search: Introduce a search engine

This is architectured in such a way that it will
allow us to introduce other searcheable terms in
the future.

All the functionality that in the past was in
GcalManager is now spread across GcalSearchModel,
GcalSearchHitEvent and GcalSearchEngine.

src/search/gcal-search-button.c

@@ -23,10 +23,16 @@
 #include "gcal-context.h"
 #include "gcal-search-button.h"
 
+#include <math.h>
+
+#define MIN_WIDTH 450
+
 struct _GcalSearchButton
 {
   DzlSuggestionButton  parent;
 
+  GCancellable        *cancellable;
+
   GcalContext         *context;
 };
 
@@ -46,6 +52,74 @@ static GParamSpec *properties [N_PROPS];
  * Callbacks
  */
 
+static void
+position_suggestion_popover_func (DzlSuggestionEntry *entry,
+                                  GdkRectangle       *area,
+                                  gboolean           *is_absolute,
+                                  gpointer            user_data)
+{
+  gint new_width;
+
+#define RIGHT_MARGIN 6
+
+  dzl_suggestion_entry_window_position_func (entry, area, is_absolute, NULL);
+
+  new_width = MAX (area->width * 2 / 5, MIN_WIDTH);
+  area->x += area->width - new_width;
+  area->width = new_width - RIGHT_MARGIN;
+  area->y -= 3;
+
+#undef RIGHT_MARGIN
+
+}
+
+static void
+on_search_finished_cb (GObject      *source_object,
+                       GAsyncResult *result,
+                       gpointer      user_data)
+{
+  g_autoptr (GListModel) model = NULL;
+  g_autoptr (GError) error = NULL;
+  DzlSuggestionEntry *entry;
+  GcalSearchButton *self;
+
+  self = GCAL_SEARCH_BUTTON (user_data);
+  model = gcal_search_engine_search_finish (GCAL_SEARCH_ENGINE (source_object), result, &error);
+
+  entry = dzl_suggestion_button_get_entry (DZL_SUGGESTION_BUTTON (self));
+  dzl_suggestion_entry_set_model (entry, model);
+}
+
+static void
+on_search_entry_changed_cb (GcalSearchButton *self)
+{
+  g_autofree gchar *sexp_query = NULL;
+  DzlSuggestionEntry *entry;
+  GcalSearchEngine *search_engine;
+  const gchar *typed_text;
+
+  entry = dzl_suggestion_button_get_entry (DZL_SUGGESTION_BUTTON (self));
+  typed_text = dzl_suggestion_entry_get_typed_text (entry);
+
+  g_cancellable_cancel (self->cancellable);
+
+  if (dzl_str_empty0 (typed_text))
+    {
+      g_debug ("Cancelling search");
+      dzl_suggestion_entry_set_model (entry, NULL);
+      return;
+    }
+
+  sexp_query = g_strdup_printf ("(contains? \"summary\" \"%s\")", typed_text);
+  search_engine = gcal_context_get_search_engine (self->context);
+  gcal_search_engine_search (search_engine,
+                             sexp_query,
+                             50,
+                             self->cancellable,
+                             on_search_finished_cb,
+                             g_object_ref (self));
+}
+
 static void
 on_unfocus_action_activated_cb (GSimpleAction *action,
                                 GVariant      *param,
@@ -89,6 +163,8 @@ gcal_search_button_finalize (GObject *object)
 {
   GcalSearchButton *self = (GcalSearchButton *)object;
 
+  g_cancellable_cancel (self->cancellable);
+  g_clear_object (&self->cancellable);
   g_clear_object (&self->context);
 
   G_OBJECT_CLASS (gcal_search_button_parent_class)->finalize (object);
@@ -177,8 +253,18 @@ gcal_search_button_init (GcalSearchButton *self)
   gtk_widget_insert_action_group (GTK_WIDGET (self), "search", G_ACTION_GROUP (group));
 
   entry = dzl_suggestion_button_get_entry (DZL_SUGGESTION_BUTTON (self));
-  controller = dzl_shortcut_controller_find (GTK_WIDGET (entry));
+  g_signal_connect_object (entry,
+                           "changed",
+                           G_CALLBACK (on_search_entry_changed_cb),
+                           self,
+                           G_CONNECT_SWAPPED);
 
+  dzl_suggestion_entry_set_position_func (entry,
+                                          position_suggestion_popover_func,
+                                          self,
+                                          NULL);
+
+  controller = dzl_shortcut_controller_find (GTK_WIDGET (entry));
   dzl_shortcut_controller_add_command_callback (controller,
                                                 "org.gnome.calendar.search",
                                                 "<Primary>f",