Invite people to events on Federated Core calendars

build-aux/org.gnome.Calendar.json

@@ -10,6 +10,7 @@
     "finish-args" : [
         "--env=G_DEBUG=fatal-criticals",
         "--device=dri",
+        "--filesystem=xdg-config/coredesktop:ro",
         "--share=ipc",
         "--share=network",
         "--socket=fallback-x11",

meson.build

@@ -96,6 +96,7 @@ assert(cc.has_function('strerror'), '"strerror" not found')
 
 # options
 config_h.set('ENABLE_TRACING', enable_tracing)
+config_h.set('ENABLE_FEDERATED_CORE', get_option('federated_core'))
 config_h.set('HANDY_USE_UNSTABLE_API', true)
 
 # _NL_TIME_FIRST_WEEKDAY is an enum and not a define
@@ -210,6 +211,9 @@ summary({
   'Source': meson.global_source_root(),
   'Prefix': calendar_prefix,
 })
+summary({
+  'Federated Core': get_option('federated_core'),
+}, section: 'Features')
 summary({
   'Debug': calendar_debug,
   'Tracing': enable_tracing,

meson_options.txt

@@ -1,2 +1,3 @@
 option('tracing', type: 'boolean', value: false, description: 'add extra debugging information')
 option('profile', type: 'combo', choices: ['default', 'development'], value: 'default')
+option('federated_core', type: 'boolean', value: true, description: 'invite people to events on the calendars of a Federated Computer Core')

src/core/gcal-event.c

@@ -2023,3 +2023,250 @@ gcal_event_get_organizer (GcalEvent *self)
 
   return self->organizer;
 }
+
+static gboolean
+mailto_equal (const gchar *uri1,
+              const gchar *uri2)
+{
+  if (!uri1 || !uri2)
+    return FALSE;
+
+  if (g_ascii_strncasecmp (uri1, "mailto:", 7) == 0)
+    uri1 += 7;
+
+  if (g_ascii_strncasecmp (uri2, "mailto:", 7) == 0)
+    uri2 += 7;
+
+  return g_ascii_strcasecmp (uri1, uri2) == 0;
+}
+
+static void
+set_component_attendees (GcalEvent *self,
+                         GSList    *ecal_attendees)
+{
+  e_cal_component_set_attendees (self->component, ecal_attendees);
+  e_cal_component_commit_sequence (self->component);
+
+  g_list_store_remove_all (self->attendees);
+  load_attendees (self);
+}
+
+/**
+ * gcal_event_set_organizer:
+ * @self: a #GcalEvent
+ * @email: (nullable): the email address of the organizer
+ * @name: (nullable): the common name of the organizer
+ *
+ * Sets the organizer of @self. Passing %NULL as @email removes the
+ * organizer.
+ */
+void
+gcal_event_set_organizer (GcalEvent   *self,
+                          const gchar *email,
+                          const gchar *name)
+{
+  ECalComponentOrganizer *organizer = NULL;
+
+  g_return_if_fail (GCAL_IS_EVENT (self));
+
+  g_clear_object (&self->organizer);
+
+  if (email && *email)
+    {
+      g_autofree gchar *uri = g_strdup_printf ("mailto:%s", email);
+
+      organizer = e_cal_component_organizer_new_full (uri, NULL, (name && *name) ? name : NULL, NULL);
+      self->organizer = gcal_event_organizer_new (organizer);
+    }
+
+  e_cal_component_set_organizer (self->component, organizer);
+  e_cal_component_commit_sequence (self->component);
+
+  e_cal_component_organizer_free (organizer);
+}
+
+/**
+ * gcal_event_has_attendee:
+ * @self: a #GcalEvent
+ * @email: an email address, with or without the "mailto:" prefix
+ *
+ * Returns: %TRUE if @email is one of the attendees of @self
+ */
+gboolean
+gcal_event_has_attendee (GcalEvent   *self,
+                         const gchar *email)
+{
+  guint n_items;
+
+  g_return_val_if_fail (GCAL_IS_EVENT (self), FALSE);
+
+  n_items = g_list_model_get_n_items (G_LIST_MODEL (self->attendees));
+
+  for (guint i = 0; i < n_items; i++)
+    {
+      g_autoptr (GcalEventAttendee) attendee = g_list_model_get_item (G_LIST_MODEL (self->attendees), i);
+
+      if (mailto_equal (gcal_event_attendee_get_uri (attendee), email))
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
+/**
+ * gcal_event_add_attendee:
+ * @self: a #GcalEvent
+ * @email: the email address of the attendee
+ * @name: (nullable): the common name of the attendee
+ *
+ * Adds a person to the attendees of @self, who is asked to respond.
+ *
+ * Returns: %FALSE if @email already was an attendee
+ */
+gboolean
+gcal_event_add_attendee (GcalEvent   *self,
+                         const gchar *email,
+                         const gchar *name)
+{
+  g_autofree gchar *uri = NULL;
+  GSList *ecal_attendees;
+
+  g_return_val_if_fail (GCAL_IS_EVENT (self), FALSE);
+  g_return_val_if_fail (email && *email, FALSE);
+
+  if (gcal_event_has_attendee (self, email))
+    return FALSE;
+
+  uri = g_strdup_printf ("mailto:%s", email);
+
+  ecal_attendees = e_cal_component_get_attendees (self->component);
+  ecal_attendees = g_slist_append (ecal_attendees,
+                                   e_cal_component_attendee_new_full (uri,
+                                                                      NULL,
+                                                                      I_CAL_CUTYPE_INDIVIDUAL,
+                                                                      I_CAL_ROLE_REQPARTICIPANT,
+                                                                      I_CAL_PARTSTAT_NEEDSACTION,
+                                                                      TRUE,
+                                                                      NULL,
+                                                                      NULL,
+                                                                      NULL,
+                                                                      (name && *name) ? name : NULL,
+                                                                      NULL));
+
+  set_component_attendees (self, ecal_attendees);
+
+  g_slist_free_full (ecal_attendees, e_cal_component_attendee_free);
+
+  return TRUE;
+}
+
+/**
+ * gcal_event_remove_attendee:
+ * @self: a #GcalEvent
+ * @email: an email address, with or without the "mailto:" prefix
+ *
+ * Removes @email from the attendees of @self.
+ */
+void
+gcal_event_remove_attendee (GcalEvent   *self,
+                            const gchar *email)
+{
+  GSList *ecal_attendees;
+  GSList *l;
+
+  g_return_if_fail (GCAL_IS_EVENT (self));
+
+  ecal_attendees = e_cal_component_get_attendees (self->component);
+
+  for (l = ecal_attendees; l != NULL; l = l->next)
+    {
+      if (mailto_equal (e_cal_component_attendee_get_value (l->data), email))
+        break;
+    }
+
+  if (l)
+    {
+      e_cal_component_attendee_free (l->data);
+      ecal_attendees = g_slist_delete_link (ecal_attendees, l);
+
+      set_component_attendees (self, ecal_attendees);
+    }
+
+  g_slist_free_full (ecal_attendees, e_cal_component_attendee_free);
+}
+
+/**
+ * gcal_event_copy_attendees:
+ * @self: a #GcalEvent
+ * @event: the #GcalEvent to copy from
+ *
+ * Replaces the organizer and attendees of @self with those of @event.
+ */
+void
+gcal_event_copy_attendees (GcalEvent *self,
+                           GcalEvent *event)
+{
+  ECalComponentOrganizer *organizer;
+  GSList *ecal_attendees;
+
+  g_return_if_fail (GCAL_IS_EVENT (self));
+  g_return_if_fail (GCAL_IS_EVENT (event));
+
+  organizer = e_cal_component_get_organizer (event->component);
+
+  g_clear_object (&self->organizer);
+  if (organizer)
+    self->organizer = gcal_event_organizer_new (organizer);
+
+  e_cal_component_set_organizer (self->component, organizer);
+
+  ecal_attendees = e_cal_component_get_attendees (event->component);
+  set_component_attendees (self, ecal_attendees);
+
+  g_slist_free_full (ecal_attendees, e_cal_component_attendee_free);
+  e_cal_component_organizer_free (organizer);
+}
+
+/**
+ * gcal_event_attendees_equal:
+ * @event1: a #GcalEvent
+ * @event2: a #GcalEvent
+ *
+ * Checks if @event1 and @event2 have the same organizer and attendees.
+ * Only the email addresses are compared.
+ *
+ * Returns: %TRUE if the events' organizer and attendees are identical
+ */
+gboolean
+gcal_event_attendees_equal (GcalEvent *event1,
+                            GcalEvent *event2)
+{
+  const gchar *organizer1 = NULL;
+  const gchar *organizer2 = NULL;
+  guint n_items;
+
+  g_assert (GCAL_IS_EVENT (event1) && GCAL_IS_EVENT (event2));
+
+  if (event1->organizer)
+    organizer1 = gcal_event_organizer_get_uri (event1->organizer);
+  if (event2->organizer)
+    organizer2 = gcal_event_organizer_get_uri (event2->organizer);
+
+  if ((organizer1 || organizer2) && !mailto_equal (organizer1, organizer2))
+    return FALSE;
+
+  n_items = g_list_model_get_n_items (G_LIST_MODEL (event1->attendees));
+
+  if (n_items != g_list_model_get_n_items (G_LIST_MODEL (event2->attendees)))
+    return FALSE;
+
+  for (guint i = 0; i < n_items; i++)
+    {
+      g_autoptr (GcalEventAttendee) attendee = g_list_model_get_item (G_LIST_MODEL (event1->attendees), i);
+
+      if (!gcal_event_has_attendee (event2, gcal_event_attendee_get_uri (attendee)))
+        return FALSE;
+    }
+
+  return TRUE;
+}

