# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1443479131 -7200
# Node ID e0ed770d17bea0884dddd26c729fc3e29a580b8a
# Parent  79493ac5b434a2c27e68e2a193a9a6021bbeee23# Parent  9cf10fe21c3ae6dc6d65fc75c53b3bde2bc6b7b6
Merged changes from branch.

diff -r 79493ac5b434 -r e0ed770d17be docs/preferences.txt
--- a/docs/preferences.txt	Thu Sep 24 19:13:39 2015 +0200
+++ b/docs/preferences.txt	Tue Sep 29 00:25:31 2015 +0200
@@ -70,15 +70,16 @@
 supporting this setting when counter-proposals are made during event
 scheduling.
 
-This setting requires a value of one of the following forms:
+This setting requires a value indicating a duration as described in the
+iCalendar format specification:
 
-  <number of seconds>
-  <number of days>d
+http://tools.ietf.org/html/rfc5545#section-3.3.6
 
 For example:
 
-  600                   extend scheduling offers for 10 minutes
-  1d                    extend offers for 1 day
+  PT10M                 extend scheduling offers for 10 minutes
+  PT600S                extend scheduling offers for 600 seconds (10 minutes)
+  PT1D                  extend offers for 1 day
 
 freebusy_publishing
 -------------------
diff -r 79493ac5b434 -r e0ed770d17be htdocs/styles.css
--- a/htdocs/styles.css	Thu Sep 24 19:13:39 2015 +0200
+++ b/htdocs/styles.css	Tue Sep 29 00:25:31 2015 +0200
@@ -1,7 +1,7 @@
 /* Table styling. */
 
-table.calendar,
 table.conflicts,
+table.counters,
 table.recurrence,
 table.object {
     border: 2px solid #000;
@@ -23,9 +23,10 @@
     background-color: #faa;
 }
 
-th.dayheading,
+caption.dayheading,
 th.mainheading {
     background-color: #f85;
+    width: 100%;
 }
 
 th.timeslot,
@@ -50,6 +51,7 @@
 td.event {
     background-color: #ff8;
     border: 2px solid #000;
+    width: 10em;
 }
 
 td.event.only-organising {
@@ -111,10 +113,15 @@
     text-decoration: line-through;
 }
 
+.objectvalue.dtstart.excluded,
 .objectvalue.dtstart.replaced {
     vertical-align: top;
 }
 
+table.counters tr.selected {
+    background-color: #ee2;
+}
+
 /* New event controls. */
 
 .newevent-with-periods {
@@ -127,13 +134,17 @@
     display: none;
 }
 
+input.newevent.selector:checked ~ p.newevent-with-periods {
+    display: block;
+}
+
 th.container,
 td.container {
     padding: 0; /* for regions covered by labels */
 }
 
-th.dayheading:hover,
-th.dayheading:focus,
+caption.dayheading:hover,
+caption.dayheading:focus,
 th.timeslot:hover,
 th.timeslot:focus,
 td.container:hover,
@@ -174,9 +185,8 @@
 
 /* Hide calendar rows depending on the selected controls. */
 
-input#hidebusy:checked ~ .calendar tr.slot.busy,
-input#showdays:not(:checked) ~ .calendar thead.separator.empty,
-input#showdays:not(:checked) ~ .calendar tbody.points.empty,
+input#hidebusy:checked ~ div.calendar tr.slot.busy,
+input#showdays:not(:checked) ~ div.calendar .calendar.empty,
 
 /* Hiding/showing end datetimes and start/end times. */
 
@@ -206,10 +216,29 @@
 
 /* Show slot endpoints when hiding adjacent busy periods. */
 
-input#hidebusy:checked ~ .calendar th.timeslot span.endpoint {
+input#hidebusy:checked ~ div.calendar th.timeslot span.endpoint {
     display: block;
 }
 
+/* Make calendar labels occupy cells completely.
+   See: http://stackoverflow.com/questions/2841484/how-can-a-label-completely-fill-its-parent-td
+*/
+
+tr.slot {
+    height: 0;
+}
+
+th.timeslot,
+td.empty {
+    height: 100%;
+}
+
+label.timepoint,
+label.newevent {
+    display: block;
+    min-height: 100%;
+}
+
 /* Style the labels. */
 
 label.day,
diff -r 79493ac5b434 -r e0ed770d17be imip_manager.py
--- a/imip_manager.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imip_manager.py	Tue Sep 29 00:25:31 2015 +0200
@@ -29,9 +29,9 @@
 
 from imipweb.calendar import CalendarPage
 from imipweb.event import EventPage
-from imipweb.resource import Resource
+from imipweb.resource import ResourceClient
 
-class Manager(Resource):
+class Manager(ResourceClient):
 
     "A simple manager application."
 
diff -r 79493ac5b434 -r e0ed770d17be imip_store.py
--- a/imip_store.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imip_store.py	Tue Sep 29 00:25:31 2015 +0200
@@ -367,7 +367,7 @@
         indicated 'uid'. Only cancelled recurrences are returned.
         """
 
-        filename = self.get_object_in_store(user, "cancelled", "recurrences", uid)
+        filename = self.get_object_in_store(user, "cancellations", "recurrences", uid)
         if not filename or not exists(filename):
             return []
 
@@ -757,29 +757,27 @@
         """
 
         for request in requests:
-            if request[:2] == (uid, recurrenceid):
+            if request[:2] == (uid, recurrenceid) and (
+                not strict or
+                not request[2:] and not type or
+                request[2:] and request[2] == type):
+
                 return True
+
         return False
 
     def get_counters(self, user, uid, recurrenceid=None):
 
         """
-        For the given 'user', return a mapping of counter-proposals from other
-        users to nodes representing those proposals for the given 'uid' and
-        optional 'recurrenceid'.
+        For the given 'user', return a list of users from whom counter-proposals
+        have been received for the given 'uid' and optional 'recurrenceid'.
         """
 
         filename = self.get_event_filename(user, uid, recurrenceid, "counters")
-        if not filename:
+        if not filename or not exists(filename):
             return False
 
-        counters = {}
-
-        for other in listdir(filename):
-            counter_filename = self.get_event_filename(user, uid, recurrenceid, "counters", other)
-            counters[other] = self._get_object(user, counter_filename)
-
-        return counters
+        return [name for name in listdir(filename) if isfile(join(filename, name))]
 
     def get_counter(self, user, other, uid, recurrenceid=None):
 
diff -r 79493ac5b434 -r e0ed770d17be imiptools/client.py
--- a/imiptools/client.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imiptools/client.py	Tue Sep 29 00:25:31 2015 +0200
@@ -25,7 +25,7 @@
                            is_new_object, make_freebusy, to_part, \
                            uri_dict, uri_items, uri_values
 from imiptools.dates import check_permitted_values, format_datetime, get_default_timezone, \
-                            get_timestamp, to_timezone
+                            get_duration, get_time, get_timestamp
 from imiptools.period import can_schedule, remove_period, \
                              remove_additional_periods, remove_affected_period, \
                              update_freebusy
@@ -139,28 +139,14 @@
 
     def get_offer_period(self):
 
-        """
-        Decode a specification of one of the following forms...
-
-        <number of seconds>
-        <number of days>d
-        """
+        "Decode a specification in the iCalendar duration format."
 
         prefs = self.get_preferences()
         duration = prefs and prefs.get("freebusy_offers", config.FREEBUSY_OFFER_DEFAULT)
-        if duration:
-            try:
-                if duration.endswith("d"):
-                    return timedelta(days=int(duration[:-1]))
-                else:
-                    return timedelta(seconds=int(duration))
 
-            # NOTE: Should probably report an error somehow.
+        # NOTE: Should probably report an error somehow if None.
 
-            except ValueError:
-                return None
-        else:
-            return None
+        return duration and get_duration(duration) or None
 
     def get_organiser_replacement(self):
         prefs = self.get_preferences()
@@ -281,16 +267,16 @@
 
     # Store operations.
 
-    def get_stored_object(self, uid, recurrenceid, section=None):
+    def get_stored_object(self, uid, recurrenceid, section=None, username=None):
 
         """
         Return the stored object for the current user, with the given 'uid' and
-        'recurrenceid' from the given 'section' (if specified), or from the
-        standard object collection otherwise.
+        'recurrenceid' from the given 'section' and for the given 'username' (if
+        specified), or from the standard object collection otherwise.
         """
 
         if section == "counters":
-            fragment = self.store.get_counter(self.user, uid, recurrenceid)
+            fragment = self.store.get_counter(self.user, username, uid, recurrenceid)
         else:
             fragment = self.store.get_event(self.user, uid, recurrenceid)
         return fragment and Object(fragment)
@@ -385,7 +371,7 @@
         "Update the DTSTAMP in the current object."
 
         dtstamp = self.obj.get_utc_datetime("DTSTAMP")
-        utcnow = to_timezone(datetime.utcnow(), "UTC")
+        utcnow = get_time()
         self.dtstamp = format_datetime(dtstamp and dtstamp > utcnow and dtstamp or utcnow)
         self.obj["DTSTAMP"] = [(self.dtstamp, {})]
 
@@ -683,7 +669,7 @@
         if offer:
             offer_period = self.get_offer_period()
             if offer_period:
-                expires = format_datetime(to_timezone(datetime.utcnow(), "UTC") + offer_period)
+                expires = get_timestamp(offer_period)
             else:
                 return
         else:
@@ -795,4 +781,85 @@
         for attendee in attendees.keys():
             self.update_freebusy_from_participant(attendee, False, self.remove_freebusy_for_participant)
 
+    # Convenience methods for updating free/busy details at the event level.
+
+    def update_event_in_freebusy(self, for_organiser=True):
+
+        """
+        Update free/busy information when handling an object, doing so for the
+        organiser of an event if 'for_organiser' is set to a true value.
+        """
+
+        freebusy = self.store.get_freebusy(self.user)
+
+        # Obtain the attendance attributes for this user, if available.
+
+        self.update_freebusy_for_participant(freebusy, self.user, for_organiser)
+
+        # Remove original recurrence details replaced by additional
+        # recurrences, as well as obsolete additional recurrences.
+
+        self.remove_freebusy_for_recurrences(freebusy, self.store.get_recurrences(self.user, self.uid))
+        self.store.set_freebusy(self.user, freebusy)
+
+        if self.publisher and self.is_sharing() and self.is_publishing():
+            self.publisher.set_freebusy(self.user, freebusy)
+
+        # Update free/busy provider information if the event may recur
+        # indefinitely.
+
+        if self.possibly_recurring_indefinitely():
+            self.store.append_freebusy_provider(self.user, self.obj)
+
+        return True
+
+    def remove_event_from_freebusy(self):
+
+        "Remove free/busy information when handling an object."
+
+        freebusy = self.store.get_freebusy(self.user)
+
+        self.remove_from_freebusy(freebusy)
+        self.remove_freebusy_for_recurrences(freebusy)
+        self.store.set_freebusy(self.user, freebusy)
+
+        if self.publisher and self.is_sharing() and self.is_publishing():
+            self.publisher.set_freebusy(self.user, freebusy)
+
+        # Update free/busy provider information if the event may recur
+        # indefinitely.
+
+        if self.possibly_recurring_indefinitely():
+            self.store.remove_freebusy_provider(self.user, self.obj)
+
+    def update_event_in_freebusy_offers(self):
+
+        "Update free/busy offers when handling an object."
+
+        freebusy = self.store.get_freebusy_offers(self.user)
+
+        # Obtain the attendance attributes for this user, if available.
+
+        self.update_freebusy_for_participant(freebusy, self.user, offer=True)
+
+        # Remove original recurrence details replaced by additional
+        # recurrences, as well as obsolete additional recurrences.
+
+        self.remove_freebusy_for_recurrences(freebusy, self.store.get_recurrences(self.user, self.uid))
+        self.store.set_freebusy_offers(self.user, freebusy)
+
+        return True
+
+    def remove_event_from_freebusy_offers(self):
+
+        "Remove free/busy offers when handling an object."
+
+        freebusy = self.store.get_freebusy_offers(self.user)
+
+        self.remove_from_freebusy(freebusy)
+        self.remove_freebusy_for_recurrences(freebusy)
+        self.store.set_freebusy_offers(self.user, freebusy)
+
+        return True
+
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r 79493ac5b434 -r e0ed770d17be imiptools/data.py
--- a/imiptools/data.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imiptools/data.py	Tue Sep 29 00:25:31 2015 +0200
@@ -409,6 +409,25 @@
 
         return old_values != set(self.get_date_values("RDATE") or [])
 
+    def update_exceptions(self, excluded):
+
+        """
+        Update the exceptions to any rule by applying the list of 'excluded'
+        periods.
+        """
+
+        to_exclude = set(excluded).difference(self.get_date_values("EXDATE") or [])
+        if not to_exclude:
+            return False
+
+        if not self.has_key("EXDATE"):
+            self["EXDATE"] = []
+
+        for p in to_exclude:
+            self["EXDATE"].append(get_period_item(p.get_start(), p.get_end()))
+
+        return True
+
     def correct_object(self, tzid, permitted_values):
 
         "Correct the object's period details."
diff -r 79493ac5b434 -r e0ed770d17be imiptools/dates.py
--- a/imiptools/dates.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imiptools/dates.py	Tue Sep 29 00:25:31 2015 +0200
@@ -132,7 +132,10 @@
 
 def get_duration(value):
 
-    "Return a duration for the given 'value'."
+    """
+    Return a duration for the given 'value' as a timedelta object.
+    Where no valid duration is specified, None is returned.
+    """
 
     if not value:
         return None
@@ -433,11 +436,19 @@
     else:
         return None, None
 
-def get_timestamp():
+def get_timestamp(offset=None):
 
     "Return the current time as an iCalendar-compatible string."
 
