[evolution-data-server] M!2 - Expose GData 'parent' and 'position' task fields

[Milan Crha <mcrha src gnome org>]

commit fb2efb3f529f7a0a7469b6fd1d39380a5234d1ad
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Tue Sep 25 11:12:49 2018 +0200

    M!2 - Expose GData 'parent' and 'position' task fields
    
    The 'parent' property of the GDataTasksTask object is exposed
    through ICAL_RELATEDTO_PROPERTY, which matches the practices
    of GNOME To Do and NextCloud and other ICal-based providers.
    
    The position, however, is exposed through an X ICal property
    named X-EVOLUTION-GTASKS-POSITION. This doesn't affect Evolution
    in any form, but will still allow external consumers of EDS to
    retrieve the position of the task. Since GData tasks themselves
    aren't backed by ICal components, we have some creative freedom
    to use X properties.
    
    Updating the task position and parent requires [1], but a compile
    check was added to not force EDS to bump the libgdata version.
    
    [1] https://gitlab.gnome.org/GNOME/libgdata/merge_requests/4
    
    Closes https://gitlab.gnome.org/GNOME/evolution-data-server/merge_requests/2

 .../backends/gtasks/e-cal-backend-gtasks.c         | 47 ++++++++++++++++++++++
 1 file changed, 47 insertions(+)
---
diff --git a/src/calendar/backends/gtasks/e-cal-backend-gtasks.c 
b/src/calendar/backends/gtasks/e-cal-backend-gtasks.c
index 5f0e005c9..62adfd8d2 100644
--- a/src/calendar/backends/gtasks/e-cal-backend-gtasks.c
+++ b/src/calendar/backends/gtasks/e-cal-backend-gtasks.c
@@ -32,6 +32,7 @@
 
 #define GTASKS_DEFAULT_TASKLIST_NAME "@default"
 #define X_EVO_GTASKS_SELF_LINK "X-EVOLUTION-GTASKS-SELF-LINK"
+#define X_EVO_GTASKS_POSITION  "X-EVOLUTION-GTASKS-POSITION"
 
 /* Current data version; when doesn't match with the stored,
    then fetches everything again. */
@@ -100,6 +101,8 @@ ecb_gtasks_gdata_to_comp (GDataTasksTask *task)
        GDataLink *data_link;
        ECalComponent *comp;
        icalcomponent *icomp;
+       const gchar *position;
+       const gchar *parent;
        const gchar *text;
        struct icaltimetype tt;
 
@@ -165,6 +168,14 @@ ecb_gtasks_gdata_to_comp (GDataTasksTask *task)
        if (data_link)
                e_cal_util_set_x_property (icomp, X_EVO_GTASKS_SELF_LINK, gdata_link_get_uri (data_link));
 
+       position = gdata_tasks_task_get_position (task);
+       if (position)
+               e_cal_util_set_x_property (icomp, X_EVO_GTASKS_POSITION, position);
+
+       parent = gdata_tasks_task_get_parent (task);
+       if (parent)
+               icalcomponent_add_property (icomp, icalproperty_new_relatedto (parent));
+
        comp = e_cal_component_new_from_icalcomponent (icomp);
        g_warn_if_fail (comp != NULL);
 
@@ -181,6 +192,9 @@ ecb_gtasks_comp_to_gdata (ECalComponent *comp,
        icalcomponent *icomp;
        icalproperty *prop;
        const gchar *text;
+#if GDATA_CHECK_VERSION(0, 17, 10)
+       gchar *position;
+#endif
        gchar *tmp;
        struct icaltimetype tt;
 
@@ -252,6 +266,39 @@ ecb_gtasks_comp_to_gdata (ECalComponent *comp,
 
        g_free (tmp);
 
+#if GDATA_CHECK_VERSION(0, 17, 10)
+       /* Position */
+       position = e_cal_util_dup_x_property (icomp, X_EVO_GTASKS_POSITION);
+       if (!position || !*position) {
+               g_free (position);
+               position = NULL;
+
+               /* If the passed-in component doesn't contain the libgdata position,
+                  then get it from the cached comp */
+               if (cached_comp) {
+                       position = e_cal_util_dup_x_property (
+                               e_cal_component_get_icalcomponent (cached_comp),
+                               X_EVO_GTASKS_POSITION);
+               }
+       }
+
+       if (position && *position)
+               gdata_tasks_task_set_position (task, position);
+
+       g_free (position);
+
+       /* Parent */
+       prop = icalcomponent_get_first_property (icomp, ICAL_RELATEDTO_PROPERTY);
+       if (!prop && cached_comp) {
+               prop = icalcomponent_get_first_property (
+                       e_cal_component_get_icalcomponent (cached_comp),
+                       ICAL_RELATEDTO_PROPERTY);
+       }
+
+       if (prop)
+               gdata_tasks_task_set_parent (task, icalproperty_get_relatedto (prop));
+#endif
+
        return task;
 }