src/core/gcal-event.h

@@ -142,6 +142,26 @@ GListModel *         gcal_event_get_attendees                    (GcalEvent
 
 GcalEventOrganizer * gcal_event_get_organizer                    (GcalEvent          *self);
 
+void                 gcal_event_set_organizer                    (GcalEvent          *self,
+                                                                  const gchar        *email,
+                                                                  const gchar        *name);
+
+gboolean             gcal_event_has_attendee                     (GcalEvent          *self,
+                                                                  const gchar        *email);
+
+gboolean             gcal_event_add_attendee                     (GcalEvent          *self,
+                                                                  const gchar        *email,
+                                                                  const gchar        *name);
+
+void                 gcal_event_remove_attendee                  (GcalEvent          *self,
+                                                                  const gchar        *email);
+
+void                 gcal_event_copy_attendees                   (GcalEvent          *self,
+                                                                  GcalEvent          *event);
+
+gboolean             gcal_event_attendees_equal                  (GcalEvent          *event1,
+                                                                  GcalEvent          *event2);
+
 gboolean             gcal_event_alarms_equal                     (GcalEvent          *event1,
                                                                   GcalEvent          *event2);
 

src/federated/gcal-federated-core.c

@@ -0,0 +1,255 @@
+/* gcal-federated-core.c
+ *
+ * Copyright (C) 2026 David Young <david@federated.computer>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define G_LOG_DOMAIN "GcalFederatedCore"
+
+#include "config.h"
+
+#include "gcal-federated-core.h"
+
+#include <libedataserver/libedataserver.h>
+#include <string.h>
+
+/**
+ * SECTION:gcal-federated-core
+ * @short_description: Federated Computer Core integration
+ * @title:GcalFederatedCore
+ *
+ * When CoreDesktop's `configure` has connected this computer to a Federated
+ * Computer Core, each Core is described in ~/.config/coredesktop/cores/<domain>.conf
+ * and its Nextcloud calendars are added through GNOME Online Accounts.
+ *
+ * Nextcloud schedules events on the server: when an event whose organizer
+ * is the calendar's owner is saved with attendees, Nextcloud emails the
+ * invitations, updates and cancellations. So inviting people to an event on
+ * a Core calendar only takes setting its organizer and attendees.
+ */
+
+typedef struct
+{
+  gchar *domain;
+  gchar *email;
+  gchar *name;
+} CoreConf;
+
+static void
+core_conf_free (CoreConf *conf)
+{
+  g_free (conf->domain);
+  g_free (conf->email);
+  g_free (conf->name);
+  g_free (conf);
+}
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (CoreConf, core_conf_free)
+
+/*
+ * The files are written by bash with printf %q, e.g. CORE_NAME=David\ Young,
+ * which g_shell_unquote() reads.
+ */
+static CoreConf *
+load_core_conf (const gchar *path)
+{
+  g_autoptr (CoreConf) conf = NULL;
+  g_autofree gchar *contents = NULL;
+  g_auto (GStrv) lines = NULL;
+
+  if (!g_file_get_contents (path, &contents, NULL, NULL))
+    return NULL;
+
+  conf = g_new0 (CoreConf, 1);
+  lines = g_strsplit (contents, "\n", -1);
+
+  for (gint i = 0; lines[i]; i++)
+    {
+      g_autofree gchar *value = NULL;
+      gchar *equals;
+      gchar **field;
+
+      equals = strchr (lines[i], '=');
+      if (!equals)
+        continue;
+
+      *equals = '\0';
+
+      if (g_str_equal (lines[i], "CORE_DOMAIN"))
+        field = &conf->domain;
+      else if (g_str_equal (lines[i], "CORE_EMAIL"))
+        field = &conf->email;
+      else if (g_str_equal (lines[i], "CORE_NAME"))
+        field = &conf->name;
+      else
+        continue;
+
+      value = g_shell_unquote (equals + 1, NULL);
+      if (value)
+        g_set_str (field, value);
+    }
+
+  if (!conf->domain || !*conf->domain || !conf->email || !strchr (conf->email, '@'))
+    return NULL;
+
+  return g_steal_pointer (&conf);
+}
+
+static GPtrArray *
+load_cores (const gchar *config_dir)
+{
+  g_autofree gchar *cores_dir = NULL;
+  g_autoptr (GPtrArray) cores = NULL;
+  g_autoptr (GDir) dir = NULL;
+  const gchar *filename;
+
+  cores = g_ptr_array_new_with_free_func ((GDestroyNotify) core_conf_free);
+  cores_dir = g_build_filename (config_dir, "cores", NULL);
+  dir = g_dir_open (cores_dir, 0, NULL);
+
+  while (dir && (filename = g_dir_read_name (dir)) != NULL)
+    {
+      g_autofree gchar *path = NULL;
+      CoreConf *conf;
+
+      if (!g_str_has_suffix (filename, ".conf"))
+        continue;
+
+      path = g_build_filename (cores_dir, filename, NULL);
+      conf = load_core_conf (path);
+
+      if (conf)
+        g_ptr_array_add (cores, conf);
+    }
+
+  /* Before CoreDesktop supported several Cores, there was only core.conf */
+  if (cores->len == 0)
+    {
+      g_autofree gchar *path = g_build_filename (config_dir, "core.conf", NULL);
+      CoreConf *conf = load_core_conf (path);
+
+      if (conf)
+        g_ptr_array_add (cores, conf);
+    }
+
+  return g_steal_pointer (&cores);
+}
+
+/**
+ * gcal_federated_core_find_core:
+ * @config_dir: CoreDesktop's configuration directory
+ * @host: the host name of a CalDAV server
+ * @out_email: (out) (optional): return location for the Core email
+ * @out_name: (out) (optional): return location for the name
+ *
+ * Looks for the Core whose Nextcloud is at @host.
+ *
+ * Returns: %TRUE if @host is the Nextcloud of a Core set up on this computer
+ */
+gboolean
+gcal_federated_core_find_core (const gchar  *config_dir,
+                               const gchar  *host,
+                               gchar       **out_email,
+                               gchar       **out_name)
+{
+  g_autoptr (GPtrArray) cores = NULL;
+
+  g_return_val_if_fail (config_dir != NULL, FALSE);
+
+  if (!host)
+    return FALSE;
+
+  cores = load_cores (config_dir);
+
+  for (guint i = 0; i < cores->len; i++)
+    {
+      CoreConf *conf = g_ptr_array_index (cores, i);
+      g_autofree gchar *nextcloud_host = g_strconcat ("nextcloud.", conf->domain, NULL);
+
+      if (g_ascii_strcasecmp (host, nextcloud_host) != 0)
+        continue;
+
+      if (out_email)
+        *out_email = g_strdup (conf->email);
+      if (out_name)
+        *out_name = g_strdup (conf->name);
+
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+/**
+ * gcal_federated_core_get_organizer:
+ * @calendar: a #GcalCalendar
+ * @out_email: (out) (optional): return location for the organizer's email
+ * @out_name: (out) (optional): return location for the organizer's name
+ *
+ * Checks whether @calendar is on the Nextcloud of a Federated Computer Core
+ * set up on this computer, where people can be invited to events, and who
+ * the organizer of those events is.
+ *
+ * Returns: %TRUE if people can be invited to events in @calendar
+ */
+gboolean
+gcal_federated_core_get_organizer (GcalCalendar  *calendar,
+                                   gchar        **out_email,
+                                   gchar        **out_name)
+{
+#ifdef ENABLE_FEDERATED_CORE
+  g_autofree gchar *config_dir = NULL;
+  g_autofree gchar *server_email = NULL;
+  g_autofree gchar *core_email = NULL;
+  g_autofree gchar *core_name = NULL;
+  g_autoptr (GUri) uri = NULL;
+  ESourceWebdav *webdav;
+  ESource *source;
+
+  g_return_val_if_fail (GCAL_IS_CALENDAR (calendar), FALSE);
+
+  if (gcal_calendar_is_read_only (calendar))
+    return FALSE;
+
+  source = gcal_calendar_get_source (calendar);
+  if (!source || !e_source_has_extension (source, E_SOURCE_EXTENSION_WEBDAV_BACKEND))
+    return FALSE;
+
+  webdav = e_source_get_extension (source, E_SOURCE_EXTENSION_WEBDAV_BACKEND);
+  uri = e_source_webdav_dup_uri (webdav);
+
+  /* CoreDesktop writes to ~/.config, even where XDG_CONFIG_HOME is elsewhere (e.g. Flatpak) */
+  config_dir = g_build_filename (g_get_home_dir (), ".config", "coredesktop", NULL);
+
+  if (!uri || !gcal_federated_core_find_core (config_dir, g_uri_get_host (uri), &core_email, &core_name))
+    return FALSE;
+
+  /*
+   * Nextcloud only sends invitations when the organizer is one of the
+   * owner's addresses. The CalDAV server says which address that is, so
+   * prefer it to the Core email.
+   */
+  server_email = e_source_webdav_dup_email_address (webdav);
+
+  if (out_email)
+    *out_email = (server_email && *server_email) ? g_steal_pointer (&server_email) : g_steal_pointer (&core_email);
+  if (out_name)
+    *out_name = g_steal_pointer (&core_name);
+
+  return TRUE;
+#else
+  return FALSE;
+#endif
+}