-    return format_datetime(to_timezone(datetime.utcnow(), "UTC"))
+    offset = offset or timedelta(0)
+    return format_datetime(to_timezone(datetime.utcnow(), "UTC") + offset)
+
+def get_time(offset=None):
+
+    "Return the current time."
+
+    offset = offset or timedelta(0)
+    return to_timezone(datetime.utcnow(), "UTC") + offset
 
 def get_tzid(dtstart_attr, dtend_attr):
 
diff -r 79493ac5b434 -r e0ed770d17be imiptools/handlers/common.py
--- a/imiptools/handlers/common.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imiptools/handlers/common.py	Tue Sep 29 00:25:31 2015 +0200
@@ -110,83 +110,4 @@
 
         self.add_result("REFRESH", [get_address(organiser)], obj.to_part("REFRESH"))
 
-    def update_event_in_freebusy(self, for_organiser=True):
-
-        """
-        Update free/busy information when handling an object, doing so for the
-        organiser of an event if 'for_organiser' is set to a true value.
-        """
-
-        freebusy = self.store.get_freebusy(self.user)
-
-        # Obtain the attendance attributes for this user, if available.
-
-        self.update_freebusy_for_participant(freebusy, self.user, for_organiser)
-
-        # Remove original recurrence details replaced by additional
-        # recurrences, as well as obsolete additional recurrences.
-
-        self.remove_freebusy_for_recurrences(freebusy, self.store.get_recurrences(self.user, self.uid))
-        self.store.set_freebusy(self.user, freebusy)
-
-        if self.publisher and self.is_sharing() and self.is_publishing():
-            self.publisher.set_freebusy(self.user, freebusy)
-
-        # Update free/busy provider information if the event may recur
-        # indefinitely.
-
-        if self.possibly_recurring_indefinitely():
-            self.store.append_freebusy_provider(self.user, self.obj)
-
-        return True
-
-    def remove_event_from_freebusy(self):
-
-        "Remove free/busy information when handling an object."
-
-        freebusy = self.store.get_freebusy(self.user)
-
-        self.remove_from_freebusy(freebusy)
-        self.remove_freebusy_for_recurrences(freebusy)
-        self.store.set_freebusy(self.user, freebusy)
-
-        if self.publisher and self.is_sharing() and self.is_publishing():
-            self.publisher.set_freebusy(self.user, freebusy)
-
-        # Update free/busy provider information if the event may recur
-        # indefinitely.
-
-        if self.possibly_recurring_indefinitely():
-            self.store.remove_freebusy_provider(self.user, self.obj)
-
-    def update_event_in_freebusy_offers(self):
-
-        "Update free/busy offers when handling an object."
-
-        freebusy = self.store.get_freebusy_offers(self.user)
-
-        # Obtain the attendance attributes for this user, if available.
-
-        self.update_freebusy_for_participant(freebusy, self.user, offer=True)
-
-        # Remove original recurrence details replaced by additional
-        # recurrences, as well as obsolete additional recurrences.
-
-        self.remove_freebusy_for_recurrences(freebusy, self.store.get_recurrences(self.user, self.uid))
-        self.store.set_freebusy_offers(self.user, freebusy)
-
-        return True
-
-    def remove_event_from_freebusy_offers(self):
-
-        "Remove free/busy offers when handling an object."
-
-        freebusy = self.store.get_freebusy_offers(self.user)
-
-        self.remove_from_freebusy(freebusy)
-        self.remove_freebusy_for_recurrences(freebusy)
-        self.store.set_freebusy_offers(self.user, freebusy)
-
-        return True
-
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r 79493ac5b434 -r e0ed770d17be imipweb/calendar.py
--- a/imipweb/calendar.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imipweb/calendar.py	Tue Sep 29 00:25:31 2015 +0200
@@ -27,9 +27,9 @@
                             to_timezone
 from imiptools.period import add_day_start_points, add_empty_days, add_slots, \
                              get_scale, get_slots, get_spans, partition_by_day, Point
-from imipweb.resource import Resource
+from imipweb.resource import ResourceClient
 
-class CalendarPage(Resource):
+class CalendarPage(ResourceClient):
 
     "A request handler for the calendar page."
 
@@ -46,13 +46,18 @@
 
         args = self.env.get_args()
 
-        if not args.has_key("newevent"):
+        for key in args.keys():
+            if key.startswith("newevent-"):
+                i = key[len("newevent-"):]
+                break
+        else:
             return
 
         # Create a new event using the available information.
 
         slots = args.get("slot", [])
         participants = args.get("participants", [])
+        summary = args.get("summary-%s" % i, [None])[0]
 
         if not slots:
             return
@@ -120,7 +125,7 @@
         end_value, end_attr = get_datetime_item(end, tzid)
 
         rwrite(("UID", {}, uid))
-        rwrite(("SUMMARY", {}, "New event at %s" % utcnow))
+        rwrite(("SUMMARY", {}, summary or ("New event at %s" % utcnow)))
         rwrite(("DTSTAMP", {}, utcnow))
         rwrite(("DTSTART", start_attr, start_value))
         rwrite(("DTEND", end_attr, end_value))
@@ -379,18 +384,7 @@
 
         add_empty_days(days, tzid)
 
-        # Show the controls permitting day selection as well as the controls
-        # configuring the new event display.
-
-        self.show_calendar_day_controls(days)
-        self.show_calendar_interval_controls(days)
-
-        # Show a button for scheduling a new event.
-
-        page.p(class_="controls")
-        page.input(name="newevent", type="submit", value="New event", id="newevent", class_="newevent-with-periods", accesskey="N")
-        page.span("Select days or periods for a new event.", class_="newevent-no-periods")
-        page.p.close()
+        page.p("Select days or periods for a new event.")
 
         # Show controls for hiding empty days and busy slots.
         # The positioning of the control, paragraph and table are important here.
@@ -409,10 +403,7 @@
 
         # Show the calendar itself.
 
-        page.table(cellspacing=5, cellpadding=5, class_="calendar")
-        self.show_calendar_participant_headings(partitioned_group_types, partitioned_group_sources, group_columns)
-        self.show_calendar_days(days, partitioned_groups, partitioned_group_types, group_columns)
-        page.table.close()
+        self.show_calendar_days(days, partitioned_groups, partitioned_group_types, partitioned_group_sources, group_columns)
 
         # End the form region.
 
@@ -420,16 +411,12 @@
 
     # More page fragment methods.
 
-    def show_calendar_day_controls(self, days):
+    def show_calendar_day_controls(self, day):
 
-        "Show controls for the given 'days' in the calendar."
+        "Show controls for the given 'day' in the calendar."
 
         page = self.page
-        slots = self.env.get_args().get("slot", [])
-
-        for day in days:
-            value, identifier = self._day_value_and_identifier(day)
-            self._slot_selector(value, identifier, slots)
+        daystr, dayid = self._day_value_and_identifier(day)
 
         # Generate a dynamic stylesheet to allow day selections to colour
         # specific days.
@@ -438,13 +425,42 @@
 
         page.style(type="text/css")
 
+        page.add("""\
+input.newevent.selector#%s:checked ~ table#region-%s label.day,
+input.newevent.selector#%s:checked ~ table#region-%s label.timepoint {
+    background-color: #5f4;
+    text-decoration: underline;
+}
+""" % (dayid, dayid, dayid, dayid))
+
+        page.style.close()
+
+        # Generate controls to select days.
+
+        slots = self.env.get_args().get("slot", [])
+        value, identifier = self._day_value_and_identifier(day)
+        self._slot_selector(value, identifier, slots)
+
+    def show_calendar_interval_controls(self, day, intervals):
+
+        "Show controls for the intervals provided by 'day' and 'intervals'."
+
+        page = self.page
+        daystr, dayid = self._day_value_and_identifier(day)
+
+        # Generate a dynamic stylesheet to allow day selections to colour
+        # specific days.
+        # NOTE: The style details need to be coordinated with the static
+        # NOTE: stylesheet.
+
         l = []
 
-        for day in days:
-            daystr, dayid = self._day_value_and_identifier(day)
+        for point, endpoint in intervals:
+            timestr, timeid = self._slot_value_and_identifier(point, endpoint)
             l.append("""\
-input.newevent.selector#%s:checked ~ table label.day.day-%s,
-input.newevent.selector#%s:checked ~ table label.timepoint.day-%s""" % (dayid, daystr, dayid, daystr))
+input.newevent.selector#%s:checked ~ table#region-%s th#region-%s""" % (timeid, dayid, timeid))
+
+        page.style(type="text/css")
 
         page.add(",\n".join(l))
         page.add(""" {
@@ -455,59 +471,47 @@
 
         page.style.close()
 
-    def show_calendar_interval_controls(self, days):
+        # Generate controls to select time periods.
+
+        slots = self.env.get_args().get("slot", [])
+        last = None
 
-        "Show controls for the intervals provided by 'days'."
+        # Produce controls for the intervals/slots. Where instants in time are
+        # encountered, they are merged with the following slots, permitting the
+        # selection of contiguous time periods. However, the identifiers
+        # employed by controls corresponding to merged periods will encode the
+        # instant so that labels may reference them conveniently.
 
-        page = self.page
-        slots = self.env.get_args().get("slot", [])
+        intervals = list(intervals)
+        intervals.sort()
+
+        for point, endpoint in intervals:
 
-        for day, intervals in days.items():
-            for point, endpoint in intervals:
-                value, identifier = self._slot_value_and_identifier(point, endpoint)
+            # Merge any previous slot with this one, producing a control.
+
+            if last:
+                _value, identifier = self._slot_value_and_identifier(last, last)
+                value, _identifier = self._slot_value_and_identifier(last, endpoint)
                 self._slot_selector(value, identifier, slots)
 
-        # Generate a dynamic stylesheet to allow day selections to colour
-        # specific days.
-        # NOTE: The style details need to be coordinated with the static
-        # NOTE: stylesheet.
+            # If representing an instant, hold the slot for merging.
 
-        page.style(type="text/css")
+            if endpoint and point.point == endpoint.point:
+                last = point
 
-        l = []; l2 = []; l3 = []
+            # If not representing an instant, produce a control.
 
-        for day, intervals in days.items():
-            for point, endpoint in intervals:
-                daystr, dayid = self._day_value_and_identifier(day)
-                timestr, timeid = self._slot_value_and_identifier(point, endpoint)
-                l.append("""\
-input.newevent.selector#%s:checked ~ p .newevent-no-periods,
-input.newevent.selector#%s:checked ~ p .newevent-no-periods""" % (dayid, timeid))
-                l2.append("""\
-input.newevent.selector#%s:checked ~ p .newevent-with-periods,
-input.newevent.selector#%s:checked ~ p .newevent-with-periods""" % (dayid, timeid))
-                l3.append("""\
-input.newevent.selector#%s:checked ~ table label.timepoint[for=%s]""" % (timeid, timeid))
+            else:
+                value, identifier = self._slot_value_and_identifier(point, endpoint)
+                self._slot_selector(value, identifier, slots)
+                last = None
 
-        page.add(",\n".join(l))
-        page.add(""" {
-    display: none;
-}""")
+        # Produce a control for any unmerged slot.
 
-        page.add(",\n".join(l2))
-        page.add(""" {
-    display: inline;
-}
-""")
-
-        page.add(",\n".join(l3))
-        page.add(""" {
-    background-color: #5f4;
-    text-decoration: underline;
-}
-""")
-
-        page.style.close()
+        if last:
+            _value, identifier = self._slot_value_and_identifier(last, last)
+            value, _identifier = self._slot_value_and_identifier(last, endpoint)
+            self._slot_selector(value, identifier, slots)
 
     def show_calendar_participant_headings(self, group_types, group_sources, group_columns):
 
@@ -535,13 +539,15 @@
         page.tr.close()
         page.thead.close()
 
-    def show_calendar_days(self, days, partitioned_groups, partitioned_group_types, group_columns):
+    def show_calendar_days(self, days, partitioned_groups, partitioned_group_types,
+        partitioned_group_sources, group_columns):
 
         """
         Show calendar days, defined by a collection of 'days', the contributing
         period information as 'partitioned_groups' (partitioned by day), the
         'partitioned_group_types' indicating the kind of contribution involved,
-        and the 'group_columns' defining the number of columns in each group.
+        the 'partitioned_group_sources' indicating the origin of each group, and
+        the 'group_columns' defining the number of columns in each group.
         """
 
         page = self.page
@@ -559,6 +565,8 @@
 
         # Produce a heading and time points for each day.
 
+        i = 0
+
         for day, intervals in all_days:
             groups_for_day = [partitioned.get(day) for partitioned in partitioned_groups]
             is_empty = True
@@ -572,18 +580,46 @@
                         is_empty = False
                         break
 
-            page.thead(class_="separator%s" % (is_empty and " empty" or ""))
-            page.tr()
-            page.th(class_="dayheading container", colspan=all_columns+1)
+            daystr, dayid = self._day_value_and_identifier(day)
+
+            # Put calendar tables within elements for quicker CSS selection.
+
+            page.div(class_="calendar")
+
+            # Show the controls permitting day selection as well as the controls
+            # configuring the new event display.
+
+            self.show_calendar_day_controls(day)
+            self.show_calendar_interval_controls(day, intervals)
+
+            # Show an actual table containing the day information.
+
+            page.table(cellspacing=5, cellpadding=5, class_="calendar %s" % (is_empty and " empty" or ""), id="region-%s" % dayid)
+
+            page.caption(class_="dayheading container separator")
             self._day_heading(day)
-            page.th.close()
-            page.tr.close()
-            page.thead.close()
+            page.caption.close()
 
-            page.tbody(class_="points%s" % (is_empty and " empty" or ""))
+            self.show_calendar_participant_headings(partitioned_group_types, partitioned_group_sources, group_columns)
+
+            page.tbody(class_="points")
             self.show_calendar_points(intervals, groups_for_day, partitioned_group_types, group_columns)
             page.tbody.close()
 
+            page.table.close()
+
+            # Show a button for scheduling a new event.
+
+            page.p(class_="newevent-with-periods")
+            page.label("Summary:")
+            page.input(name="summary-%d" % i, type="text")
+            page.input(name="newevent-%d" % i, type="submit", value="New event", accesskey="N")
+            page.p.close()
+
+            page.div.close()
+
+            i += 1
+
     def show_calendar_points(self, intervals, groups, group_types, group_columns):
 
         """
@@ -629,12 +665,16 @@
                 ])
 
             page.tr(class_=css)
+
+            # Produce a time interval heading, spanning two rows if this point
+            # represents an instant.
+
             if point.indicator == Point.PRINCIPAL:
-                page.th(class_="timeslot")
+                timestr, timeid = self._slot_value_and_identifier(point, endpoint)
+                page.th(class_="timeslot", id="region-%s" % timeid,
+                    rowspan=(endpoint and point.point == endpoint.point and 2 or 1))
                 self._time_point(point, endpoint)
-            else:
-                page.th()
-            page.th.close()
+                page.th.close()
 
             # Obtain slots for the time point from each group.
 
@@ -687,7 +727,8 @@
                                 "event",
                                 has_continued and "continued" or "",
                                 will_continue and "continues" or "",
-                                p.transp == "ORG" and "only-organising" or is_organiser and "organising" or "attending"
+                                p.transp == "ORG" and "only-organising" or is_organiser and "organising" or "attending",
+                                self._have_request(p.uid, p.recurrenceid, "COUNTER", True) and "counter" or "",
                                 ])
 
                             # Only anchor the first cell of events.
@@ -710,13 +751,12 @@
 
                                 page.span(p.summary or "(Participant is busy)")
 
-                            # Link to counter-proposals.
+                            # Link to requests and events (including ones for
+                            # which counter-proposals exist).
 
