[add]: ability to like books

Author: Stanislawa Kutyepov

app/books/migrations/0004_like.py

@@ -0,0 +1,24 @@
+# Generated by Django 3.2.6 on 2021-08-05 20:31
+
+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),
+        ('books', '0003_book_posted_by'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Like',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('book', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='likes', to='books.book')),
+                ('user', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+    ]

app/books/models.py

@@ -8,4 +8,9 @@ class Book(models.Model):
     description = models.TextField(blank=True)
     url = models.URLField()
     created_at = models.DateTimeField(auto_now_add=True)
-    posted_by = models.ForeignKey(get_user_model(), null=True, on_delete=models.CASCADE)
+    posted_by = models.ForeignKey(get_user_model(), null=True, on_delete=models.CASCADE)
+
+
+class Like(models.Model):
+    user = models.ForeignKey(get_user_model(), null=True, on_delete=models.CASCADE)
+    book = models.ForeignKey('books.Book', related_name='likes', on_delete=models.CASCADE)

app/books/schema.py

@@ -1,6 +1,7 @@
 import graphene 
 from graphene_django import DjangoObjectType
-from .models import Book
+from .models import Book, Like
+from users.schema import UserType
 
 
 class BookType(DjangoObjectType):
@@ -76,7 +77,32 @@ def mutate(self, info, book_id):
 
         return DeleteBook(book_id=book_id)
 
+class CreateLike(graphene.Mutation):
+    user = graphene.Field(UserType)
+    book = graphene.Field(BookType)
+
+    class Arguments:
+        book_id = graphene.Int(required=True)
+
+    def mutate(self, info, book_id):
+        user = info.context.user
+
+        if user.is_anonymous:
+            raise Exception("Login first")
+
+        book = Book.objects.get(id=book_id)
+        if not book:
+            raise Exception('Cannot find a book with id {}'.format(book_id))
+
+        Like.objects.create(
+            user=user,
+            book=book
+        )
+
+        return CreateLike(user=user, book=book)
+
 class Mutation(graphene.ObjectType):
     create_book = CreateBook.Field()
     update_book = UpdateBook.Field()
-    delete_book = DeleteBook.Field()
+    delete_book = DeleteBook.Field()
+    create_like = CreateLike.Field()