From 7075cef8f99f715fbf77a67e45bbc1e7edcada42 Mon Sep 17 00:00:00 2001
From: Eugen Rochko <eugen@zeonfederated.com>
Date: Sat, 15 Oct 2016 16:43:52 +0200
Subject: [PATCH] Adding sort by node rank to follow suggestions and fallback
 to most influential users

---
 .travis.yml                     |  6 ++++-
 README.md                       |  3 +++
 app/models/follow_suggestion.rb | 43 ++++++++++++++++++++++++++++++---
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index a2e309d984..f096c08be6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,7 @@ env:
     - RAILS_ENV=test
     - NEO4J_HOST=localhost
     - NEO4J_PORT=7575
+    - TRAVIS_NODE_VERSION="4"
 
 addons:
   postgresql: 9.4
@@ -21,6 +22,7 @@ services:
 bundler_args: --without development production --retry=3 --jobs=3
 
 install:
+  - rm -rf ~/.nvm && git clone https://github.com/creationix/nvm.git ~/.nvm && (cd ~/.nvm && git checkout `git describe --abbrev=0 --tags`) && source ~/.nvm/nvm.sh && nvm install $TRAVIS_NODE_VERSION
   - npm install -g npm@3
   - npm install -g yarn
   - bundle install
@@ -29,4 +31,6 @@ install:
 before_script:
   - bundle exec rails db:create db:migrate
 
-script: bundle exec rspec
+script:
+  - bundle exec rspec
+  - npm test
diff --git a/README.md b/README.md
index aa5801c5d7..0ca699212c 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,8 @@ Consult the example configuration file, `.env.production.sample` for the full li
 
 - PostgreSQL
 - Redis
+- Neo4J (optional)
+  - GraphAware NodeRank
 
 ## Running with Docker and Docker-Compose
 
@@ -86,6 +88,7 @@ The container has two volumes, for the assets and for user uploads. The default
 - `rake mastodon:push:clear` unsubscribes from PuSH notifications for remote users that have no local followers. You may not want to actually do that, to keep a fuller footprint of the fediverse or in case your users will soon re-follow
 - `rake mastodon:push:refresh` re-subscribes PuSH for expiring remote users, this should be run periodically from a cronjob and quite often as the expiration time depends on the particular hub of the remote user
 - `rake mastodon:feeds:clear` removes all timelines, which forces them to be re-built on the fly next time a user tries to fetch their home/mentions timeline. Only for troubleshooting
+- `rake mastodon:graphs:sync` re-imports all follow relationships into Neo4J. Only for troubleshooting
 
 Running any of these tasks via docker-compose would look like this:
 
diff --git a/app/models/follow_suggestion.rb b/app/models/follow_suggestion.rb
index 108a948a29..4f06db69cf 100644
--- a/app/models/follow_suggestion.rb
+++ b/app/models/follow_suggestion.rb
@@ -1,10 +1,47 @@
 class FollowSuggestion
   def self.get(for_account_id, limit = 6)
     neo = Neography::Rest.new
-    account_ids = neo.execute_query('START a=node:account_index(Account={id}) MATCH (a)-[:follows]->(b)-[:follows]->(c) WHERE a <> c AND NOT (a)-[:follows]->(c) RETURN DISTINCT c.account_id', id: for_account_id)
-    Account.where(id: account_ids['data'].map(&:first) - Block.where(account_id: for_account_id).pluck(:target_account_id)).limit(limit) unless account_ids.empty?
+
+    query = <<END
+START a=node:account_index(Account={id})
+MATCH (a)-[:follows]->(b)-[:follows]->(c)
+WHERE a <> c
+AND NOT (a)-[:follows]->(c)
+RETURN DISTINCT c.account_id
+ORDER BY c.nodeRank
+LIMIT {limit}
+END
+
+    results = neo.execute_query(query, id: for_account_id, limit: limit)
+
+    return fallback(for_account_id, limit) if results.empty?
+
+    map_to_accounts(for_account_id, results)
   rescue Neography::NeographyError, Excon::Error::Socket => e
     Rails.logger.error e
-    []
+    return []
+  end
+
+  private
+
+  def self.fallback(for_account_id, limit)
+    neo     = Neography::Rest.new
+    query   = 'MATCH (a) WHERE a.account_id <> {id} RETURN a.account_id ORDER BY a.nodeRank DESC LIMIT {limit}'
+    results = neo.execute_query(query, id: for_account_id, limit: limit)
+
+    map_to_accounts(for_account_id, results)
+  rescue Neography::NeographyError, Excon::Error::Socket => e
+    Rails.logger.error e
+    return []
+  end
+
+  def self.map_to_accounts(for_account_id, results)
+    return [] if results.empty?
+
+    account_ids  = results['data'].map(&:first)
+    blocked_ids  = Block.where(account_id: for_account_id).pluck(:target_account_id)
+    accounts_map = Account.where(id: account_ids - blocked_ids).map { |a| [a.id, a] }.to_h
+
+    account_ids.map { |id| accounts_map[id] }.compact
   end
 end