                             elif group_type == "request" and self._have_request(p.uid, p.recurrenceid, "COUNTER", True):
-                                page.a(p.summary, href=self.link_to(p.uid, p.recurrenceid, "counter"))
-
-                            # Link to requests and events (including ones for
-                            # which counter-proposals exist).
+                                page.a(p.summary, href=self.link_to(p.uid, p.recurrenceid,
+                                    {"counter" : self._period_identifier(p)}))
 
                             else:
                                 page.a(p.summary, href=self.link_to(p.uid, p.recurrenceid))
@@ -739,13 +779,12 @@
         """
         Generate a heading for 'day' of the following form:
 
-        <label class="day day-20150203" for="day-20150203">Tuesday, 3 February 2015</label>
+        <label class="day" for="day-20150203">Tuesday, 3 February 2015</label>
         """
 
         page = self.page
-        daystr = format_datetime(day)
         value, identifier = self._day_value_and_identifier(day)
-        page.label(self.format_date(day, "full"), class_="day day-%s" % daystr, for_=identifier)
+        page.label(self.format_date(day, "full"), class_="day", for_=identifier)
 
     def _time_point(self, point, endpoint):
 
@@ -753,15 +792,14 @@
         Generate headings for the 'point' to 'endpoint' period of the following
         form:
 
-        <label class="timepoint day-20150203" for="slot-20150203T090000-20150203T100000">09:00:00 CET</label>
+        <label class="timepoint" for="slot-20150203T090000-20150203T100000">09:00:00 CET</label>
         <span class="endpoint">10:00:00 CET</span>
         """
 
         page = self.page
         tzid = self.get_tzid()
-        daystr = format_datetime(point.point.date())
         value, identifier = self._slot_value_and_identifier(point, endpoint)
-        page.label(self.format_time(point.point, "long"), class_="timepoint day-%s" % daystr, for_=identifier)
+        page.label(self.format_time(point.point, "long"), class_="timepoint", for_=identifier)
         page.span(self.format_time(endpoint and endpoint.point or get_end_of_day(point.point, tzid), "long"), class_="endpoint")
 
     def _slot_selector(self, value, identifier, slots):
@@ -813,4 +851,7 @@
         identifier = "slot-%s" % value
         return value, identifier
 
+    def _period_identifier(self, period):
+        return "%s-%s" % (format_datetime(period.get_start()), format_datetime(period.get_end()))
+
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r 79493ac5b434 -r e0ed770d17be imipweb/client.py
--- a/imipweb/client.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imipweb/client.py	Tue Sep 29 00:25:31 2015 +0200
@@ -130,7 +130,7 @@
             for p in to_unschedule:
                 if not p.origin:
                     continue
-                obj["RECURRENCE-ID"] = [p.get_start_item()]
+                obj["RECURRENCE-ID"] = [(format_datetime(p.get_start()), p.get_start_attr())]
                 parts.append(obj.to_part("CANCEL"))
 
         # Send the updated event, along with a cancellation for each of the
diff -r 79493ac5b434 -r e0ed770d17be imipweb/env.py
--- a/imipweb/env.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imipweb/env.py	Tue Sep 29 00:25:31 2015 +0200
@@ -19,7 +19,7 @@
 this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
-import cgi, os, sys
+import cgi, os, sys, urlparse
 
 getenv = os.environ.get
 setenv = os.environ.__setitem__
@@ -35,10 +35,13 @@
         self.path = None
         self.path_info = None
         self.user = None
+        self.query_string = None
 
     def get_args(self):
         if self.args is None:
             if self.get_method() != "POST":
+                if not self.query_string:
+                    self.query_string = getenv("QUERY_STRING")
                 setenv("QUERY_STRING", "")
             args = cgi.parse(keep_blank_values=True)
 
@@ -51,6 +54,11 @@
 
         return self.args
 
+    def get_query(self):
+        if not self.query_string:
+            self.query_string = getenv("QUERY_STRING")
+        return urlparse.parse_qs(self.query_string or "", keep_blank_values=True)
+
     def get_method(self):
         if self.method is None:
             self.method = getenv("REQUEST_METHOD") or "GET"
diff -r 79493ac5b434 -r e0ed770d17be imipweb/event.py
--- a/imipweb/event.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imipweb/event.py	Tue Sep 29 00:25:31 2015 +0200
@@ -19,26 +19,20 @@
 this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
-from datetime import date, timedelta
-from imiptools.data import get_uri, uri_dict, uri_values
-from imiptools.dates import format_datetime, get_datetime_item, \
-                            to_date, to_timezone
+from imiptools.data import get_uri, uri_dict, uri_items, uri_values
+from imiptools.dates import format_datetime, to_timezone
 from imiptools.mail import Messenger
 from imiptools.period import have_conflict
-from imipweb.data import EventPeriod, \
-                         event_period_from_period, form_period_from_period, \
-                         FormDate, FormPeriod, PeriodError
+from imipweb.data import EventPeriod, event_period_from_period, FormPeriod, PeriodError
 from imipweb.client import ManagerClient
-from imipweb.resource import Resource
-import pytz
+from imipweb.resource import DateTimeFormUtilities, FormUtilities, ResourceClientForObject
 
-class EventPage(Resource):
-
-    "A request handler for the event page."
+class EventPageFragment(ResourceClientForObject, DateTimeFormUtilities, FormUtilities):
 
-    def __init__(self, resource=None, messenger=None):
-        Resource.__init__(self, resource)
-        self.messenger = messenger or Messenger()
+    "A resource presenting the details of an event."
+
+    def __init__(self, resource=None):
+        ResourceClientForObject.__init__(self, resource)
 
     # Various property values and labels.
 
@@ -59,414 +53,131 @@
         (None, "Not indicated"),
         ]
 
-    # Access to stored object information.
-
-    def is_organiser(self, obj):
-        return get_uri(obj.get_value("ORGANIZER")) == self.user
-
-    def get_stored_attendees(self, obj):
-        return uri_values(obj.get_values("ATTENDEE") or [])
-
-    def get_stored_main_period(self, obj):
+    def can_remove_recurrence(self, recurrence):
 
         """
-        Return the main event period for the given 'obj'.
+        Return whether the 'recurrence' can be removed from the current object
+        without notification.
+        """
+
+        return self.can_edit_recurrence(recurrence) and recurrence.origin != "RRULE"
+
+    def can_edit_recurrence(self, recurrence):
+
+        "Return whether 'recurrence' can be edited."
+
+        return self.recurrence_is_new(recurrence) or not self.obj.is_shared()
+
+    def recurrence_is_new(self, recurrence):
+
+        "Return whether 'recurrence' is new to the current object."
+
+        return recurrence not in self.get_stored_recurrences()
+
+    def can_remove_attendee(self, attendee):
+
+        """
+        Return whether 'attendee' can be removed from the current object without
+        notification.
         """
 
-        dtstart, dtstart_attr = obj.get_datetime_item("DTSTART")
+        return self.can_edit_attendee(attendee) or attendee == self.user
+
+    def can_edit_attendee(self, attendee):
+
+        "Return whether 'attendee' can be edited by an organiser."
+
+        return self.attendee_is_new(attendee) or not self.obj.is_shared()
+
+    def attendee_is_new(self, attendee):
+
+        "Return whether 'attendee' is new to the current object."
+
+        return attendee not in self.get_stored_attendees()
 
-        if obj.has_key("DTEND"):
-            dtend, dtend_attr = obj.get_datetime_item("DTEND")
-        elif obj.has_key("DURATION"):
-            duration = obj.get_duration("DURATION")
-            dtend = dtstart + duration
-            dtend_attr = dtstart_attr
-        else:
-            dtend, dtend_attr = dtstart, dtstart_attr
+    # Access to stored object information.
+
+    def is_organiser(self):
+        return get_uri(self.obj.get_value("ORGANIZER")) == self.user
 
+    def get_stored_attendees(self):
+        return uri_values(self.obj.get_values("ATTENDEE") or [])
+
+    def get_stored_main_period(self):
+
+        "Return the main event period for the current object."
+
+        (dtstart, dtstart_attr), (dtend, dtend_attr) = self.obj.get_main_period_items(self.get_tzid())
         return EventPeriod(dtstart, dtend, self.get_tzid(), None, dtstart_attr, dtend_attr)
 
-    def get_stored_recurrences(self, obj):
+    def get_stored_recurrences(self):
 
-        "Return recurrences computed using the given 'obj'."
+        "Return recurrences computed using the current object."
 
         recurrences = []
-        for period in self.get_periods(obj):
+        for period in self.get_periods(self.obj):
             if period.origin != "DTSTART":
                 recurrences.append(period)
         return recurrences
 
-    # Request logic methods.
-
-    def is_initial_load(self):
-
-        "Return whether the event is being loaded and shown for the first time."
-
-        return not self.env.get_args().has_key("editing")
-
-    def handle_request(self, obj):
-
-        """
-        Handle actions involving the given 'obj' as an object's representation,
-        returning an error if one occurred, or None if the request was
-        successfully handled.
-        """
-
-        # Handle a submitted form.
-
-        args = self.env.get_args()
-        uid = obj.get_uid()
-        recurrenceid = obj.get_recurrenceid()
-
-        # Get the possible actions.
-
-        reply = args.has_key("reply")
-        discard = args.has_key("discard")
-        create = args.has_key("create")
-        cancel = args.has_key("cancel")
-        ignore = args.has_key("ignore")
-        save = args.has_key("save")
-
-        have_action = reply or discard or create or cancel or ignore or save
-
-        if not have_action:
-            return ["action"]
-
-        # If ignoring the object, return to the calendar.
-
-        if ignore:
-            self.redirect(self.env.get_path())
-            return None
-
-        # Update the object.
-
-        single_user = False
-
-        if reply or create or cancel or save:
-
-            # Update principal event details if organiser.
-
-            if self.is_organiser(obj):
-
-                # Update time periods (main and recurring).
-
-                try:
-                    period = self.handle_main_period()
-                except PeriodError, exc:
-                    return exc.args
-
-                try:
-                    periods = self.handle_recurrence_periods()
-                except PeriodError, exc:
-                    return exc.args
-
-                # Set the periods in the object, first obtaining removed and
-                # modified period information.
-
-                to_unschedule = self.get_removed_periods()
-
-                obj.set_period(period)
-                obj.set_periods(periods)
-
-                # Update summary.
-
-                if args.has_key("summary"):
-                    obj["SUMMARY"] = [(args["summary"][0], {})]
-
-                # Obtain any participants and those to be removed.
+    # Access to current object information.
 