src/federated/gcal-federated-core.h

@@ -0,0 +1,34 @@
+/* gcal-federated-core.h
+ *
+ * Copyright (C) 2026 David Young <david@federated.computer>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "gcal-calendar.h"
+
+G_BEGIN_DECLS
+
+gboolean             gcal_federated_core_get_organizer           (GcalCalendar       *calendar,
+                                                                  gchar             **out_email,
+                                                                  gchar             **out_name);
+
+gboolean             gcal_federated_core_find_core               (const gchar        *config_dir,
+                                                                  const gchar        *host,
+                                                                  gchar             **out_email,
+                                                                  gchar             **out_name);
+
+G_END_DECLS

src/federated/meson.build

@@ -0,0 +1,5 @@
+calendar_incs +=  include_directories('.')
+
+sources += files(
+  'gcal-federated-core.c',
+)

src/gui/event-editor/gcal-attendee-details-page.c

@@ -54,6 +54,8 @@ struct _GcalAttendeeDetailsPage
   GtkWidget                *group_not_responded;
 
   GcalEventAttendeeTypeFilterFlags attendee_type_filter_flags;
+
+  gboolean                  removable;
 };
 
 enum
@@ -64,6 +66,7 @@ enum
   PROP_MODEL_DELEGATED,
   PROP_MODEL_NOT_RESPONDED,
   PROP_ATTENDEE_TYPE,
+  PROP_REMOVABLE,
   N_PROPS
 };
 
@@ -83,7 +86,11 @@ static GtkWidget *
 create_attendee_row_widget (void *attendee,
                             void *user_data)
 {
-  return gcal_attendee_row_new (attendee);
+  GtkWidget *row = gcal_attendee_row_new (attendee);
+
+  g_object_bind_property (user_data, "removable", row, "removable", G_BINDING_SYNC_CREATE);
+
+  return row;
 }
 
 static void
@@ -237,6 +244,9 @@ gcal_attendee_details_page_get_property (GObject    *object,
     case PROP_ATTENDEE_TYPE:
       g_value_set_flags (value, self->attendee_type_filter_flags);
       break;
+    case PROP_REMOVABLE:
+      g_value_set_boolean (value, self->removable);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
     }
@@ -255,6 +265,9 @@ gcal_attendee_details_page_set_property (GObject      *object,
     case PROP_ATTENDEE_TYPE:
       set_type_filter_flags (self, g_value_get_flags (value));
       break;
+    case PROP_REMOVABLE:
+      gcal_attendee_details_page_set_removable (self, g_value_get_boolean (value));
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
     }
@@ -275,27 +288,27 @@ gcal_attendee_details_page_init (GcalAttendeeDetailsPage *instance)
   adw_preferences_group_bind_model (ADW_PREFERENCES_GROUP (instance->group_accepted),
                                     G_LIST_MODEL (instance->filter_list_accepted),
                                     create_attendee_row_widget,
-                                    NULL, NULL);
+                                    instance, NULL);
 
   adw_preferences_group_bind_model (ADW_PREFERENCES_GROUP (instance->group_tentative),
                                     G_LIST_MODEL (instance->filter_list_tentative),
                                     create_attendee_row_widget,
-                                    NULL, NULL);
+                                    instance, NULL);
 
   adw_preferences_group_bind_model (ADW_PREFERENCES_GROUP (instance->group_declined),
                                     G_LIST_MODEL (instance->filter_list_declined),
                                     create_attendee_row_widget,
-                                    NULL, NULL);
+                                    instance, NULL);
 
   adw_preferences_group_bind_model (ADW_PREFERENCES_GROUP (instance->group_delegated),
                                     G_LIST_MODEL (instance->filter_list_delegated),
                                     create_attendee_row_widget,
-                                    NULL, NULL);
+                                    instance, NULL);
 
   adw_preferences_group_bind_model (ADW_PREFERENCES_GROUP (instance->group_not_responded),
                                     G_LIST_MODEL (instance->filter_list_not_responded),
                                     create_attendee_row_widget,
-                                    NULL, NULL);
+                                    instance, NULL);
 }
 
 static void
@@ -370,6 +383,16 @@ gcal_attendee_details_page_class_init (GcalAttendeeDetailsPageClass *klass)
                         GCAL_EVENT_ATTENDEE_TYPE_FILTER_NONE,
                         G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
 
+  /**
+   * GcalAttendeeDetailsPage:removable:
+   *
+   * Whether attendees can be removed from the event.
+   */
+  properties[PROP_REMOVABLE] =
+    g_param_spec_boolean ("removable", NULL, NULL,
+                          FALSE,
+                          G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY | G_PARAM_STATIC_STRINGS);
+
   g_object_class_install_properties (object_class, N_PROPS, properties);
 
