Fix bug in time_util library

The add_duration library didn't calculate the days correctly. These
fixes make it compliant with the format described in
https://www.w3.org/TR/xmlschema-2/#adding-durations-to-dateTimes

Author: nsklikas

src/saml2/time_util.py

@@ -140,19 +140,20 @@ def add_duration(tid, duration):
         carry = f_quotient(temp, 60)
         # hours
         temp = tid.tm_hour + dur["tm_hour"] + carry
-        hour = modulo(temp, 60)
-        carry = f_quotient(temp, 60)
+        hour = modulo(temp, 24)
+        carry = f_quotient(temp, 24)
         # days
-        if dur["tm_mday"] > maximum_day_in_month_for(year, month):
+        if tid.tm_mday > maximum_day_in_month_for(year, month):
             temp_days = maximum_day_in_month_for(year, month)
-        elif dur["tm_mday"] < 1:
+        elif tid.tm_mday < 1:
             temp_days = 1
         else:
-            temp_days = dur["tm_mday"]
-        days = temp_days + tid.tm_mday + carry
+            temp_days = tid.tm_mday
+        days = temp_days + dur["tm_mday"] + carry
         while True:
             if days < 1:
-                pass
+                days = days + maximum_day_in_month_for(year, month - 1)
+                carry = -1
             elif days > maximum_day_in_month_for(year, month):
                 days -= maximum_day_in_month_for(year, month)
                 carry = 1

tests/test_10_time_util.py

@@ -92,7 +92,7 @@ def test_parse_duration_n():
         assert d == _val
 
 def test_add_duration_1():
-    #2000-01-12T12:13:14Z	P1Y3M5DT7H10M3S	2001-04-17T19:23:17Z    
+    #2000-01-12T12:13:14Z	P1Y3M5DT7H10M3S	2001-04-17T19:23:17Z
     t = add_duration(str_to_time("2000-01-12T12:13:14Z"), "P1Y3M5DT7H10M3S")
     assert t.tm_year == 2001
     assert t.tm_mon == 4
@@ -107,7 +107,7 @@ def test_add_duration_2():
     t = add_duration(str_to_time("2000-01-12T00:00:00Z"), "PT33H")
     assert t.tm_year == 2000
     assert t.tm_mon == 1
-    assert t.tm_mday == 14
+    assert t.tm_mday == 13
     assert t.tm_hour == 9
     assert t.tm_min == 0
     assert t.tm_sec == 0
@@ -119,7 +119,7 @@ def test_str_to_time():
     #t = time.mktime(str_to_time("2000-01-12T00:00:00Z"))
     #assert t == 947631600.0
     #TODO: add something to show how this time was arrived at
-    # do this as an external method in the 
+    # do this as an external method in the
     assert t == 947635200
     # some IdPs omit the trailing Z, and SAML spec is unclear if it is actually required
     t = calendar.timegm(str_to_time("2000-01-12T00:00:00"))