-                attendees = self.get_attendees_from_page()
-                removed = [attendees[int(i)] for i in args.get("remove", [])]
-                to_cancel = self.update_attendees(obj, attendees, removed)
-                single_user = not attendees or attendees == [self.user]
-
-            # Update attendee participation for the current user.
-
-            if args.has_key("partstat"):
-                self.update_participation(obj, args["partstat"][0])
-
-        # Process any action.
-
-        invite = not save and create and not single_user
-        save = save or create and single_user
-
-        handled = True
-
-        if reply or invite or cancel:
-
-            client = ManagerClient(obj, self.user, self.messenger)
-
-            # Process the object and remove it from the list of requests.
-
-            if reply and client.process_received_request():
-                self.remove_request(uid, recurrenceid)
-
-            elif self.is_organiser(obj) and (invite or cancel):
-
-                # Invitation, uninvitation and unscheduling...
-
-                if client.process_created_request(
-                    invite and "REQUEST" or "CANCEL", to_cancel, to_unschedule):
-
-                    self.remove_request(uid, recurrenceid)
-
-        # Save single user events.
-
-        elif save:
-            self.store.set_event(self.user, uid, recurrenceid, node=obj.to_node())
-            self.update_freebusy(uid, recurrenceid, obj)
-            self.remove_request(uid, recurrenceid)
-
-        # Remove the request and the object.
-
-        elif discard:
-            self.remove_from_freebusy(uid, recurrenceid)
-            self.remove_event(uid, recurrenceid)
-            self.remove_request(uid, recurrenceid)
-
-        else:
-            handled = False
-
-        # Upon handling an action, redirect to the main page.
-
-        if handled:
-            self.redirect(self.env.get_path())
-
-        return None
-
-    def handle_main_period(self):
-
-        "Return period details for the main start/end period in an event."
-
-        return self.get_main_period().as_event_period()
-
-    def handle_recurrence_periods(self):
-
-        "Return period details for the recurrences specified for an event."
-
-        return [p.as_event_period(i) for i, p in enumerate(self.get_recurrences())]
-
-    def get_date_control_values(self, name, multiple=False, tzid_name=None):
-
-        """
-        Return a dictionary containing date, time and tzid entries for fields
-        starting with 'name'. If 'multiple' is set to a true value, many
-        dictionaries will be returned corresponding to a collection of
-        datetimes. If 'tzid_name' is specified, the time zone information will
-        be acquired from a field starting with 'tzid_name' instead of 'name'.
-        """
+    def get_current_main_period(self):
+        return self.get_stored_main_period()
 
-        args = self.env.get_args()
-
-        dates = args.get("%s-date" % name, [])
-        hours = args.get("%s-hour" % name, [])
-        minutes = args.get("%s-minute" % name, [])
-        seconds = args.get("%s-second" % name, [])
-        tzids = args.get("%s-tzid" % (tzid_name or name), [])
-
-        # Handle absent values by employing None values.
-
-        field_values = map(None, dates, hours, minutes, seconds, tzids)
-
-        if not field_values and not multiple:
-            all_values = FormDate()
-        else:
-            all_values = []
-            for date, hour, minute, second, tzid in field_values:
-                value = FormDate(date, hour, minute, second, tzid or self.get_tzid())
-
-                # Return a single value or append to a collection of all values.
-
-                if not multiple:
-                    return value
-                else:
-                    all_values.append(value)
-
-        return all_values
-
-    def get_current_main_period(self, obj):
-
-        """
-        Return the currently active main period for 'obj' depending on whether
-        editing has begun or whether the object has just been loaded.
-        """
-
-        if self.is_initial_load() or not self.is_organiser(obj):
-            return self.get_stored_main_period(obj)
-        else:
-            return self.get_main_period()
-
-    def get_main_period(self):
-
-        "Return the main period defined in the event form."
-
-        args = self.env.get_args()
-
-        dtend_enabled = args.get("dtend-control", [None])[0]
-        dttimes_enabled = args.get("dttimes-control", [None])[0]
-        start = self.get_date_control_values("dtstart")
-        end = self.get_date_control_values("dtend")
-
-        return FormPeriod(start, end, dtend_enabled, dttimes_enabled, self.get_tzid())
-
-    def get_current_recurrences(self, obj):
-
-        """
-        Return recurrences for 'obj' using the original object where no editing
-        is in progress, using form data otherwise.
-        """
-
-        if self.is_initial_load() or not self.is_organiser(obj):
-            return self.get_stored_recurrences(obj)
-        else:
-            return self.get_recurrences()
-
-    def get_recurrences(self):
-
-        "Return the recurrences defined in the event form."
-
-        args = self.env.get_args()
-
-        all_dtend_enabled = args.get("dtend-control-recur", [])
-        all_dttimes_enabled = args.get("dttimes-control-recur", [])
-        all_starts = self.get_date_control_values("dtstart-recur", multiple=True)
-        all_ends = self.get_date_control_values("dtend-recur", multiple=True, tzid_name="dtstart-recur")
-        all_origins = args.get("recur-origin", [])
-
-        periods = []
+    def get_current_recurrences(self):
+        return self.get_stored_recurrences()
 
-        for index, (start, end, dtend_enabled, dttimes_enabled, origin) in \
-            enumerate(map(None, all_starts, all_ends, all_dtend_enabled, all_dttimes_enabled, all_origins)):
-
-            dtend_enabled = str(index) in all_dtend_enabled
-            dttimes_enabled = str(index) in all_dttimes_enabled
-            period = FormPeriod(start, end, dtend_enabled, dttimes_enabled, self.get_tzid(), origin)
-            periods.append(period)
-
-        return periods
-
-    def get_removed_periods(self):
-
-        "Return a list of recurrence periods to remove upon updating an event."
-
-        to_unschedule = []
-        args = self.env.get_args()
-        for i in args.get("recur-remove", []):
-            to_unschedule.append(periods[int(i)])
-        return to_unschedule
-
-    def get_current_attendees(self, obj):
-
-        """
-        Return attendees for 'obj' depending on whether the object is being
-        edited.
-        """
-
-        if self.is_initial_load() or not self.is_organiser(obj):
-            return self.get_stored_attendees(obj)
-        else:
-            return self.get_attendees_from_page()
-
-    def get_attendees_from_page(self):
-
-        """
-        Return attendees from the request, normalised for iCalendar purposes,
-        and without duplicates.
-        """
-
-        args = self.env.get_args()
-
-        attendees = args.get("attendee", [])
-        unique_attendees = set()
-        ordered_attendees = []
-
-        for attendee in attendees:
-            if not attendee.strip():
-                continue
-            attendee = get_uri(attendee)
-            if attendee not in unique_attendees:
-                unique_attendees.add(attendee)
-                ordered_attendees.append(attendee)
-
-        return ordered_attendees
-
-    def update_attendees_from_page(self, obj):
-
-        "Add or remove attendees. This does not affect the stored object."
-
-        args = self.env.get_args()
-
-        attendees = self.get_attendees_from_page()
-        existing_attendees = self.get_stored_attendees(obj)
-
-        if args.has_key("add"):
-            attendees.append("")
-
-        # Only actually remove attendees if the event is unsent, if the attendee
-        # is new, or if it is the current user being removed.
-
-        if args.has_key("remove"):
-            for i in args["remove"]:
-                try:
-                    attendee = attendees[int(i)]
-                except IndexError:
-                    continue
-
-                existing = attendee in existing_attendees
-
-                if not existing or not obj.is_shared() or attendee == self.user:
-                    attendees.remove(attendee)
-
-        return attendees
+    def get_current_attendees(self):
+        return self.get_stored_attendees()
 
     # Page fragment methods.
 
-    def show_request_controls(self, obj):
+    def show_request_controls(self):
 
-        "Show form controls for a request concerning 'obj'."
+        "Show form controls for a request."
 
         page = self.page
         args = self.env.get_args()
 
-        attendees = self.get_current_attendees(obj)
+        attendees = self.get_current_attendees()
         is_attendee = self.user in attendees
-        is_request = self._have_request(obj.get_uid(), obj.get_recurrenceid())
+        is_request = self._have_request(self.uid, self.recurrenceid)
 
         # Show appropriate options depending on the role of the user.
 
-        if is_attendee and not self.is_organiser(obj):
+        if is_attendee and not self.is_organiser():
             page.p("An action is required for this request:")
 
             page.p()
-            self._control("reply", "submit", "Send reply")
+            self.control("reply", "submit", "Send reply")
             page.add(" ")
-            self._control("discard", "submit", "Discard event")
+            self.control("discard", "submit", "Discard event")
             page.add(" ")
-            self._control("ignore", "submit", "Do nothing for now")
+            self.control("ignore", "submit", "Do nothing for now")
             page.p.close()
 
-        if self.is_organiser(obj):
+        if self.is_organiser():
             page.p("As organiser, you can perform the following:")
 
             page.p()
-            self._control("create", "submit", not obj.is_shared() and "Create event" or "Update event")
+            self.control("create", "submit", not self.obj.is_shared() and "Create event" or "Update event")
             page.add(" ")
 
-            if obj.is_shared() and not is_request:
-                self._control("cancel", "submit", "Cancel event")
+            if self.obj.is_shared() and not is_request:
+                self.control("cancel", "submit", "Cancel event")
             else:
-                self._control("discard", "submit", "Discard event")
+                self.control("discard", "submit", "Discard event")
 
             page.add(" ")
-            self._control("save", "submit", "Save without sending")
+            self.control("save", "submit", "Save without sending")
             page.p.close()
 
-    def show_object_on_page(self, obj, errors=None):
+    def show_object_on_page(self, errors=None):
 
         """
-        Show the calendar object with the representation 'obj' on the current
-        page. If 'errors' is given, show a suitable message for the different
-        errors provided.
+        Show the calendar object on the current page. If 'errors' is given, show
+        a suitable message for the different errors provided.
         """
 
         page = self.page
@@ -474,26 +185,21 @@
 
         # Add a hidden control to help determine whether editing has already begun.
 
-        self._control("editing", "hidden", "true")
+        self.control("editing", "hidden", "true")
 
-        uid = obj.get_uid()
         args = self.env.get_args()
 
         # Obtain basic event information, generating any necessary editing controls.
 
-        if self.is_initial_load() or not self.is_organiser(obj):
-            attendees = self.get_stored_attendees(obj)
-        else:
-            attendees = self.update_attendees_from_page(obj)
-
-        p = self.get_current_main_period(obj)
-        self.show_object_datetime_controls(p)
+        attendees = self.get_current_attendees()
+        period = self.get_current_main_period()
+        self.show_object_datetime_controls(period)
 
         # Obtain any separate recurrences for this event.
 
-        recurrenceid = obj.get_recurrenceid()
-        recurrenceids = self._get_active_recurrences(uid)
-        replaced = not recurrenceid and p.is_replaced(recurrenceids)
+        recurrenceids = self._get_active_recurrences(self.uid)
+        replaced = not self.recurrenceid and period.is_replaced(recurrenceids)
+        excluded = period not in self.get_periods(self.obj)
 
         # Provide a summary of the object.
 
@@ -508,7 +214,7 @@
         for name, label in self.property_items:
             field = name.lower()
 
-            items = obj.get_items(name) or []
+            items = uri_items(self.obj.get_items(name) or [])
             rowspan = len(items)
 
             if name == "ATTENDEE":
@@ -522,7 +228,7 @@
             # Handle datetimes specially.
 
             if name in ["DTSTART", "DTEND"]:
-                if not replaced:
+                if not replaced and not excluded:
 
                     # Obtain the datetime.
 
@@ -532,23 +238,36 @@
                     # basis of any potential datetime specified if dt-control is
                     # set.
 
-                    self.show_datetime_controls(obj, is_start and p.get_form_start() or p.get_form_end(), is_start)
+                    self.show_datetime_controls(is_start and period.get_form_start() or period.get_form_end(), is_start)
 
                 elif name == "DTSTART":
-                    page.td(class_="objectvalue %s replaced" % field, rowspan=2)
-                    page.a("First occurrence replaced by a separate event", href=self.link_to(uid, replaced))
-                    page.td.close()
+
+                    # Replaced occurrences link to their replacements.
+
+                    if replaced:
+                        page.td(class_="objectvalue %s replaced" % field, rowspan=2)
+                        page.a("First occurrence replaced by a separate event", href=self.link_to(self.uid, replaced))
+                        page.td.close()
+
+                    # NOTE: Should provide a way of editing recurrences when the
+                    # NOTE: first occurrence is excluded, plus a way of
+                    # NOTE: reinstating the occurrence.
+
+                    elif excluded:
+                        page.td(class_="objectvalue %s excluded" % field, rowspan=2)
+                        page.add("First occurrence excluded")
+                        page.td.close()
 
                 page.tr.close()
 
             # Handle the summary specially.
 
             elif name == "SUMMARY":
-                value = args.get("summary", [obj.get_value(name)])[0]
+                value = args.get("summary", [self.obj.get_value(name)])[0]
 
                 page.td(class_="objectvalue summary")
-                if self.is_organiser(obj):
-                    self._control("summary", "text", value, size=80)
+                if self.is_organiser():
+                    self.control("summary", "text", value, size=80)
                 else:
                     page.add(value)
                 page.td.close()
@@ -568,17 +287,17 @@
 
                     # Obtain details of attendees to supply attributes.
 
-                    self.show_attendee(obj, i, value, attendee_map.get(value))
+                    self.show_attendee(i, value, attendee_map.get(value))
                     page.tr.close()
 
                 # Allow more attendees to be specified.
 
-                if self.is_organiser(obj):
+                if self.is_organiser():
                     if not first:
                         page.tr()
 
                     page.td()
-                    self._control("add", "submit", "add", id="add", class_="add")
+                    self.control("add", "submit", "add", id="add", class_="add")
                     page.label("Add attendee", for_="add", class_="add")
                     page.td.close()
                     page.tr.close()
@@ -602,59 +321,62 @@
         page.tbody.close()
         page.table.close()
 
-        self.show_recurrences(obj, errors)
-        self.show_conflicting_events(obj)
-        self.show_request_controls(obj)
+        self.show_recurrences(errors)
+        self.show_counters()
+        self.show_conflicting_events()
+        self.show_request_controls()
 
         page.form.close()
 
-    def show_attendee(self, obj, i, attendee, attendee_attr):
+    def show_attendee(self, i, attendee, attendee_attr):
 
         """
-        For the given object 'obj', show the attendee in position 'i' with the
-        given 'attendee' value, having 'attendee_attr' as any stored attributes.
+        For the current object, show the attendee in position 'i' with the given
+        'attendee' value, having 'attendee_attr' as any stored attributes.
         """
 
         page = self.page
         args = self.env.get_args()
 
-        existing = attendee_attr is not None
         partstat = attendee_attr and attendee_attr.get("PARTSTAT")
 
         page.td(class_="objectvalue")
 
         # Show a form control as organiser for new attendees.
 
-        if self.is_organiser(obj) and (not existing or not obj.is_shared()):
-            self._control("attendee", "value", attendee, size="40")
+        if self.is_organiser() and self.can_edit_attendee(attendee):
+            self.control("attendee", "value", attendee, size="40")
         else:
-            self._control("attendee", "hidden", attendee)
+            self.control("attendee", "hidden", attendee)
             page.add(attendee)
         page.add(" ")
 
         # Show participation status, editable for the current user.
 
         if attendee == self.user:
-            self._show_menu("partstat", partstat, self.partstat_items, "partstat")
+            self.menu("partstat", partstat, self.partstat_items, "partstat")
 
         # Allow the participation indicator to act as a submit
         # button in order to refresh the page and show a control for
         # the current user, if indicated.
 
