add helper function to filter invisible posts

backend/src/schema/resolvers/helpers/filterInvisiblePosts.js

@@ -0,0 +1,44 @@
+import { mergeWith, isArray } from 'lodash'
+
+const getInvisiblePosts = async (context) => {
+  const session = context.driver.session()
+  const readTxResultPromise = await session.readTransaction(async (transaction) => {
+    let cypher = ''
+    if (context.user) {
+      cypher = `
+        MATCH (post:Post)<-[:CANNOT_SEE]-(user:User { id: $userId })
+        RETURN collect(post.id) AS invisiblePostIds`
+    } else {
+      cypher = `
+        MATCH (post:Post)-[:IN]->(group:Group)
+        WHERE NOT group.groupType = 'public'
+        RETURN  collect(post.id) AS invisiblePostIds`
+    }
+    const invisiblePostIdsResponse = await transaction.run(cypher, { userId: context.user.id })
+    return invisiblePostIdsResponse.records.map((record) => record.get('invisiblePostIds'))
+  })
+  try {
+    const [invisiblePostIds] = readTxResultPromise
+    return invisiblePostIds
+  } finally {
+    session.close()
+  }
+}
+
+export const filterInvisiblePosts = async (params, context) => {
+  const invisiblePostIds = await getInvisiblePosts(context)
+  if (!invisiblePostIds.length) return params
+
+  params.filter = mergeWith(
+    params.filter,
+    {
+      id_not_in: invisiblePostIds,
+    },
+    (objValue, srcValue) => {
+      if (isArray(objValue)) {
+        return objValue.concat(srcValue)
+      }
+    },
+  )
+  return params
+}