   /* widget */
@@ -420,3 +443,24 @@ gcal_attendee_details_page_set_type_filter (GcalAttendeeDetailsPage         *sel
   g_assert (GCAL_IS_ATTENDEE_DETAILS_PAGE (self));
   set_type_filter_flags (self, flags);
 }
+
+/**
+ * gcal_attendee_details_page_set_removable:
+ * @self: a #GcalAttendeeDetailsPage instance.
+ * @removable: whether attendees can be removed
+ *
+ * Sets whether each attendee is shown with a button that removes them
+ * from the event.
+ */
+void
+gcal_attendee_details_page_set_removable (GcalAttendeeDetailsPage *self,
+                                          gboolean                 removable)
+{
+  g_assert (GCAL_IS_ATTENDEE_DETAILS_PAGE (self));
+
+  if (self->removable == removable)
+    return;
+
+  self->removable = removable;
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_REMOVABLE]);
+}

src/gui/event-editor/gcal-attendee-details-page.h

@@ -34,6 +34,9 @@ void                 gcal_attendee_details_page_set_attendees          (GcalAtte
 void                 gcal_attendee_details_page_set_type_filter        (GcalAttendeeDetailsPage         *self,
                                                                         GcalEventAttendeeTypeFilterFlags flags);
 
+void                 gcal_attendee_details_page_set_removable          (GcalAttendeeDetailsPage *self,
+                                                                        gboolean                 removable);
+
 G_END_DECLS
 
 #endif

src/gui/event-editor/gcal-attendee-row.blp

@@ -12,6 +12,18 @@ template $GcalAttendeeRow: Adw.ActionRow {
       "dimmed",
     ]
   }
+
+  [suffix]
+  Button remove_button {
+    visible: bind template.removable;
+    valign: center;
+    icon-name: "list-remove-symbolic";
+    tooltip-text: _("Remove Participant");
+
+    styles [
+      "flat",
+    ]
+  }
 }
 
 PopoverMenu context_menu {

src/gui/event-editor/gcal-attendee-row.c

@@ -34,10 +34,13 @@ struct _GcalAttendeeRow
   GcalEventAttendee *attendee;
 
   GtkWidget         *role;
+  GtkWidget         *remove_button;
   GtkWidget         *context_menu;
   GtkGestureClick   *gesture_click;
 
   GSimpleActionGroup *action_group;
+
+  gboolean           removable;
 };
 
 G_DEFINE_FINAL_TYPE (GcalAttendeeRow, gcal_attendee_row, ADW_TYPE_ACTION_ROW);
@@ -46,6 +49,7 @@ enum
 {
   PROP_0,
   PROP_ATTENDEE,
+  PROP_REMOVABLE,
   N_PROPS,
 };
 
@@ -164,6 +168,16 @@ gcal_attendee_row_set_property (GObject      *object,
       g_assert (self->attendee == NULL);
       self->attendee = g_value_get_object (value);
       set_up_row_content (self);
+      gtk_actionable_set_action_target (GTK_ACTIONABLE (self->remove_button), "s",
+                                        gcal_event_attendee_get_uri (self->attendee) ? gcal_event_attendee_get_uri (self->attendee) : "");
+      gtk_actionable_set_action_name (GTK_ACTIONABLE (self->remove_button), "event-editor.remove-attendee");
+      break;
+    case PROP_REMOVABLE:
+      if (self->removable != g_value_get_boolean (value))
+        {
+          self->removable = g_value_get_boolean (value);
+          g_object_notify_by_pspec (object, pspec);
+        }
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
@@ -183,6 +197,9 @@ gcal_attendee_row_get_property (GObject    *object,
     case PROP_ATTENDEE:
       g_value_set_object (value, self->attendee);
       break;
+    case PROP_REMOVABLE:
+      g_value_set_boolean (value, self->removable);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
     }
@@ -209,12 +226,23 @@ gcal_attendee_row_class_init (GcalAttendeeRowClass *klass)
                          GCAL_TYPE_EVENT_ATTENDEE,
                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_STRINGS);
 
+  /**
+   * GcalAttendeeRow:removable:
+   *
+   * Whether the row offers to remove the attendee from the event.
+   */
+  properties[PROP_REMOVABLE] =
+    g_param_spec_boolean ("removable", NULL, NULL,
+                          FALSE,
+                          G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY | G_PARAM_STATIC_STRINGS);
+
   g_object_class_install_properties (object_class, N_PROPS, properties);
 
   gtk_widget_class_set_template_from_resource (widget_class, "/org/gnome/calendar/ui/event-editor/gcal-attendee-row.ui");
 
   gtk_widget_class_bind_template_child (widget_class, GcalAttendeeRow, context_menu);
   gtk_widget_class_bind_template_child (widget_class, GcalAttendeeRow, gesture_click);
+  gtk_widget_class_bind_template_child (widget_class, GcalAttendeeRow, remove_button);
   gtk_widget_class_bind_template_child (widget_class, GcalAttendeeRow, role);
 }
 

src/gui/event-editor/gcal-attendees-section.blp

@@ -11,6 +11,16 @@ template $GcalAttendeesSection: $GcalEventEditorSection {
     filter-flags: GCAL_EVENT_ATTENDEE_TYPE_FILTER_PERSON;
   }
 
+  Adw.EntryRow invite_row {
+    title: _("Invite by Email");
+    visible: bind template.can-invite;
+    input-purpose: email;
+    show-apply-button: true;
+    apply => $on_invite_row_apply_cb(template) not-swapped;
+    entry-activated => $on_invite_row_apply_cb(template) not-swapped;
+    changed => $on_invite_row_changed_cb(template) not-swapped;
+  }
+
   $GcalAttendeeSummaryRow {
     title: _("Resources");
     attendees: bind template.attendees;

src/gui/event-editor/gcal-attendees-section.c

@@ -27,17 +27,25 @@
 #include "gcal-event-organizer.h"
 #include "gcal-event.h"
 #include "gcal-organizer-row.h"
+#include "gcal-utils.h"
 #include "glib-object.h"
 
 struct _GcalAttendeesSection
 {
   GcalEventEditorSection  parent_instance;
 
+  GcalEvent           *event;
   GcalEventOrganizer  *organizer;
 
+  GtkWidget           *invite_row;
+  GtkWidget           *organizer_row;
   AdwActionRow        *summary_row;
 
   GListModel          *attendees;
+
+  /* Who invitations come from; NULL when people can't be invited */
+  gchar               *inviter_email;
+  gchar               *inviter_name;
 };
 
 G_DEFINE_FINAL_TYPE (GcalAttendeesSection, gcal_attendees_section, GCAL_TYPE_EVENT_EDITOR_SECTION)
@@ -46,6 +54,7 @@ enum
 {
   PROP_0,
   PROP_ATTENDEES,
+  PROP_CAN_INVITE,
   PROP_ORGANIZER,
   N_PROPS
 };
@@ -53,6 +62,97 @@ enum
 static GParamSpec *properties[N_PROPS] = { NULL, };
 