-        elif self.is_organiser(obj) and not existing:
-            self._control("partstat-refresh", "submit", "refresh", id="partstat-%d" % i, class_="refresh")
+        elif self.is_organiser() and self.attendee_is_new(attendee):
+            self.control("partstat-refresh", "submit", "refresh", id="partstat-%d" % i, class_="refresh")
             page.label(dict(self.partstat_items).get(partstat, ""), for_="partstat-%s" % i, class_="partstat")
+
+        # Otherwise, just show a label with the participation status.
+
         else:
             page.span(dict(self.partstat_items).get(partstat, ""), class_="partstat")
 
         # Permit organisers to remove attendees.
 
-        if self.is_organiser(obj):
+        if self.is_organiser():
 
             # Permit the removal of newly-added attendees.
 
-            remove_type = (not existing or not obj.is_shared() or attendee == self.user) and "submit" or "checkbox"
-            self._control("remove", remove_type, str(i), str(i) in args.get("remove", []), id="remove-%d" % i, class_="remove")
+            remove_type = self.can_remove_attendee(attendee) and "submit" or "checkbox"
+            self.control("remove", remove_type, str(i), str(i) in args.get("remove", []), id="remove-%d" % i, class_="remove")
 
             page.label("Remove", for_="remove-%d" % i, class_="remove")
             page.label(for_="remove-%d" % i, class_="removed")
@@ -664,48 +386,44 @@
 
         page.td.close()
 
-    def show_recurrences(self, obj, errors=None):
+    def show_recurrences(self, errors=None):
 
         """
-        Show recurrences for the object having the given representation 'obj'.
-        If 'errors' is given, show a suitable message for the different errors
-        provided.
+        Show recurrences for the current object. If 'errors' is given, show a
+        suitable message for the different errors provided.
         """
 
         page = self.page
 
         # Obtain any parent object if this object is a specific recurrence.
 
-        uid = obj.get_uid()
-        recurrenceid = obj.get_recurrenceid()
-
-        if recurrenceid:
-            parent = self.get_stored_object(uid, None)
+        if self.recurrenceid:
+            parent = self.get_stored_object(self.uid, None)
             if not parent:
                 return
 
             page.p()
-            page.a("This event modifies a recurring event.", href=self.link_to(uid))
+            page.a("This event modifies a recurring event.", href=self.link_to(self.uid))
             page.p.close()
 
         # Obtain the periods associated with the event.
         # NOTE: Add a control to add recurrences here.
 
-        recurrences = self.get_current_recurrences(obj)
+        recurrences = self.get_current_recurrences()
 
         if len(recurrences) < 1:
             return
 
-        recurrenceids = self._get_recurrences(uid)
+        recurrenceids = self._get_recurrences(self.uid)
 
         page.p("This event occurs on the following occasions within the next %d days:" % self.get_window_size())
 
         # Show each recurrence in a separate table if editable.
 
-        if self.is_organiser(obj) and recurrences:
+        if self.is_organiser() and recurrences:
 
             for index, period in enumerate(recurrences):
-                self.show_recurrence(obj, index, period, recurrenceid, recurrenceids, errors)
+                self.show_recurrence(index, period, self.recurrenceid, recurrenceids, errors)
 
         # Otherwise, use a compact single table.
 
@@ -722,21 +440,21 @@
 
             for index, period in enumerate(recurrences):
                 page.tr()
-                self.show_recurrence_label(period, recurrenceid, recurrenceids, True)
-                self.show_recurrence_label(period, recurrenceid, recurrenceids, False)
+                self.show_recurrence_label(period, self.recurrenceid, recurrenceids, True)
+                self.show_recurrence_label(period, self.recurrenceid, recurrenceids, False)
                 page.tr.close()
 
             page.tbody.close()
             page.table.close()
 
-    def show_recurrence(self, obj, index, period, recurrenceid, recurrenceids, errors=None):
+    def show_recurrence(self, index, period, recurrenceid, recurrenceids, errors=None):
 
         """
-        Show recurrence controls for a recurrence provided by 'obj' with the
-        given 'index' position in the list of periods, the given 'period'
-        details, where a 'recurrenceid' indicates any specific recurrence, and
-        where 'recurrenceids' indicates all known additional recurrences for the
-        object.
+        Show recurrence controls for a recurrence provided by the current object
+        with the given 'index' position in the list of periods, the given
+        'period' details, where a 'recurrenceid' indicates any specific
+        recurrence, and where 'recurrenceids' indicates all known additional
+        recurrences for the object.
 
         If 'errors' is given, show a suitable message for the different errors
         provided.
@@ -761,12 +479,12 @@
         page.tr()
         error = errors and ("dtstart", index) in errors and " error" or ""
         page.th("Start", class_="objectheading start%s" % error)
-        self.show_recurrence_controls(obj, index, period, recurrenceid, recurrenceids, True)
+        self.show_recurrence_controls(index, period, recurrenceid, recurrenceids, True)
         page.tr.close()
         page.tr()
         error = errors and ("dtend", index) in errors and " error" or ""
         page.th("End", class_="objectheading end%s" % error)
-        self.show_recurrence_controls(obj, index, period, recurrenceid, recurrenceids, False)
+        self.show_recurrence_controls(index, period, recurrenceid, recurrenceids, False)
         page.tr.close()
 
         # Permit the removal of recurrences.
@@ -776,8 +494,9 @@
             page.th("")
             page.td()
 
-            remove_type = not obj.is_shared() or not period.origin and "submit" or "checkbox"
-            self._control("recur-remove", remove_type, str(index),
+            remove_type = self.can_remove_recurrence(period) and "submit" or "checkbox"
+
+            self.control("recur-remove", remove_type, str(index),
                 str(index) in args.get("recur-remove", []),
                 id="recur-remove-%d" % index, class_="remove")
 
@@ -795,53 +514,107 @@
 
         page.div.close()
 
-    def show_conflicting_events(self, obj):
+    def show_counters(self):
 
-        """
-        Show conflicting events for the object having the representation 'obj'.
-        """
+        "Show any counter-proposals for the current object."
 
         page = self.page
-        uid = obj.get_uid()
-        recurrenceid = obj.get_recurrenceid()
-        recurrenceids = self._get_active_recurrences(uid)
+        query = self.env.get_query()
+        counter = query.get("counter", [None])[0]
+
+        attendees = self._get_counters(self.uid, self.recurrenceid)
+        tzid = self.get_tzid()
+
+        if not attendees:
+            return
+
+        page.p("The following counter-proposals have been received for this event:")
+
+        page.table(cellspacing=5, cellpadding=5, class_="counters")
+        page.thead()
+        page.tr()
+        page.th("Attendee", rowspan=2)
+        page.th("Periods", colspan=2)
+        page.tr.close()
+        page.tr()
+        page.th("Start")
+        page.th("End")
+        page.tr.close()
+        page.thead.close()
+        page.tbody()
+
+        for attendee in attendees:
+            obj = self.get_stored_object(self.uid, self.recurrenceid, "counters", attendee)
+            periods = self.get_periods(obj)
+
+            first = True
+            for p in periods:
+                identifier = "%s-%s" % (format_datetime(p.get_start_point()), format_datetime(p.get_end_point()))
+                css = identifier == counter and "selected" or ""
+
+                if first:
+                    page.tr(rowspan=len(periods), class_=css)
+                    page.td(attendee)
+                    first = False
+                else:
+                    page.tr(class_=css)
+
+                start = self.format_datetime(to_timezone(p.get_start(), tzid), "long")
+                end = self.format_datetime(to_timezone(p.get_end(), tzid), "long")
+
+                page.td(start)
+                page.td(end)
+
+                page.tr.close()
+
+        page.tbody.close()
+        page.table.close()
+
+    def show_conflicting_events(self):
+
+        "Show conflicting events for the current object."
+
+        page = self.page
+        recurrenceids = self._get_active_recurrences(self.uid)
 
         # Obtain the user's timezone.
 
         tzid = self.get_tzid()
-        periods = self.get_periods(obj)
+        periods = self.get_periods(self.obj)
 
         # Indicate whether there are conflicting events.
 
         conflicts = []
-        attendee_map = uri_dict(obj.get_value_map("ATTENDEE"))
+        attendee_map = uri_dict(self.obj.get_value_map("ATTENDEE"))
 
-        for participant in self.get_current_attendees(obj):
+        for participant in self.get_current_attendees():
             if participant == self.user:
                 freebusy = self.store.get_freebusy(participant)
+            elif participant:
+                freebusy = self.store.get_freebusy_for_other(self.user, participant)
             else:
-                freebusy = self.store.get_freebusy_for_other(self.user, participant)
+                continue
 
             if not freebusy:
                 continue
 
             # Obtain any time zone details from the suggested event.
 
-            _dtstart, attr = obj.get_item("DTSTART")
+            _dtstart, attr = self.obj.get_item("DTSTART")
             tzid = attr.get("TZID", tzid)
 
             # Show any conflicts with periods of actual attendance.
 
             participant_attr = attendee_map.get(participant)
             partstat = participant_attr and participant_attr.get("PARTSTAT")
-            recurrences = obj.get_recurrence_start_points(recurrenceids, tzid)
+            recurrences = self.obj.get_recurrence_start_points(recurrenceids, tzid)
 
             for p in have_conflict(freebusy, periods, True):
-                if not recurrenceid and p.is_replaced(recurrences):
+                if not self.recurrenceid and p.is_replaced(recurrences):
                     continue
 
                 if ( # Unidentified or different event
-                     (p.uid != uid or recurrenceid and p.recurrenceid and p.recurrenceid != recurrenceid) and
+                     (p.uid != self.uid or self.recurrenceid and p.recurrenceid and p.recurrenceid != self.recurrenceid) and
                      # Different period or unclear participation with the same period
                      (p not in periods or not partstat in ("ACCEPTED", "TENTATIVE")) and
                      # Participant not limited to organising
@@ -893,188 +666,396 @@
             page.tbody.close()
             page.table.close()
 
-    # Generation of controls within page fragments.
+class EventPage(EventPageFragment):
+
+    "A request handler for the event page."
+
+    def __init__(self, resource=None, messenger=None):
+        ResourceClientForObject.__init__(self, resource)
+        self.messenger = messenger or Messenger()
 
-    def show_object_datetime_controls(self, period, index=None):
+    # Request logic methods.
+
+    def is_initial_load(self):
+
+        "Return whether the event is being loaded and shown for the first time."
+
+        return not self.env.get_args().has_key("editing")
+
+    def handle_request(self):
 
         """
-        Show datetime-related controls if already active or if an object needs
-        them for the given 'period'. The given 'index' is used to parameterise
-        individual controls for dynamic manipulation.
+        Handle actions involving the current object, returning an error if one
+        occurred, or None if the request was successfully handled.
         """
 
-        p = form_period_from_period(period)
+        # Handle a submitted form.
 
-        page = self.page
         args = self.env.get_args()
-        _id = self.element_identifier
-        _name = self.element_name
-        _enable = self.element_enable
+
+        # Get the possible actions.
+
+        reply = args.has_key("reply")
+        discard = args.has_key("discard")
+        create = args.has_key("create")
+        cancel = args.has_key("cancel")
+        ignore = args.has_key("ignore")
+        save = args.has_key("save")
 
-        # Add a dynamic stylesheet to permit the controls to modify the display.
-        # NOTE: The style details need to be coordinated with the static
-        # NOTE: stylesheet.
+        have_action = reply or discard or create or cancel or ignore or save
+
+        if not have_action:
+            return ["action"]
 
-        if index is not None:
-            page.style(type="text/css")
+        # If ignoring the object, return to the calendar.
 
-            # Unlike the rules for object properties, these affect recurrence
-            # properties.
+        if ignore:
+            self.redirect(self.env.get_path())
+            return None
+
+        # Update the object.
 
-            page.add("""\
-input#dttimes-enable-%(index)d,
-input#dtend-enable-%(index)d,
-input#dttimes-enable-%(index)d:not(:checked) ~ .recurrence td.objectvalue .time.enabled,
-input#dttimes-enable-%(index)d:checked ~ .recurrence td.objectvalue .time.disabled,
-input#dtend-enable-%(index)d:not(:checked) ~ .recurrence td.objectvalue.dtend .dt.enabled,
-input#dtend-enable-%(index)d:checked ~ .recurrence td.objectvalue.dtend .dt.disabled {
-    display: none;
-}""" % {"index" : index})
+        single_user = False
+
+        if reply or create or cancel or save:
+
+            # Update principal event details if organiser.
+
+            if self.is_organiser():
+
+                # Update time periods (main and recurring).
 
-            page.style.close()
+                try:
+                    period = self.handle_main_period()
+                except PeriodError, exc:
+                    return exc.args
 
-        self._control(
-            _name("dtend-control", "recur", index), "checkbox",
-            _enable(index), p.end_enabled,
-            id=_id("dtend-enable", index)
-            )
+                try:
+                    periods = self.handle_recurrence_periods()
+                except PeriodError, exc:
+                    return exc.args
+
+                # Set the periods in the object, first obtaining removed and
+                # modified period information.
+
+                to_unschedule, to_exclude = self.get_removed_periods(periods)
+
+                self.obj.set_period(period)
+                self.obj.set_periods(periods)
+                self.obj.update_exceptions(to_exclude)
 
-        self._control(
-            _name("dttimes-control", "recur", index), "checkbox",
-            _enable(index), p.times_enabled,
-            id=_id("dttimes-enable", index)
-            )
+                # Update summary.
+
+                if args.has_key("summary"):
+                    self.obj["SUMMARY"] = [(args["summary"][0], {})]
+
+                # Obtain any participants and those to be removed.
 
