feat(rating-articles): Users can rate articles

- create ratings app in apps folder
- Add ratings app to settings.py file
- Add model for ratings in models.py
- Create rating serializer in serializer.py
- Create corresponding views in views.py
- Add urls.py file to register the views
- Include the rating urls file in main urls.py file

[Starts #162949218]

authors/apps/articles/migrations/0001_initial.py

@@ -1,4 +1,4 @@
-# Generated by Django 2.1.4 on 2019-01-30 06:35
+# Generated by Django 2.1.4 on 2019-01-30 15:26
 
 from django.conf import settings
 from django.db import migrations, models

authors/apps/articles/migrations/0002_auto_20190130_1803.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.1.4 on 2019-01-30 18:03
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('articles', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='article',
+            name='updated_at',
+            field=models.DateTimeField(auto_now=True),
+        ),
+    ]

authors/apps/articles/migrations/0003_rating.py

@@ -0,0 +1,25 @@
+# Generated by Django 2.1.4 on 2019-01-31 08:06
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('articles', '0002_auto_20190130_1803'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Rating',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('rating', models.FloatField(default=0)),
+                ('article', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='articles.Article')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+    ]

authors/apps/articles/models.py

@@ -5,8 +5,6 @@
 from django.db.models.signals import pre_save
 
 from .utils import get_unique_slug
-from django.db.models.signals import pre_save
-
 # local imports
 from ..authentication.models import User
 
@@ -59,7 +57,7 @@ class Article(models.Model):
     description = models.CharField(max_length=230, blank=False)
     body = models.TextField(blank=False)
     created_at = models.DateTimeField(auto_now_add=True)
-    updated_at = models.DateField(auto_now=True)
+    updated_at = models.DateTimeField(auto_now=True)
     votes = GenericRelation(LikeDislike, related_query_name='articles')
 
     def __str__(self):
@@ -102,3 +100,12 @@ class FavoriteArticle(models.Model):
 
     def __str__(self):
         return "{}".format(self.article)
+
+
+class Rating(models.Model):
+    """
+    Rating model
+    """
+    rating = models.FloatField(null=False, default=0)
+    article = models.ForeignKey(Article, on_delete=models.CASCADE)
+    user = models.ForeignKey(User, on_delete=models.CASCADE)

authors/apps/articles/serializers.py

@@ -3,23 +3,28 @@
 from authors.apps.profiles.models import UserProfile
 from authors.apps.articles.models import FavoriteArticle
 from authors.apps.profiles.serializers import ProfileSerialiazer
+from ..utils import get_article_rating
 
 
 class ArticleSerializer(serializers.ModelSerializer):
     author = serializers.SerializerMethodField()
     body = serializers.CharField(required=True)
     title = serializers.CharField(required=True)
     description = serializers.CharField(required=True)
+    rating = serializers.SerializerMethodField(read_only=True)
 
     def get_author(self, article):
         author = ProfileSerialiazer(article.author.profiles)
         return author.data
 
+    def get_rating(self, article):
+        return get_article_rating(article)
+
     class Meta:
         model = Article
 
         fields = ['slug', 'title', 'description', 'body', 'created_at',
-                  'updated_at', 'author']
+                  'updated_at', 'author', 'rating']
 
     def validate(self, data):
 
@@ -49,15 +54,19 @@ class UpdateArticleSerializer(serializers.ModelSerializer):
     body = serializers.CharField(required=True)
     title = serializers.CharField(required=True)
     description = serializers.CharField(required=True)
+    rating = serializers.SerializerMethodField()
 
     def get_author(self, article):
         author = ProfileSerialiazer(article.author.profiles)
         return author.data
 
+    def get_rating(self, article):
+        return get_article_rating(article)
+
     class Meta:
         model = Article
         fields = ['slug', 'title', 'description', 'body', 'created_at',
-                  'updated_at', 'author']
+                  'updated_at', 'author', 'rating']
 
 
 class CommentSerializer(serializers.ModelSerializer):

authors/apps/ratings/migrations/0001_initial.py

@@ -0,0 +1,27 @@
+# Generated by Django 2.1.4 on 2019-01-30 15:26
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ('articles', '0001_initial'),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Rating',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('rating', models.FloatField(default=0)),
+                ('article', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='articles.Article')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+    ]

authors/apps/ratings/migrations/0002_auto_20190131_0806.py

@@ -0,0 +1,24 @@
+# Generated by Django 2.1.4 on 2019-01-31 08:06
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('ratings', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='rating',
+            name='article',
+        ),
+        migrations.RemoveField(
+            model_name='rating',
+            name='user',
+        ),
+        migrations.DeleteModel(
+            name='Rating',
+        ),
+    ]

authors/apps/ratings/responses.py

@@ -0,0 +1,26 @@
+error_messages = {
+    'maximum_rating': 'The maximum allowed rating is 5',
+    'minimum_rating': 'The minimum allowed rating is 1',
+    'not_exist': {
+        'message': 'Article not found'
+    },
+    'unauthorized': {
+        'error': 'You cannot rate your own article'
+    },
+    'not_rated': 'Sorry, there are no ratings yet',
+    'required': 'Please provide a valid rating',
+    'login': 'Please login to rate an article'
+}
+
+success_messages = {
+    'message': 'article rating',
+    'data': {
+        'article': 'another-post',
+        'average_rating': 3.0,
+        'rating': 3
+    }
+}
+
+successful_submission = {
+    'message': 'Rating submitted successfully!'
+}

