diagram: interpolator ergänzt,

asset: berechnung 'nextupdate' korrigiert

diagram.py

@@ -89,6 +89,43 @@ class GraphDef(metaclass=PoolMeta):
 class ChartPoint(metaclass=PoolMeta):
     __name__ = 'diagram.point'
 
+    @classmethod
+    def get_interpolated_val(cls, keyname, query_date):
+        """ query two neighbour-values to
+            interpolate missing value
+        """
+        Rate = Pool().get('investment.rate')
+
+        if keyname is None:
+            return None
+
+        # check if query is for us
+        if keyname.startswith('asset'):
+            asset_id = int(keyname[len('asset'):])
+
+            before = Rate.search([
+                ('date', '<', query_date),
+                ('asset.id', '=', asset_id),
+                ], limit=1, order=[('date', 'DESC')])
+
+            after = Rate.search([
+                ('date', '>', query_date),
+                ('asset.id', '=', asset_id),
+                ], limit=1, order=[('date', 'ASC')])
+
+            if (len(before) == 1) and (len(after) == 1):
+                result = cls.interpolate_linear(
+                        (after[0].date, after[0].rate),
+                        (before[0].date, before[0].rate),
+                        query_date
+                    )
+                return result
+            elif len(before) == 1:
+                return before[0].rate
+            elif len(after) == 1:
+                return after[0].rate
+        return super(ChartPoint, cls).get_interpolated_val(keyname, query_date)
+
     @classmethod
     def get_table_parts(cls):
         """ return a list of tables to union,