From 4fd6d1d7e01f2a7e5dcb874fbc8a81cf3906e492 Mon Sep 17 00:00:00 2001
From: benfitzpatrick <ben.fitzpatrick@metoffice.gov.uk>
Date: Wed, 26 Feb 2014 17:06:59 +0000
Subject: [PATCH] #2: support 2nd recurrence format e.g. R/P2Y.

---
 isodatetime/parsers.py | 28 ++++++++++++++++++++++++++--
 isodatetime/tests.py   | 12 +++++++++++-
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/isodatetime/parsers.py b/isodatetime/parsers.py
index deb4fe7..314e75f 100644
--- a/isodatetime/parsers.py
+++ b/isodatetime/parsers.py
@@ -67,8 +67,28 @@ def __init__(self, timepoint_parser=None, timeinterval_parser=None):
         else:
             self.timepoint_parser = timeinterval_parser
 
-    def parse(self, expression):
-        """Parse a recurrence string into a TimeRecurrence instance."""
+    def parse(self, expression, context_point=None):
+        """Parse a recurrence string into a TimeRecurrence instance.
+
+        expression should be a string that looks like one of the four
+        ISO 8601 recurrence formats - e.g.
+        "R5/20140228T0630Z/20140228T0830Z"
+        "R5/PT10M"  (with a supplied context)
+        "R5/20140228T0630Z/PT10M"
+        "R5/PT10M/20140228T0830Z"
+        
+        where the slash is a delimiter, the number following the R is
+        an optional limit for the number of recurrences, strings
+        beginning with "2014" are ISO 8601 date/time representations,
+        and string beginning with "P" are ISO 8601 duration
+        representations.
+
+        context_point should be given for the second format, which will
+        then behave in the same way as the third format - start at
+        the context point and apply the interval counting forwards in
+        time.
+
+        """
         for regex in self.RECURRENCE_REGEXES:
             result = regex.search(expression)
             if not result:
@@ -87,6 +107,10 @@ def parse(self, expression):
             if "intv" in result_map:
                 interval = self.timeinterval_parser.parse(
                     result_map["intv"])
+            if (context_point is not None and start_point is None and
+                    end_point is None):
+                # Second ISO 8601 recurrence format.
+                start_point = context_point
             return data.TimeRecurrence(
                 repetitions=repetitions,
                 start_point=start_point,
diff --git a/isodatetime/tests.py b/isodatetime/tests.py
index 3e4414f..e068fc8 100644
--- a/isodatetime/tests.py
+++ b/isodatetime/tests.py
@@ -444,6 +444,12 @@ def get_timerecurrenceparser_tests():
                     yield expr_1, {"repetitions": reps,
                                     "start_point": start_point,
                                     "end_point": end_point}
+                expr_2 = ("R" + reps_string + "/" + str(interval))
+                yield (expr_2, start_point), {
+                    "repetitions": reps,
+                    "start_point": start_point,
+                    "interval": interval
+                }
                 expr_3 = ("R" + reps_string + "/" + str(start_point) +
                             "/" + str(interval))
                 yield expr_3, {"repetitions": reps,
@@ -588,8 +594,12 @@ def test_timerecurrence_parser(self):
         """Test the recurring date/time series parsing."""
         parser = parsers.TimeRecurrenceParser()
         for expression, test_info in get_timerecurrenceparser_tests():
+            context_point=None
+            if isinstance(expression, tuple):
+                expression, context_point = expression
             try:
-                test_data = str(parser.parse(expression))
+                test_data = str(parser.parse(expression,
+                                context_point=context_point))
             except parsers.TimeSyntaxError:
                 raise ValueError("Parsing failed for %s" % expression)
             ctrl_data = str(data.TimeRecurrence(**test_info))