# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1505234033 -7200
# Node ID 3835eb7e67296a4dc5dbf88bf8633e2e2ed31ff7
# Parent  d6c6544c04d31efa63cbd5dc71766998b0f5a2dd
Tidied and consolidated period-related code. Added commentary.

diff -r d6c6544c04d3 -r 3835eb7e6729 imiptools/data.py
--- a/imiptools/data.py	Mon Sep 11 23:57:30 2017 +0200
+++ b/imiptools/data.py	Tue Sep 12 18:33:53 2017 +0200
@@ -946,6 +946,12 @@
         return address
 
 def is_mailto_uri(value):
+
+    """
+    Return whether 'value' is a mailto: URI, with the protocol potentially being
+    in upper case.
+    """
+
     return value.lower().startswith("mailto:")
 
 def get_uri(value):
@@ -953,6 +959,9 @@
     "Return a URI for the given 'value'."
 
     if not value: return None
+
+    # Normalise to "mailto:" or return other URI form.
+
     return is_mailto_uri(value) and ("mailto:%s" % value[7:]) or \
            ":" in value and value or \
            "mailto:%s" % get_address(value)
diff -r d6c6544c04d3 -r 3835eb7e6729 imiptools/period.py
--- a/imiptools/period.py	Mon Sep 11 23:57:30 2017 +0200
+++ b/imiptools/period.py	Tue Sep 12 18:33:53 2017 +0200
@@ -33,6 +33,12 @@
     if x is None: return y
     else: return x
 
+def start_point(obj):
+    return Comparable(ifnone(obj.get_start_point(), StartOfTime()))
+
+def end_point(obj):
+    return Comparable(ifnone(obj.get_end_point(), EndOfTime()))
+
 class Comparable:
 
     "A date/datetime wrapper that allows comparisons with other types."
@@ -158,23 +164,23 @@
 
         if isinstance(other, PeriodBase):
             return cmp(
-                (Comparable(ifnone(self.get_start_point(), StartOfTime())), Comparable(ifnone(self.get_end_point(), EndOfTime()))),
-                (Comparable(ifnone(other.get_start_point(), StartOfTime())), Comparable(ifnone(other.get_end_point(), EndOfTime())))
+                (start_point(self), end_point(self)),
+                (start_point(other), end_point(other))
                 )
         else:
             return 1
 
     def overlaps(self, other):
-        return Comparable(ifnone(self.get_end_point(), EndOfTime())) > Comparable(ifnone(other.get_start_point(), StartOfTime())) and \
-               Comparable(ifnone(self.get_start_point(), StartOfTime())) < Comparable(ifnone(other.get_end_point(), EndOfTime()))
+        return end_point(self) > start_point(other) and \
+               start_point(self) < end_point(other)
 
     def within(self, other):
-        return Comparable(ifnone(self.get_start_point(), StartOfTime())) >= Comparable(ifnone(other.get_start_point(), StartOfTime())) and \
-               Comparable(ifnone(self.get_end_point(), EndOfTime())) <= Comparable(ifnone(other.get_end_point(), EndOfTime()))
+        return start_point(self) >= start_point(other) and \
+               end_point(self) <= end_point(other)
 
     def common(self, other):
-        start = max(Comparable(ifnone(self.get_start_point(), StartOfTime())), Comparable(ifnone(other.get_start_point(), StartOfTime())))
-        end = min(Comparable(ifnone(self.get_end_point(), EndOfTime())), Comparable(ifnone(other.get_end_point(), EndOfTime())))
+        start = max(start_point(self), start_point(other))
+        end = min(end_point(self), end_point(other))
         if start <= end:
             return self.make_corrected(start.dt, end.dt)
         else:
diff -r d6c6544c04d3 -r 3835eb7e6729 imipweb/data.py
--- a/imipweb/data.py	Mon Sep 11 23:57:30 2017 +0200
+++ b/imipweb/data.py	Tue Sep 12 18:33:53 2017 +0200
@@ -129,17 +129,23 @@
 
         dtstart, dtstart_attr = self.get_start_item()
         if not dtstart:
-            raise PeriodError(*[index is not None and ("dtstart", index) or "dtstart"])
+            if index is not None:
+                raise PeriodError(("dtstart", index))
+            else:
+                raise PeriodError("dtstart")
 
         dtend, dtend_attr = self.get_end_item()
         if not dtend:
-            raise PeriodError(*[index is not None and ("dtend", index) or "dtend"])
+            if index is not None:
+                raise PeriodError(("dtend", index))
+            else:
+                raise PeriodError("dtend")
 
         if dtstart > dtend:
-            raise PeriodError(*[
-                index is not None and ("dtstart", index) or "dtstart",
-                index is not None and ("dtend", index) or "dtend"
-                ])
+            if index is not None:
+                raise PeriodError(("dtstart", index), ("dtend", index))
+            else:
+                raise PeriodError("dtstart", "dtend")
 
         return EventPeriod(dtstart, end_date_to_calendar(dtend), self.tzid,
                            self.origin, dtstart_attr, dtend_attr,