feat(rating): Users should be able to rate an article

- Enable users to rate an article authored byu others
- Enable a user to modify his rating on an article

[Finishes  #159952007]

authors/apps/articles/models.py

@@ -4,6 +4,7 @@ class to declare an article
 """
 
 from django.db import models
+from django.db.models import Avg
 from django.utils import timezone
 
 from authors.apps.articles.utils import generate_slug
@@ -17,7 +18,7 @@ class Article(models.Model):
     """
     slug = models.SlugField(max_length=100, unique=True)
 
-    author = models.ForeignKey(User, on_delete=models.CASCADE)
+    author = models.ForeignKey(User, on_delete=models.CASCADE, related_name="articles", null=True)
 
     title = models.CharField(max_length=255, null=False, blank=False,
                              error_messages={"required": "Write a short title for your article."})
@@ -54,6 +55,28 @@ def save(self, *args, **kwargs):
 
         super(Article, self).save(*args, **kwargs)
 
+    @property
+    def average_rating(self):
+        """
+        calculates the average rating of the article.
+        :return:
+        """
+        ratings = self.scores.all().aggregate(score=Avg("score"))
+        return float('%.2f' % (ratings["score"] if ratings['score'] else 0))
+
     class Meta:
         get_latest_by = 'created_at'
         ordering = ['-created_at', 'author']
+
+
+class Rating(models.Model):
+    """
+    Model for creating article ratings or votes
+    """
+    article = models.ForeignKey(Article, related_name="scores", on_delete=models.CASCADE)
+    rated_by = models.ForeignKey(User, on_delete=models.CASCADE, related_name="scores", null=True)
+    rated_at = models.DateTimeField(auto_created=True, default=timezone.now, auto_now=False)
+    score = models.DecimalField(max_digits=4, decimal_places=2)
+
+    class Meta:
+        ordering = ('-score',)

authors/apps/articles/renderer.py

@@ -29,7 +29,8 @@ def render(self, data, accepted_media_type=None, renderer_context=None):
         if val and isinstance(val, list) and len(val) is 1:
             val = val[0]
 
-        data.update({"results": val})
+        if val is not None:
+            data.update({"results": val})
 
         errors = data.get('errors', None)
 

authors/apps/articles/serializers.py

@@ -5,10 +5,9 @@
 from rest_framework.pagination import PageNumberPagination
 
 from authors.apps.articles.exceptions import NotFoundException
-from authors.apps.articles.models import Article
+from authors.apps.articles.models import Article, Rating
 from authors.apps.articles.utils import get_date
 from authors.apps.authentication.models import User
-from authors.apps.authentication.serializers import UserSerializer
 from authors.apps.profiles.models import UserProfile
 from authors.apps.profiles.serializers import UserProfileSerializer
 
@@ -19,6 +18,7 @@ class ArticleSerializer(serializers.ModelSerializer):
     """
 
     author = serializers.PrimaryKeyRelatedField(queryset=User.objects.all(), required=False)
+    user_rating = serializers.CharField(source='author.average_rating', required=False)
     slug = serializers.CharField(read_only=True)
 
     def create(self, validated_data):
@@ -78,7 +78,7 @@ class behaviours
         """
         model = Article
         # noinspection SpellCheckingInspection
-        fields = ('slug', 'title', 'description', 'body', 'created_at',
+        fields = ('slug', 'title', 'description', 'body', 'created_at', 'average_rating', 'user_rating',
                   'updated_at', 'favorited', 'favorites_count', 'photo_url', 'author')
 
 
@@ -104,3 +104,78 @@ def get_paginated_response(self, data):
             'count': self.page.paginator.count,
             'results': data
         }
+
+
+class RatingSerializer(serializers.ModelSerializer):
+    """
+    Define action logic for an article rating
+    """
+    article = serializers.PrimaryKeyRelatedField(queryset=Article.objects.all())
+    rated_at = serializers.DateTimeField(read_only=True)
+    rated_by = serializers.PrimaryKeyRelatedField(queryset=User.objects.all())
+    score = serializers.DecimalField(required=True, max_digits=4, decimal_places=2)
+
+    @staticmethod
+    def update_request_data(data, slug, user: User):
+        """
+        :param user:
+        :param slug:
+        :param data:
+        :return:
+        """
+        try:
+            article = Article.objects.get(slug__exact=slug)
+        except Article.DoesNotExist:
+            raise NotFoundException("Article is not found.")
+
+        if article.author == user:
+            raise serializers.ValidationError({
+                "article": ["You can not rate your self"]
+            })
+
+        score = data.get("score", 0)
+        if score > 5 or score < 0:
+            raise serializers.ValidationError({
+                "score": ["Score value must not go below `0` and not go beyond `5`"]
+            })
+
+        data.update({"article": article.pk})
+        data.update({"rated_by": user.pk})
+        return data
+
+    def create(self, validated_data):
+        """
+        :param validated_data:
+        :return:
+        """
+        rated_by = validated_data.get("rated_by", None)
+        article = validated_data.get("article", None)
+        score = validated_data.get("score", 0)
+
+        try:
+            rating = Rating.objects.get(rated_by=rated_by, article__slug=article.slug)
+        except Rating.DoesNotExist:
+            return Rating.objects.create(**validated_data)
+
+        rating.score = score
+        rating.save()
+        return rating
+
+    def to_representation(self, instance):
+        """
+        :param instance:
+        :return:
+        """
+        response = super().to_representation(instance)
+
+        response['article'] = instance.article.slug
+        response['rated_by'] = instance.rated_by.username
+        response['average_rating'] = instance.article.average_rating
+        return response
+
+    class Meta:
+        """
+        class behaviours
+        """
+        model = Rating
+        fields = ("score", "rated_by", "rated_at", "article")

authors/apps/articles/tests/test_articles.py

@@ -3,8 +3,7 @@
 """
 import json
 
-import unittest
-
+from django.test import TestCase
 from rest_framework import status
 from rest_framework.test import APIClient
 
@@ -13,7 +12,7 @@
 from .test_data import TestData
 
 
-class Tests(unittest.TestCase, TestData):
+class Tests(TestCase, TestData):
 
     def setUp(self):
         """

authors/apps/articles/tests/test_models.py

@@ -1,16 +1,15 @@
 """
 test models
 """
-import unittest
-
+from django.test import TestCase
 from rest_framework.test import APIClient
 
 from authors.apps.articles.models import Article
 from authors.apps.authentication.models import User
 
 
 # noinspection SpellCheckingInspection
-class Tests(unittest.TestCase):
+class Tests(TestCase):
 
     def setUp(self):
         """