-    def show_datetime_controls(self, obj, formdate, show_start):
+                attendees = self.get_attendees_from_page()
+                removed = [attendees[int(i)] for i in args.get("remove", [])]
+                to_cancel = self.update_attendees(self.obj, attendees, removed)
+                single_user = not attendees or attendees == [self.user]
+
+            # Update attendee participation for the current user.
 
-        """
-        Show datetime details from the given 'obj' for the 'formdate', showing
-        start details if 'show_start' is set to a true value. Details will
-        appear as controls for organisers and labels for attendees.
-        """
+            if args.has_key("partstat"):
+                self.update_participation(self.obj, args["partstat"][0])
+
+        # Process any action.
 
-        page = self.page
+        invite = not save and create and not single_user
+        save = save or create and single_user
 
-        # Show controls for editing as organiser.
+        handled = True
 
-        if self.is_organiser(obj):
-            page.td(class_="objectvalue dt%s" % (show_start and "start" or "end"))
+        if reply or invite or cancel:
+
+            client = ManagerClient(self.obj, self.user, self.messenger)
 
-            if show_start:
-                page.div(class_="dt enabled")
-                self._show_date_controls("dtstart", formdate)
-                page.br()
-                page.label("Specify times", for_="dttimes-enable", class_="time disabled enable")
-                page.label("Specify dates only", for_="dttimes-enable", class_="time enabled disable")
-                page.div.close()
+            # Process the object and remove it from the list of requests.
+
+            if reply and client.process_received_request():
+                self.remove_request(self.uid, self.recurrenceid)
+
+            elif self.is_organiser() and (invite or cancel):
+
+                # Invitation, uninvitation and unscheduling...
+
+                if client.process_created_request(
+                    invite and "REQUEST" or "CANCEL", to_cancel, to_unschedule):
+
+                    self.remove_request(self.uid, self.recurrenceid)
 
-            else:
-                page.div(class_="dt disabled")
-                page.label("Specify end date", for_="dtend-enable", class_="enable")
-                page.div.close()
-                page.div(class_="dt enabled")
-                self._show_date_controls("dtend", formdate)
-                page.br()
-                page.label("End on same day", for_="dtend-enable", class_="disable")
-                page.div.close()
+        # Save single user events.
+
+        elif save:
+            self.store.set_event(self.user, self.uid, self.recurrenceid, node=self.obj.to_node())
+            self.update_event_in_freebusy()
+            self.remove_request(self.uid, self.recurrenceid)
 
-            page.td.close()
+        # Remove the request and the object.
 
-        # Show a label as attendee.
+        elif discard:
+            self.remove_event_from_freebusy()
+            self.remove_event(self.uid, self.recurrenceid)
+            self.remove_request(self.uid, self.recurrenceid)
 
         else:
-            dt = formdate.as_datetime()
-            if dt:
-                page.td(self.format_datetime(dt, "full"))
-            else:
-                page.td("(Unrecognised date)")
+            handled = False
+
+        # Upon handling an action, redirect to the main page.
+
+        if handled:
+            self.redirect(self.env.get_path())
+
+        return None
+
+    def handle_main_period(self):
+
+        "Return period details for the main start/end period in an event."
+
+        return self.get_main_period_from_page().as_event_period()
+
+    def handle_recurrence_periods(self):
+
+        "Return period details for the recurrences specified for an event."
+
+        return [p.as_event_period(i) for i, p in enumerate(self.get_recurrences_from_page())]
+
+    # Access to form-originating object information.
+
+    def get_main_period_from_page(self):
+
+        "Return the main period defined in the event form."
+
+        args = self.env.get_args()
+
+        dtend_enabled = args.get("dtend-control", [None])[0]
+        dttimes_enabled = args.get("dttimes-control", [None])[0]
+        start = self.get_date_control_values("dtstart")
+        end = self.get_date_control_values("dtend")
+
+        period = FormPeriod(start, end, dtend_enabled, dttimes_enabled, self.get_tzid())
+
+        # Handle absent main period details.
+
+        if not period.get_start():
+            return self.get_stored_main_period()
+        else:
+            return period
+
+    def get_recurrences_from_page(self):
+
+        "Return the recurrences defined in the event form."
 
-    def show_recurrence_controls(self, obj, index, period, recurrenceid, recurrenceids, show_start):
+        args = self.env.get_args()
+
+        all_dtend_enabled = args.get("dtend-control-recur", [])
+        all_dttimes_enabled = args.get("dttimes-control-recur", [])
+        all_starts = self.get_date_control_values("dtstart-recur", multiple=True)
+        all_ends = self.get_date_control_values("dtend-recur", multiple=True, tzid_name="dtstart-recur")
+        all_origins = args.get("recur-origin", [])
+
+        periods = []
+
+        for index, (start, end, dtend_enabled, dttimes_enabled, origin) in \
+            enumerate(map(None, all_starts, all_ends, all_dtend_enabled, all_dttimes_enabled, all_origins)):
+
+            dtend_enabled = str(index) in all_dtend_enabled
+            dttimes_enabled = str(index) in all_dttimes_enabled
+            period = FormPeriod(start, end, dtend_enabled, dttimes_enabled, self.get_tzid(), origin)
+            periods.append(period)
+
+        return periods
+
+    def set_recurrences_in_page(self, recurrences):
+
+        "Set the recurrences defined in the event form."
+
+        args = self.env.get_args()
+
+        args["dtend-control-recur"] = []
+        args["dttimes-control-recur"] = []
+        args["recur-origin"] = []
+
+        all_starts = []
+        all_ends = []
+
+        for index, period in enumerate(recurrences):
+            if period.end_enabled:
+                args["dtend-control-recur"].append(str(index))
+            if period.times_enabled:
+                args["dttimes-control-recur"].append(str(index))
+            args["recur-origin"].append(period.origin or "")
+
+            all_starts.append(period.get_form_start())
+            all_ends.append(period.get_form_end())
+
+        self.set_date_control_values("dtstart-recur", all_starts)
+        self.set_date_control_values("dtend-recur", all_ends, tzid_name="dtstart-recur")
+
+    def get_removed_periods(self, periods):
 
         """
-        Show datetime details from the given 'obj' for the recurrence having the
-        given 'index', with the recurrence period described by 'period',
-        indicating a start, end and origin of the period from the event details,
-        employing any 'recurrenceid' and 'recurrenceids' for the object to
-        configure the displayed information.
+        Return those from the recurrence 'periods' to remove upon updating an
+        event along with those to exclude in a tuple of the form (unscheduled,
+        excluded).
+        """
+
+        args = self.env.get_args()
+        to_unschedule = []
+        to_exclude = []
 
-        If 'show_start' is set to a true value, the start details will be shown;
-        otherwise, the end details will be shown.
+        for i in args.get("recur-remove", []):
+            try:
+                period = periods[int(i)]
+            except (IndexError, ValueError):
+                continue
+
+            if not self.can_edit_recurrence(period):
+                to_unschedule.append(period)
+            else:
+                to_exclude.append(period)
+
+        return to_unschedule, to_exclude
+
+    def get_attendees_from_page(self):
+
+        """
+        Return attendees from the request, normalised for iCalendar purposes.
         """
 
-        page = self.page
-        _id = self.element_identifier
-        _name = self.element_name
+        args = self.env.get_args()
+        attendees = []
+
+        for attendee in args.get("attendee", []):
+            if attendee.strip():
+                attendee = get_uri(attendee)
+            attendees.append(attendee)
 
-        p = event_period_from_period(period)
-        replaced = not recurrenceid and p.is_replaced(recurrenceids)
+        return attendees
+
+    def update_attendees_from_page(self):
 
-        # Show controls for editing as organiser.
+        "Add or remove attendees. This does not affect the stored object."
+
+        args = self.env.get_args()
+
+        attendees = self.get_attendees_from_page()
 
-        if self.is_organiser(obj) and not replaced:
-            page.td(class_="objectvalue dt%s" % (show_start and "start" or "end"))
+        if args.has_key("add"):
+            attendees.append("")
 
-            read_only = period.origin == "RRULE"
+        # Only actually remove attendees if the event is unsent, if the attendee
+        # is new, or if it is the current user being removed.
+
+        if args.has_key("remove"):
+            still_to_remove = []
 
-            if show_start:
-                page.div(class_="dt enabled")
-                self._show_date_controls(_name("dtstart", "recur", index), p.get_form_start(), index=index, read_only=read_only)
-                if not read_only:
-                    page.br()
-                    page.label("Specify times", for_=_id("dttimes-enable", index), class_="time disabled enable")
-                    page.label("Specify dates only", for_=_id("dttimes-enable", index), class_="time enabled disable")
-                page.div.close()
+            for i in args["remove"]:
+                try:
+                    attendee = attendees[int(i)]
+                except IndexError:
+                    continue
+
+                if self.can_remove_attendee(attendee):
+                    attendees.remove(attendee)
+                else:
+                    still_to_remove.append(i)
 
-                # Put the origin somewhere.
+            args["remove"] = still_to_remove
+
+        args["attendee"] = attendees
+        return attendees
+
+    def update_recurrences_from_page(self):
+
+        "Add or remove recurrences. This does not affect the stored object."
 
-                self._control("recur-origin", "hidden", p.origin or "")
+        args = self.env.get_args()
+
+        recurrences = self.get_recurrences_from_page()
+
+        # NOTE: Addition of recurrences to be supported.
+
+        # Only actually remove recurrences if the event is unsent, or if the
+        # recurrence is new, but only for explicit recurrences.
 
-            else:
-                page.div(class_="dt disabled")
-                if not read_only:
-                    page.label("Specify end date", for_=_id("dtend-enable", index), class_="enable")
-                page.div.close()
-                page.div(class_="dt enabled")
-                self._show_date_controls(_name("dtend", "recur", index), p.get_form_end(), index=index, show_tzid=False, read_only=read_only)
-                if not read_only:
-                    page.br()
-                    page.label("End on same day", for_=_id("dtend-enable", index), class_="disable")
-                page.div.close()
+        if args.has_key("recur-remove"):
+            still_to_remove = []
+
+            for i in args["recur-remove"]:
+                try:
+                    recurrence = recurrences[int(i)]
+                except IndexError:
+                    continue
 
-            page.td.close()
+                if self.can_remove_recurrence(recurrence):
+                    recurrences.remove(recurrence)
+                else:
+                    still_to_remove.append(i)
 
-        # Show label as attendee.
+            args["recur-remove"] = still_to_remove
 
-        else:
-            self.show_recurrence_label(p, recurrenceid, recurrenceids, show_start)
+        self.set_recurrences_in_page(recurrences)
+        return recurrences
 
-    def show_recurrence_label(self, period, recurrenceid, recurrenceids, show_start):
+    # Access to current object information.
+
+    def get_current_main_period(self):
 
         """
-        Show datetime details for the given 'period', employing any
-        'recurrenceid' and 'recurrenceids' for the object to configure the
-        displayed information.
+        Return the currently active main period for the current object depending
+        on whether editing has begun or whether the object has just been loaded.
+        """
 
-        If 'show_start' is set to a true value, the start details will be shown;
-        otherwise, the end details will be shown.
+        if self.is_initial_load() or not self.is_organiser():
+            return self.get_stored_main_period()
+        else:
+            return self.get_main_period_from_page()
+
+    def get_current_recurrences(self):
+
+        """
+        Return recurrences for the current object using the original object
+        details where no editing is in progress, using form data otherwise.
         """
 
-        page = self.page
+        if self.is_initial_load() or not self.is_organiser():
+            return self.get_stored_recurrences()
+        else:
+            return self.get_recurrences_from_page()
+
+    def update_current_recurrences(self):
 
-        p = event_period_from_period(period)
-        replaced = not recurrenceid and p.is_replaced(recurrenceids)
+        "Return an updated collection of recurrences for the current object."
+
+        if self.is_initial_load() or not self.is_organiser():
+            return self.get_stored_recurrences()
+        else:
+            return self.update_recurrences_from_page()
+
+    def get_current_attendees(self):
 
-        css = " ".join([
-            replaced and "replaced" or "",
-            p.is_affected(recurrenceid) and "affected" or ""
-            ])
+        """
+        Return attendees for the current object depending on whether the object
+        has been edited or instead provides such information from its stored
+        form.
+        """
 
-        formdate = show_start and p.get_form_start() or p.get_form_end()
-        dt = formdate.as_datetime()
-        if dt:
-            page.td(self.format_datetime(dt, "long"), class_=css)
+        if self.is_initial_load() or not self.is_organiser():
+            return self.get_stored_attendees()
         else:
-            page.td("(Unrecognised date)")
+            return self.get_attendees_from_page()
+
+    def update_current_attendees(self):
+
+        "Return an updated collection of attendees for the current object."
+
+        if self.is_initial_load() or not self.is_organiser():
+            return self.get_stored_attendees()
+        else:
+            return self.update_attendees_from_page()
 
     # Full page output methods.
 
@@ -1082,146 +1063,24 @@
 
         "Show an object request using the given 'path_info' for the current user."
 