 
+/*
+ * Auxiliary methods
+ */
+
+static void
+update_from_event (GcalAttendeesSection *self)
+{
+  self->organizer = self->event ? gcal_event_get_organizer (self->event) : NULL;
+  self->attendees = self->event ? gcal_event_get_attendees (self->event) : NULL;
+
+  gtk_widget_set_visible (self->organizer_row, self->organizer != NULL);
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_ATTENDEES]);
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_ORGANIZER]);
+}
+
+static gboolean
+invite (GcalAttendeesSection *self,
+        const gchar          *text)
+{
+  g_autofree gchar *email = NULL;
+  g_autofree gchar *name = NULL;
+
+  if (!gcal_util_parse_email_address (text, &email, &name))
+    return FALSE;
+
+  /* The organizer doesn't invite themselves */
+  if (g_ascii_strcasecmp (email, self->inviter_email) == 0)
+    return TRUE;
+
+  if (!gcal_event_get_organizer (self->event))
+    gcal_event_set_organizer (self->event, self->inviter_email, self->inviter_name);
+
+  gcal_event_add_attendee (self->event, email, name);
+
+  return TRUE;
+}
+
+
+/*
+ * Callbacks
+ */
+
+static void
+on_invite_row_apply_cb (AdwEntryRow          *row,
+                        GcalAttendeesSection *self)
+{
+  g_autoptr (GStrvBuilder) not_invited = NULL;
+  g_auto (GStrv) addresses = NULL;
+  g_auto (GStrv) remaining = NULL;
+  g_autofree gchar *remaining_text = NULL;
+
+  if (!self->event || !self->inviter_email)
+    return;
+
+  /* Several addresses can be pasted at once */
+  addresses = g_strsplit_set (gtk_editable_get_text (GTK_EDITABLE (row)), ",;\n", -1);
+  not_invited = g_strv_builder_new ();
+
+  for (gint i = 0; addresses[i]; i++)
+    {
+      g_strstrip (addresses[i]);
+
+      if (*addresses[i] && !invite (self, addresses[i]))
+        g_strv_builder_add (not_invited, addresses[i]);
+    }
+
+  /* Leave what isn't an email address, so it can be corrected */
+  remaining = g_strv_builder_end (not_invited);
+  remaining_text = g_strjoinv (", ", remaining);
+
+  gtk_editable_set_text (GTK_EDITABLE (row), remaining_text);
+
+  if (*remaining_text)
+    gtk_widget_add_css_class (GTK_WIDGET (row), "error");
+}
+
+static void
+on_invite_row_changed_cb (AdwEntryRow          *row,
+                          GcalAttendeesSection *self)
+{
+  gtk_widget_remove_css_class (GTK_WIDGET (row), "error");
+}
+
+static void
+on_attendees_changed_cb (GcalAttendeesSection *self)
+{
+  update_from_event (self);
+}
+
+
 /*
  * GcalEventEditorSection overrides
  */
@@ -63,19 +163,23 @@ gcal_attendees_section_event_set_cb (GcalEventEditorSection *section,
 {
   GcalAttendeesSection *self = GCAL_ATTENDEES_SECTION (section);
 
+  gtk_editable_set_text (GTK_EDITABLE (self->invite_row), "");
+
+  if (self->event)
+    g_signal_handlers_disconnect_by_func (gcal_event_get_attendees (self->event), on_attendees_changed_cb, self);
+
+  g_set_weak_pointer (&self->event, event);
+
   if (event)
     {
-      self->organizer = gcal_event_get_organizer (event);
-      self->attendees = gcal_event_get_attendees (event);
-    }
-  else
-    {
-      self->organizer = NULL;
-      self->attendees = NULL;
+      g_signal_connect_object (gcal_event_get_attendees (event),
+                               "items-changed",
+                               G_CALLBACK (on_attendees_changed_cb),
+                               self,
+                               G_CONNECT_SWAPPED);
     }
 
-  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_ATTENDEES]);
-  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_ORGANIZER]);
+  update_from_event (self);
 }
 
 
@@ -97,6 +201,10 @@ gcal_attendees_section_get_property (GObject *object,
       g_value_set_object (value, self->attendees);
       break;
 
+    case PROP_CAN_INVITE:
+      g_value_set_boolean (value, self->inviter_email != NULL);
+      break;
+
     case PROP_ORGANIZER:
       g_value_set_object (value, self->organizer);
       break;
@@ -132,6 +240,13 @@ gcal_attendees_section_finalize (GObject *object)
 
   self->attendees = NULL; /* not owned */
 
+  if (self->event)
+    g_signal_handlers_disconnect_by_func (gcal_event_get_attendees (self->event), on_attendees_changed_cb, self);
+  g_clear_weak_pointer (&self->event);
+
+  g_clear_pointer (&self->inviter_email, g_free);
+  g_clear_pointer (&self->inviter_name, g_free);
+
   G_OBJECT_CLASS (gcal_attendees_section_parent_class)->finalize (object);
 }
 
@@ -168,6 +283,17 @@ gcal_attendees_section_class_init (GcalAttendeesSectionClass *klass)
                          G_TYPE_LIST_MODEL,
                          G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);
 
+  /**
+   * GcalAttendeesSection:can-invite:
+   *
+   * Whether people can be invited to the event.
+   * See gcal_attendees_section_set_inviter().
+   */
+  properties[PROP_CAN_INVITE] =
+    g_param_spec_boolean ("can-invite", NULL, NULL,
+                          FALSE,
+                          G_PARAM_READABLE | G_PARAM_EXPLICIT_NOTIFY | G_PARAM_STATIC_STRINGS);
+
   /**
    * GcalAttendeesSection:organizer:
    *
@@ -183,5 +309,37 @@ gcal_attendees_section_class_init (GcalAttendeesSectionClass *klass)
 
   gtk_widget_class_set_template_from_resource (widget_class, "/org/gnome/calendar/ui/event-editor/gcal-attendees-section.ui");
 
+  gtk_widget_class_bind_template_child (widget_class, GcalAttendeesSection, invite_row);
+  gtk_widget_class_bind_template_child (widget_class, GcalAttendeesSection, organizer_row);
   gtk_widget_class_bind_template_child (widget_class, GcalAttendeesSection, summary_row);
+
+  gtk_widget_class_bind_template_callback (widget_class, on_invite_row_apply_cb);
+  gtk_widget_class_bind_template_callback (widget_class, on_invite_row_changed_cb);
+}
+
+/**
+ * gcal_attendees_section_set_inviter:
+ * @self: a #GcalAttendeesSection
+ * @email: (nullable): the email address invitations come from
+ * @name: (nullable): the name invitations come from
+ *
+ * Lets people be invited to the event, on behalf of @email, who becomes
+ * its organizer. Passing %NULL as @email stops people from being invited.
+ */
+void
+gcal_attendees_section_set_inviter (GcalAttendeesSection *self,
+                                    const gchar          *email,
+                                    const gchar          *name)
+{
+  gboolean could_invite;
+
+  g_return_if_fail (GCAL_IS_ATTENDEES_SECTION (self));
+
+  could_invite = self->inviter_email != NULL;
+
+  g_set_str (&self->inviter_email, email);
+  g_set_str (&self->inviter_name, email ? name : NULL);
+
+  if (could_invite != (self->inviter_email != NULL))
+    g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_CAN_INVITE]);
 }

src/gui/event-editor/gcal-attendees-section.h

@@ -27,4 +27,8 @@ G_BEGIN_DECLS
 #define GCAL_TYPE_ATTENDEES_SECTION (gcal_attendees_section_get_type ())
 G_DECLARE_FINAL_TYPE (GcalAttendeesSection, gcal_attendees_section, GCAL, ATTENDEES_SECTION, GcalEventEditorSection)
 
+void                 gcal_attendees_section_set_inviter          (GcalAttendeesSection *self,
+                                                                  const gchar          *email,
+                                                                  const gchar          *name);
+
 G_END_DECLS

src/gui/event-editor/gcal-event-editor-dialog.c

@@ -28,6 +28,7 @@
 #include "gcal-event-editor-dialog.h"
 #include "gcal-event-editor-section.h"
 #include "gcal-event.h"
+#include "gcal-federated-core.h"
 #include "gcal-notes-section.h"
 #include "gcal-reminders-section.h"
 #include "gcal-schedule-section.h"
@@ -128,6 +129,48 @@ set_writable (GcalEventEditorDialog *self,
   g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_WRITABLE]);
 }
 
