "Europe/Oslo"))
+ts1 = Timespan(d1, d1)
+ts2 = Timespan(d1, d2)
+
+#                              expected         result        operands
+print "%r : %r <- %r < %r"  % (d1 < d2,         d1 < d2,      d1, d2)
+print "%r : %r <- %r == %r" % (not d1 == d2,    d1 == d2,     d1, d2)
+print "%r : %r <- %r < %r"  % (ts1 < ts2,       ts1 < ts2,    ts1, ts2)
+print "%r : %r <- %r == %r" % (not ts1 == ts2,  ts1 == ts2,   ts1, ts2)
+
+d2_offset = d2.utc_offset()
+
+#                                     expected             result       operands
+print "%r : %r <- %r.utc_offset()" % (d2_offset == (2, 0), d2_offset,   d2)
+
+d3 = DateTime((2012, 3, 25, 21, 05, 25, "America/Montreal"))
+d4 = DateTime((2012, 3, 25, 21, 05, 25, "America/Anchorage"))
+d5 = DateTime((2012, 3, 25, 21, 05, 25, "America/St_Johns"))
+d6 = DateTime((2012, 3, 25, 21, 05, 25, "America/Vancouver"))
+d7 = DateTime((2012, 3, 25, 21, 05, 25, "-05:45"))
+d8 = DateTime((2012, 3, 25, 21, 05, 25, "05:45"))
+
+#                              expected         result        operands
+print "%r : %r <- %r < %r"  % (d2 < d3,         d2 < d3,      d2, d3)
+print "%r : %r <- %r < %r"  % (d3 < d4,         d3 < d4,      d3, d4)
+print "%r : %r <- %r > %r"  % (d4 > d5,         d4 > d5,      d4, d5)
+print "%r : %r <- %r > %r"  % (not d5 > d6,     d5 > d6,      d5, d6)
+print "%r : %r <- %r > %r"  % (d6 > d7,         d6 > d7,      d6, d7)
+print "%r : %r <- %r > %r"  % (d7 > d8,         d7 > d8,      d7, d8)
+
+d3_offset = d3.utc_offset()
+d4_offset = d4.utc_offset()
+d5_offset = d5.utc_offset()
+d6_offset = d6.utc_offset()
+d7_offset = d7.utc_offset()
+d8_offset = d8.utc_offset()
+
+#                                     expected                  result       operands
+print "%r : %r <- %r.utc_offset()" % (d3_offset == (-4, 0),     d3_offset,   d3)
+print "%r : %r <- %r.utc_offset()" % (d4_offset == (-8, 0),     d4_offset,   d4)
+print "%r : %r <- %r.utc_offset()" % (d5_offset == (-2, -30),   d5_offset,   d5)
+print "%r : %r <- %r.utc_offset()" % (d6_offset == (-7, 0),     d6_offset,   d6)
+print "%r : %r <- %r.utc_offset()" % (d7_offset == (-5, -45),   d7_offset,   d7)
+print "%r : %r <- %r.utc_offset()" % (d8_offset == (5, 45),     d8_offset,   d8)
+
+#                              expected                 result        operands
+print "%r : %r <- %r - %r"  % (d2 - d2 == 0,            d2 - d2,      d2, d2)
+print "%r : %r <- %r - %r"  % (d3 - d2 == 6 * 3600,     d3 - d2,      d3, d2)
+print "%r : %r <- %r - %r"  % (d4 - d2 == 10 * 3600,    d4 - d2,      d4, d2)
+print "%r : %r <- %r - %r"  % (d5 - d2 == 4.5 * 3600,   d5 - d2,      d5, d2)
+print "%r : %r <- %r - %r"  % (d6 - d2 == 9 * 3600,     d6 - d2,      d6, d2)
+print "%r : %r <- %r - %r"  % (d7 - d2 == 7.75 * 3600,  d7 - d2,      d7, d2)
+print "%r : %r <- %r - %r"  % (d8 - d2 == -3.75 * 3600, d8 - d2,      d8, d2)
+
+# vim: tabstop=4 expandtab shiftwidth=4