From c0238468aae4e8c26e0fb1b0d5bdea2c9aa000ae Mon Sep 17 00:00:00 2001
From: Scott Yargeau <scottyargeau@gmail.com>
Date: Mon, 2 Jul 2018 22:25:24 -0400
Subject: [PATCH] Increase ranking efficiency

---
 leaderboard/models.py              | 26 +++++++++++++++++++-------
 leaderboard/rankings.py            |  8 +++++++-
 leaderboard/tests/test_models.py   |  1 +
 leaderboard/tests/test_rankings.py |  9 +++++++++
 4 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/leaderboard/models.py b/leaderboard/models.py
index f93e84d..749a361 100644
--- a/leaderboard/models.py
+++ b/leaderboard/models.py
@@ -57,31 +57,43 @@ def date(self):
     
     @property
     def description(self):
+        """Description of who defeated who and what the score was."""
         description = (
             f'{self.date}: {self.winner} defeated {self.loser} {self.score}'
         )
         return description
 
     def save(self, *args, **kwargs):
-        super().save(*args, **kwargs)
-        PlayerRating.generate_ratings()
+        if self.id:  # occurs when the match already exists and is being updated
+            super().save(*args, **kwargs)
+            PlayerRating.generate_ratings()
+        else:  # occurs when it's a new match being added
+            super().save(*args, **kwargs)
+            elo_rating = EloRating(use_current_ratings=True)
+            elo_rating.update_ratings(self.winner, self.loser)
+            PlayerRating.add_ratings(elo_rating)
 
 
 class PlayerRating(models.Model):
     """Table for keeping track of a player's rating."""
     player = models.OneToOneField(Player, default=None, primary_key=True)
     rating = models.IntegerField(default=None, blank=False)
+    
+    @staticmethod
+    def add_ratings(elo_rating: EloRating):
+        """Add ratings to database given EloRating object."""
+        PlayerRating.objects.all().delete()
+        for player, rating in elo_rating.ratings.items():
+            PlayerRating.objects.create(player=player, rating=rating)
 
     @staticmethod
     def generate_ratings():
-        """Generate ratings from all previous matches."""
-        PlayerRating.objects.all().delete()
-        matches = Match.objects.all().order_by('datetime')
+        """Generate ratings from scratch based on all previous matches."""
         elo_rating = EloRating()
+        matches = Match.objects.all().order_by('datetime')
         for match in matches:
             elo_rating.update_ratings(match.winner, match.loser)
-        for player, rating in elo_rating.ratings.items():
-            PlayerRating.objects.create(player=player, rating=rating)
+        PlayerRating.add_ratings(elo_rating)
 
     @property
     def games_played(self):
diff --git a/leaderboard/rankings.py b/leaderboard/rankings.py
index ad46a89..f36d2dc 100644
--- a/leaderboard/rankings.py
+++ b/leaderboard/rankings.py
@@ -1,3 +1,5 @@
+import leaderboard.models
+
 DEFAULT_ELO_RATING = 1000
 DEFAULT_K_FACTOR = 30
 
@@ -5,8 +7,12 @@
 class EloRating(object):
     """Uses Elo rating system to rate players."""
 
-    def __init__(self):
+    def __init__(self, use_current_ratings=False):
         self.ratings = {}
+        if use_current_ratings:
+            rated_players = leaderboard.models.PlayerRating.objects.all()
+            for rated_player in rated_players:
+                self.ratings[rated_player.player] = rated_player.rating
         
     def get_rating(self, player):
         """Return the rating of the specified player."""
diff --git a/leaderboard/tests/test_models.py b/leaderboard/tests/test_models.py
index fe00420..cb25484 100644
--- a/leaderboard/tests/test_models.py
+++ b/leaderboard/tests/test_models.py
@@ -238,6 +238,7 @@ def test_generate_ratings_in_order(self):
             losing_score=19,
             datetime=pytz.utc.localize(datetime(2000, 1, 1))
         )
+        PlayerRating.generate_ratings()
         ranking1 = PlayerRating.objects.get(pk=self.player1.id)
         ranking2 = PlayerRating.objects.get(pk=self.player2.id)
         self.assertGreater(ranking2.rating, ranking1.rating)
diff --git a/leaderboard/tests/test_rankings.py b/leaderboard/tests/test_rankings.py
index 072a605..5eeacbc 100644
--- a/leaderboard/tests/test_rankings.py
+++ b/leaderboard/tests/test_rankings.py
@@ -1,6 +1,7 @@
 from django.test import TestCase
 
 from leaderboard.rankings import EloRating, DEFAULT_ELO_RATING, DEFAULT_K_FACTOR
+from leaderboard.models import PlayerRating, Player
 
 
 class EloRatingTest(TestCase):
@@ -69,3 +70,11 @@ def test_rating_updates(self):
         expected_loser_rating = DEFAULT_ELO_RATING - DEFAULT_K_FACTOR * 0.5
         self.assertEqual(winner_rating, expected_winner_rating)
         self.assertEqual(loser_rating, expected_loser_rating)
+
+    def test_use_current_rating(self):
+        """Test that the EloRating class can use current ratings."""
+        player = Player.objects.create(first_name='Bob', last_name='Hope')
+        test_rating = 1013
+        rated_player = PlayerRating.objects.create(player=player, rating=test_rating)
+        rating = EloRating(use_current_ratings=True)
+        self.assertEqual(test_rating, rating.get_rating(player))