-        uid, recurrenceid, section = self.get_identifiers(path_info)
-        obj = self.get_stored_object(uid, recurrenceid, section)
+        uid, recurrenceid = self.get_identifiers(path_info)
+        obj = self.get_stored_object(uid, recurrenceid)
+        self.set_object(obj)
 
         if not obj:
             return False
 
-        errors = self.handle_request(obj)
+        errors = self.handle_request()
 
         if not errors:
             return True
 
+        self.update_current_attendees()
+        self.update_current_recurrences()
+
         self.new_page(title="Event")
-        self.show_object_on_page(obj, errors)
+        self.show_object_on_page(errors)
 
         return True
 
-    # Utility methods.
-
-    def _control(self, name, type, value, selected=False, **kw):
-
-        """
-        Show a control with the given 'name', 'type' and 'value', with
-        'selected' indicating whether it should be selected (checked or
-        equivalent), and with keyword arguments setting other properties.
-        """
-
-        page = self.page
-        if selected:
-            page.input(name=name, type=type, value=value, checked=selected, **kw)
-        else:
-            page.input(name=name, type=type, value=value, **kw)
-
-    def _show_menu(self, name, default, items, class_="", index=None):
-
-        """
-        Show a select menu having the given 'name', set to the given 'default',
-        providing the given (value, label) 'items', and employing the given CSS
-        'class_' if specified.
-        """
-
-        page = self.page
-        values = self.env.get_args().get(name, [default])
-        if index is not None:
-            values = values[index:]
-            values = values and values[0:1] or [default]
-
-        page.select(name=name, class_=class_)
-        for v, label in items:
-            if v is None:
-                continue
-            if v in values:
-                page.option(label, value=v, selected="selected")
-            else:
-                page.option(label, value=v)
-        page.select.close()
-
-    def _show_date_controls(self, name, default, index=None, show_tzid=True, read_only=False):
-
-        """
-        Show date controls for a field with the given 'name' and 'default' form
-        date value.
-
-        If 'index' is specified, default field values will be overridden by the
-        element from a collection of existing form values with the specified
-        index; otherwise, field values will be overridden by a single form
-        value.
-
-        If 'show_tzid' is set to a false value, the time zone menu will not be
-        provided.
-
-        If 'read_only' is set to a true value, the controls will be hidden and
-        labels will be employed instead.
-        """
-
-        page = self.page
-
-        # Show dates for up to one week around the current date.
-
-        dt = default.as_datetime()
-        if not dt:
-            dt = date.today()
-
-        base = to_date(dt)
-
-        # Show a date label with a hidden field if read-only.
-
-        if read_only:
-            self._control("%s-date" % name, "hidden", format_datetime(base))
-            page.span(self.format_date(base, "long"))
-
-        # Show dates for up to one week around the current date.
-        # NOTE: Support paging to other dates.
-
-        else:
-            items = []
-            for i in range(-7, 8):
-                d = base + timedelta(i)
-                items.append((format_datetime(d), self.format_date(d, "full")))
-            self._show_menu("%s-date" % name, format_datetime(base), items, index=index)
-
-        # Show time details.
-
-        page.span(class_="time enabled")
-
-        if read_only:
-            page.span("%s:%s:%s" % (default.get_hour(), default.get_minute(), default.get_second()))
-            self._control("%s-hour" % name, "hidden", default.get_hour())
-            self._control("%s-minute" % name, "hidden", default.get_minute())
-            self._control("%s-second" % name, "hidden", default.get_second())
-        else:
-            self._control("%s-hour" % name, "text", default.get_hour(), maxlength=2, size=2)
-            page.add(":")
-            self._control("%s-minute" % name, "text", default.get_minute(), maxlength=2, size=2)
-            page.add(":")
-            self._control("%s-second" % name, "text", default.get_second(), maxlength=2, size=2)
-
-        # Show time zone details.
-
-        if show_tzid:
-            page.add(" ")
-            tzid = default.get_tzid() or self.get_tzid()
-
-            # Show a label if read-only or a menu otherwise.
-
-            if read_only:
-                self._control("%s-tzid" % name, "hidden", tzid)
-                page.span(tzid)
-            else:
-                self._show_timezone_menu("%s-tzid" % name, tzid, index)
-
-        page.span.close()
-
-    def _show_timezone_menu(self, name, default, index=None):
-
-        """
-        Show timezone controls using a menu with the given 'name', set to the
-        given 'default' unless a field of the given 'name' provides a value.
-        """
-
-        entries = [(tzid, tzid) for tzid in pytz.all_timezones]
-        self._show_menu(name, default, entries, index=index)
-
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r 79493ac5b434 -r e0ed770d17be imipweb/resource.py
--- a/imipweb/resource.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/imipweb/resource.py	Tue Sep 29 00:25:31 2015 +0200
@@ -19,27 +19,34 @@
 this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
-from datetime import datetime
-from imiptools.client import Client
+from datetime import datetime, timedelta
+from imiptools.client import Client, ClientForObject
 from imiptools.data import get_uri, uri_values
-from imiptools.dates import get_recurrence_start_point
+from imiptools.dates import format_datetime, get_recurrence_start_point, to_date
 from imiptools.period import remove_period, remove_affected_period
+from imipweb.data import event_period_from_period, form_period_from_period, FormDate
 from imipweb.env import CGIEnvironment
+from urllib import urlencode
 import babel.dates
 import imip_store
 import markup
+import pytz
 
-class Resource(Client):
+class Resource:
 
-    "A Web application resource and calendar client."
+    "A Web application resource."
 
     def __init__(self, resource=None):
+
+        """
+        Initialise a resource, allowing it to share the environment of any given
+        existing 'resource'.
+        """
+
         self.encoding = "utf-8"
         self.env = CGIEnvironment(self.encoding)
 
-        user = self.env.get_user()
-        Client.__init__(self, user and get_uri(user) or None)
-
+        self.objects = {}
         self.locale = None
         self.requests = None
 
@@ -47,14 +54,6 @@
         self.page = resource and resource.page or markup.page()
         self.html_ids = None
 
-        self.store = imip_store.FileStore()
-        self.objects = {}
-
-        try:
-            self.publisher = imip_store.FilePublisher()
-        except OSError:
-            self.publisher = None
-
     # Presentation methods.
 
     def new_page(self, title):
@@ -83,30 +82,19 @@
         self.new_page(title="Redirect")
         self.page.p("Redirecting to: %s" % url)
 
-    def link_to(self, uid, recurrenceid=None, section=None):
+    def link_to(self, uid, recurrenceid=None, args=None):
 
         """
-        Return a link to an object with the given 'uid', 'recurrenceid' and
-        'section'. See get_identifiers for the decoding of such links.
+        Return a link to an object with the given 'uid' and 'recurrenceid'.
+        See get_identifiers for the decoding of such links.
+
+        If 'args' is specified, the given dictionary is encoded and included.
         """
 
         path = [uid]
         if recurrenceid:
             path.append(recurrenceid)
-        if section:
-            path.append(section)
-        return self.env.new_url("/".join(path))
-
-    # Control naming helpers.
-
-    def element_identifier(self, name, index=None):
-        return index is not None and "%s-%d" % (name, index) or name
-
-    def element_name(self, name, suffix, index=None):
-        return index is not None and "%s-%s" % (name, suffix) or name
-
-    def element_enable(self, index=None):
-        return index is not None and str(index) or "enable"
+        return "%s%s" % (self.env.new_url("/".join(path)), args and ("?%s" % urlencode(args)) or "")
 
     # Access to objects.
 
@@ -122,26 +110,18 @@
         # UID only.
 
         if len(parts) == 1:
-            return parts[0], None, None
-
-        # UID and RECURRENCE-ID or UID and section.
+            return parts[0], None
 
-        elif len(parts) == 2:
-            if parts[1] == "counter":
-                return parts[0], None, "counters"
-            else:
-                return parts[0], parts[1], parts[2] == "counter" and "counters" or None
-
-        # UID, RECURRENCE-ID and section.
+        # UID and RECURRENCE-ID.
 
         else:
-            return parts[:3]
+            return parts[:2]
 
-    def _get_object(self, uid, recurrenceid=None, section=None):
-        if self.objects.has_key((uid, recurrenceid, section)):
-            return self.objects[(uid, recurrenceid, section)]
+    def _get_object(self, uid, recurrenceid=None, section=None, username=None):
+        if self.objects.has_key((uid, recurrenceid, section, username)):
+            return self.objects[(uid, recurrenceid, section, username)]
 
-        obj = self.objects[(uid, recurrenceid, section)] = self.get_stored_object(uid, recurrenceid, section)
+        obj = self.objects[(uid, recurrenceid, section, username)] = self.get_stored_object(uid, recurrenceid, section, username)
         return obj
 
     def _get_recurrences(self, uid):
@@ -158,6 +138,9 @@
     def _have_request(self, uid, recurrenceid=None, type=None, strict=False):
         return self.store.have_request(self._get_requests(), uid, recurrenceid, type, strict)
 
+    def _get_counters(self, uid, recurrenceid=None):
+        return self.store.get_counters(self.user, uid, recurrenceid)
+
     def _get_request_summary(self):
 
         "Return a list of periods comprising the request summary."
@@ -165,15 +148,27 @@
         summary = []
 
         for uid, recurrenceid, request_type in self._get_requests():
-            obj = self.get_stored_object(uid, recurrenceid)
-            if obj:
-                recurrenceids = self._get_active_recurrences(uid)
+
+            # Obtain either normal objects or counter-proposals.
+
+            if not request_type:
+                objs = [self._get_object(uid, recurrenceid)]
+            elif request_type == "COUNTER":
+                objs = []
+                for attendee in self.store.get_counters(self.user, uid, recurrenceid):
+                    objs.append(self._get_object(uid, recurrenceid, "counters", attendee))
 
-                # Obtain only active periods, not those replaced by redefined
-                # recurrences, converting to free/busy periods.
+            # For each object, obtain the periods involved.
+
+            for obj in objs:
+                if obj:
+                    recurrenceids = self._get_active_recurrences(uid)
 
-                for p in obj.get_active_periods(recurrenceids, self.get_tzid(), self.get_window_end()):
-                    summary.append(obj.get_freebusy_period(p))
+                    # Obtain only active periods, not those replaced by redefined
+                    # recurrences, converting to free/busy periods.
+
+                    for p in obj.get_active_periods(recurrenceids, self.get_tzid(), self.get_window_end()):
+                        summary.append(obj.get_freebusy_period(p))
 
         return summary
 
@@ -208,55 +203,403 @@
     def remove_event(self, uid, recurrenceid=None):
         return self.store.remove_event(self.user, uid, recurrenceid)
 
-    def update_freebusy(self, uid, recurrenceid, obj):
+class ResourceClient(Resource, Client):
+
+    "A Web application resource and calendar client."
+
+    def __init__(self, resource=None):
+        Resource.__init__(self, resource)
+        user = self.env.get_user()
+        Client.__init__(self, user and get_uri(user) or None)
+
+class ResourceClientForObject(Resource, ClientForObject):
+
+    "A Web application resource and calendar client for a specific object."
+
+    def __init__(self, resource=None):
+        Resource.__init__(self, resource)
+        user = self.env.get_user()
+        ClientForObject.__init__(self, None, user and get_uri(user) or None)
+
+class FormUtilities:
+
+    "Utility methods resource mix-in."
+
+    def control(self, name, type, value, selected=False, **kw):
+
+        """
+        Show a control with the given 'name', 'type' and 'value', with
+        'selected' indicating whether it should be selected (checked or
+        equivalent), and with keyword arguments setting other properties.
+        """
+
+        page = self.page
+        if type in ("checkbox", "radio") and selected:
+            page.input(name=name, type=type, value=value, checked=selected, **kw)
+        else:
+            page.input(name=name, type=type, value=value, **kw)
+
+    def menu(self, name, default, items, class_="", index=None):
+
+        """
+        Show a select menu having the given 'name', set to the given 'default',
+        providing the given (value, label) 'items', and employing the given CSS
+        'class_' if specified.
+        """
+
+        page = self.page
+        values = self.env.get_args().get(name, [default])
+        if index is not None:
+            values = values[index:]
+            values = values and values[0:1] or [default]
+
+        page.select(name=name, class_=class_)
+        for v, label in items:
+            if v is None:
+                continue
+            if v in values:
+                page.option(label, value=v, selected="selected")
+            else:
+                page.option(label, value=v)
+        page.select.close()
+
+    def date_controls(self, name, default, index=None, show_tzid=True, read_only=False):
 
         """
-        Update stored free/busy details for the event with the given 'uid' and
-        'recurrenceid' having a representation of 'obj'.
+        Show date controls for a field with the given 'name' and 'default' form
+        date value.
+
+        If 'index' is specified, default field values will be overridden by the
+        element from a collection of existing form values with the specified
+        index; otherwise, field values will be overridden by a single form
+        value.
+
+        If 'show_tzid' is set to a false value, the time zone menu will not be
+        provided.
+
+        If 'read_only' is set to a true value, the controls will be hidden and
+        labels will be employed instead.
+        """
+
+        page = self.page
+
+        # Show dates for up to one week around the current date.
+
+        dt = default.as_datetime()
+        if not dt:
+            dt = date.today()
+
+        base = to_date(dt)
+
+        # Show a date label with a hidden field if read-only.
+
+        if read_only:
+            self.control("%s-date" % name, "hidden", format_datetime(base))
+            page.span(self.format_date(base, "long"))
+
+        # Show dates for up to one week around the current date.
+        # NOTE: Support paging to other dates.
+
+        else:
+            items = []
+            for i in range(-7, 8):
+                d = base + timedelta(i)
+                items.append((format_datetime(d), self.format_date(d, "full")))
+            self.menu("%s-date" % name, format_datetime(base), items, index=index)
+
+        # Show time details.
+
+        page.span(class_="time enabled")
+
+        if read_only:
+            page.span("%s:%s:%s" % (default.get_hour(), default.get_minute(), default.get_second()))
+            self.control("%s-hour" % name, "hidden", default.get_hour())
+            self.control("%s-minute" % name, "hidden", default.get_minute())
+            self.control("%s-second" % name, "hidden", default.get_second())
+        else:
+            self.control("%s-hour" % name, "text", default.get_hour(), maxlength=2, size=2)
+            page.add(":")
+            self.control("%s-minute" % name, "text", default.get_minute(), maxlength=2, size=2)
+            page.add(":")
+            self.control("%s-second" % name, "text", default.get_second(), maxlength=2, size=2)
+
+        # Show time zone details.
+
+        if show_tzid:
+            page.add(" ")
+            tzid = default.get_tzid() or self.get_tzid()
+
+            # Show a label if read-only or a menu otherwise.
+
+            if read_only:
+                self.control("%s-tzid" % name, "hidden", tzid)
+                page.span(tzid)
+            else:
+                self.timezone_menu("%s-tzid" % name, tzid, index)
+
+        page.span.close()
+
+    def timezone_menu(self, name, default, index=None):
+
+        """
+        Show timezone controls using a menu with the given 'name', set to the
+        given 'default' unless a field of the given 'name' provides a value.
+        """
+
+        entries = [(tzid, tzid) for tzid in pytz.all_timezones]
+        self.menu(name, default, entries, index=index)
+
+class DateTimeFormUtilities:
+
+    "Date/time control methods resource mix-in."
+
+    # Control naming helpers.
+
+    def element_identifier(self, name, index=None):
+        return index is not None and "%s-%d" % (name, index) or name
+
+    def element_name(self, name, suffix, index=None):
+        return index is not None and "%s-%s" % (name, suffix) or name
+
+    def element_enable(self, index=None):
+        return index is not None and str(index) or "enable"
+
+    def show_object_datetime_controls(self, period, index=None):
+
+        """
+        Show datetime-related controls if already active or if an object needs
+        them for the given 'period'. The given 'index' is used to parameterise
+        individual controls for dynamic manipulation.
         """
 
-        is_only_organiser = self.user not in uri_values(obj.get_values("ATTENDEE"))
+        p = form_period_from_period(period)
+
+        page = self.page
+        args = self.env.get_args()
+        _id = self.element_identifier
+        _name = self.element_name
+        _enable = self.element_enable
 
-        freebusy = self.store.get_freebusy(self.user)
+        # Add a dynamic stylesheet to permit the controls to modify the display.
+        # NOTE: The style details need to be coordinated with the static
+        # NOTE: stylesheet.
+
+        if index is not None:
+            page.style(type="text/css")
+
+            # Unlike the rules for object properties, these affect recurrence
+            # properties.
 