authors/apps/ratings/serializers.py

@@ -0,0 +1,41 @@
+"""
+Serializer module for the ratings model
+"""
+from django.core.validators import MinValueValidator, MaxValueValidator
+from django.db.models import Avg
+from rest_framework import serializers
+
+from .responses import error_messages
+from ..articles.models import Rating
+
+
+class RatingSerializer(serializers.ModelSerializer):
+    """
+    Serializer for the rating model
+    """
+    rating = serializers.IntegerField(
+        required=True,
+        validators=[
+            MaxValueValidator(5, message=error_messages['maximum_rating']),
+            MinValueValidator(1, message=error_messages['minimum_rating'])
+        ],
+        error_messages={
+            'required': 'Please provide a valid rating'
+        }
+    )
+    article = serializers.SerializerMethodField()
+    average_rating = serializers.SerializerMethodField()
+
+    def get_average_rating(self, rating_object):
+        """Returns an average rating for an article"""
+        average_rating = Rating.objects.filter(
+            article=rating_object.article.id).aggregate(Avg('rating'))
+        return round(average_rating['rating__avg'], 1)
+
+    def get_article(self, rating_object):
+        """Returns the slug of the article from the ratings table"""
+        return rating_object.article.slug
+
+    class Meta:
+        model = Rating
+        fields = ('article', 'average_rating', 'rating')

authors/apps/ratings/urls.py

@@ -0,0 +1,11 @@
+from django.urls import path
+from .views import ArticleRatingAPIView
+
+app_name = 'ratings'
+
+article_rating = ArticleRatingAPIView.as_view()
+
+urlpatterns = [
+    path('articles/<slug>/rate-article', article_rating,
+         name='article_rating'),
+]

authors/apps/ratings/views.py

@@ -0,0 +1,101 @@
+from rest_framework import status
+from rest_framework.exceptions import NotFound
+from rest_framework.generics import (
+    GenericAPIView
+)
+from rest_framework.permissions import (
+    IsAuthenticatedOrReadOnly
+)
+from rest_framework.response import Response
+
+from .responses import (
+    error_messages, successful_submission, success_messages
+)
+from .serializers import RatingSerializer
+from ..articles.models import Article, Rating
+from ..utils import get_article_rating
+
+
+class ArticleRatingAPIView(GenericAPIView):
+    queryset = Rating.objects.all()
+    serializer_class = RatingSerializer
+    permission_classes = (IsAuthenticatedOrReadOnly,)
+
+    @staticmethod
+    def get_article(slug):
+        """Returns the first record in the articles table with the slug"""
+        article = Article.objects.all().filter(slug=slug).first()
+        return article
+
+    def post(self, request, slug):
+        """POST Request to rate an article"""
+        rating = request.data
+        article = self.get_article(slug)
+
+        if check_article_exists(article):
+            return check_article_exists(article)
+
+        if request.user.id == article.author.id:
+            return Response(
+                error_messages['unauthorized'],
+                status=status.HTTP_403_FORBIDDEN
+            )
+        try:
+            current_article_rating = Rating.objects.get(
+                user=request.user.id,
+                article=article.id
+            )
+            serializer = self.serializer_class(
+                current_article_rating, data=rating)
+        except Rating.DoesNotExist:
+            serializer = self.serializer_class(data=rating)
+
+        serializer.is_valid(raise_exception=True)
+        serializer.save(user=request.user, article=article)
+        return Response({
+            'message': successful_submission['message'],
+            'data': serializer.data
+        }, status=status.HTTP_201_CREATED)
+
+    def get(self, request, slug):
+        """Returns an article's ratings"""
+        article = self.get_article(slug)
+        rating = None
+
+        # check if the article exists
+        if check_article_exists(article):
+            return check_article_exists(article)
+
+        # if the user is authenticated fetch their ratings
+        if request.user.is_authenticated:
+            try:
+                rating = Rating.objects.get(
+                    user=request.user, article=article
+                )
+            except Rating.DoesNotExist:
+                raise NotFound(
+                    detail=error_messages['not_rated']
+                )
+        # for unauthenticated users
+        if rating is None:
+            average_rating = get_article_rating(article)
+
+            if request.user.is_authenticated is False:
+                return Response({
+                    'article': article.slug,
+                    'average_rating': average_rating,
+                    'rating': error_messages['login']
+                }, status=status.HTTP_200_OK)
+        serializer = self.serializer_class(rating)
+        return Response({
+            'message': success_messages['message'],
+            'data': serializer.data
+        }, status=status.HTTP_200_OK)
+
+
+def check_article_exists(article):
+    if not article:
+        return Response(
+            error_messages['not_exist'],
+            status=status.HTTP_404_NOT_FOUND
+        )

authors/apps/utils.py

@@ -0,0 +1,20 @@
+from authors.apps.articles.models import Rating
+from django.db.models import Avg
+
+
+def get_article_rating(article):
+    """
+    Returns the average rating of an article
+    """
+
+    # searches for the article with the given slug
+    # and returns the average ratings
+    average_rating = Rating.objects.filter(
+        article__slug=article.slug).aggregate(Avg('rating'))
+    response = average_rating['rating__avg']
+
+    # set the average rating to 0 if the article has not been rated
+    if average_rating['rating__avg'] is None:
+        response = average_rating['rating__avg'] = 0
+        return response
+    return round(response, 1)

authors/settings.py

@@ -54,6 +54,7 @@
     'authors.apps.core',
     'authors.apps.profiles',
     'authors.apps.articles',
+    'authors.apps.ratings'
 
 ]