add mock recommender service for development, add user-context recommended posts

app/models/recommender_service.rb

@@ -1,25 +1,26 @@
 module RecommenderService
   extend self
 
-  SCORE_THRESHOLD = 10
+  SCORE_THRESHOLD = 5
 
   def enabled?
     Danbooru.config.recommender_server.present?
   end
 
-  def available?(post)
+  def available_for_post?(post)
     return true if Rails.env.development?
+
     enabled? && CurrentUser.enable_recommended_posts? && post.created_at > Date.civil(2018, 1, 1) && post.score >= SCORE_THRESHOLD
   end
 
-  def similar(post)
-    if Danbooru.config.recommender_server == "development"
-      return Post.order("random()").limit(6).map {|x| [x.id, "1.000"]}
-    end
+  def available_for_user?
+    enabled? && CurrentUser.is_gold?
+  end
 
-    Cache.get("rss:#{post.id}", 1.day) do
+  def recommend_for_user(user_id)
+    ids = Cache.get("rsu:#{user_id}", 1.day) do
       resp = HTTParty.get(
-        "#{Danbooru.config.recommender_server}/similar/#{post.id}", 
+        "#{Danbooru.config.recommender_server}/recommend/#{user_id}", 
         Danbooru.config.httparty_options.merge(
           basic_auth: {
             username: "danbooru", 
@@ -29,5 +30,30 @@ module RecommenderService
       )
       JSON.parse(resp.body)
     end
+    Post.find(ids.map(&:first))
+  end
+
+  def recommend_for_post(post_id)
+    ids = 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
+    Post.find(ids.reject {|x| x[0] == post_id}.map(&:first))
+  end
+
+  def recommend(post_id: nil, user_id: nil)
+    if post_id
+      recommend_for_post(post_id)
+    elsif user_id
+      recommend_for_user(user_id)
+    end
   end
 end