Implement+test filterBubble middleware

@Tirokk @ulfgebhardt @ogerly @mattwr18

This is interesting because I found out that `neo4j-graphql-js` allows
to customize graphql queries. If you define it, then it will merge the
other inputs and stuff on top of it. Fair enough!

backend/src/middleware/filterBubble/filterBubble.js

@@ -0,0 +1,12 @@
+import replaceParams from './replaceParams'
+
+const replaceFilterBubbleParams = async (resolve, root, args, context, resolveInfo) => {
+  args = await replaceParams(args, context)
+  return resolve(root, args, context, resolveInfo)
+}
+
+export default {
+  Query: {
+    Post: replaceFilterBubbleParams,
+  },
+}

backend/src/middleware/filterBubble/filterBubble.spec.js

@@ -0,0 +1,76 @@
+import { GraphQLClient } from 'graphql-request'
+import { host, login } from '../../jest/helpers'
+import Factory from '../../seed/factories'
+
+const factory = Factory()
+
+const currentUserParams = {
+  email: 'you@example.org',
+  name: 'This is you',
+  password: '1234',
+}
+const followedAuthorParams = {
+  id: 'u2',
+  email: 'followed@example.org',
+  name: 'Followed User',
+  password: '1234',
+}
+const randomAuthorParams = {
+  email: 'someone@example.org',
+  name: 'Someone else',
+  password: 'else',
+}
+
+beforeEach(async () => {
+  await Promise.all([
+    factory.create('User', currentUserParams),
+    factory.create('User', followedAuthorParams),
+    factory.create('User', randomAuthorParams),
+  ])
+  const [asYourself, asFollowedUser, asSomeoneElse] = await Promise.all([
+    Factory().authenticateAs(currentUserParams),
+    Factory().authenticateAs(followedAuthorParams),
+    Factory().authenticateAs(randomAuthorParams),
+  ])
+  await asYourself.follow({ id: 'u2', type: 'User' })
+  await asFollowedUser.create('Post', { title: 'This is the post of a followed user' })
+  await asSomeoneElse.create('Post', { title: 'This is some random post' })
+})
+
+afterEach(async () => {
+  await factory.cleanDatabase()
+})
+
+describe('FilterBubble middleware', () => {
+  describe('given an authenticated user', () => {
+    let authenticatedClient
+
+    beforeEach(async () => {
+      const headers = await login(currentUserParams)
+      authenticatedClient = new GraphQLClient(host, { headers })
+    })
+
+    describe('no filter bubble', () => {
+      it('returns all posts', async () => {
+        const query = '{ Post( filterBubble: {}) { title } }'
+        const expected = {
+          Post: [
+            { title: 'This is some random post' },
+            { title: 'This is the post of a followed user' },
+          ],
+        }
+        await expect(authenticatedClient.request(query)).resolves.toEqual(expected)
+      })
+    })
+
+    describe('filtering for posts of followed users only', () => {
+      it('returns only posts authored by followed users', async () => {
+        const query = '{ Post( filterBubble: { author: followed }) { title } }'
+        const expected = {
+          Post: [{ title: 'This is the post of a followed user' }],
+        }
+        await expect(authenticatedClient.request(query)).resolves.toEqual(expected)
+      })
+    })
+  })
+})

backend/src/middleware/index.js

@@ -13,6 +13,7 @@ import includedFields from './includedFieldsMiddleware'
 import orderBy from './orderByMiddleware'
 import validation from './validation'
 import notifications from './notifications'
+import filterBubble from './filterBubble/filterBubble'
 
 export default schema => {
   const middlewares = {
@@ -30,11 +31,13 @@ export default schema => {
     user: user,
     includedFields: includedFields,
     orderBy: orderBy,
+    filterBubble: filterBubble,
   }
 
   let order = [
     'permissions',
     'activityPub',
+    'filterBubble',
     'password',
     'dateTime',
     'validation',

backend/src/schema/types/type/Post.gql

@@ -1,3 +1,18 @@
+enum FilterBubbleAuthorEnum {
+  followed
+  all
+}
+
+input FilterBubble {
+  author: FilterBubbleAuthorEnum
+}
+
+type Query {
+  Post(
+    filterBubble: FilterBubble
+  ): [Post]
+}
+
 type Post {
   id: ID!
   activityId: String
@@ -40,4 +55,4 @@ type Post {
       RETURN COUNT(u) >= 1
     """
   )
-}
+}