--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wokkel/delay.py	Mon Dec 15 12:46:58 2014 +0100
@@ -0,0 +1,117 @@
+# -*- test-case-name: wokkel.test.test_delay -*-
+#
+# Copyright (c) Ralph Meijer.
+# See LICENSE for details.
+
+"""
+Delayed Delivery.
+
+Support for comunicating Delayed Delivery information as specified by
+U{XEP-0203<http://xmpp.org/extensions/xep-0203.html>} and its predecessor
+U{XEP-0091<http://xmpp.org/extensions/xep-0091.html>}.
+"""
+
+from dateutil.parser import parse
+from dateutil.tz import tzutc
+
+from twisted.words.protocols.jabber.jid import InvalidFormat, JID
+from twisted.words.xish import domish
+
+NS_DELAY = 'urn:xmpp:delay'
+NS_JABBER_DELAY = 'jabber:x:delay'
+
+class Delay(object):
+    """
+    Delayed Delivery information.
+
+    Instances of this class represent delayed delivery information that can be
+    parsed from and rendered into both XEP-0203 and legacy XEP-0091 formats.
+
+    @ivar stamp: The timestamp the stanza was originally sent.
+    @type stamp: L{datetime.datetime}
+    @ivar sender: The optional entity that originally sent the stanza or
+        delayed its delivery.
+    @type sender: L{JID}
+    """
+
+    def __init__(self, stamp, sender=None):
+        self.stamp = stamp
+        self.sender = sender
+
+
+    def toElement(self, legacy=False):
+        """
+        Render this instance into a domish Element.
+
+        @param legacy: If C{True}, use the legacy XEP-0091 format.
+        @type legacy: C{bool}
+        """
+        if not self.stamp:
+            raise ValueError("stamp is required")
+        if self.stamp.tzinfo is None:
+            raise ValueError("stamp is not offset-aware")
+
+        if legacy:
+            element = domish.Element((NS_JABBER_DELAY, 'x'))
+            stampFormat = '%Y%m%dT%H:%M:%S'
+        else:
+            element = domish.Element((NS_DELAY, 'delay'))
+            stampFormat = '%Y-%m-%dT%H:%M:%SZ'
+
+        stamp = self.stamp.astimezone(tzutc())
+        element['stamp'] = stamp.strftime(stampFormat)
+
+        if self.sender:
+            element['from'] = self.sender.full()
+
+        return element
+
+
+    @staticmethod
+    def fromElement(element):
+        """
+        Create an instance from a domish Element.
+        """
+        try:
+            stamp = parse(element[u'stamp'])
+
+            # Assume UTC if no timezone was given
+            if stamp.tzinfo is None:
+                stamp = stamp.replace(tzinfo=tzutc())
+        except (KeyError, ValueError, TypeError):
+            stamp = None
+
+        try:
+            sender = JID(element[u'from'])
+        except (KeyError, InvalidFormat):
+            sender = None
+
+        delay = Delay(stamp, sender)
+        return delay
+
+
+
+class DelayMixin(object):
+    """
+    Mixin for parsing delayed delivery information from stanzas.
+
+    This can be used as a mixin for subclasses of L{wokkel.generic.Stanza}
+    for parsing delayed delivery information. If both XEP-0203 and XEP-0091
+    formats are present, the former takes precedence.
+    """
+
+    delay = None
+
+    childParsers = {
+            (NS_DELAY, 'delay'): '_childParser_delay',
+            (NS_JABBER_DELAY, 'x'): '_childParser_legacyDelay',
+            }
+
+
+    def _childParser_delay(self, element):
+        self.delay = Delay.fromElement(element)
+
+
+    def _childParser_legacyDelay(self, element):
+        if not self.delay:
+            self.delay = Delay.fromElement(element)