[evolution-data-server/wip/offline-cache] e_cal_meta_backend_get_changes_sync: Provide default implementation

[Milan Crha <mcrha src gnome org>]

commit 1e1277f9cf5ca7ba3358f6c64f27ffce6293a9ca
Author: Milan Crha <mcrha redhat com>
Date:   Fri Mar 3 11:23:29 2017 +0100

    e_cal_meta_backend_get_changes_sync: Provide default implementation

 src/calendar/libedata-cal/e-cal-meta-backend.c |  116 +++++++++++++++++++++++-
 1 files changed, 115 insertions(+), 1 deletions(-)
---
diff --git a/src/calendar/libedata-cal/e-cal-meta-backend.c b/src/calendar/libedata-cal/e-cal-meta-backend.c
index b66d5d9..3f46426 100644
--- a/src/calendar/libedata-cal/e-cal-meta-backend.c
+++ b/src/calendar/libedata-cal/e-cal-meta-backend.c
@@ -186,6 +186,30 @@ ecmb_steal_view_cancellable (ECalMetaBackend *meta_backend,
 }
 
 static gboolean
+ecmb_gather_locally_cached_objects_cb (ECalCache *cal_cache,
+                                      const gchar *uid,
+                                      const gchar *rid,
+                                      const gchar *revision,
+                                      const gchar *object,
+                                      const gchar *extra,
+                                      EOfflineState offline_state,
+                                      gpointer user_data)
+{
+       GHashTable *locally_cached = user_data;
+
+       g_return_val_if_fail (uid != NULL, FALSE);
+       g_return_val_if_fail (locally_cached != NULL, FALSE);
+
+       if (offline_state == E_OFFLINE_STATE_SYNCED) {
+               g_hash_table_insert (locally_cached,
+                       e_cal_component_id_new (uid, rid),
+                       g_strdup (revision));
+       }
+
+       return TRUE;
+}
+
+static gboolean
 ecmb_get_changes_sync (ECalMetaBackend *meta_backend,
                       const gchar *last_sync_tag,
                       gchar **out_new_sync_tag,
@@ -196,7 +220,97 @@ ecmb_get_changes_sync (ECalMetaBackend *meta_backend,
                       GCancellable *cancellable,
                       GError **error)
 {
-       return FALSE;
+       GHashTable *locally_cached; /* ECalComponentId * ~> gchar *revision */
+       GHashTableIter iter;
+       GSList *existing_objects = NULL, *link;
+       ECalCache *cal_cache;
+       gpointer key, value;
+
+       g_return_val_if_fail (E_IS_CAL_META_BACKEND (meta_backend), FALSE);
+       g_return_val_if_fail (out_created_objects, FALSE);
+       g_return_val_if_fail (out_modified_objects, FALSE);
+       g_return_val_if_fail (out_removed_objects, FALSE);
+
+       *out_created_objects = NULL;
+       *out_modified_objects = NULL;
+       *out_removed_objects = NULL;
+
+       if (!e_backend_get_online (E_BACKEND (meta_backend)))
+               return TRUE;
+
+       cal_cache = e_cal_meta_backend_ref_cache (meta_backend);
+       if (!cal_cache) {
+               g_propagate_error (error, e_data_cal_create_error (OtherError, NULL));
+               return FALSE;
+       }
+
+       if (!e_cal_meta_backend_connect_sync (meta_backend, cancellable, error) ||
+           !e_cal_meta_backend_list_existing_sync (meta_backend, out_new_sync_tag, &existing_objects, 
cancellable, error)) {
+               g_object_unref (cal_cache);
+               return FALSE;
+       }
+
+       locally_cached = g_hash_table_new_full (
+               (GHashFunc) e_cal_component_id_hash,
+               (GEqualFunc) e_cal_component_id_equal,
+               (GDestroyNotify) e_cal_component_free_id,
+               g_free);
+
+       g_warn_if_fail (e_cal_cache_search_with_callback (cal_cache, NULL,
+               ecmb_gather_locally_cached_objects_cb, locally_cached, cancellable, error));
+
+       for (link = existing_objects; link; link = g_slist_next (link)) {
+               ECalMetaBackendInfo *nfo = link->data;
+               ECalComponentId id;
+
+               if (!nfo)
+                       continue;
+
+               id.uid = nfo->uid;
+               id.rid = nfo->rid;
+
+               if (!g_hash_table_contains (locally_cached, &id)) {
+                       link->data = NULL;
+
+                       *out_created_objects = g_slist_prepend (*out_created_objects, nfo);
+               } else {
+                       const gchar *local_revision = g_hash_table_lookup (locally_cached, &id);
+
+                       if (g_strcmp0 (local_revision, nfo->revision) != 0) {
+                               link->data = NULL;
+
+                               *out_modified_objects = g_slist_prepend (*out_modified_objects, nfo);
+                       }
+
+                       g_hash_table_remove (locally_cached, &id);
+               }
+       }
+
+       /* What left in the hash table is removed from the remote side */
+       g_hash_table_iter_init (&iter, locally_cached);
+       while (g_hash_table_iter_next (&iter, &key, &value)) {
+               const ECalComponentId *id = key;
+               const gchar *revision = value;
+               ECalMetaBackendInfo *nfo;
+
+               if (!id) {
+                       g_warn_if_reached ();
+                       continue;
+               }
+
+               nfo = e_cal_meta_backend_info_new (id->uid, id->rid, revision);
+               *out_removed_objects = g_slist_prepend (*out_removed_objects, nfo);
+       }
+
+       g_slist_free_full (existing_objects, e_cal_meta_backend_info_free);
+       g_hash_table_destroy (locally_cached);
+       g_object_unref (cal_cache);
+
+       *out_created_objects = g_slist_reverse (*out_created_objects);
+       *out_modified_objects = g_slist_reverse (*out_modified_objects);
+       *out_removed_objects = g_slist_reverse (*out_removed_objects);
+
+       return TRUE;
 }
 
 static void