+/*
+ * People can be invited to events on the calendars of a Federated Computer
+ * Core, which sends the invitations, unless someone else organizes the event.
+ */
+static void
+update_invite_state (GcalEventEditorDialog *self)
+{
+  g_autofree gchar *email = NULL;
+  g_autofree gchar *name = NULL;
+  GcalEventOrganizer *organizer;
+  GcalCalendar *calendar;
+  gboolean can_invite = FALSE;
+
+  if (!self->edited_event)
+    return;
+
+  calendar = gcal_calendar_combo_row_get_calendar (self->calendar_combo_row);
+  if (!calendar)
+    calendar = gcal_event_get_calendar (self->edited_event);
+
+  organizer = gcal_event_get_organizer (self->edited_event);
+
+  if (self->writable && calendar && gcal_federated_core_get_organizer (calendar, &email, &name))
+    {
+      g_autofree const gchar *organizer_email = NULL;
+
+      if (organizer)
+        organizer_email = gcal_util_get_email_from_mailto_uri (gcal_event_organizer_get_uri (organizer));
+
+      can_invite = !organizer_email || g_ascii_strcasecmp (organizer_email, email) == 0;
+    }
+
+  gcal_attendees_section_set_inviter (GCAL_ATTENDEES_SECTION (self->attendees_section),
+                                      can_invite ? email : NULL,
+                                      can_invite ? name : NULL);
+
+  gcal_attendee_details_page_set_removable (GCAL_ATTENDEE_DETAILS_PAGE (self->attendee_details_page), can_invite);
+  gtk_widget_action_set_enabled (GTK_WIDGET (self), "event-editor.remove-attendee", can_invite);
+
+  gtk_widget_set_visible (GTK_WIDGET (self->attendees_section), organizer != NULL || can_invite);
+}
+
 static void
 set_event (GcalEventEditorDialog *self,
            GcalEvent             *event,
@@ -165,8 +208,7 @@ set_event (GcalEventEditorDialog *self,
   gcal_calendar_combo_row_set_calendar (self->calendar_combo_row, calendar);
 
   set_writable (self, !gcal_calendar_is_read_only (calendar));
-  gboolean has_participants = gcal_event_get_organizer (self->edited_event) != NULL;
-  gtk_widget_set_visible (GTK_WIDGET (self->attendees_section), has_participants);
+  update_invite_state (self);
 
   gtk_widget_set_visible (self->cancel_button, self->writable);
 
@@ -235,6 +277,9 @@ apply_event_properties_to_template_event (GcalEvent *template_event,
       if (alarm)
         gcal_event_add_alarm (template_event, alarm);
     }
+
+  if (!gcal_event_attendees_equal (template_event, event))
+    gcal_event_copy_attendees (template_event, event);
 }
 
 static void
@@ -275,7 +320,7 @@ save_event (GcalEventEditorDialog *self,
   GcalContext *context;
   GcalManager *manager;
 
-  gboolean calendar_equal, alarms_equal, schedule_equal, strings_equal, event_equal;
+  gboolean calendar_equal, alarms_equal, schedule_equal, strings_equal, attendees_equal, event_equal;
 
   GCAL_ENTRY;
 
@@ -284,11 +329,20 @@ save_event (GcalEventEditorDialog *self,
 
   selected_calendar = gcal_calendar_combo_row_get_calendar (self->calendar_combo_row);
 
+  /* Everyone invited here was removed again, so there's nothing to organize */
+  if (!gcal_event_get_organizer (self->event) &&
+      gcal_event_get_organizer (self->edited_event) &&
+      g_list_model_get_n_items (gcal_event_get_attendees (self->edited_event)) == 0)
+    {
+      gcal_event_set_organizer (self->edited_event, NULL, NULL);
+    }
+
   calendar_equal = selected_calendar && calendar == selected_calendar;
   alarms_equal = gcal_event_alarms_equal (self->event, self->edited_event);
   schedule_equal = gcal_event_schedule_equal (self->event, self->edited_event);
   strings_equal = gcal_event_strings_equal (self->event, self->edited_event);
-  event_equal = calendar_equal && alarms_equal && schedule_equal && strings_equal;
+  attendees_equal = gcal_event_attendees_equal (self->event, self->edited_event);
+  event_equal = calendar_equal && alarms_equal && schedule_equal && strings_equal && attendees_equal;
 
   if (self->event_is_new)
     {
@@ -357,6 +411,25 @@ on_show_attendees_detail_page_action_activated_cb (GtkWidget  *widget,
                             ADW_NAVIGATION_PAGE (self->attendee_details_page));
 }
 
+static void
+on_remove_attendee_action_activated_cb (GtkWidget  *widget,
+                                        const char *action_name,
+                                        GVariant   *param)
+{
+  GcalEventEditorDialog *self = GCAL_EVENT_EDITOR_DIALOG (widget);
+
+  gcal_event_remove_attendee (self->edited_event, g_variant_get_string (param, NULL));
+
+  if (g_list_model_get_n_items (self->attendees_model) == 0)
+    adw_navigation_view_pop (ADW_NAVIGATION_VIEW (self->nav_view));
+}
+
+static void
+on_calendar_selected_cb (GcalEventEditorDialog *self)
+{
+  update_invite_state (self);
+}
+
 static void
 on_cancel_button_clicked_cb (GtkButton             *button,
                              GcalEventEditorDialog *self)
@@ -638,6 +711,8 @@ gcal_event_editor_dialog_class_init (GcalEventEditorDialogClass *klass)
   gtk_widget_class_install_action (widget_class, "event-editor.save", NULL, on_event_editor_save_action_activated_cb);
   gtk_widget_class_install_action (widget_class, "event-editor.show-attendees-detail-page", "u",
                                    on_show_attendees_detail_page_action_activated_cb);
+  gtk_widget_class_install_action (widget_class, "event-editor.remove-attendee", "s",
+                                   on_remove_attendee_action_activated_cb);
 }
 
 static void
@@ -648,6 +723,7 @@ gcal_event_editor_dialog_init (GcalEventEditorDialog *self)
   set_up_context (self);
 
   g_signal_connect_swapped (self, "validation-requested", G_CALLBACK (on_validation_requested_cb), self);
+  g_signal_connect_swapped (self->calendar_combo_row, "notify::selected-item", G_CALLBACK (on_calendar_selected_cb), self);
 }
 
 /**

src/gui/event-editor/gcal-organizer-row.c

@@ -89,6 +89,10 @@ generate_subtitle (GcalOrganizerRow   *self,
     return NULL;
 
   email = gcal_util_get_email_from_mailto_uri (gcal_event_organizer_get_uri (organizer));
+
+  if (!gcal_event_organizer_get_name (organizer))
+    return g_strdup (email);
+
   name_with_email = g_strdup_printf ("%s (%s)", gcal_event_organizer_get_name (organizer), email);
 
   return g_strdup (name_with_email);

src/meson.build

@@ -75,6 +75,7 @@ sources = files()
 subdir('appdata')
 subdir('contrib')
 subdir('core')
+subdir('federated')
 subdir('gui')
 subdir('search')
 subdir('theme')

src/utils/gcal-utils.c

@@ -1081,6 +1081,93 @@ gcal_util_get_email_from_mailto_uri (const gchar *mailto_uri)
   return address;
 }
 
+static gboolean
+is_valid_email (const gchar *email)
+{
+  const gchar *at;
+  const gchar *domain;
+
+  at = strchr (email, '@');
+  if (!at || at == email || strchr (at + 1, '@'))
+    return FALSE;
+
+  domain = at + 1;
+  if (!strchr (domain, '.') || *domain == '.' || g_str_has_suffix (domain, "."))
+    return FALSE;
+
+  for (const gchar *c = email; *c; c++)
+    {
+      if (g_ascii_isspace (*c) || strchr ("<>()[],;:\\\"", *c))
+        return FALSE;
+    }
+
+  return TRUE;
+}
+
+/**
+ * gcal_util_parse_email_address:
+ * @text: an address as typed, e.g. "ana@example.com" or "Ana Lima <ana@example.com>"
+ * @out_email: (out) (optional): return location for the email address
+ * @out_name: (out) (optional) (nullable): return location for the name, if any
+ *
+ * Reads an email address, optionally with a name in front of it.
+ *
+ * Returns: %TRUE if @text is an email address
+ */
+gboolean
+gcal_util_parse_email_address (const gchar  *text,
+                               gchar       **out_email,
+                               gchar       **out_name)
+{
+  g_autofree gchar *stripped = NULL;
+  g_autofree gchar *email = NULL;
+  g_autofree gchar *name = NULL;
+  gchar *open_bracket;
+
+  if (!text)
+    return FALSE;
+
+  stripped = g_strstrip (g_strdup (text));
+  open_bracket = strrchr (stripped, '<');
+
+  if (open_bracket && g_str_has_suffix (stripped, ">"))
+    {
+      stripped[strlen (stripped) - 1] = '\0';
+      email = g_strstrip (g_strdup (open_bracket + 1));
+
+      *open_bracket = '\0';
+      name = g_strstrip (g_strdup (stripped));
+
+      /* "Ana Lima" <ana@example.com> */
+      if (g_str_has_prefix (name, "\"") && g_str_has_suffix (name, "\"") && strlen (name) >= 2)
+        {
+          name[strlen (name) - 1] = '\0';
+          memmove (name, name + 1, strlen (name));
+          g_strstrip (name);
+        }
+
+      if (!*name)
+        g_clear_pointer (&name, g_free);
+    }
+  else
+    {
+      email = g_strdup (stripped);
+    }
+
+  if (g_ascii_strncasecmp (email, "mailto:", 7) == 0)
+    memmove (email, email + 7, strlen (email + 7) + 1);
+
+  if (!is_valid_email (email))
+    return FALSE;
+
+  if (out_email)
+    *out_email = g_steal_pointer (&email);
+  if (out_name)
+    *out_name = g_steal_pointer (&name);
+
+  return TRUE;
+}
+
 /**
  * gcal_create_activate_signal_shortcuts:
  * @widget_class: the class to add the bindings to

