# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1508865208 -7200
# Node ID b3ba19f3e74dee1118e73f73618549365baf7522
# Parent  c32240f8019d2cf160069dac38445f98bd7b5d26
Fixed and reorganised the rule period abstractions.

diff -r c32240f8019d -r b3ba19f3e74d imiptools/data.py
--- a/imiptools/data.py	Tue Oct 24 18:57:49 2017 +0200
+++ b/imiptools/data.py	Tue Oct 24 19:13:28 2017 +0200
@@ -1119,21 +1119,22 @@
         """
 
         self.rrule = rrule
-        self.start = main_period.get_start()
-        self.attr = main_period.get_start_attr()
-        self.duration = main_period.get_duration()
+        self.main_period = main_period
+        self.tzid = tzid
 
         parameters = rrule and get_parameters(rrule)
         until = parameters.get("UNTIL")
 
+        # Any UNTIL qualifier changes the nature of the end of the collection.
+
         if until:
+            attr = main_period.get_start_attr()
             until_dt = to_timezone(get_datetime(until, attr), tzid)
-            end = end and min(until_dt, end) or until_dt
-            inclusive = True
-
-        self.tzid = tzid
-        self.end = end
-        self.inclusive = inclusive
+            self.end = end and min(until_dt, end) or until_dt
+            self.inclusive = True
+        else:
+            self.end = end
+            self.inclusive = inclusive
 
     def __iter__(self):
 
@@ -1143,19 +1144,19 @@
         done after the instances have been obtained.
         """
 
-        selector = get_rule(self.start, self.rrule)
+        start = self.main_period.get_start()
+        selector = get_rule(start, self.rrule)
 
-        return RulePeriodIterator(self.duration, self.attr, self.tzid,
-                                  selector.select(self.start, self.end,
-                                                  self.inclusive))
+        return RulePeriodIterator(self.main_period, self.tzid,
+                               selector.select(start, self.end, self.inclusive))
 
 class RulePeriodIterator:
 
     "An iterator over rule periods."
 
-    def __init__(self, duration, attr, tzid, iterator):
-        self.duration = duration
-        self.attr = attr
+    def __init__(self, main_period, tzid, iterator):
+        self.attr = main_period.get_start_attr()
+        self.duration = main_period.get_duration()
         self.tzid = tzid
         self.iterator = iterator