[entities] minor refactoring: next_entity and previous_entity actually share 99% of the code

entities.py

@@ -98,6 +98,5 @@
         return []
 
     # IPrevNext interface #####################################################
-
-    def next_entity(self):
+    def _sibling_entry(self, order, operator):
         if self.entry_of:
@@ -103,6 +102,7 @@
         if self.entry_of:
-            rql = ('Any B ORDERBY B ASC LIMIT 1 '
-                   'WHERE B is BlogEntry, B entry_of BL, BL eid %(blog)s, '
-                   'B eid > %(eid)s')
-            rset = self.req.execute(rql, {'blog': self.entry_of[0].eid, 'eid': self.eid})
+            rql = ('Any B ORDERBY B %s LIMIT 1 '
+                   'WHERE B is BlogEntry, B entry_of BL, BL eid %%(blog)s, '
+                   'B eid %s %%(eid)s')
+            rset = self.req.execute(rql % (order, operator),
+                                    {'blog': self.entry_of[0].eid, 'eid': self.eid})
         else:
@@ -108,8 +108,7 @@
         else:
-            rql = ('Any B ORDERBY B ASC LIMIT 1 '
-                   'WHERE B is BlogEntry, B eid > %(eid)s')
-            rset = self.req.execute(rql, {'eid': self.eid})
-
+            rql = ('Any B ORDERBY B %s LIMIT 1 '
+                   'WHERE B is BlogEntry, B eid %s %%(eid)s')
+            rset = self.req.execute(rql % (order, operator), {'eid': self.eid})
         if rset:
             return rset.get_entity(0,0)
 
@@ -113,4 +112,7 @@
         if rset:
             return rset.get_entity(0,0)
 
+    def next_entity(self):
+        return self._sibling_entry('ASC', '>')
+
     def previous_entity(self):
@@ -116,13 +118,2 @@
     def previous_entity(self):
-        if self.entry_of:
-            rql = ('Any B ORDERBY B DESC LIMIT 1 '
-                   'WHERE B is BlogEntry, B entry_of BL, BL eid %(blog)s, '
-                   'B eid < %(eid)s')
-            rset = self.req.execute(rql, {'blog': self.entry_of[0].eid, 'eid': self.eid})
-        else:
-            rql = ('Any B ORDERBY B DESC LIMIT 1 '
-                   'WHERE B is BlogEntry, B eid < %(eid)s')
-            rset = self.req.execute(rql, {'eid': self.eid})
-        if rset:
-            return rset.get_entity(0,0)
-
+        return self._sibling_entry('DESC', '<')