src/utils/gcal-utils.h

@@ -118,6 +118,10 @@ GListModel *         gcal_util_create_writable_calendars_model   (GcalManager
 
 const gchar *        gcal_util_get_email_from_mailto_uri         (const gchar        *mailto_uri);
 
+gboolean             gcal_util_parse_email_address               (const gchar        *text,
+                                                                  gchar             **out_email,
+                                                                  gchar             **out_name);
+
 guint                gcal_util_create_activate_signal_and_shortcuts (GtkWidgetClass *widget_class,
                                                                      GType           widget_type);
 #endif /* __GCAL_UTILS_H__ */

tests/meson.build

@@ -43,6 +43,7 @@ tests = [
   'server',
   'utils',
   'event-attendee',
+  'federated-core',
 ]
 
 foreach test : tests

tests/test-event.c

@@ -17,6 +17,7 @@
  */
 
 #include <glib.h>
+#include <string.h>
 
 #include "gcal-event-attendee.h"
 #include "gcal-event-organizer.h"
@@ -454,6 +455,97 @@ event_get_attendees (void)
 
 /*********************************************************************************************************************/
 
+static void
+event_invite_attendees (void)
+{
+  g_autoptr (GcalEvent) event = NULL;
+  g_autoptr (GcalEvent) clone = NULL;
+  g_autoptr (GError) error = NULL;
+  g_autofree gchar *ical = NULL;
+  GcalEventOrganizer *organizer;
+  GListModel *attendees;
+
+  event = create_event_for_string (STUB_EVENT, &error);
+  g_assert_no_error (error);
+
+  attendees = gcal_event_get_attendees (event);
+  g_assert_cmpuint (g_list_model_get_n_items (attendees), ==, 0);
+  g_assert_null (gcal_event_get_organizer (event));
+
+  clone = gcal_event_new_from_event (event);
+  g_assert_true (gcal_event_attendees_equal (event, clone));
+
+  gcal_event_set_organizer (clone, "me@example.com", "Me Myself");
+  organizer = gcal_event_get_organizer (clone);
+  g_assert_nonnull (organizer);
+  g_assert_cmpstr (gcal_event_organizer_get_uri (organizer), ==, "mailto:me@example.com");
+  g_assert_cmpstr (gcal_event_organizer_get_name (organizer), ==, "Me Myself");
+  g_assert_false (gcal_event_attendees_equal (event, clone));
+
+  g_assert_true (gcal_event_add_attendee (clone, "ana@example.com", "Ana Lima"));
+  g_assert_true (gcal_event_add_attendee (clone, "bo@example.com", NULL));
+  g_assert_false (gcal_event_add_attendee (clone, "ANA@example.com", NULL));
+
+  attendees = gcal_event_get_attendees (clone);
+  g_assert_cmpuint (g_list_model_get_n_items (attendees), ==, 2);
+  g_assert_true (gcal_event_has_attendee (clone, "mailto:Ana@Example.com"));
+  g_assert_false (gcal_event_has_attendee (clone, "carl@example.com"));
+
+  {
+    g_autoptr (GcalEventAttendee) attendee = g_list_model_get_item (attendees, 0);
+
+    g_assert_cmpstr (gcal_event_attendee_get_uri (attendee), ==, "mailto:ana@example.com");
+    g_assert_cmpstr (gcal_event_attendee_get_name (attendee), ==, "Ana Lima");
+    g_assert_cmpint (gcal_event_attendee_get_attendee_type (attendee), ==, GCAL_EVENT_ATTENDEE_TYPE_INDIVIDUAL);
+    g_assert_cmpint (gcal_event_attendee_get_role (attendee), ==, GCAL_EVENT_ATTENDEE_ROLE_REQUIRED);
+    g_assert_cmpint (gcal_event_attendee_get_part_status (attendee), ==, GCAL_EVENT_ATTENDEE_PART_NEEDS_ACTION);
+    g_assert_true (gcal_event_attendee_get_requires_rsvp (attendee));
+  }
+
+  /* What the server sees */
+  ical = e_cal_component_get_as_string (gcal_event_get_component (clone));
+  g_assert_nonnull (strstr (ical, "ORGANIZER;CN=Me Myself:mailto:me@example.com"));
+  g_assert_nonnull (strstr (ical, "mailto:ana@example.com"));
+  g_assert_nonnull (strstr (ical, "mailto:bo@example.com"));
+
+  gcal_event_remove_attendee (clone, "mailto:ANA@example.com");
+  g_assert_cmpuint (g_list_model_get_n_items (attendees), ==, 1);
+  g_assert_false (gcal_event_has_attendee (clone, "ana@example.com"));
+
+  /* Removing someone who isn't invited does nothing */
+  gcal_event_remove_attendee (clone, "carl@example.com");
+  g_assert_cmpuint (g_list_model_get_n_items (attendees), ==, 1);
+
+  gcal_event_remove_attendee (clone, "bo@example.com");
+  gcal_event_set_organizer (clone, NULL, NULL);
+  g_assert_null (gcal_event_get_organizer (clone));
+  g_assert_true (gcal_event_attendees_equal (event, clone));
+}
+
+static void
+event_copy_attendees (void)
+{
+  g_autoptr (GcalEvent) with_attendees = NULL;
+  g_autoptr (GcalEvent) event = NULL;
+  g_autoptr (GError) error = NULL;
+
+  with_attendees = create_event_for_string (STUB_EVENT_WITH_ATTENDEES, &error);
+  g_assert_no_error (error);
+
+  event = create_event_for_string (STUB_EVENT, &error);
+  g_assert_no_error (error);
+
+  g_assert_false (gcal_event_attendees_equal (event, with_attendees));
+
+  gcal_event_copy_attendees (event, with_attendees);
+
+  g_assert_true (gcal_event_attendees_equal (event, with_attendees));
+  g_assert_cmpuint (g_list_model_get_n_items (gcal_event_get_attendees (event)), ==, 2);
+  g_assert_cmpstr (gcal_event_organizer_get_uri (gcal_event_get_organizer (event)), ==, "mailto:alice@example.com");
+}
+
+/*********************************************************************************************************************/
+
 static GDateTime *
 dt_add_second_random (GDateTime *dt)
 {
@@ -595,6 +687,8 @@ main (gint   argc,
   g_test_add_func ("/event/date/create-tzid", event_date_create_tzid);
   g_test_add_func ("/event/date/check-tz", event_date_check_tz);
   g_test_add_func ("/event/date/get-attendees", event_get_attendees);
+  g_test_add_func ("/event/attendees/invite", event_invite_attendees);
+  g_test_add_func ("/event/attendees/copy", event_copy_attendees);
   g_test_add_func ("/event/equal/schedule", event_schedule_equal);
 
   return g_test_run ();

