# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1508188283 -7200
# Node ID 66c8a5c98b25da1a171a7b517625d0fa65582179
# Parent  f276b162de500e428b2ad6863e9a50436a4b0a77
Tidied up slightly, making use of existing functions where appropriate.

diff -r f276b162de50 -r 66c8a5c98b25 imiptools/client.py
--- a/imiptools/client.py	Mon Oct 16 22:09:15 2017 +0200
+++ b/imiptools/client.py	Mon Oct 16 23:11:23 2017 +0200
@@ -21,7 +21,8 @@
 
 from datetime import datetime, timedelta
 from imiptools.config import settings
-from imiptools.data import Object, check_delegation, get_address, get_uri, \
+from imiptools.data import Object, check_delegation, get_address, \
+                           get_sender_identities, get_uri, \
                            get_window_end, is_new_object, make_freebusy, \
                            make_uid, to_part, uri_dict, uri_item, uri_items, \
                            uri_parts, uri_values
@@ -469,12 +470,21 @@
 
         # Search for the sender of the message or the calendar system address.
 
-        senders = self.senders or self.messenger and [self.messenger.sender] or []
+        senders = set(uri_values(self.senders or self.messenger and [self.messenger.sender] or []))
+
+        if senders:
+
+            # Obtain a mapping from sender URI to attendee URI, where the sender
+            # is taken from the SENT-BY attribute if present, or from the
+            # attendee value otherwise.
 
-        for attendee, attendee_attr in uri_items(self.obj.get_items("ATTENDEE")):
-            if get_address(attendee) in senders or \
-               get_address(attendee_attr.get("SENT-BY")) in senders:
-                return get_uri(attendee)
+            sent_by = get_sender_identities(uri_dict(self.obj.get_value_map("ATTENDEE")))
+
+            # Obtain the attendee for the first sender matching the SENT-BY or
+            # attendee value.
+
+            for sender in senders.intersection(sent_by.keys()):
+                return sent_by[sender][0]
 
         return None
 
diff -r f276b162de50 -r 66c8a5c98b25 imiptools/data.py
--- a/imiptools/data.py	Mon Oct 16 22:09:15 2017 +0200
+++ b/imiptools/data.py	Mon Oct 16 23:11:23 2017 +0200
@@ -1168,7 +1168,8 @@
     """
     Return a mapping from actual senders to the identities for which they
     have provided data, extracting this information from the given
-    'mapping'.
+    'mapping'. The SENT-BY attribute provides sender information in preference
+    to the property values given as the mapping keys.
     """
 
     senders = {}
diff -r f276b162de50 -r 66c8a5c98b25 imiptools/handlers/__init__.py
--- a/imiptools/handlers/__init__.py	Mon Oct 16 22:09:15 2017 +0200
+++ b/imiptools/handlers/__init__.py	Mon Oct 16 23:11:23 2017 +0200
@@ -145,7 +145,13 @@
 
             # Return the true identities.
 
-            return reduce(lambda a, b: a + b, [identities[get_uri(address)] for address in valid], [])
+            attendees = []
+            for address in valid:
+                attendees += identities[get_uri(address)]
+            return attendees
+
+        # Rely on the mapping keys being accessible as a sequence.
+
         else:
             return mapping
 
@@ -159,6 +165,9 @@
         if self.recipient:
             addresses = set(map(get_address, mapping))
             return map(get_uri, addresses.intersection([self.recipient]))
+
+        # Rely on the mapping keys being accessible as a sequence.
+
         else:
             return mapping