# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1505426618 -7200
# Node ID 7819b77d9330ef54bbe0ccb6129cc64817095aa6
# Parent  e3cda8fa8ee7e22afbc0b775db3b4ee9ae0ddbab
Introduced a tentative means of classifying periods for suitable operations upon
updating an event.

diff -r e3cda8fa8ee7 -r 7819b77d9330 imipweb/data.py
--- a/imipweb/data.py	Thu Sep 14 23:18:30 2017 +0200
+++ b/imipweb/data.py	Fri Sep 15 00:03:38 2017 +0200
@@ -343,46 +343,80 @@
 
 # Form period processing.
 
-def get_active_periods(periods):
+def get_existing_periods(periods, still_to_remove):
 
-    "Return a mapping of non-replaced periods to counts, given 'periods'."
+    """
+    Find all periods that existed before editing, given 'periods', applying
+    the periods in 'still_to_remove' and producing retained, replaced and
+    to-remove collections containing these existing periods.
+    """
 
-    active_periods = {}
+    retained = []
+    replaced = []
+    to_remove = []
+
     for p in periods:
-        if not p.replaced:
-            if not active_periods.has_key(p):
-                active_periods[p] = 1
+        p = form_period_from_period(p)
+        if p.recurrenceid:
+            if p.replaced:
+                replaced.append(p)
+            elif p in still_to_remove:
+                to_remove.append(p)
             else:
-                active_periods[p] += 1
-    return active_periods
+                retained.append(p)
+
+    return retained, replaced, to_remove
+
+def get_new_periods(periods):
+
+    "Return all periods introduced during editing, given 'periods'."
+
+    new = []
+    for p in periods:
+        fp = form_period_from_period(p)
+        if not fp.recurrenceid:
+            new.append(p)
+    return new
 
-def get_removed_periods(periods, still_to_remove):
+def get_changed_periods(periods):
+
+    "Return changed and unchanged periods, given 'periods'."
+
+    changed = []
+    unchanged = []
+
+    for p in periods:
+        fp = form_period_from_period(p)
+        if fp.is_changed():
+            changed.append(p)
+        else:
+            unchanged.append(p)
+
+    return changed, unchanged
+
+def classify_periods(periods, still_to_remove):
 
     """
     From the recurrence 'periods', given details of those 'still_to_remove',
-    return the remaining active periods and the periods to unschedule or
-    exclude, using a tuple of the form (active, unscheduled, excluded).
+    return a tuple containing collections of new, changed, unchanged, replaced
+    and to-be-removed periods.
     """
 
-    to_remove = set()
-
-    # Get all periods that are not replaced.
+    retained, replaced, to_remove = get_existing_periods(periods, still_to_remove)
 
-    active_periods = get_active_periods(periods)
+    # Filter new periods with the existing period information.
 
-    for period in still_to_remove:
-        active_periods[period] -= 1
-        to_remove.add(period)
+    new = set(get_new_periods(periods))
 
-    # Determine whether some periods are both removed and added.
+    new.difference_update(retained)
+    new.difference_update(replaced)
+    new.difference_update(to_remove)
 
-    remaining = []
-    for period, n in active_periods.items():
-        if n > 0:
-            remaining.append(period)
+    # Divide retained periods into changed and unchanged collections.
 
-    to_remove.difference_update(remaining)
-    return remaining, to_remove
+    changed, unchanged = get_changed_periods(retained)
+
+    return list(new), changed, unchanged, replaced, to_remove
 
 
 
diff -r e3cda8fa8ee7 -r 7819b77d9330 imipweb/event.py
--- a/imipweb/event.py	Thu Sep 14 23:18:30 2017 +0200
+++ b/imipweb/event.py	Fri Sep 15 00:03:38 2017 +0200
@@ -25,8 +25,8 @@
 from imiptools.mail import Messenger
 from imipweb.data import EventPeriod, event_period_from_period, \
                          form_period_from_period, \
-                         filter_duplicates, get_active_periods, \
-                         get_removed_periods, remove_from_collection, \
+                         classify_periods, filter_duplicates, \
+                         remove_from_collection, \
                          get_period_control_values, \
                          PeriodError
 from imipweb.resource import DateTimeFormUtilities, FormUtilities, ResourceClientForObject
@@ -857,7 +857,11 @@
             # modified period information.
             # NOTE: Currently, rules are not updated.
 
-            active_periods, to_unschedule, to_exclude = self.get_removed_periods(periods)
+            editable_periods, to_change, to_remove = self.classify_periods(periods)
+
+            active_periods = editable_periods + to_change
+            to_unschedule = self.is_organiser() and to_remove or []
+            to_exclude = not self.is_organiser() and to_remove or []
 
             periods = set(periods)
             changed = self.obj.set_period(period) or changed
@@ -1037,32 +1041,20 @@
             recurrenceid_name="recur-id",
             tzid=self.get_tzid())
 
-    def get_removed_periods(self, periods):
+    def classify_periods(self, periods):
 
         """
         From the recurrence 'periods' and information provided in the request,
-        return the remaining active periods, the periods to unschedule, and the
-        periods to exclude, in a tuple of the form (active, unscheduled,
-        excluded).
+        return a tuple containing the new and unchanged periods, the changed
+        periods, and the periods to be removed.
         """
 
         # Get remaining periods and those whose removal is deferred.
 
-        remaining, to_remove = get_removed_periods(periods,
+        new, changed, unchanged, replaced, to_remove = classify_periods(periods,
             self.get_state("recur-remove", list))
 
-        # Sort the deferred removal periods into categories.
-
-        to_unschedule = set()
-        to_exclude = set()
-
-        for period in to_remove:
-            if not self.can_edit_recurrence(period) and self.is_organiser():
-                to_unschedule.add(period)
-            else:
-                to_exclude.add(period)
-
-        return remaining, to_unschedule, to_exclude
+        return new + unchanged, changed, to_remove
 
     def get_attendees_from_page(self):