From b88a61e48960e38c3c8669aa47bcb0dd142fdf6c Mon Sep 17 00:00:00 2001
From: Muhammed Zafar <muhammedzafar.mm@gmail.com>
Date: Tue, 17 Oct 2023 22:01:04 +0530
Subject: [PATCH] [OPTIM] Leaderboard patches (#1348)

---
 api/leaderboard/leaderboard_view.py | 34 ++++++++++++++++-------------
 api/leaderboard/serializers.py      | 26 +++++++++++++++++-----
 2 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/api/leaderboard/leaderboard_view.py b/api/leaderboard/leaderboard_view.py
index 3f206840..65811990 100644
--- a/api/leaderboard/leaderboard_view.py
+++ b/api/leaderboard/leaderboard_view.py
@@ -1,7 +1,8 @@
-from django.db.models import Sum, F, Value, OuterRef, Subquery, Count, Q
+from django.db.models import Sum, F, Value, OuterRef, Subquery, Count, Q, Prefetch
 from django.db.models.functions import Concat, Coalesce
 from rest_framework.views import APIView
 import datetime
+from . import serializers
 
 from db.organization import Organization, UserOrganizationLink
 from db.user import User
@@ -12,14 +13,6 @@
 
 class StudentsLeaderboard(APIView):
     def get(self, request):
-        user_college = (
-            UserOrganizationLink.objects.filter(
-                user_id=OuterRef("id"), org__org_type=OrganizationType.COLLEGE.value
-            )
-            .order_by("id")
-            .values("org__title")[:1]
-        )
-
         students_leaderboard = (
             User.objects.filter(
                 user_organization_link_user__org__org_type=OrganizationType.COLLEGE.value,
@@ -28,14 +21,25 @@ def get(self, request):
                 active=True,
             )
             .distinct()
-            .values(
-                total_karma=F("wallet_user__karma"),
-                full_name=Concat(F("first_name"), Value(" "), F("last_name")),
-                institution=Subquery(user_college),
+            .select_related("wallet_user")
+            .prefetch_related(
+                Prefetch(
+                    "user_organization_link_user",
+                    queryset=UserOrganizationLink.objects.filter(
+                        org__org_type=OrganizationType.COLLEGE.value
+                    ).select_related("org"),
+                    to_attr="colleges"
+                )
             )
-            .order_by("-total_karma")[:20]
+            .order_by("-wallet_user__karma")[:20]
+        )
+        serialized_students_leaderboard = serializers.StudentLeaderboardSerializer(
+            students_leaderboard, many=True
         )
-        return CustomResponse(response=students_leaderboard).get_success_response()
+
+        return CustomResponse(
+            response=serialized_students_leaderboard.data
+        ).get_success_response()
 
 
 class StudentsMonthlyLeaderboard(APIView):
diff --git a/api/leaderboard/serializers.py b/api/leaderboard/serializers.py
index fb591aba..e35a4dc3 100644
--- a/api/leaderboard/serializers.py
+++ b/api/leaderboard/serializers.py
@@ -5,6 +5,7 @@
 
 from db.organization import UserOrganizationLink
 from db.task import KarmaActivityLog
+from db.user import User
 from utils.types import OrganizationType
 from utils.utils import DateTimeUtils
 
@@ -46,12 +47,12 @@ def get_active_members(self, obj):
 
     def get_total_karma(self, obj):
         return (
-                obj.org.user_organization_link_org.filter(
-                    org__org_type=OrganizationType.COLLEGE.value,
-                    verified=True,
-                    user__wallet_user__isnull=False,
-                ).aggregate(total_karma=Sum("user__wallet_user__karma"))["total_karma"]
-                or 0
+            obj.org.user_organization_link_org.filter(
+                org__org_type=OrganizationType.COLLEGE.value,
+                verified=True,
+                user__wallet_user__isnull=False,
+            ).aggregate(total_karma=Sum("user__wallet_user__karma"))["total_karma"]
+            or 0
         )
 
     def get_rank(self, obj):
@@ -74,3 +75,16 @@ def get_rank(self, obj):
             keys_list = list(sorted_rank_dict.keys())
             position = keys_list.index(obj.org.id)
             return position + 1
+
+
+class StudentLeaderboardSerializer(serializers.ModelSerializer):
+    institution = serializers.SerializerMethodField()
+    total_karma = serializers.IntegerField(source="wallet_user.karma", default=0)
+    full_name = serializers.CharField(source="fullname")
+
+    def get_institution(self, user):
+        return user.colleges[0].org.title if user.colleges else None
+
+    class Meta:
+        model = User
+        fields = ["full_name", "total_karma", "institution"]