Recommend posts on /posts/show based on voting patterns

.env

@@ -80,8 +80,8 @@
 # export DANBOORU_AWS_SQS_REGION=
 # export DANBOORU_IQDBS_AUTH_KEY=
 # export DANBOORU_IQDBS_SERVER=
-# export DANBOORU_CCS_SERVER=
-# export DANBOORU_CCS_KEY=
 # export DANBOORU_CLOUDFLARE_KEY=
 # export DANBOORU_CLOUDFLARE_EMAIL=
-# export DANBOORU_CLOUDFLARE_ZONE=
+# export DANBOORU_CLOUDFLARE_ZONE=
+# export DANBOORU_RECOMMENDER_KEY=
+# export DANBOORU_RECOMMENDER_SERVER=

app/logical/post_sets/similar.rb

@@ -0,0 +1,19 @@
+module PostSets
+  class Similar < PostSets::Post
+    def initialize(post)
+      super(tags)
+    end
+
+    def posts
+      @posts ||= begin
+        post_ids, scores = RecommenderService.similar(post)
+        post_ids = post_ids.reject {|x| x == post.id}.slice(0, 5)
+        Post.find(post_ids)
+      end
+    end
+
+    def presenter
+      ::Presenters::PostSetPresenters::Post.new(self)
+    end
+  end
+end

app/models/recommender_service.rb

@@ -0,0 +1,26 @@
+module RecommenderService
+  extend self
+
+  def enabled?
+    Danbooru.config.recommender_server.present?
+  end
+
+  def available?(post)
+    enabled? && CurrentUser.id == 1 && post.created_at > 6.months.ago && post.score >= 10
+  end
+
+  def similar(post)
+    Cache.get("rss:#{post.id}", 1.day) do
+      resp = HTTParty.get(
+        "#{Danbooru.config.recommender_server}/similar/#{post.id}", 
+        Danbooru.config.httparty_options.merge(
+          basic_auth: {
+            username: "danbooru", 
+            password: Danbooru.config.recommender_key
+          }
+        )
+      )
+      JSON.parse(resp.body)
+    end
+  end
+end

app/views/posts/partials/index/_similar.html.erb

@@ -0,0 +1,7 @@
+<div class="recent-posts">
+  <p>You might also like:</p>
+
+  <div>
+    <%= PostSets::Similar.new(post).presenter.post_previews_html(self) %>
+  </div>
+</div>

app/views/posts/show.html.erb

@@ -82,6 +82,10 @@
         </div>
       <% end %>
 
+      <% if RecommenderService.available?(@post) %>
+        <%= render "posts/partials/index/similar", post: @post %>
+      <% end %>
+
       <% if @post.presenter.has_nav_links?(self) %>
         <%= render "posts/partials/show/nav_links", :post => @post, :position => "bottom" %>
       <% end %>