# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1439153849 -7200
# Node ID cb98880e024feda4c52dfa282d332cbb8b449657
# Parent  62b87431494268f29355575f078b079bd1f1dde2
Introduced a common method for obtaining the "main period" of an object.
Fixed period enumeration where an object specifies an UNTIL property but where
no overriding limit is given.

diff -r 62b874314942 -r cb98880e024f imiptools/data.py
--- a/imiptools/data.py	Thu Aug 06 22:00:45 2015 +0200
+++ b/imiptools/data.py	Sun Aug 09 22:57:29 2015 +0200
@@ -174,6 +174,27 @@
 
     # Computed results.
 
+    def get_main_period_items(self, tzid):
+
+        """
+        Return two (value, attributes) items corresponding to the main start-end
+        period for the object.
+        """
+
+        dtstart, dtstart_attr = self.get_datetime_item("DTSTART")
+
+        if self.has_key("DTEND"):
+            dtend, dtend_attr = self.get_datetime_item("DTEND")
+            duration = dtend - dtstart
+        elif self.has_key("DURATION"):
+            duration = self.get_duration("DURATION")
+            dtend = dtstart + duration
+            dtend_attr = dtstart_attr
+        else:
+            dtend, dtend_attr = dtstart, dtstart_attr
+
+        return (dtstart, dtstart_attr), (dtend, dtend_attr)
+
     def get_periods(self, tzid, end=None):
 
         """
@@ -294,6 +315,33 @@
 
         return self.get_value("SEQUENCE") is not None
 
+    def possibly_active_from(self, dt, tzid):
+
+        """
+        Return whether the object is possibly active from or after the given
+        datetime 'dt' using 'tzid' to convert any dates or floating datetimes.
+        """
+
+        dt = to_datetime(dt, tzid)
+        periods = self.get_periods(tzid)
+
+        for p in periods:
+            if p.get_end_point() > dt:
+                return True
+
+        rrule = self.get_value("RRULE")
+        parameters = rrule and get_parameters(rrule)
+        until = parameters and parameters.get("UNTIL")
+
+        if not rrule:
+            return False
+        elif not until:
+            return True
+
+        dtstart, dtstart_attr = self.get_datetime_item("DTSTART")
+        until = get_datetime(until, dtstart_attr)
+        return until > dt
+
     # Modification methods.
 
     def set_datetime(self, name, dt, tzid=None):
@@ -649,17 +697,8 @@
 
     # Use localised datetimes.
 
-    dtstart, dtstart_attr = obj.get_datetime_item("DTSTART")
-
-    if obj.has_key("DTEND"):
-        dtend, dtend_attr = obj.get_datetime_item("DTEND")
-        duration = dtend - dtstart
-    elif obj.has_key("DURATION"):
-        duration = obj.get_duration("DURATION")
-        dtend = dtstart + duration
-        dtend_attr = dtstart_attr
-    else:
-        dtend, dtend_attr = dtstart, dtstart_attr
+    (dtstart, dtstart_attr), (dtend, dtend_attr) = obj.get_main_period_items(tzid)
+    duration = dtend - dtstart
 
     # Attempt to get time zone details from the object, using the supplied zone
     # only as a fallback.
@@ -681,7 +720,8 @@
 
         until = parameters.get("UNTIL")
         if until:
-            end = min(to_timezone(get_datetime(until, dtstart_attr), obj_tzid), end)
+            until_dt = to_timezone(get_datetime(until, dtstart_attr), obj_tzid)
+            end = end and min(until_dt, end) or until_dt
             inclusive = True
 
         for recurrence_start in selector.materialise(dtstart, end, parameters.get("COUNT"), parameters.get("BYSETPOS"), inclusive):