artists: move artist finding code from controller to model.

app/controllers/artists_controller.rb

@@ -101,14 +101,7 @@ class ArtistsController < ApplicationController
   end
 
   def finder
-    begin
+    @artists = Artist.find_artists(params[:url], params[:referer_url])
-      @artists = Artist.url_matches(params[:url]).order("id desc").limit(10)
-      if @artists.empty? && params[:referer_url].present? && params[:referer_url] != params[:url]
-        @artists = Artist.url_matches(params[:referer_url]).order("id desc").limit(20)
-      end
-    rescue PixivApiClient::Error => e
-      @artists = []
-    end
 
     respond_with(@artists) do |format|
       format.xml do

app/models/artist.rb

@@ -357,6 +357,18 @@ class Artist < ApplicationRecord
   end
 
   module SearchMethods
+    def find_artists(url, referer_url = nil)
+      artists = url_matches(url).order("id desc").limit(10)
+
+      if artists.empty? && referer_url.present? && referer_url != url
+        artists = url_matches(referer_url).order("id desc").limit(20)
+      end
+
+      artists
+    rescue PixivApiClient::Error => e
+      []
+    end
+
     def url_matches(string)
       matches = find_all_by_url(string).map(&:id)