# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1439672237 -7200
# Node ID 7a2cf3dead31215aa0c328657c0e661922cb2bd3
# Parent  0549289186cde22e9ea191ceeb3776857e7da6a4
Added functions for correcting invalid datetimes.

diff -r 0549289186cd -r 7a2cf3dead31 imiptools/dates.py
--- a/imiptools/dates.py	Sat Aug 15 22:56:51 2015 +0200
+++ b/imiptools/dates.py	Sat Aug 15 22:57:17 2015 +0200
@@ -19,6 +19,7 @@
 this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
+from bisect import bisect_left
 from datetime import date, datetime, timedelta
 from os.path import exists
 from pytz import timezone, UnknownTimeZoneError
@@ -470,4 +471,72 @@
 
     return to_utc_datetime(get_datetime(recurrenceid), tzid)
 
+# Time corrections.
+
+def correct_datetime(dt, resolution):
+
+    "Correct 'dt' using the given 'resolution' details."
+
+    carry, hour, minute, second = correct_value((dt.hour, dt.minute, dt.second), resolution)
+    return datetime(dt.year, dt.month, dt.day, hour, minute, second, dt.microsecond, dt.tzinfo) + \
+           (carry and timedelta(1) or timedelta(0))
+
+def correct_value(value, resolution):
+
+    """
+    Correct the given (hour, minute, second) tuple 'value' according to the
+    'resolution' details.
+    """
+
+    limits = 23, 59, 59
+
+    corrected = []
+    reset = False
+
+    # Find invalid values and reset all following values.
+
+    for v, values, limit in zip(value, resolution, limits):
+        if reset:
+            if values:
+                v = values[0]
+            else:
+                v = 0
+
+        elif values and v not in values:
+            reset = True
+
+        corrected.append(v)
+
+    value = corrected
+    corrected = []
+    carry = 0
+
+    # Find invalid values and update them to the next valid value, updating more
+    # significant values if the next valid value is the first in the appropriate
+    # series.
+
+    for v, values, limit in zip(value, resolution, limits)[::-1]:
+        if carry:
+            v += 1
+            if v > limit:
+                if values:
+                    v = values[0]
+                else:
+                    v = 0
+                corrected.append(v)
+                continue
+            else:
+                carry = 0
+
+        i = bisect_left(values, v)
+        if i < len(values):
+            v = values[i]
+        else:
+            v = values[0]
+            carry = 1
+
+        corrected.append(v)
+
+    return [carry] + corrected[::-1]
+
 # vim: tabstop=4 expandtab shiftwidth=4