-        Client.update_freebusy(self, freebusy, self.get_periods(obj),
-            is_only_organiser and "ORG" or obj.get_value("TRANSP"),
-            uid, recurrenceid,
-            obj.get_value("SUMMARY"),
-            obj.get_value("ORGANIZER"))
+            page.add("""\
+input#dttimes-enable-%(index)d,
+input#dtend-enable-%(index)d,
+input#dttimes-enable-%(index)d:not(:checked) ~ .recurrence td.objectvalue .time.enabled,
+input#dttimes-enable-%(index)d:checked ~ .recurrence td.objectvalue .time.disabled,
+input#dtend-enable-%(index)d:not(:checked) ~ .recurrence td.objectvalue.dtend .dt.enabled,
+input#dtend-enable-%(index)d:checked ~ .recurrence td.objectvalue.dtend .dt.disabled {
+    display: none;
+}""" % {"index" : index})
+
+            page.style.close()
+
+        self.control(
+            _name("dtend-control", "recur", index), "checkbox",
+            _enable(index), p.end_enabled,
+            id=_id("dtend-enable", index)
+            )
+
+        self.control(
+            _name("dttimes-control", "recur", index), "checkbox",
+            _enable(index), p.times_enabled,
+            id=_id("dttimes-enable", index)
+            )
+
+    def show_datetime_controls(self, formdate, show_start):
+
+        """
+        Show datetime details from the current object for the 'formdate',
+        showing start details if 'show_start' is set to a true value. Details
+        will appear as controls for organisers and labels for attendees.
+        """
+
+        page = self.page
+
+        # Show controls for editing as organiser.
 
-        # Subtract any recurrences from the free/busy details of a parent
-        # object.
+        if self.is_organiser():
+            page.td(class_="objectvalue dt%s" % (show_start and "start" or "end"))
+
+            if show_start:
+                page.div(class_="dt enabled")
+                self.date_controls("dtstart", formdate)
+                page.br()
+                page.label("Specify times", for_="dttimes-enable", class_="time disabled enable")
+                page.label("Specify dates only", for_="dttimes-enable", class_="time enabled disable")
+                page.div.close()
 
-        for recurrenceid in self._get_recurrences(uid):
-            remove_affected_period(freebusy, uid, obj.get_recurrence_start_point(recurrenceid, self.get_tzid()))
+            else:
+                page.div(class_="dt disabled")
+                page.label("Specify end date", for_="dtend-enable", class_="enable")
+                page.div.close()
+                page.div(class_="dt enabled")
+                self.date_controls("dtend", formdate)
+                page.br()
+                page.label("End on same day", for_="dtend-enable", class_="disable")
+                page.div.close()
+
+            page.td.close()
+
+        # Show a label as attendee.
 
-        self.store.set_freebusy(self.user, freebusy)
-        self.publish_freebusy(freebusy)
+        else:
+            dt = formdate.as_datetime()
+            if dt:
+                page.td(self.format_datetime(dt, "full"))
+            else:
+                page.td("(Unrecognised date)")
+
+    def show_recurrence_controls(self, index, period, recurrenceid, recurrenceids, show_start):
+
+        """
+        Show datetime details from the current object for the recurrence having
+        the given 'index', with the recurrence period described by 'period',
+        indicating a start, end and origin of the period from the event details,
+        employing any 'recurrenceid' and 'recurrenceids' for the object to
+        configure the displayed information.
 
-        # Update free/busy provider information if the event may recur
-        # indefinitely.
+        If 'show_start' is set to a true value, the start details will be shown;
+        otherwise, the end details will be shown.
+        """
+
+        page = self.page
+        _id = self.element_identifier
+        _name = self.element_name
+
+        p = event_period_from_period(period)
+        replaced = not recurrenceid and p.is_replaced(recurrenceids)
+
+        # Show controls for editing as organiser.
+
+        if self.is_organiser() and not replaced:
+            page.td(class_="objectvalue dt%s" % (show_start and "start" or "end"))
+
+            read_only = period.origin == "RRULE"
 
-        if obj.possibly_recurring_indefinitely():
-            self.store.append_freebusy_provider(self.user, obj)
+            if show_start:
+                page.div(class_="dt enabled")
+                self.date_controls(_name("dtstart", "recur", index), p.get_form_start(), index=index, read_only=read_only)
+                if not read_only:
+                    page.br()
+                    page.label("Specify times", for_=_id("dttimes-enable", index), class_="time disabled enable")
+                    page.label("Specify dates only", for_=_id("dttimes-enable", index), class_="time enabled disable")
+                page.div.close()
+
+                # Put the origin somewhere.
+
+                self.control("recur-origin", "hidden", p.origin or "")
+
+            else:
+                page.div(class_="dt disabled")
+                if not read_only:
+                    page.label("Specify end date", for_=_id("dtend-enable", index), class_="enable")
+                page.div.close()
+                page.div(class_="dt enabled")
+                self.date_controls(_name("dtend", "recur", index), p.get_form_end(), index=index, show_tzid=False, read_only=read_only)
+                if not read_only:
+                    page.br()
+                    page.label("End on same day", for_=_id("dtend-enable", index), class_="disable")
+                page.div.close()
 
-    def remove_from_freebusy(self, uid, recurrenceid=None):
-        freebusy = self.store.get_freebusy(self.user)
-        remove_period(freebusy, uid, recurrenceid)
-        self.store.set_freebusy(self.user, freebusy)
-        self.publish_freebusy(freebusy)
+            page.td.close()
+
+        # Show label as attendee.
+
+        else:
+            self.show_recurrence_label(p, recurrenceid, recurrenceids, show_start)
+
+    def show_recurrence_label(self, period, recurrenceid, recurrenceids, show_start):
+
+        """
+        Show datetime details for the given 'period', employing any
+        'recurrenceid' and 'recurrenceids' for the object to configure the
+        displayed information.
+
+        If 'show_start' is set to a true value, the start details will be shown;
+        otherwise, the end details will be shown.
+        """
+
+        page = self.page
+
+        p = event_period_from_period(period)
+        replaced = not recurrenceid and p.is_replaced(recurrenceids)
+
+        css = " ".join([
+            replaced and "replaced" or "",
+            p.is_affected(recurrenceid) and "affected" or ""
+            ])
 
-        # Update free/busy provider information if the event may recur
-        # indefinitely.
+        formdate = show_start and p.get_form_start() or p.get_form_end()
+        dt = formdate.as_datetime()
+        if dt:
+            page.td(self.format_datetime(dt, "long"), class_=css)
+        else:
+            page.td("(Unrecognised date)")
+
+    def get_date_control_values(self, name, multiple=False, tzid_name=None):
+
+        """
+        Return a form date object representing fields starting with 'name'. If
+        'multiple' is set to a true value, many date objects will be returned
+        corresponding to a collection of datetimes.
 
-        if obj.possibly_recurring_indefinitely():
-            self.store.remove_freebusy_provider(self.user, obj)
+        If 'tzid_name' is specified, the time zone information will be acquired
+        from fields starting with 'tzid_name' instead of 'name'.
+        """
+
+        args = self.env.get_args()
+
+        dates = args.get("%s-date" % name, [])
+        hours = args.get("%s-hour" % name, [])
+        minutes = args.get("%s-minute" % name, [])
+        seconds = args.get("%s-second" % name, [])
+        tzids = args.get("%s-tzid" % (tzid_name or name), [])
+
+        # Handle absent values by employing None values.
+
+        field_values = map(None, dates, hours, minutes, seconds, tzids)
 
-    def publish_freebusy(self, freebusy):
+        if not field_values and not multiple:
+            all_values = FormDate()
+        else:
+            all_values = []
+            for date, hour, minute, second, tzid in field_values:
+                value = FormDate(date, hour, minute, second, tzid or self.get_tzid())
+
+                # Return a single value or append to a collection of all values.
+
+                if not multiple:
+                    return value
+                else:
+                    all_values.append(value)
+
+        return all_values
 
-        "Publish the details if configured to share them."
+    def set_date_control_values(self, name, formdates, tzid_name=None):
+
+        """
+        Replace form fields starting with 'name' using the values of the given
+        'formdates'.
 
-        if self.publisher and self.is_sharing() and self.is_publishing():
-            self.publisher.set_freebusy(self.user, freebusy)
+        If 'tzid_name' is specified, the time zone information will be stored in
+        fields starting with 'tzid_name' instead of 'name'.
+        """
+
+        args = self.env.get_args()
+
+        args["%s-date" % name] = [d.date for d in formdates]
+        args["%s-hour" % name] = [d.hour for d in formdates]
+        args["%s-minute" % name] = [d.minute for d in formdates]
+        args["%s-second" % name] = [d.second for d in formdates]
+        args["%s-tzid" % (tzid_name or name)] = [d.tzid for d in formdates]
 
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r 79493ac5b434 -r e0ed770d17be tests/test_resource_invitation_constraints.sh
--- a/tests/test_resource_invitation_constraints.sh	Thu Sep 24 19:13:39 2015 +0200
+++ b/tests/test_resource_invitation_constraints.sh	Tue Sep 29 00:25:31 2015 +0200
@@ -35,7 +35,7 @@
 echo 'Europe/Oslo' > "$PREFS/$USER/TZID"
 echo 'share' > "$PREFS/$USER/freebusy_sharing"
 echo '10,12,14,16,18:0,15,30,45' > "$PREFS/$USER/permitted_times"
-echo '60' > "$PREFS/$USER/freebusy_offers"
+echo 'PT60S' > "$PREFS/$USER/freebusy_offers"
 
   "$RESOURCE_SCRIPT" $ARGS < "$TEMPLATES/fb-request-sauna-all.txt" 2>> $ERROR \
 | "$SHOWMAIL" \
diff -r 79493ac5b434 -r e0ed770d17be tests/test_resource_invitation_constraints_alternative.sh
--- a/tests/test_resource_invitation_constraints_alternative.sh	Thu Sep 24 19:13:39 2015 +0200
+++ b/tests/test_resource_invitation_constraints_alternative.sh	Tue Sep 29 00:25:31 2015 +0200
@@ -35,7 +35,7 @@
 echo 'Europe/Oslo' > "$PREFS/$USER/TZID"
 echo 'share' > "$PREFS/$USER/freebusy_sharing"
 echo '10,12,14,16,18:0,15,30,45' > "$PREFS/$USER/permitted_times"
-echo '60' > "$PREFS/$USER/freebusy_offers"
+echo 'PT60S' > "$PREFS/$USER/freebusy_offers"
 
   "$RESOURCE_SCRIPT" $ARGS < "$TEMPLATES/fb-request-sauna-all.txt" 2>> $ERROR \
 | "$SHOWMAIL" \
diff -r 79493ac5b434 -r e0ed770d17be vContent.py
--- a/vContent.py	Thu Sep 24 19:13:39 2015 +0200
+++ b/vContent.py	Tue Sep 29 00:25:31 2015 +0200
@@ -62,6 +62,12 @@
 
     pass
 
+class WriteError(Exception):
+
+    "General writing errors."
+
+    pass
+
 # Reader and parser classes.
 
 class Reader:
@@ -570,12 +576,15 @@
         encoding = parameters.get("ENCODING")
         charset = parameters.get("CHARSET")
 
-        if encoding == "QUOTED-PRINTABLE":
-            value = quopri.encodestring(value.encode(charset or "iso-8859-1"))
-        elif encoding == "BASE64":
-            value = base64.encodestring(value)
+        try:
+            if encoding == "QUOTED-PRINTABLE":
+                value = quopri.encodestring(value.encode(charset or "iso-8859-1"))
+            elif encoding == "BASE64":
+                value = base64.encodestring(value)
 
-        return self.encode_content(value)
+            return self.encode_content(value)
+        except TypeError:
+            raise WriteError, "Property %r value with parameters %r cannot be encoded: %r" % (name, parameters, value)
 
     # Overrideable methods.