add error handling

app/logical/pixiv_api_client.rb

@@ -1,8 +1,14 @@
 class PixivApiClient
+  API_VERSION = "1"
   CLIENT_ID = "bYGKuGVw91e0NMfPGp44euvGt59s"
   CLIENT_SECRET = "HP3RmkgAmEGro0gn1x9ioawQE8WMfvLXDz3ZqxpK"
 
+  class Error < Exception ; end
+
   def works(illust_id)
+    # Sample response: 
+    # {"status":"success","response":[{"id":49270482,"title":"ツイログ","caption":null,"tags":["神崎蘭子","双葉杏","アイドルマスターシンデレラガールズ","Star!!","アイマス5000users入り"],"tools":["CLIP STUDIO PAINT"],"image_urls":{"large":"http://i3.pixiv.net/img-original/img/2015/03/14/17/53/32/49270482_p0.jpg"},"width":1200,"height":951,"stats":{"scored_count":8247,"score":81697,"views_count":191630,"favorited_count":{"public":7804,"private":745},"commented_count":182},"publicity":0,"age_limit":"all-age","created_time":"2015-03-14 17:53:32","reuploaded_time":"2015-03-14 17:53:32","user":{"id":341433,"account":"nardack","name":"Nardack","is_following":false,"is_follower":false,"is_friend":false,"is_premium":null,"profile_image_urls":{"px_50x50":"http://i1.pixiv.net/img19/profile/nardack/846482_s.jpg"},"stats":null,"profile":null},"is_manga":true,"is_liked":false,"favorite_id":0,"page_count":2,"book_style":"none","type":"illustration","metadata":{"pages":[{"image_urls":{"large":"http://i3.pixiv.net/img-original/img/2015/03/14/17/53/32/49270482_p0.jpg","medium":"http://i3.pixiv.net/c/1200x1200/img-master/img/2015/03/14/17/53/32/49270482_p0_master1200.jpg"}},{"image_urls":{"large":"http://i3.pixiv.net/img-original/img/2015/03/14/17/53/32/49270482_p1.jpg","medium":"http://i3.pixiv.net/c/1200x1200/img-master/img/2015/03/14/17/53/32/49270482_p1_master1200.jpg"}}]},"content_type":null}],"count":1}
+
     headers = {
       "Referer" => "http://www.pixiv.net",
       "User-Agent" => "#{Danbooru.config.safe_app_name}/#{Danbooru.config.version}",
@@ -13,7 +19,7 @@ class PixivApiClient
       "image_sizes" => "large",
       "include_stats" => "true"
     }
-    url = URI.parse("https://public-api.secure.pixiv.net/v1/works/#{illust_id.to_i}.json")
+    url = URI.parse("https://public-api.secure.pixiv.net/v#{API_VERSION}/works/#{illust_id.to_i}.json")
     url.query = URI.encode_www_form(params)
     json = nil
 
@@ -21,6 +27,8 @@ class PixivApiClient
       resp = http.request_get(url.request_uri, headers)
       if resp.is_a?(Net::HTTPSuccess)
         json = JSON.parse(resp.body)
+      else
+        raise Error.new("Pixiv API call failed (status=#{resp.code} body=#{resp.body})")
       end
     end
 
@@ -37,7 +45,7 @@ private
     }
   end
 
-	def access_token
+  def access_token
     Cache.get("pixiv-papi-access-token", 3000) do
       access_token = nil
       headers = {
@@ -58,6 +66,8 @@ private
         if resp.is_a?(Net::HTTPSuccess)
           json = JSON.parse(resp.body)
           access_token = json["response"]["access_token"]
+        else
+          raise Error.new("Pixiv API access token call failed (status=#{resp.code} body=#{resp.body})")
         end
       end