# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1513457531 -3600
# Node ID 2181c56d858117bce7b62b75369467d8145e4dea
# Parent  4d0d5b25bbbd7d5cf8ce25d8dc5d0e278aeaf0d1
Introduced initial support for UNTIL as an observed qualifier.

diff -r 4d0d5b25bbbd -r 2181c56d8581 tests/internal/qualifiers.py
--- a/tests/internal/qualifiers.py	Sat Dec 16 21:50:17 2017 +0100
+++ b/tests/internal/qualifiers.py	Sat Dec 16 21:52:11 2017 +0100
@@ -102,7 +102,7 @@
     dt = (1997, 9, 2, 9, 0, 0)
     s = select(dt, qualifiers)
 
-    l = s.materialise(dt, (1997, 12, 24, 0, 0, 0), True)
+    l = s.materialise(dt, (1997, 12, 25, 0, 0, 0), True)
     print len(l) == 113, 113, len(l)
     print l[0] == (1997, 9, 2, 9, 0, 0), (1997, 9, 2, 9, 0, 0), l[0]
     print l[-1] == (1997, 12, 23, 9, 0, 0), (1997, 12, 23, 9, 0, 0), l[-1]
diff -r 4d0d5b25bbbd -r 2181c56d8581 vRecurrence.py
--- a/vRecurrence.py	Sat Dec 16 21:50:17 2017 +0100
+++ b/vRecurrence.py	Sat Dec 16 21:52:11 2017 +0100
@@ -87,7 +87,7 @@
 
 # Add labels corresponding to negative indexes.
 
-level_labels += ("COUNT", "DTSTART")
+level_labels += ("COUNT", "UNTIL", "DTSTART")
 
 # Symbols corresponding to resolution levels.
 
@@ -99,7 +99,7 @@
 
 # Special levels used by non-qualifier-originating selectors.
 
-COUNT, DTSTART, BYSETPOS = -2, -1, None
+COUNT, UNTIL, DTSTART, BYSETPOS = -3, -2, -1, None
 
 # Levels defining days.
 
@@ -207,6 +207,30 @@
 
             qualifier = (key, {"values" : values})
 
+        # Accept until datetimes.
+        # NOTE: This should be a UTC datetime unless DTSTART is a date or
+        # NOTE: floating datetime.
+
+        elif key == "UNTIL":
+            try:
+                # YYYYMMDD
+
+                if len(value) == 8:
+                    end = map(int, (value[:4], value[4:6], value[6:]))
+
+                # YYYYMMDDTHHMMSS[Z]
+
+                elif len(value) in (15, 16):
+                    end = map(int, (value[:4], value[4:6], value[6:8], value[9:11], value[11:13], value[13:15]))
+
+                else:
+                    continue
+
+                qualifier = (key, {"end" : tuple(end)})
+
+            except ValueError:
+                continue
+
         # Ignore other items.
 
         else:
@@ -308,6 +332,9 @@
     elif qualifier == "COUNT":
         return LimitSelector(COUNT, args, "COUNT")
 
+    elif qualifier == "UNTIL":
+        return UntilSelector(UNTIL, args, "UNTIL")
+
     else:
         return Pattern(freq[qualifier], args, qualifier)
 
@@ -1154,6 +1181,17 @@
     def get_start(self):
         return self.args["start"]
 
+class UntilSelector(Selector):
+
+    "A selector ensuring that the until datetime is not passed."
+
+    def materialise_items(self, context, start, end, inclusive=False):
+        return UntilIterator(self, context, start, end, inclusive,
+                             self.get_end())
+
+    def get_end(self):
+        return self.args["end"]
+
 special_enum_levels = {
     "BYDAY" : WeekDayFilter,
     "BYMONTHDAY" : MonthDayFilter,
@@ -1548,6 +1586,26 @@
 
         return result
 
+class UntilIterator(SelectorIterator):
+
+    "An iterator ensuring that the until datetime is not passed."
+
+    def __init__(self, selector, current, start, end, inclusive, until):
+        SelectorIterator.__init__(self, selector, current, start, end, inclusive)
+        self.until = until
+
+    def next(self):
+
+        "Return the next value, stopping if it is beyond the until limit."
+
+        while True:
+            current = self.next_item(self.start, self.end)
+            if current >= self.until:
+                break
+            return current
+
+        raise StopIteration
+
 def connect_selectors(selectors):
 
     """