tests/test-federated-core.c

@@ -0,0 +1,165 @@
+/* test-federated-core.c
+ *
+ * Copyright (C) 2026 David Young <david@federated.computer>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <glib.h>
+#include <glib/gstdio.h>
+
+#include "gcal-federated-core.h"
+
+/*
+ * Written by CoreDesktop's configure with bash's printf %q
+ */
+#define CORE_CONF(domain, email, name) \
+  "CORE_DOMAIN=" domain "\n"           \
+  "CORE_EMAIL=" email "\n"             \
+  "CORE_NAME=" name "\n"
+
+static gchar *
+create_config_dir (void)
+{
+  g_autoptr (GError) error = NULL;
+  gchar *config_dir;
+
+  config_dir = g_dir_make_tmp ("gcal-federated-core-XXXXXX", &error);
+  g_assert_no_error (error);
+
+  return config_dir;
+}
+
+static void
+write_file (const gchar *config_dir,
+            const gchar *filename,
+            const gchar *contents)
+{
+  g_autoptr (GError) error = NULL;
+  g_autofree gchar *path = g_build_filename (config_dir, filename, NULL);
+  g_autofree gchar *dir = g_path_get_dirname (path);
+
+  g_mkdir_with_parents (dir, 0700);
+  g_file_set_contents (path, contents, -1, &error);
+  g_assert_no_error (error);
+}
+
+static void
+remove_config_dir (const gchar *config_dir)
+{
+  g_autoptr (GFile) dir = g_file_new_for_path (config_dir);
+  g_autoptr (GFileEnumerator) children = NULL;
+  GFileInfo *info;
+  GFile *child;
+
+  children = g_file_enumerate_children (dir, G_FILE_ATTRIBUTE_STANDARD_NAME, G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS, NULL, NULL);
+
+  while (children && g_file_enumerator_iterate (children, &info, &child, NULL, NULL) && info)
+    {
+      if (g_file_info_get_file_type (info) == G_FILE_TYPE_DIRECTORY)
+        {
+          g_autofree gchar *path = g_file_get_path (child);
+          remove_config_dir (path);
+        }
+      else
+        {
+          g_file_delete (child, NULL, NULL);
+        }
+    }
+
+  g_file_delete (dir, NULL, NULL);
+}
+
+/*********************************************************************************************************************/
+
+static void
+federated_core_find_core (void)
+{
+  g_autofree gchar *config_dir = create_config_dir ();
+  g_autofree gchar *email = NULL;
+  g_autofree gchar *name = NULL;
+
+  /* Nothing set up */
+  g_assert_false (gcal_federated_core_find_core (config_dir, "nextcloud.example.com", NULL, NULL));
+
+  write_file (config_dir, "cores/example.com.conf", CORE_CONF ("example.com", "ana@example.com", "Ana\\ Lima"));
+  write_file (config_dir, "cores/example.org.conf", CORE_CONF ("example.org", "bo@example.org", "Bo"));
+
+  g_assert_true (gcal_federated_core_find_core (config_dir, "nextcloud.example.com", &email, &name));
+  g_assert_cmpstr (email, ==, "ana@example.com");
+  g_assert_cmpstr (name, ==, "Ana Lima");
+
+  g_clear_pointer (&email, g_free);
+  g_clear_pointer (&name, g_free);
+
+  g_assert_true (gcal_federated_core_find_core (config_dir, "NextCloud.Example.Org", &email, &name));
+  g_assert_cmpstr (email, ==, "bo@example.org");
+  g_assert_cmpstr (name, ==, "Bo");
+
+  /* Only the Core's own Nextcloud */
+  g_assert_false (gcal_federated_core_find_core (config_dir, "example.com", NULL, NULL));
+  g_assert_false (gcal_federated_core_find_core (config_dir, "caldav.example.com", NULL, NULL));
+  g_assert_false (gcal_federated_core_find_core (config_dir, "nextcloud.example.com.evil.net", NULL, NULL));
+  g_assert_false (gcal_federated_core_find_core (config_dir, NULL, NULL, NULL));
+
+  remove_config_dir (config_dir);
+}
+
+static void
+federated_core_single_core_conf (void)
+{
+  g_autofree gchar *config_dir = create_config_dir ();
+  g_autofree gchar *email = NULL;
+  g_autofree gchar *name = NULL;
+
+  /* Before CoreDesktop supported several Cores */
+  write_file (config_dir, "core.conf", CORE_CONF ("example.com", "ana@example.com", "\\'Ana\\'"));
+
+  g_assert_true (gcal_federated_core_find_core (config_dir, "nextcloud.example.com", &email, &name));
+  g_assert_cmpstr (email, ==, "ana@example.com");
+  g_assert_cmpstr (name, ==, "'Ana'");
+
+  remove_config_dir (config_dir);
+}
+
+static void
+federated_core_incomplete_conf (void)
+{
+  g_autofree gchar *config_dir = create_config_dir ();
+
+  write_file (config_dir, "cores/example.com.conf", "CORE_DOMAIN=example.com\n");
+  write_file (config_dir, "cores/example.org.conf", CORE_CONF ("example.org", "not-an-email", "Bo"));
+  write_file (config_dir, "cores/example.net.conf.bak", CORE_CONF ("example.net", "cy@example.net", "Cy"));
+
+  g_assert_false (gcal_federated_core_find_core (config_dir, "nextcloud.example.com", NULL, NULL));
+  g_assert_false (gcal_federated_core_find_core (config_dir, "nextcloud.example.org", NULL, NULL));
+  g_assert_false (gcal_federated_core_find_core (config_dir, "nextcloud.example.net", NULL, NULL));
+
+  remove_config_dir (config_dir);
+}
+
+/*********************************************************************************************************************/
+
+gint
+main (gint   argc,
+      gchar *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/federated-core/find-core", federated_core_find_core);
+  g_test_add_func ("/federated-core/single-core-conf", federated_core_single_core_conf);
+  g_test_add_func ("/federated-core/incomplete-conf", federated_core_incomplete_conf);
+
+  return g_test_run ();
+}

tests/test-utils.c

@@ -233,6 +233,52 @@ test_first_weekday (void)
 
 /*********************************************************************************************************************/
 
+static void
+parse_email_address (void)
+{
+  struct {
+    const gchar *text;
+    const gchar *email;
+    const gchar *name;
+  } valid[] = {
+    { "ana@example.com", "ana@example.com", NULL },
+    { "  ana@example.com  ", "ana@example.com", NULL },
+    { "mailto:ana@example.com", "ana@example.com", NULL },
+    { "Ana Lima <ana@example.com>", "ana@example.com", "Ana Lima" },
+    { "\"Lima, Ana\" <ana@example.com>", "ana@example.com", "Lima, Ana" },
+    { "<ana@example.com>", "ana@example.com", NULL },
+    { "ana.lima+work@mail.example.co.uk", "ana.lima+work@mail.example.co.uk", NULL },
+  };
+  const gchar *invalid[] = {
+    NULL,
+    "",
+    "ana",
+    "ana@",
+    "@example.com",
+    "ana@example",
+    "ana@example.",
+    "ana@.example.com",
+    "ana@@example.com",
+    "ana lima@example.com",
+    "Ana Lima <ana>",
+  };
+
+  for (gsize i = 0; i < G_N_ELEMENTS (valid); i++)
+    {
+      g_autofree gchar *email = NULL;
+      g_autofree gchar *name = NULL;
+
+      g_assert_true (gcal_util_parse_email_address (valid[i].text, &email, &name));
+      g_assert_cmpstr (email, ==, valid[i].email);
+      g_assert_cmpstr (name, ==, valid[i].name);
+    }
+
+  for (gsize i = 0; i < G_N_ELEMENTS (invalid); i++)
+    g_assert_false (gcal_util_parse_email_address (invalid[i], NULL, NULL));
+}
+
+/*********************************************************************************************************************/
+
 gint
 main (gint   argc,
       gchar *argv[])
@@ -245,6 +291,7 @@ main (gint   argc,
   g_test_add_func ("/utils/date-time/date_time_from_icaltime", date_time_from_icaltime);
   g_test_add_func ("/utils/misc/extract_meeting_url", extract_meeting_url);
   g_test_add_func ("/utils/misc/get_first_weekday", test_first_weekday);
+  g_test_add_func ("/utils/misc/parse_email_address", parse_email_address);
 
   return g_test_run ();
 }