Save spent time on activities

Use set_active and save events to keep track of the time,
in seconds, that the activity is on the main screen. The
time is calculated and stored each time an activity is
open/resumed and closed. Therefore, each activity entry
will have an array of seconds for each time it was used.

This makes a 1 to 1 relationship between the spent and
lauch times. In orders words, we can reflect not only the
"when", but also the " for how long".

Even though this time does not necessarily represents the
real time the user "used" the activity, it is a low-cost
approach for reflecting time.

This is a long requested featured from deployments that have
been using statistics tools on journal metadata, and this
patch is already being used by OLPC-AU.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>

src/sugar3/activity/activity.py

@@ -327,6 +327,8 @@ class Activity(Window, Gtk.Container):
         self.connect('delete-event', self.__delete_event_cb)
 
         self._active = False
+        self._active_time = None
+        self._spent_time = 0
         self._activity_id = handle.activity_id
         self.shared_activity = None
         self._join_id = None
@@ -367,6 +369,11 @@ class Activity(Window, Gtk.Container):
                 self._jobject.metadata['launch-times'] = \
                     str(int(time.time()))
 
+            if 'spent-times' in self._jobject.metadata:
+                self._jobject.metadata['spent-times'] += ', 0'
+            else:
+                self._jobject.metadata['spent-times'] = '0'
+
         self.shared_activity = None
         self._join_id = None
 
@@ -420,6 +427,7 @@ class Activity(Window, Gtk.Container):
         jobject.metadata['share-scope'] = SCOPE_PRIVATE
         jobject.metadata['icon-color'] = icon_color
         jobject.metadata['launch-times'] = str(int(time.time()))
+        jobject.metadata['spent-times'] = '0'
         jobject.file_path = ''
 
         # FIXME: We should be able to get an ID synchronously from the DS,
@@ -485,9 +493,21 @@ class Activity(Window, Gtk.Container):
     def get_active(self):
         return self._active
 
+    def _update_spent_time(self):
+        if self._active is True and self._active_time is None:
+            self._active_time = time.time()
+        elif self._active is False and self._active_time is not None:
+            self._spent_time += time.time() - self._active_time
+            self._active_time = None
+        elif self._active is True and self._active_time is not None:
+            current = time.time()
+            self._spent_time += current - self._active_time
+            self._active_time = current
+
     def set_active(self, active):
         if self._active != active:
             self._active = active
+            self._update_spent_time()
             if not self._active and self._jobject:
                 self.save()
 
@@ -778,6 +798,19 @@ class Activity(Window, Gtk.Container):
             self.metadata['buddies_id'] = json.dumps(buddies_dict.keys())
             self.metadata['buddies'] = json.dumps(self._get_buddies())
 
+        # update spent time before saving
+        self._update_spent_time()
+
+        def set_last_value(values_list, new_value):
+            if ', ' not in values_list:
+                return '%d' % new_value
+            else:
+                partial_list = ', '.join(values_list.split(', ')[:-1])
+                return partial_list + ', %d' % new_value
+
+        self.metadata['spent-times'] = set_last_value(
+            self.metadata['spent-times'], self._spent_time)
+
         preview = self.get_preview()
         if preview is not None:
             self.metadata['preview'] = dbus.ByteArray(preview)