added new fields to KyuDanRanking that allow to pick up the calculation from the last state of the KyuDanRanking.

last_hanchan_date: it contains the start of the latest hanchan content for this players ranking.
wins_in_row: to save the currents wins in a row

Added option to calcuclate rankings until a given datetime.

src/mahjong_ranking/models.py

@@ -4,7 +4,7 @@
 # werden dürfen.
 
 from __future__ import division
-
+from datetime import datetime, time
 from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.core.urlresolvers import reverse
@@ -345,10 +345,10 @@ class KyuDanRanking(models.Model):
     legacy_hanchan_count = models.PositiveIntegerField(default=0)
     legacy_dan_points = models.PositiveIntegerField(default=0)
     legacy_kyu_points = models.PositiveIntegerField(default=0)
-    wins_in_a_row = 0
+    wins_in_a_row = models.PositiveIntegerField(default=0)
+    last_hanchan_date = models.DateTimeField(blank=True, null=True)
     objects = managers.KyuDanRankingManager()
 
-
     class Meta(object):
         ordering = ('-dan_points', 'dan', '-kyu_points')
         verbose_name = _(u'Kyū/Dan Ranking')
@@ -436,28 +436,43 @@ class KyuDanRanking(models.Model):
         else:
             return reverse('player-kyu-score', args=[self.user.username])
 
-    def recalculate(self, hanchan_start=None):
+    def calculate(self, since=None, until=None, force_recalc=False):
         """
         Fetches all valid Hanchans from this Player and recalculates his
         Kyu/Dan Ranking.
         """
-        self.dan = None
-        self.dan_points = self.legacy_dan_points or 0
-        self.kyu = None
-        self.kyu_points = self.legacy_kyu_points or 0
-        self.hanchan_count = self.legacy_hanchan_count or 0
-        self.good_hanchans = 0
-        self.won_hanchans = 0
-        self.update_rank()
-
+        valid_hanchans = Hanchan.objects.confirmed_hanchans(user=self.user)
+        valid_hanchans = valid_hanchans.order_by('start')
+        if since and self.last_hanchan_date and since < self.last_hanchan_date:
+            force_recalc = True
+        if until and self.last_hanchan_date and until < self.last_hanchan_date:
+            force_recalc = True
+        if force_recalc:
+            # Setze alles auf die legacy Werte und berechne alles von neuem.
+            self.dan = None
+            self.dan_points = self.legacy_dan_points or 0
+            self.kyu = None
+            self.kyu_points = self.legacy_kyu_points or 0
+            self.hanchan_count = self.legacy_hanchan_count or 0
+            self.good_hanchans = 0
+            self.won_hanchans = 0
+            self.update_rank()
+            self.last_hanchan_date = None
+            if self.legacy_date:
+                since = timezone.make_aware(
+                    datetime.combine(self.legacy_date, time(0, 0, 0)))
+            else:
+                since = None
+        else:
+            since = self.last_hanchan_date or self.legacy_date
         LOGGER.info(
-            "recalculating Kyu/Dan points for %s since %s...",
-            self.user, str(hanchan_start)
+            "recalculating Kyu/Dan points for %(user)s since %(since)s...",
+            {'user': self.user, 'since': str(since)}
         )
-        valid_hanchans = Hanchan.objects.confirmed_hanchans(
-            user=self.user).order_by('start')
-        if self.legacy_date:
-            valid_hanchans = valid_hanchans.filter(start__gt=self.legacy_date)
+        if since:
+            valid_hanchans = valid_hanchans.filter(start__gt=since)
+        if until:
+            valid_hanchans = valid_hanchans.filter(start__lte=until)
 
         """ TODO: Hanchan Punkte nur neu berechnen wenn sie nach hachan_start
         lagen. Es müssen aber alle durch die Schleife rennen, damit die Punkte
@@ -465,7 +480,7 @@ class KyuDanRanking(models.Model):
         self.hanchan_count += valid_hanchans.count()
         for hanchan in valid_hanchans:
             hanchan.get_playerdata(self.user)
-            if hanchan_start and hanchan_start < hanchan.start:
+            if since and since < hanchan.start:
                 self.dan_points += hanchan.dan_points or 0
                 self.kyu_points += hanchan.kyu_points or 0
                 self.update_rank()
@@ -482,6 +497,7 @@ class KyuDanRanking(models.Model):
                 hanchan.save(recalculate=False)
             self.won_hanchans += 1 if hanchan.placement == 1 else 0
             self.good_hanchans += 1 if hanchan.placement == 2 else 0
+            self.last_hanchan_date = hanchan.start
             LOGGER.debug(
                 'id: %(id)d, start: %(start)s, placement: %(placement)d, '
                 'score: %(score)d, kyu points: %(kyu_points)d, dan points: '
@@ -593,9 +609,9 @@ class SeasonRanking(models.Model):
     def get_absolute_url(self):
         return reverse('player-ladder-score', args=[self.user.username])
 
-    def recalculate(self):
+    def recalculate(self, until=None):
         season_hanchans = Hanchan.objects.season_hanchans(
-            user=self.user, season=self.season)
+            user=self.user, season=self.season, until=until)
         sum_placement = 0
         sum_score = 0
         self.placement = None